Упругие свойства и ангармонизм твердых тел

The squares of the velocities of the longitudinal and transverse acoustic waves separately are practically not associated with anharmonicity, and their ratio (vL2 / vS2) turns out to be a linear function of the Grüneisen parameter γ - the measure of anharmonicity. The obtained dependence of (vL2 / vS2) on γ is in satisfactory agreement with the experimental data. The relationship between the quantity (vL2 / vS2) and anharmonicity is explained through its dependence on the ratio of the tangential and normal stiffness of the interatomic bond λ, which is a single-valued function of the Grüneisen parameter λ (γ). The relationship between Poisson's ratio μ and Grüneisen parameter γ, established by Belomestnykh and Tesleva, can be substantiated within the framework of Pineda's theory. Attention is drawn to the nature of the Leont'ev formula, derived directly from the definition of the Grüneisen parameter by averaging the frequency of normal lattice vibration modes. The connection between Grüneisen, Leontiev and Belomestnykh-Tesleva relations is considered. The possibility of a correlation between the harmonic and anharmonic characteristics of solids is discussed.

Enhancement Thermoelectric Properties of Cux-doped Nanostructure Bi-Sb-Te Thermoelectric Materials by Spark Plasma Sintering

Nanostructure Cux-doped Bi0.5Sb1.5-xTe3 thermoelectric materials was successfully prepared by Mechanical alloys and spark plasma sintering. In the reasearch, the crystallinity, particle size, and chemical composition were characterized by XRD, EDS, respectively. Thermoelectric properties with a maximum ZT value up to 1.17 has been obtained at 407 K in prepared Cu0.04-doped Bi0.5Sb1.496Te3 sample. The achieved higher ZT value is attributed that Cu as doping at the Sb sites introduced additional holes to enhance carrier mobility and Cu dopants interrupted the periodicity of lattice vibration to decrease lattice thermal conductivity. It is suggested that the as-prepared nanostructure Cux-doped Bi0.5Sb1.5-xTe3 thermoelectric materials has high potential for thermoelectric energy conversion application.

Computerized Fdtd Method for Longitudinal Optical Phonon Energy on Semiconductor Hybrid Structure for High Power Devices Fabrication

The research problem in this study is the longitudinal optical phonon energy on metal/semiconductor interface for high performance semiconductor device. The research solution is to make the software model with finite difference time domain (FDTD) solution for transmission and reflection pulse between metal and semiconductor interface for carrier dynamics effects. The objective of this study is to find the quantum mechanics understanding on interface engineering for fabricating the high performance device for future semiconductor technology development. The analysis was carried out with the help of MATLAB. The quantum mechanical spatial field on metal-semiconductor stripe structure have been analyzed by FDTD techniques. This emission reveals a characteristic polar radiation distribution of electric dipoles and a wavelength independent of the structure size or the direction of emission; consequently, it is attributed to thermally generate electric dipoles resonating with the longitudinal optical phonon energy. Phonon energy occur lattice vibration of material by the polarization of light, if the material has rigid structure reflect back the incident light. So, high reflective metal- semiconductor structure always use as photodectors devices in optical fiber communication. No lattice vibration material structure has no phonon effect, so this structure based devices can get high performance any other structure based devices. The transmission and reflection coefficient of metal-semiconductor GaN/Au layer structure compare with GaN/Ti and GaN/Pt structure. Parallel (P) and transverse (S) polarization of light incident on metal-semiconductor nanolayer structure with IR wavelength. Efficient use of the layer by layer (LbL) method to fabricate nanofilms requires meeting certain conditions and limitations that were revealed in the course of research on model systems.