Тепловий аналіз твердотільних наноструктур
| dc.contributor.advisor | Семеновська, Олена Володимирівна | |
| dc.contributor.author | Рукодій, Сергій Анатолійович | |
| dc.date.accessioned | 2023-08-29T13:18:13Z | |
| dc.date.available | 2023-08-29T13:18:13Z | |
| dc.date.issued | 2021 | |
| dc.description.abstract | Об’єктом дослідження є тепловий аналіз у низькорозмірних твердотільних наноструктурах. Предметом роботи є взаємозв’язок між тепловими та електричними характеристиками у низькорозмірних твердотільних наноструктурах шляхом математичного моделювання. Метою роботи є оцінка теплових параметрів низькорозмірних твердотільних наноструктур AlGaAs/GaAs. Це дозволить підвищити якість і надійність роботи низькорозмірних твердотільних наноструктур на етапі моделювання і знизити витрати при їх виробництві та випробуванні. У першому розділі описані фундаментальні явища у наноструктурах, теплопровідність наноструктур. У другому розділі було розглянуто наступні методи теплового аналізу: аналітичні, числові та еквівалентні. Були описані переваги та недоліки даних методів. У третьому розділі розраховано значення поперечних енергій електрона в квантовій потенціальній ямі твердотільної наноструктури та встановлено взаємозв'язок між тепловими та геометричними розмірами твердотільної наноструктури. | uk |
| dc.description.abstractother | The study of nanostructures began in 1970-1980 in the physics of semiconductor heterostructures. In 1982-1984, Glyther proposed the concept of a solid nanostructure. Studies of nanostructures give us the opportunity to solve scientific problems and to create new quantum devices. Today we observe a period of transition of the characteristic sizes of electronics elements to the sizes which can be compared with the sizes of molecules and atoms. These dimensions correspond to hundreds, tens, units of nanometers. Structures with such dimensions are called nanostructures. The wave properties of an electron are manifested in the nanostructure, the size of which can be compared with the de Broglie wavelength of a free electron. It follows that the behavior of electrons depends on the geometry of the structure. The free motion of electrons in low-dimensional structures must be limited in at least one direction. Nanostructures are distinguished by their morphology, dimension and mutual spatial position of structural elements. In turn, the structures are divided into zero- dimensional (0D), one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D). According to the physical state, nanostructures can be divided into solid and amorphous. The phase composition is divided into single-phase and multiphase. According to the chemical composition of nanostructures are divided into organic and inorganic. Today, nanostructures are a new class of artificial semiconductor materials with a controlled spectrum of charge carriers. The use of semiconductor nanostructures in electronic technology gives us the opportunity to miniaturize electronic devices, to create a new generation of processors. Due to miniaturization there is an increase in the degree of integration, a decrease in the geometric dimensions of the devices, as well as an increase in the amount of heat dissipated. Therefore, the task of heat dissipation and control of the properties of the nanostructure is relevant today. Effective heat dissipation from the core of powerful semiconductor devices is a difficult task. Therefore, control and detailed analysis of heat fluxes in semiconductor devices is required. There is another problem associated with changes in the nature of heat transfer within a low-dimensional structure, in addition to the problem associated with heat dissipation on the spatial scale of the crystal with a decrease in geometric dimensions. Transport in conductors of considerable length is diffusion, which has a trajectory that is similar to random wanderings. Electron transport will switch to ballistic transfer mode if the length of the conduction channel becomes less than the average free path length. If the length of the conduction channel is even smaller, the wave nature of electrons will begin to manifest itself in the form of the following quantum effects: tunneling, ballistic transport. Ballistic transport of carriers is determined by their Fermi, not drift speed associated with the mobility of carriers. To implement such a transport, it is necessary to exclude scattering on the defects of the crystal. Ballistic transport is the transfer of charge carriers that occurs without scattering. The effects associated with ballistic transport can be determined by the relationship between the size of the structure in which the charge carriers are transferred, and the free path length. In metal nanostructures it is very difficult to carry out ballistic transport of carriers, because in metal the average free path length does not exceed 10 nm, this value is approximately equal to the size of the nanostructure. The transport of charge carriers in semiconductors is characterized by a fairly large average electron free path length, for example, in GaAs the average electron free path length is 120 nm. This value shows that ballistic transport of carriers is much easier to implement in semiconductors than in metals. Quantum constraints are constraints on the motion of electrons or holes that occur in a low-dimensional structure; this constraint causes the difference between the minimum energy and the discreteness of the spectrum of allowable values from zero. Quantum constraint occurs when the free motion of the de Broglie wave of electrons in one direction is limited by the potential barriers through which the nanostructure is formed. This limitation affects the transfer of charge carriers through the nanostructure and also changes the range of allowable energy levels. The transport of carriers is carried out both in parallel and perpendicular to the potential barriers, thus showing the wave nature of the electron. When moving carriers along potential barriers, the dominant effects are: - ballistic transport; - quantum interference. The passage of charge carriers through potential barriers occurs exclusively through their tunneling, which ensures the transfer of carriers from one zone of the nanoelectronic device to another. Electron tunneling that occurs through a potential barrier is a typical manifestation of the wave properties of a potential barrier. Tunneling means the transfer of a particle through an area bounded by a potential barrier whose height exceeds the energy of the particle. In low-dimensional structures, the phenomenon of electron tunneling acquires specific features associated with the discreteness of the charge carried by the electron, and with the additional quantization of energy states caused by quantum constraint. These features are most characteristic of single-electron tunneling and resonant tunneling. Modern studies of heat transfer in nanostructures are focused on semiconductor devices, mainly heat transfer by phonons is studied. The thermal conductivity equation can be used to calculate the heat distribution in nanostructures in two or one dimension. For example, large sheets of graphene and nanofilms, nanotubes and nanowires, if their length is much longer than the free path of the particles. Features of thermal analysis in low-dimensional transistor structures: - Ballistic thermal conductivity. In massive samples, the condition of small free path length l in comparison with the characteristic dimensions of sample L is fulfilled. The inverse condition l >> L corresponds to ballistic thermal conductivity, when heat transfer in nanostructures is realized without collision. The thermal resistance of the samples in these cases is zero. - Contact thermal resistance, which was opened by Kapitza. When studying heat transfer in nanostructures, it usually becomes of paramount importance. - Particle scattering at the boundaries of nanostructures. Nanowires are a typical example of the importance of accounting for collisions of phonons with boundaries whose diameter is much smaller than the free path length of phonons. In this case, the main question is the nature of the scattering at the boundary: mirror or diffuse. In the first case, the path length to diffuse scattering is the same as in massive bodies. If the scattering at the boundary is diffuse, then the free path length is comparable to the wire diameter. Both types of phonon scattering must be considered. - Quantum-dimensional structures. The wavelength of phonons is comparable to the size of nanoobjects, such as nanofilms. Under such conditions, there are phonons if the perpendicular component of the wavelengths satisfies the condition: the ratio of the film thickness to the half-wavelength of the phonon is an integer. In such cases, the equilibrium distribution of phonons by energy level differs from the generally accepted Bose-Einstein distribution. Under these conditions, it is necessary to take into account two effects: reduction of phonon density, change in the equations of phonon dispersion and the associated decrease in the speed of sound. There are the following methods of thermal analysis: - Analytical methods - the real structure is replaced by a thermophysical model, which is described by mathematical equations of heat transfer conditions in the thermal model. In order to solve linear problems of thermal conductivity, the Fourier method, the Green's function, thermal potentials, and integral transformations in finite and infinite limits must be used. - Numerical methods are divided into finite element methods, finite differences and boundary elements. The finite element method is more often used to determine the temperature distribution in microelectronic devices. The finite difference method is based on the replacement of the differential equation by difference equations. Advantages: can be used for complex structures with arbitrary geometry of the heat-dissipating zone, disadvantages: larger computation and complexity of preparation for solving the problem. - Equivalent methods: thermal methods and methods of electrothermal analogy. The electrothermal analogy is based on the identity of heat distribution and electric current flow in solids. Thermal method - replacement of the structure by the thermal equivalent according to the geometric dimensions of the crystal and the heat source. Advantages: can be used for several heat sources, the disadvantage is the cumbersome calculations. The task of the thesis is thermal analysis of solid nanostructures. The aim of this work is to estimate the thermal parameters of low-dimensional solid-state nanostructures AlGaAs/GaAs. This will improve the quality and reliability of low-dimensional solid-state nanostructures at the modeling stage and reduce costs in their production and testing. The object of research is thermal analysis in low-dimensional solid-state nanostructures. The subject of the work is the relationship between thermal and electrical characteristics in low-dimensional solid-state nanostructures by mathematical modeling. The first section describes the fundamental phenomena in nanostructures, the thermal conductivity of nanostructures. In the second section, the following methods of thermal analysis were considered: analytical, numerical and equivalent. The advantages and disadvantages of these methods have been described. In the third section, the values of the transverse energies of the electron in the quantum potential well of the solid-state nanostructure are calculated and the relationship between the thermal and geometric dimensions of the solid-state nanostructure is established. | uk |
| dc.format.extent | 60 с. | uk |
| dc.identifier.citation | Рукодій, C. А. Тепловий аналіз твердотільних наноструктур : дипломна робота … бакалавра : 153 Мікро- та наносистемна техніка / Рукодій Сергій Анатолійович. – Київ, 2021. – 60 с. | uk |
| dc.identifier.uri | https://ela.kpi.ua/handle/123456789/59626 | |
| dc.language.iso | uk | uk |
| dc.publisher | КПІ ім. Ігоря Сікорського | uk |
| dc.publisher.place | Київ | uk |
| dc.subject | твердотільні наноструктури | uk |
| dc.subject | методи теплового аналізу | uk |
| dc.subject | поле температур | uk |
| dc.subject | електротепловий аналіз | uk |
| dc.title | Тепловий аналіз твердотільних наноструктур | uk |
| dc.type | Bachelor Thesis | uk |
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