G. G. Yelenin
Brief information about the author: Professor of the Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University. M.V. Lomonosov, Leading Researcher, Institute of Applied Mathematics. M.V. Keldysh RAS.
If a steel cube or a crystal of salt, composed of identical atoms, can exhibit interesting properties; if water - mere droplets, indistinguishable from each other and covering the surface of the Earth for miles and miles - is able to create waves and foam, the thunder of the surf and strange patterns on the granite of the embankment; if all this, all the richness of the life of the waters, is just a property of bunches of atoms, then how many more possibilities are hidden in them? If, instead of arranging the atoms in order, line by line, column by column, even instead of building them into the intricate molecules of the smell of violets, if instead of arranging them in a new way each time, diversifying their mosaic without repeating it, what has already happened - imagine how much unusual, unexpected things can arise in their behavior.
R. P. Feynman
Subject, goals and main directions in nanotechnology
According to the Encyclopedic Dictionary, technology is a set of methods of processing, manufacturing, changing the state, properties, form of raw materials, material or semi-finished products carried out in the production process.
The peculiarity of nanotechnology lies in the fact that the processes under consideration and the actions performed occur in the nanometer range of spatial dimensions 1 . "Raw materials" are individual atoms, molecules, molecular systems, and not micron or macroscopic volumes of material that are customary in traditional technology, containing at least billions of atoms and molecules. Unlike traditional technology, nanotechnology is characterized by an "individual" approach, in which external control reaches individual atoms and molecules, which makes it possible to create from them both "defect-free" materials with fundamentally new physicochemical and biological properties, and new classes of devices with characteristic nanometer sizes. The concept of "nanotechnology" has not yet settled down. Apparently, the following working definition can be followed.
Nanotechnology is an interdisciplinary field of science in which the regularities of physical and chemical processes in spatial regions of nanometer sizes are studied in order to control individual atoms, molecules, molecular systems when creating new molecules, nanostructures, nanodevices and materials with special physical, chemical and biological properties.
An analysis of the current state of the rapidly developing region allows us to identify a number of important areas in it.
Molecular design. Preparation of existing molecules and synthesis of new molecules in highly inhomogeneous electromagnetic fields.
Materials Science. Creation of "defect-free" high-strength materials, materials with high conductivity.
Instrumentation. Creation of scanning tunneling microscopes, atomic force microscopes 2 , magnetic force microscopes, multipoint systems for molecular design, miniature supersensitive sensors, nanorobots.
Electronics. Designing nanometer element base for next generation computers, nanowires, transistors, rectifiers, displays, acoustic systems.
Optics. Creation of nanolasers. Synthesis of multipoint systems with nanolasers.
heterogeneous catalysis. Development of catalysts with nanostructures for classes of reactions of selective catalysis.
Medicine. Designing nanotools for the destruction of viruses, local "repair" of organs, high-precision delivery of drug doses to certain places in a living organism.
Tribology. Determination of the relationship between the nanostructure of materials and friction forces and the use of this knowledge for the manufacture of promising friction pairs.
Controlled nuclear reactions. Nanoaccelerators of particles, non-statistical nuclear reactions.
Scanning tunneling microscopy
At least two events played a significant role in the unstoppable exploration of the nanoworld:
Creation of a scanning tunneling microscope (G. Bennig, G. Rohrer, 1982) and a scanning atomic force microscope (G. Bennig, K. Kuatt, K. Gerber, 1986) (Nobel Prize 1992);
Discovery of a new form of carbon existence in nature - fullerenes (N. Kroto, J. Health, S. O "Brien, R. Curl, R. Smalley, 1985) (Nobel Prize 1996).
New microscopes made it possible to observe the atomic-molecular structure of the surface of single crystals in the nanometer size range. The best spatial resolution of instruments is a hundredth of a nanometer along the normal to the surface. The operation of a scanning tunneling microscope is based on the tunneling of electrons through a vacuum barrier. The high resolution is due to the fact that the tunneling current changes by three orders of magnitude when the barrier width changes by the size of the atom. The theory of quantum tunneling effect was founded by G.A. Gamow in 1928 in his work on a-decay.
With the help of various scanning microscopes, the atomic structure of the surfaces of single crystals of metals, semiconductors, high-temperature superconductors, organic molecules, and biological objects is currently observed. On fig. 1 shows the reconstructed surface of the lower terrace of the (100) face of a silicon single crystal. Gray circles are images of silicon atoms. Dark areas are local nanometer defects. On fig. Figure 2 shows the atomic structure of a clean surface of the (110) face of silver (left frame) and the same surface covered with oxygen atoms (right frame). It turned out that oxygen is not adsorbed chaotically, but rather forms rather long chains along a certain crystallographic direction. The presence of double and single chains indicates two forms of oxygen.
These forms play an important role in the selective oxidation of hydrocarbons such as ethylene. On fig. 3, one can see the nanostructure of the high-temperature superconductor Bi 2 Sr 2 CaCu 2 O 2 . In the left frame of Fig. 4, rings of benzene molecules (C 6 H 6) are clearly visible. The right frame shows the CH 2 chains of polyethylene. The paper presents a sequence of frames of a laboratory film about the penetration of a virus into a living cell.
New microscopes are useful not only for studying the atomic and molecular structure of matter. They turned out to be suitable for designing nanostructures. With the help of certain movements with the tip of the microscope, it is possible to create atomic structures. Figure 5 shows the stages of creating the "IBM" inscription from individual xenon atoms on the (110) face of a nickel single crystal. The movements of the tip during the creation of nanostructures from individual atoms resemble the techniques of a hockey player when advancing the puck with a stick. It is of interest to create computer algorithms that establish a non-trivial connection between the movements of the tip and the movements of manipulated atoms on the basis of appropriate mathematical models. Models and algorithms are necessary for the development of automatic "assemblers" of nanostructures.
Rice. 4: a - C 6 H 6 ; b - CH 2 -CH 2
Rice. 5. Xe/Ni (110)
Nanomaterials
Fullerenes, as a new form of the existence of carbon in nature, along with the long-known diamond and graphite, were discovered in 1985 when astrophysicists tried to explain the spectra of interstellar dust. It turned out that carbon atoms can form a highly symmetrical C 60 molecule. Such a molecule consists of 60 carbon atoms located on a sphere with a diameter of approximately one nanometer and resembles a soccer ball (Fig. 6). In accordance with L. Euler's theorem, carbon atoms form 12 regular pentagons and 20 regular hexagons. The molecule is named after the architect R. Fuller, who built a house of pentagons and hexagons. Initially, C 60 was obtained in small quantities, and then, in 1990, the technology for their large-scale production was discovered.
Fullerites. C 60 molecules, in turn, can form a fullerite crystal with a face-centered cubic lattice and fairly weak intermolecular bonds. This crystal has octahedral and tetrahedral cavities, which can contain foreign atoms. If the octahedral cavities are filled with alkali metal ions (¦ = K (potassium), Rb (rubidium), Cs (cesium)), then at temperatures below room temperature the structure of these substances is rearranged and a new polymeric material ¦1C60 is formed. If the tetrahedral cavities are also filled, then a superconducting material ¦3С60 with a critical temperature of 20–40 K is formed. Max Planck in Stuttgart. There are fullerites with other additives that give the material unique properties. For example, C60-ethylene has ferromagnetic properties. High activity in the new field of chemistry led to the fact that by 1997 there were more than 9000 fullerene compounds.
Carbon nanotubes. Molecules with a gigantic number of atoms can be obtained from carbon. Such a molecule, for example C=1000000, can be a single-layer tube with a diameter of about a nanometer and a length of several tens of microns (Fig. 7). On the surface of the tube, carbon atoms are located at the vertices of regular hexagons. The ends of the tube are closed with six regular pentagons. It should be noted the role of the number of sides of regular polygons in the formation of two-dimensional surfaces consisting of
Rice. 7. Non-chiral nanotubes: a - C(n", n) - metal;
b-c(n, 0): mod (n, 3) = 0 - semimetal
mod(n, 3)!= 0 is a semiconductor.
Rice. 8. Curved tube
carbon atoms, in three-dimensional space. Regular hexagons are a cell in a flat graphite sheet that can be rolled into tubes of various chirality (m, n) 3 . Regular pentagons (heptagons) are local defects in a graphite sheet, which make it possible to obtain its positive (negative) curvature. Thus, combinations of regular five-, six-, and heptagons make it possible to obtain various forms of carbon surfaces in three-dimensional space (Fig. 8). The geometry of these nanostructures determines their unique physical and chemical properties and, consequently, the possibility of the existence of fundamentally new materials and technologies for their production. The prediction of the physicochemical properties of new carbon materials is carried out both with the help of quantum models and calculations within the framework of molecular dynamics. Along with single-layer tubes, it is also possible to create multi-layer tubes. Special catalysts are used to produce nanotubes.
What is unique about the new materials? Let's just focus on three important features.
Super strong materials. The bonds between carbon atoms in a graphite sheet are the strongest known, so defect-free carbon tubes are two orders of magnitude stronger than steel and about four times lighter than steel! One of the most important tasks of technology in the field of new carbon materials is to create nanotubes of "infinite" length. Such tubes can be used to produce lightweight composite materials of ultimate strength for the needs of new age technology. These are power elements of bridges and buildings, load-bearing structures of compact aircraft, turbine elements, engine power blocks with extremely low specific fuel consumption, etc. At present, they have learned how to make tubes tens of microns in length with a diameter of the order of one nanometer.
highly conductive materials. It is known that in crystalline graphite the conductivity along the plane of the layer is the highest among known materials and, on the contrary, in the direction perpendicular to the sheet is low. Therefore, electrical cables made from nanotubes are expected to have electrical conductivity two orders of magnitude higher than copper cables at room temperature. It's up to the technology to produce tubes of sufficient length and in sufficient quantity,
nanoclusters
The set of nano-objects includes ultra-small particles consisting of tens, hundreds or thousands of atoms. The properties of clusters are fundamentally different from the properties of macroscopic volumes of materials of the same composition. From nanoclusters, as from large building blocks, it is possible to purposefully design new materials with predetermined properties and use them in catalytic reactions, for separating gas mixtures and storing gases. One example is Zn 4 O(BDC) 3 (DMF) 8 (C 6 H 5 Cl) 4 . Of great interest are magnetic clusters consisting of atoms of transition metals, lantinides, and actinides. These clusters have their own magnetic moment, which makes it possible to control their properties using an external magnetic field. An example is the high spin organometallic molecule Mn 12 O 12 (CH 3 COO) 16 (H 2 O) 4 . This elegant construction consists of four Mn 4+ ions with spin 3/2 located at the vertices of the tetrahedron, eight Mn 3+ ions with spin 2 surrounding this tetrahedron. The interaction between manganese ions is carried out by oxygen ions. The antiferromagnetic interactions of the spins of the Mn 4+ and Mn 3+ ions lead to a sufficiently large total spin equal to 10. Acetate groups and water molecules separate the Mn 12 clusters from each other in the molecular crystal. The interaction of clusters in a crystal is extremely small. Nanomagnets are of interest in the design of processors for quantum computers. In addition, in the study of this quantum system, the phenomena of bistability and hysteresis were discovered. If we take into account that the distance between molecules is about 10 nanometers, then the memory density in such a system can be on the order of 10 gigabytes per square centimeter.
nanodevices
Nanotubes can form the basis of new designs of flat acoustic systems and flat displays, that is, familiar macroscopic devices. Certain nanodevices can be created from nanomaterials, for example, nanomotors, nanomanipulators, molecular pumps, high-density memory, elements of nanorobot mechanisms. Let us briefly dwell on the models of some nanodevices.
Molecular gears and pumps. Models of nanodevices were proposed by K.E. Drexler and R. Merkle of IMM (Institute for Molecular Manufacturing, Palo Alto) . The shafts of the gears in the gearbox are carbon nanotubes, and the teeth are benzene molecules. The characteristic frequencies of rotation of the gears are several tens of gigahertz. The devices "work" either in a high vacuum or in an inert atmosphere at room temperature. Inert gases are used to "cool" the device.
Diamond memory for computers. The high-density memory model was developed by Ch. Bauschlicher and R. Merkle of NASA. The scheme of the device is simple and consists of a probe and a diamond surface. The probe is a (9, O) or (5, 5) carbon nanotube ending in a C 60 hemisphere, to which a C 5 H 5 N molecule is attached. The diamond surface is covered with a monolayer of hydrogen atoms. Some hydrogen atoms are replaced by fluorine atoms. When the probe is scanned along a diamond surface covered with an adsorbate monolayer, the C 5 H 5 N molecule, according to quantum models, is able to distinguish an adsorbed fluorine atom from an adsorbed hydrogen atom. Since about 1015 atoms fit on one square centimeter of the surface, the recording density can reach 100 terabytes per square centimeter.
The above examples of laboratory experiment results and nanodevice models are a new challenge to theory, computational physics, chemistry and mathematics. Understanding of "seen" and "received" is required. It requires the development of intuition to work in the nanometer range of sizes. Once again, Faust's remark to Wagner is heard:
"What does it mean to understand?
That, my friend, is the question.
In this regard, we are not all right."
New branches of computational physics and computational chemistry
More than fifty years ago, the atomic and thermonuclear problems, the problems of creating new aircraft and the exploration of near-Earth space once again raised the Faustian question of a new level of understanding of physical and chemical phenomena. Successful work on these problems led to the emergence and development
1) computational physics, in particular its areas such as
magnetic and radiation hydro- and aerodynamics,
spacecraft flight mechanics,
theory of plasma and controlled thermonuclear fusion;
2) computational chemistry with sections such as
theory of the equation of state of matter,
molecular Dynamics,
theory of chemical processes and apparatuses;
3) computational mathematics and computer science with such areas as
numerical methods of mathematical physics,
automata theory,
optimal control,
pattern recognition,
expert systems,
automatic design.
Modern possibilities of the laboratory experiment for observation and study of phenomena in the nanometer scale of spatial dimensions and tempting prospects for the creation of unique materials and nanodevices give rise to new theoretical problems.
I would like to understand what is actually "observed" in scanning tunneling microscopy?
What new things can potentially be observed and what new things can potentially be obtained in nanosystems? And under what conditions?
How to manage individual atoms and groups of atoms and molecules to achieve certain goals? What are the limits of this control?
How to organize the self-assembly of nanodevices and unique "defect-free" materials?
To what extent does the macroenvironment "constrict" the quantum states of the nanosystem?
The need for a constructive solution of these problems leads to intensive research, forming new branches in computational physics and computational chemistry. We single out such sections in metrology, mechanics, electrodynamics, optics, and the theory of self-organization. In each of these sections, we outline several problems.
Metrology
1. Creation of computer models of "instrument-nanoobject" systems and their calibration.
2. Automation of nanometer measurements and creation of databanks.
Mechanics
1. Study of mechanical stresses and strains in nanomaterials and nanoobjects, friction analysis.
2. Simulation of probe movements during targeted manipulation of a nanoobject.
3. Modeling of movements in nanomechanisms for nanodevices, calculation of nanomanipulators.
4. Development of control systems for nanorobots.
Electrodynamics
1. Simulation of the dynamics of atoms and molecules in extremely inhomogeneous electromagnetic fields created by multipoint systems.
2. Calculation of electrical and magnetic properties of nanomaterials.
1. Modeling of the mechanisms of emission, propagation and absorption of light in nanoobjects.
2. Calculation of nanolasers and hybrid systems "probes + nanolaser".
Theory of self-organization
1. Formulation of the fundamental principles of self-assembly of nanostructures.
2. Creation of computer self-assembly algorithms.
3. Development of computational algorithms for qualitative analysis of self-assembly models.
4. Simulation of the phenomena of spatio-temporal self-organization in the creation of nanomaterials.
Molecular beam epitaxy and nanolithography
1. Creation of thin metal films that serve as the basis for high-quality magnetic materials.
2. Designing the basic elements of nanoelectronics.
3. Creation of catalysts for selective catalysis.
I would like to once again emphasize the need to maintain a strict balance between laboratory experiment, theory and mathematical modeling. Sometimes one can hear statements that a precision experiment is currently very expensive and can be replaced by cheaper mathematical modeling. There is also an opposite position, in which the role of mathematical research methods is belittled. The simplest examples of nontrivial phenomena in the nanometer range of spatial dimensions demonstrate the complete failure of radical positions.
Phenomena of space-time self-organization on the surface of single crystals of metals
Consider, at first glance, the simplest, but, as it turns out, non-trivial problem. Suppose we would like to grow a high quality, uniform metal film, such as a platinum film. To do this, one should take a densely packed and spatially homogeneous face of a single crystal as a substrate and deposit a layer of atoms on it from a Knudsen cell under high vacuum conditions. Atoms fly out of the cell, are adsorbed on a homogeneous surface, migrate along it and form a new layer. Once the first layer is formed, the next layer is formed on top of it, and so on. The process is determined by only two external control macroparameters - the surface temperature and the flow of atoms to the surface. It is only necessary to choose the temperature and the rate of supply of atoms in such a way that, during the characteristic time of supply of a new atom, an atom migrating over the surface has time to integrate into the growing layer. It seems that there is nothing easier than to simulate film growth within the framework of classical mathematical physics models. Only one process needs to be described: the surface diffusion of incoming particles. To do this, one can use the diffusion equation with a constant source in a two-dimensional spatial domain, supplement it with an appropriate boundary condition, for example, a homogeneous boundary condition of the second kind, and carry out calculations. Obviously, with a sufficiently fast migration, regardless of the initial conditions, a spatially homogeneous solution will be obtained with a sufficiently high accuracy, monotonically increasing in time. However, such modeling does not at all describe the growth of a new layer and its spatial structure.
An experiment performed using a scanning tunneling microscope with a Pt/Pt(111) 5 homosystem shows (Fig. 9) that adsorbed platinum atoms migrate over the surface of the (111) face of a platinum single crystal, not obeying Fick's law. They form islands of a new layer with different spatial structures depending on the values of the surface temperature and the rate of supply of atoms. These can be loose islands of a fractal structure with a fractal
Fig.9. Pt/Pt (111)
Rice. 10. Co/Re (0001): a - CoRe; b - Co 2 Re; c - Co 3 Re
dimension 1.78 (Fig. 9a), or compact islands with Platonic shapes in the form of regular triangles (Figs. 9b, 9d) and hexagons (Fig. 9c), moreover, equally oriented relative to the crystallographic axes. Thus, at a temperature of 400 K, the vertices of the triangles look "down" (Fig. 9b). At a temperature of 455 K, the growing islands take the form of regular hexagons (Fig. 9c). At a higher temperature, the regular triangular shape of the islands is again formed, but this time their tops look "up" (Fig. 9d). The shape and orientation of the triangular islands are stable. Further supply of atoms leads to a three-dimensional growth regime, as a result of which the growing layer is always inhomogeneous and has a pyramidal three-dimensional structure.
In connection with the peculiarities of growth, at least two fundamental questions arise.
How to theoretically describe the non-trivial dynamic behavior of the simplest system?
What are the ways to control the system to ensure layered growth and obtain a high quality spatially uniform layer?
Similar questions also arise in heterosystems, when a film of another metal is grown on the surface of one metal. So, in the case of growing a silver film on platinum, one can observe islands of fractal and dendritic structures, islands in the form of a three-beam star from the Mercedes company, and other spatiotemporal self-organization phenomena that accompany the uneven three-dimensional growth of a thin metal film. In the case of cobalt film growth on a homogeneous (0001) face of a rhenium single crystal, surface alloys are formed with different stoichiometry and, accordingly, spatial structure: CoRe (Fig. 10a), Co 2 Re (Fig. 10b), Co 3 Re (Fig. 10c) and nontrivial surface structure. In the illustrations presented in fig. 10, it can be seen that large circles (rhenium atoms) are surrounded by a different number of small circles (cobalt atoms). These alloys have interesting magnetic properties.
It is impossible not to dwell on one more paradoxical phenomenon - the anomalously high mobility of large compact clusters. Following the authors of a remarkable experimental work, let us consider a compact cluster of regular shape, consisting of the "magic" number of iridium atoms N = 1 + Зn(n - 1), n = 2, 3, ... , for example, N = 19, on the surface of a densely packed face (111) iridium. It would seem that the mobility of a cluster containing two dozen atoms, as a whole, should be many orders of magnitude less than the mobility of a single atom, since the migration of atoms seems to be a random process. The experiment found that the rate of migration of "correct" clusters is comparable to the rate of migration of a single atom! This consequence of the collective motion of cluster atoms requires a detailed theoretical description and mathematical modeling. The results of such an analysis are of considerable interest in calculating the pre-exponential and effective activation energies of migration for the dynamic Monte Carlo method and for the kinetic equations of a non-ideal layer. Knowing the actual migration rates, one can correctly estimate the lifetime of nanoscale structures.
There is no need to convince the reader that the listed results of the laboratory experiment demonstrate the need for the development of classical models of mathematical physics. In the study of nanoobjects, where it is required, one should abandon the idea of a continuous medium, which underlies the vast majority of models of mathematical physics. Modeling by inertia, without taking into account the results of a laboratory experiment, leads to absolutely wrong results. The need for a new modern course in mathematical physics, which takes into account the features of nanoobjects, is also obvious. In this course, in particular, attention should be paid to
Rice. 11. (CO + O 2)/Pt(210)
methods of discrete mathematics, enumerative combinatorics, group theory.
More complex examples of nontrivial dynamic behavior of open nonideal systems are given by model reactions of heterogeneous catalysis on certain faces of noble metal single crystals (Pt(111), Pt(100), Pt(110), Pt(210), Pd(111), Pd(110) ) at low partial pressures in the gas phase. These are the oxidation reactions of carbon monoxide (CO) with oxygen (O 2), as well as the reduction of nitrogen monoxide (NO) with hydrogen (H 2), ammonia (NH 3) and carbon monoxide. These reactions play a significant role in the environmental problem of afterburning toxic emissions (NO, CO, etc.) from internal combustion engines and thermal power plants. Research carried out in recent years has revealed the fascinating nano- and mesodynamics of these systems. Phase transitions of the order-disorder type, accompanied by the formation of superstructures in the adsorbate monolayer, phase transitions of the type of separation into phases, spontaneous and adsorbate-induced reconstruction of the surface of the faces of single crystals, and corrosion of the catalyst were found. The processes of spatiotemporal self-organization occurring in the nanometer scale are closely related to similar phenomena observed with the help of emission photoelectron microscopy in the micrometer range. Such phenomena include micrometer spiral, standing and trigger waves, double metastability, and chemical turbulence. Figure 11 shows the results of a study of spatiotemporal self-organization in the reaction of carbon monoxide oxidation on the face of a Pt(210) single crystal by the method of emission photoelectron microscopy. Each frame (380 x 380 mm) shows the spatial distribution of adsorbed CO molecules (light areas) and oxygen atoms (dark areas) on the catalyst surface for various CO and oxygen partial pressures in the gas phase at a constant surface temperature. Spiral waves and autowaves of a phase transition such as separation into phases, phenomena of double metastability, etc. are clearly visible.
1 The size of an atom is a few tenths of a nanometer.
2 Description of devices and principles of their operation is contained in.
3 A pair of natural numbers (m, n) determines the chirality vector in the graphite sheet plane. The nanotube axis is perpendicular to the chirality vector. Thus, for (n, n) ((n, 0)) the axis of the tube is parallel (perpendicular) to the side of a regular hexagon.
4 The abbreviation BDC stands for benzene dicarboxyl and DMF stands for dimethylformamide.
5 The numbers in parentheses denote the Miller indices of the face of the single-crystal substrate.
Key technologies and materials have always played an important role in the history of civilization, performing not only narrow production functions, but also social ones. Suffice it to recall how much the Stone and Bronze Ages, the age of steam and electricity, atomic energy and computers differed greatly. According to many experts, the 21st century will be the century of nanoscience and nanotechnologies, which will determine its face.
Nanoscience can be defined as a body of knowledge about the behavior of matter on a nanometer scale, and nanotechnology as the art of creating and operating objects with sizes ranging from fractions to hundreds of nanometers (at least in one or two of the three dimensions).
The main components of nanotechnology are shown in fig. 2.1. Its fundamental foundation is the physics, chemistry and molecular biology of artificial and natural volumes, consisting of a countable number of atoms, i.e. such objects, in which a strong dependence of all properties on their size (size effects), a discrete atomic-molecular structure of a substance and/or quantum laws of its behavior are already manifested to a large extent.
Another important component of nanotechnology is the ability to purposefully create or find in nature nanostructured materials and objects with predetermined properties. The next component of nanotechnology
Creation of finished products, multi-component products with new consumer qualities and purpose (super-capacity memory, ultra-fast processors, intelligent nanorobots, etc.). Finally, the means of control, certification and research of nanoproducts and nanostructured materials at all stages of manufacture and use is also a necessary component of nanotechnology.
Dozens of major programs are already being implemented in the field of nanoscience and nanotechnology in all developed countries of the world. Nanotechnologies are used in such important areas for society as healthcare and medicine, biotechnology and environmental protection, defense and aerospace, electronics and computers, chemical and petrochemical production, energy and transport. The growth rates of investments and the introduction of nanotechnology in the industrialized countries of the world are now very high, and in the next 10-20 years it will determine the level of economic development and, to a large extent, social progress in the society.
Such a prospect poses new challenges to the entire system of education, primarily professional education. Since nanotechnology implies the integration of fundamental knowledge and high-tech methods for the production of nanostructured materials and finished products, there has been a tendency in Western universities to reduce the volume of training of both "pure" physicists, mathematicians, chemists, biologists, and traditional engineers: metallurgists, mechanics, power engineers, technologists, and increasing the share of "synthetic" specialties in the field of physical materials science and nanotechnology.
Over the past few years, about 10 thousand articles on nanoproblems have been published in world periodicals and about a dozen monthly specialized journals have been published in certain areas of nanoscience.
So, what is now understood by nanotechnology? The decimal prefix "nano" itself means one billionth of something. Thus, purely formally, objects with characteristic dimensions R (at least along one coordinate) measured in nanometers (1 nm = 10-9 m = 10E) fall into the scope of this activity.
In reality, the range of objects and phenomena under consideration is much wider - from individual atoms (R< 0,1 нм) до их конгломератов и органических молекул, со- держащих более 109 атомов и имеющих размеры гораздо более 1 мкм в одном или двух измерениях (рис.2.2). В силу действия различных причин (как чисто геометрических, так и физических) вместе с уменьшением размеров падает и характерное время протекания разнообразных процессов в системе, т.е. возрастает ее потенциальное быстродействие, что очень важно для электроники и вычислительной техники. Реально уже сейчас достигнутое быстродействие - время, затрачиваемое на одну элементарную операцию в серийно производимых компьютерах, составляет около 1 нc (10-9 с), но может быть еще уменьшено на несколько порядков величины в ряде наноструктур.
It would be naive to think that before the advent of the era of nanotechnology, a person did not encounter and did not use objects and processes at the nanolevel. So, biochemical reactions between macromolecules that make up all living things, obtaining photographic images, catalysis in chemical production, fermentation processes in the manufacture of wine, cheese, bread, and others occur at the nanolevel. However, "intuitive nanotechnology", which initially developed spontaneously, without a proper understanding of the nature of the objects and processes used, cannot be a reliable basis in the future. Therefore, fundamental research aimed at creating fundamentally new technological processes and products is of paramount importance. It is possible that nanotechnologies will be able to replace some of the obsolete and inefficient technologies, but still, its main place is in new areas in which it is impossible in principle to achieve the required results by traditional methods.
Thus, in the vast and still poorly mastered gap between the macro level, where well-developed continuum theories of continuous media and engineering methods of calculation and design operate, and the atomic level, subject to the laws of quantum mechanics, there is an extensive meso-hierarchical level of the structure of matter (texos - medium, intermediate with Greek). At this level, vital biochemical processes take place between the macromolecules of DNA, RNA, proteins, enzymes, subcellular structures, which require a deeper understanding. At the same time, previously unseen products and technologies can be artificially created here that can radically change the life of the entire human community. At the same time, it will not require large expenditures of raw materials and energy, as well as means for their transportation, the amount of waste and environmental pollution will decrease, labor will become more intelligent and healthy.
Lecture #19
Nanotechnology in recent years has become one of the most important and exciting areas of knowledge at the forefront of physics, chemistry, biology, and engineering sciences. It gives great hopes for early breakthroughs and new directions in technological development in many areas of activity. In order to facilitate and accelerate the wide-scale use of this new approach, it is important to have general ideas and some specific knowledge, which, on the one hand, would be detailed and deep enough to cover the topic in detail, and at the same time, accessible and complete enough to be useful to a wide range of specialists, wishing to learn more about the essence of the issue and the prospects in this area.
The current widespread interest in nanotechnology dates back to 1996 - 1998, when a government commission, with the assistance of the World Technology Evaluation Center (WTEC), funded by the US National Science Foundation and other federal agencies, undertook a study of world experience in research and development in the field nanotechnologies in order to assess their technological innovation potential. Nanotechnology is based on the understanding that particles smaller than 100 nanometers (a nanometer is one billionth of a meter) impart new properties and behavior to materials made from them. This is because objects smaller than the characteristic length (which is due to the nature of the particular phenomenon) often exhibit different physics and chemistry, leading to so-called size effects, a new behavior dependent on particle size. So, for example, changes in the electronic structure, conductivity, reactivity, melting temperature and mechanical characteristics were observed at particle sizes less critical. The dependence of behavior on particle sizes allows one to design materials with new properties from the same initial atoms.
According to WTEC, this technology has great potential for use in an extremely large and diverse range of practical areas - from the production of stronger and lighter structural materials to reducing the delivery time of nanostructured drugs to the circulatory system, increasing the capacity of magnetic media and creating triggers for fast computers. The recommendations given by this and subsequent committees have led to the allocation of very large funds for the development of nanoscience and nanotechnology in recent years. Interdisciplinary research has covered a wide range of topics - from the chemistry of catalysis by nanoparticles to the physics of quantum dot lasers. As a result, in order to appreciate the most general perspectives and implications of the development of nanotechnology and to make a contribution to this new exciting field of activity, it was realized that researchers need to periodically go beyond their narrow professional area of knowledge. Technical managers, experts, and those who make financial decisions need to understand a very wide range of disciplines.
Nanotechnology has come to be seen not only as one of the most promising branches of high technology, but also as a system-forming factor in the economy of the 21st century - an economy based on knowledge, rather than the use of natural resources or their processing. In addition to the fact that nanotechnology stimulates the development of a new paradigm of all production activities ("bottom-up" - from individual atoms - to the product, and not "top-down", as in traditional technology, in which the product is obtained by cutting off excess material from a more massive blanks), it is itself a source of new approaches to raising the standard of living and solving many social problems in a post-industrial society. According to most experts in the field of science and technology policy and investment, the nanotechnology revolution that has begun will cover all vital areas of human activity (from space exploration to medicine, from national security to ecology and agriculture), and its consequences will be wider and deeper than the computer revolutions of the last third of the 20th century. All this raises tasks and questions not only in the scientific and technical sphere, but also before administrators at various levels, potential investors, the education sector, and state bodies. management, etc.
In recent years, there have been a sufficient number of publications devoted to the theory, properties and practical application of nanomaterials and nanotechnology. In particular, this topic is widely presented in the book by Ch. Pool and Jr.F. Owens, Nanotechnology, trans. from English, 2nd, revised edition, ed. "Technosphere", M., 2006, 335s. The authors note that although this book was originally planned as an introduction to nanotechnology, due to the very nature of this science, it has become an introduction to certain areas of nanotechnology, which, apparently, are its typical representatives. Due to the high speed of development and the interdisciplinary nature, it is impossible to give a truly comprehensive presentation of the subject. The topics presented were selected based on the achieved depth of understanding of the issue, the volume of their potential or existing applications in technology. Many chapters discuss current and future opportunities. For those who wish to learn more about the specific areas in which this technology is being developed, references to the literature are provided.
The authors have attempted to provide an introduction to the subject of nanotechnology, written at such a level that researchers in various fields can appreciate the development of the field outside their professional interests, and technical leaders and managers can get an overview of the subject. Perhaps this book can be used as the basis for a university course on nanotechnology. Many chapters provide introductions to the physical and chemical principles underlying the areas discussed. Thus, many chapters are self-sufficient and can be studied independently of each other. Thus, Chapter 2 begins with a brief overview of the properties of bulk materials, which is necessary to understand how and why the properties of materials change as the size of their structural units approaches the nanometer. An important stimulus for such a rapid development of nanotechnology was the creation of new tools (such as the scanning tunneling microscope), which made it possible to see nanometer-sized features on the surface of materials. Therefore, Chapter 3 describes the most important instrumental systems and provides illustrations of measurements in nanomaterials. The rest of the chapters deal with other aspects of the problem. The book covers a very wide range of problems and topics: effects associated with the size and dimension of nanoscience and technology objects, magnetic, electrical and optical properties of nanostructured materials, methods for their preparation and study, self-assembly and catalysis in nanostructures, nanobiotechnology, integrated nanoelectromechanical devices, fullerites , nanotubes and much more. A number of modern methods of research and certification of nanostructures and nanoobjects are described: electron and ion-field microscopy, optical, X-ray and magnetic spectroscopy.
At the same time, gaps in the structure and content of individual sections are also obvious. Thus, information about nanoelectronics, spintronics, new ideas regarding quantum computing and computers is almost completely absent. Most of them are not even mentioned. Absolutely insufficient attention has been paid to the extremely powerful and widespread probe scanning methods of research, certification, lithography, and atomic and molecular design. A tiny paragraph devoted to these issues is completely out of proportion to the role and place of probe nanotechnology. A very modest place is given to weak superconductivity and very promising devices based on it. Films and heterostructures that play an important role in modern planar electronics, superhard and wear-resistant coatings, etc. are sparingly presented. ing, nanoscraping, etc.).
We also note that no systematization of objects and processes of nanotechnology is given anywhere, as a result of which it remains unclear to an inexperienced reader what part of the subject he will be able to get acquainted with after reading this book.
Despite the shortcomings noted above, in general, the book can be considered useful for a wide range of readers, including students of physical, chemical and materials science specialties. The latter is all the more relevant because educational literature on nanotechnology in Russian is almost completely absent, and the need for it is great due to the training of specialists in nanomaterials and nanoelectronics that began in 2003 in 12 Russian universities.
Not all ideas and interpretations of the authors can be agreed unconditionally. However, in order not to clutter up the text with a large number of comments, additions and criticisms, only obvious errors, inconsistencies and typos have been eliminated during translation and editing.
During the writing of the book and its reprinting in Russian, many useful books have been published, some of which are listed below. According to them, the interested reader can get acquainted with the individual sections and the panorama of nanotechnology as a whole in more depth.
Nanomaterials conventionally include dispersed and massive materials containing structural elements (grains, crystallites, blocks, clusters, and others), the geometric dimensions of which do not exceed 100 nm in at least one dimension, and possessing qualitatively new functional and operational characteristics. Nanotechnologies include technologies that provide the ability to create and modify nanomaterials in a controlled manner, as well as to integrate them into fully functioning large-scale systems. Among the main components of the science of nanomaterials and nanotechnologies, the following can be distinguished:
fundamental studies of the properties of materials at the nanoscale level;
development of nanotechnologies for the purposeful creation of nanomaterials, as well as the search for and use of natural objects with nanostructural elements, the creation of finished products using nanomaterials and the integration of nanomaterials and nanotechnologies into various industries and sciences;
development of tools and methods for studying the structure and properties of nanomaterials, as well as methods for monitoring and certifying products and semi-finished products for nanotechnologies.
The 21st century was marked by a revolutionary start in the development of nanotechnologies and nanomaterials. They are already used in all developed countries of the world in the most significant areas of human activity (industry, defense, information sphere, radio electronics, energy, transport, biotechnology, medicine). An analysis of the growth in investments, the number of publications on this topic and the pace of implementation of fundamental and search developments allows us to conclude that in the next 20 years the use of nanotechnologies and nanomaterials will be one of the determining factors in the scientific, economic and defense development of states. At present, interest in a new class of materials in the field of both fundamental and applied science, as well as industry and business, is constantly increasing. This is due to the following reasons:
striving for miniaturization of products,
unique properties of materials in the nanostructured state,
the need to develop and implement materials with qualitatively and quantitatively new properties,
the development of new technological methods and methods based on the principles of self-assembly and self-organization,
practical implementation of modern instruments for research, diagnostics and modification of nanomaterials (scanning probe microscopy),
development and implementation of new technologies, which are a sequence of lithography processes, technologies for obtaining nanopowders.
The direction of nanostructural research has almost completely shifted from obtaining and studying nanocrystalline substances and materials to the field of nanotechnology, i.e., the creation of products, devices, and systems with nanosized elements. The main areas of application of nanoscale elements are electronics, medicine, chemical pharmaceuticals and biology.
Russian President Dmitry Medvedev is confident that the country has all the conditions for the successful development of nanotechnology.
Nanotechnology is a new area of science and technology that has been actively developing in recent decades. Nanotechnologies include the creation and use of materials, devices and technical systems, the functioning of which is determined by the nanostructure, that is, its ordered fragments ranging in size from 1 to 100 nanometers.
The prefix "nano", which came from the Greek language ("nanos" in Greek - dwarf), means one billionth part. One nanometer (nm) is one billionth of a meter.
The term "nanotechnology" (nanotechnology) was coined in 1974 by professor-materials scientist from the University of Tokyo Norio Taniguchi (Norio Taniguchi), who defined it as "manufacturing technology that allows to achieve ultra-high precision and ultra-small dimensions ... of the order of 1 nm ..." .
Nanoscience is clearly distinguished from nanotechnology in the world literature. The term nanoscale science is also used for nanoscience.
In Russian and in the practice of Russian legislation and regulations, the term "nanotechnologies" combines "nanoscience", "nanotechnologies", and sometimes even "nanoindustry" (areas of business and production where nanotechnologies are used).
The most important component of nanotechnology are nanomaterials, that is, materials whose unusual functional properties are determined by the ordered structure of their nanofragments ranging in size from 1 to 100 nm.
- nanoporous structures;
- nanoparticles;
- nanotubes and nanofibers
- nanodispersions (colloids);
- nanostructured surfaces and films;
- nanocrystals and nanoclusters.
Nanosystem technology- fully or partially created on the basis of nanomaterials and nanotechnologies, functionally complete systems and devices, the characteristics of which are fundamentally different from those of systems and devices of a similar purpose, created using traditional technologies.
Applications of nanotechnology
It is almost impossible to list all the areas in which this global technology can significantly affect technological progress. We can name just a few of them:
- elements of nanoelectronics and nanophotonics (semiconductor transistors and lasers;
- photodetectors; Solar cells; various sensors)
- devices for ultra-dense recording of information;
- telecommunications, information and computing technologies; supercomputers;
- video equipment - flat screens, monitors, video projectors;
- molecular electronic devices, including switches and electronic circuits at the molecular level;
- nanolithography and nanoimprinting;
- fuel cells and energy storage devices;
- devices of micro- and nanomechanics, including molecular motors and nanomotors, nanorobots;
- nanochemistry and catalysis, including combustion control, coating, electrochemistry and pharmaceuticals;
- aviation, space and defense applications;
- devices for monitoring the state of the environment;
- targeted delivery of drugs and proteins, biopolymers and healing of biological tissues, clinical and medical diagnostics, creation of artificial muscles, bones, implantation of living organs;
- biomechanics; genomics; bioinformatics; bioinstrumentation;
- registration and identification of carcinogenic tissues, pathogens and biologically harmful agents;
- safety in agriculture and food production.
Computers and microelectronics
Nanocomputer- a computing device based on electronic (mechanical, biochemical, quantum) technologies with the size of logical elements of the order of several nanometers. The computer itself, developed on the basis of nanotechnology, also has microscopic dimensions.
DNA computer- a computing system that uses the computational capabilities of DNA molecules. Biomolecular computing is a collective name for various techniques related to DNA or RNA in one way or another. In DNA computing, data is not represented in the form of zeros and ones, but in the form of a molecular structure built on the basis of the DNA helix. The role of software for reading, copying and managing data is performed by special enzymes.
Atomic force microscope- high-resolution scanning probe microscope, based on the interaction of the cantilever needle (probe) with the surface of the sample under study. Unlike a scanning tunneling microscope (STM), it can examine both conductive and non-conductive surfaces even through a liquid layer, which makes it possible to work with organic molecules (DNA). The spatial resolution of an atomic force microscope depends on the size of the cantilever and the curvature of its tip. The resolution reaches atomic horizontally and significantly exceeds it vertically.
Antenna oscillator- On February 9, 2005, an oscillator antenna with a size of about 1 micron was received in the laboratory of Boston University. This device has 5,000 million atoms and is capable of oscillating at a frequency of 1.49 gigahertz, which allows you to transfer huge amounts of information with it.
Nanomedicine and pharmaceutical industry
A direction in modern medicine based on the use of the unique properties of nanomaterials and nanoobjects for tracking, designing and changing human biological systems at the nanomolecular level.
DNA nanotechnologies- use the specific bases of DNA molecules and nucleic acids to create clearly defined structures on their basis.
Industrial synthesis of molecules of drugs and pharmacological preparations of a well-defined shape (bis-peptides).
At the beginning of 2000, thanks to the rapid progress in the technology of manufacturing nano-sized particles, an impetus was given to the development of a new field of nanotechnology - nanoplasmonics. It turned out to be possible to transmit electromagnetic radiation along a chain of metal nanoparticles by excitation of plasmon oscillations.
Robotics
Nanobots- robots created from nanomaterials and comparable in size to a molecule, with the functions of movement, processing and transmission of information, execution of programs. Nanorobots capable of creating copies of themselves, i.e. self-reproducing are called replicators.
At present, electromechanical nanodevices with limited mobility have already been created, which can be considered prototypes of nanorobots.
Molecular rotors- Synthetic nanoscale motors capable of generating torque when enough energy is applied to them.
Place of Russia among the countries developing and producing nanotechnologies
The world leaders in terms of total investment in the field of nanotechnology are the EU countries, Japan and the United States. Recently, Russia, China, Brazil and India have significantly increased investments in this industry. In Russia, the amount of financing within the framework of the program "Development of nanoindustry infrastructure in the Russian Federation for 2008-2010" will amount to 27.7 billion rubles.
The latest (2008) report of the London-based research firm Cientifica, called the "Nanotechnology Outlook Report", says the following verbatim about Russian investments: "Although the EU still ranks first in terms of investment, China and Russia have already overtaken the United States."
There are such areas in nanotechnology where Russian scientists became the first in the world, having obtained results that laid the foundation for the development of new scientific trends.
Among them are the production of ultrafine nanomaterials, the design of single-electron devices, as well as work in the field of atomic force and scanning probe microscopy. Only at a special exhibition held within the framework of the XII St. Petersburg Economic Forum (2008), 80 specific developments were presented at once.
Russia already produces a number of nanoproducts that are in demand on the market: nanomembranes, nanopowders, nanotubes. However, according to experts, Russia is ten years behind the United States and other developed countries in the commercialization of nanotechnological developments.
The material was prepared on the basis of information from open sources
