In our theoretical approach, the relaxation mechanism of the quasi-positronium (qPs) in alkali halides has been studied. It can be shown that the electronic cloud polarization in the medium results in the screening effect on the Coulomb potential of electron-positron pairs, so as to lead to the relaxation phenomena. Because the mean distance between the electron and positron in qPs is of the order of the lattice constant in alkali halide crystal, the Toyozawa's Hamiltonian in which only long range interaction between a charged particle and the medium is considered, could not be fitted in with the case of the qPs. So we try to make 'the short range force correction' to the interactive Hamiltonian by using phenomenological method. Then we can solve the total Hamiltonian into the effective Hamiltonian of the qPs by means of the method which had been used to treat the exciton by Ku Shih-wei. It is shown that the result of variational treatment of the effective Hamiltonian is in good agreement with the experimental data, so the relaxation mechanism of qPs can be interpreted quantitatively.
In our theoretical approach, the relaxation mechanism of the quasi-positronium (qPs) in alkali halides has been studied. It can be shown that the electronic cloud polarization in the medium results in the screening effect on the Coulomb potential of electron-positron pairs, so as to lead to the relaxation phenomena. Because the mean distance between the electron and positron in qPs is of the order of the lattice constant in alkali halide crystal, the Toyozawa's Hamiltonian in which only long range interaction between a charged particle and the medium is considered, could not be fitted in with the case of the qPs. So we try to make 'the short range force correction' to the interactive Hamiltonian by using phenomenological method. Then we can solve the total Hamiltonian into the effective Hamiltonian of the qPs by means of the method which had been used to treat the exciton by Ku Shih-wei. It is shown that the result of variational treatment of the effective Hamiltonian is in good agreement with the experimental data, so the relaxation mechanism of qPs can be interpreted quantitatively.
The structural defects, quenching defects and electron-irradiation defects in the in-termetallic compounds NiAl have been studies with the positron annihilation technique. The recovery behaviour of quenching defects and irradiation defects have been inversti-gated. Two distinct recovery stages have been, found, one at about 280℃ and the other at about 500℃. The experimental results show that the low-temperature stage is due to the annealing out of the divacancies and the high-temperature stage is due to the annealing out of the vacancies; and the density of the conduction electrons at the vacancies and the lattice interstitial sites are nearly equal to each other, but the momentum of the conduction electrons at the vacancies is lower than that at the latties interstitialsites in NiAl.
The structural defects, quenching defects and electron-irradiation defects in the in-termetallic compounds NiAl have been studies with the positron annihilation technique. The recovery behaviour of quenching defects and irradiation defects have been inversti-gated. Two distinct recovery stages have been, found, one at about 280℃ and the other at about 500℃. The experimental results show that the low-temperature stage is due to the annealing out of the divacancies and the high-temperature stage is due to the annealing out of the vacancies; and the density of the conduction electrons at the vacancies and the lattice interstitial sites are nearly equal to each other, but the momentum of the conduction electrons at the vacancies is lower than that at the latties interstitialsites in NiAl.
The electronic energies of hydrogenated silicon vacancy which has Td symmetry are calculated. Using the method of completely neglecting of differential overlap (CNDO), we find the probability of the formation of the hydride quartet, and the effect of interaction between four SiH units in the model. We conclude that the hydride quartet complex is a more plausible model for the hydrogenated vacancy in crystalline silicon than that with four SiH bonds unrelated one another.
The electronic energies of hydrogenated silicon vacancy which has Td symmetry are calculated. Using the method of completely neglecting of differential overlap (CNDO), we find the probability of the formation of the hydride quartet, and the effect of interaction between four SiH units in the model. We conclude that the hydride quartet complex is a more plausible model for the hydrogenated vacancy in crystalline silicon than that with four SiH bonds unrelated one another.
The n-type FZ silicon (P～1014/cm3) grown in hydrogen is irradiated with neutrons of the total flux of (2.9-6.0)×1017n/cm2 and with Cd ratio about 10 at room temperature. An S=1/2 EPR spectrum, labeled Si-PK2, is found in X band and at 77K. The angular dependence of the geff values with H in the (011) plane has a tricliuic symmetry. For one of the equivalent defect orientations the principle values of the g tensor and the direction cosines of the principle axes with respect to the cubic axes are as follows: g(±0.0004) n[100] n[010] n[001] g1=2.0028 -0.5154 0.8473 -0.1283 g2=2.0063 -0.7386 -0.5151 -0.4347 g3=1.9971 -0.4344 -0.1293 0.8914 The simulated EPR spectra computed from the g tensor are consistent with the experimental results.The PK2 EPR spectrumappears in the unannealed neutron irradiated samples and remains until 300℃ annealing. It is probebly due to a kind of defects which is depen-tent of the hydrogen.
The n-type FZ silicon (P～1014/cm3) grown in hydrogen is irradiated with neutrons of the total flux of (2.9-6.0)×1017n/cm2 and with Cd ratio about 10 at room temperature. An S=1/2 EPR spectrum, labeled Si-PK2, is found in X band and at 77K. The angular dependence of the geff values with H in the (011) plane has a tricliuic symmetry. For one of the equivalent defect orientations the principle values of the g tensor and the direction cosines of the principle axes with respect to the cubic axes are as follows: g(±0.0004) n[100] n[010] n[001] g1=2.0028 -0.5154 0.8473 -0.1283 g2=2.0063 -0.7386 -0.5151 -0.4347 g3=1.9971 -0.4344 -0.1293 0.8914 The simulated EPR spectra computed from the g tensor are consistent with the experimental results.The PK2 EPR spectrumappears in the unannealed neutron irradiated samples and remains until 300℃ annealing. It is probebly due to a kind of defects which is depen-tent of the hydrogen.
The photoluminescence spectra and optical absorption spectra were measured for GD a-Si :H films prepared at different substrate temperatures. It is found that increasing bonded hydrogen centent results in a systematic increase of the photoluminescence peak intensity, peak energy, linewidth, Stokes shift, and thermal quenching. From the experimental results we infer that: (1) The bonded hydrogen may generate radiative recombination centers as well as may remove non-radiative recombination centers; (2) The increase of the bonded hydrogen centent results in increase of the elec-tron-phonon interaction and a slight reduction in the band tail width.
The photoluminescence spectra and optical absorption spectra were measured for GD a-Si :H films prepared at different substrate temperatures. It is found that increasing bonded hydrogen centent results in a systematic increase of the photoluminescence peak intensity, peak energy, linewidth, Stokes shift, and thermal quenching. From the experimental results we infer that: (1) The bonded hydrogen may generate radiative recombination centers as well as may remove non-radiative recombination centers; (2) The increase of the bonded hydrogen centent results in increase of the elec-tron-phonon interaction and a slight reduction in the band tail width.
In this paper, we present a new method of determination of the gap state distribution in a-Si :H—the internal photoemission transient current temperature spectroscopy(IPETCTS). By this method, we suceeded in determining the GDOS distribution N(E) in a GD a-Si:H film. The result agrees in shape with that obtain ed from the typical field effect measurement, while the magnitude of the gap state density.obtained from the IPBTCTS is smaller by one to two orders than that from field effect measurement.
In this paper, we present a new method of determination of the gap state distribution in a-Si :H—the internal photoemission transient current temperature spectroscopy(IPETCTS). By this method, we suceeded in determining the GDOS distribution N(E) in a GD a-Si:H film. The result agrees in shape with that obtain ed from the typical field effect measurement, while the magnitude of the gap state density.obtained from the IPBTCTS is smaller by one to two orders than that from field effect measurement.
In this paper, with stochastic process method, we try to construct a microscopic kinetic theory of structural reliability from microscopic mechanism of structual element fracture. The kinetic equation of failure evolution and the primary probability function of reliability analysis are given, and the failure probability, failure probability density, reliability, failure rate and average life have been derived.
In this paper, with stochastic process method, we try to construct a microscopic kinetic theory of structural reliability from microscopic mechanism of structual element fracture. The kinetic equation of failure evolution and the primary probability function of reliability analysis are given, and the failure probability, failure probability density, reliability, failure rate and average life have been derived.
The microcracks caused by the transforming inclusions associate closely with the mechanism of fracture and toughness in ceramic materials. Exact analytical expressions for dislocation density, opening displacement and stress intensity factors of microcracks in the matrix, caused by a circular transforming inclusion, have been derived by using dislocation theory method. The results obtained have been analyzed and discussed.
The microcracks caused by the transforming inclusions associate closely with the mechanism of fracture and toughness in ceramic materials. Exact analytical expressions for dislocation density, opening displacement and stress intensity factors of microcracks in the matrix, caused by a circular transforming inclusion, have been derived by using dislocation theory method. The results obtained have been analyzed and discussed.
In this paper, we derive an analytic solution in condition of homogeneous electric field to discuss the characteristics of the ion motion driven by electrons with two-Maxwell distribution. The characteristics and scaling laws about the ion enegy obtained here agree reasonably with the numerical and experimental results.
In this paper, we derive an analytic solution in condition of homogeneous electric field to discuss the characteristics of the ion motion driven by electrons with two-Maxwell distribution. The characteristics and scaling laws about the ion enegy obtained here agree reasonably with the numerical and experimental results.
The two-box Schl?gl model is analysed. The Ω-expansion of the Green function is applied to such model, and then the time-dependent problem of Fokker-Planck equation of many variables with a multi-stable potential is solved cm the basis of the approximation of the leaoling order of the system size.
The two-box Schl?gl model is analysed. The Ω-expansion of the Green function is applied to such model, and then the time-dependent problem of Fokker-Planck equation of many variables with a multi-stable potential is solved cm the basis of the approximation of the leaoling order of the system size.
The optical intensity distribution of a generalized two-grating interferometer is derived in this paper. The influence of ratio of grating period to slit width on Lau fringesis analyzed. We show that the clear Lau fringes for β>p/(2a) do exist and their existe-nce is verified by experiment and numerical calculations.
The optical intensity distribution of a generalized two-grating interferometer is derived in this paper. The influence of ratio of grating period to slit width on Lau fringesis analyzed. We show that the clear Lau fringes for β>p/(2a) do exist and their existe-nce is verified by experiment and numerical calculations.
The two-photon resonance fluoresence distribution of a two-level atom is investigated. The spectrum and intensity distribution off two-photon resonance fluoresence is obtained by a canonical transformation of the Hamiltonian of the system and from the solution of the Heisenberg equations of fluoresence field operators.
The two-photon resonance fluoresence distribution of a two-level atom is investigated. The spectrum and intensity distribution off two-photon resonance fluoresence is obtained by a canonical transformation of the Hamiltonian of the system and from the solution of the Heisenberg equations of fluoresence field operators.
In this paper, on the basis of a single-particle model, the dispersion equation is obtained after considering the first perturbation term of relativistic energy factor. The results show that the frequency spectrum of free electron laser amplifier (FELA) exhibit oscillating phenomenon when injected electron energy is large enough. The origin of this phenomenon is attributed to perturbing effect of the relativistic energy factor. A some what detailed discussion is given.
In this paper, on the basis of a single-particle model, the dispersion equation is obtained after considering the first perturbation term of relativistic energy factor. The results show that the frequency spectrum of free electron laser amplifier (FELA) exhibit oscillating phenomenon when injected electron energy is large enough. The origin of this phenomenon is attributed to perturbing effect of the relativistic energy factor. A some what detailed discussion is given.
The ellipsometric parameters of LPCVD poly-Si on insulating SiO2 (Si SOI) before or after annealing with laser or RF inducting graphite strip heater were measured by speetroscopic ellipsometry over the wavelength interval 3000-5000?. The four-phase model of ellipsometric spectra was presented by matrix multiplication and the Monte Carlo simulation was used to calculate both ε1 and ε2 of Si SOI. The lattice perfec-tion of Si SOI after annealing is discussed
The ellipsometric parameters of LPCVD poly-Si on insulating SiO2 (Si SOI) before or after annealing with laser or RF inducting graphite strip heater were measured by speetroscopic ellipsometry over the wavelength interval 3000-5000?. The four-phase model of ellipsometric spectra was presented by matrix multiplication and the Monte Carlo simulation was used to calculate both ε1 and ε2 of Si SOI. The lattice perfec-tion of Si SOI after annealing is discussed
We analysed the high resolution lattice image of interface between crystalline region and amorphous region produced by ion implantation in GaAs with optical diffra-ctometer. The preliminary results show the structure variation at the interface. There are five districts from amorphous to crystalline region. They are: amcrphous area; nuclei, crystallite and low dimensional ordered area; polycrystalline area; distorted mo-nocrystalline area; and monocrystalline area.
We analysed the high resolution lattice image of interface between crystalline region and amorphous region produced by ion implantation in GaAs with optical diffra-ctometer. The preliminary results show the structure variation at the interface. There are five districts from amorphous to crystalline region. They are: amcrphous area; nuclei, crystallite and low dimensional ordered area; polycrystalline area; distorted mo-nocrystalline area; and monocrystalline area.
The energy levels of the ideal divacancy states in band gap for more than 10 cubic semiconductors are invesgated by using the basic equations given in ref. [1] and the tight binding Hamiltonian given by vogl et al. A simple physical model is used to describe the basic physics of the divacancy problem.
The energy levels of the ideal divacancy states in band gap for more than 10 cubic semiconductors are invesgated by using the basic equations given in ref. [1] and the tight binding Hamiltonian given by vogl et al. A simple physical model is used to describe the basic physics of the divacancy problem.
On the basis of a simple model of a simple cubic crystal and by using the Green's function method, calculations are carried out on the mean-square displacements of atoms in a semi-infinite superlattice. The effect of surface and interfaces on lattice vibra-tion are discussed.
On the basis of a simple model of a simple cubic crystal and by using the Green's function method, calculations are carried out on the mean-square displacements of atoms in a semi-infinite superlattice. The effect of surface and interfaces on lattice vibra-tion are discussed.
The geodesic motion in the globally regular space-time of a Schwarzschild black hole is studied. The analytic solutions of the geodesic equations for a test particle inside the space-time without singularity are derived. Our results are compared with the ones for the black hole with singularity.
The geodesic motion in the globally regular space-time of a Schwarzschild black hole is studied. The analytic solutions of the geodesic equations for a test particle inside the space-time without singularity are derived. Our results are compared with the ones for the black hole with singularity.
A non-topological soliton solution of φ4 equation has been obtained, then the size effect and related problems were discussed in K-S model.
A non-topological soliton solution of φ4 equation has been obtained, then the size effect and related problems were discussed in K-S model.
An explicit expression for any higher cocycles in translation group is given by means of Kronecker mapping from the n-dimensional flat space (translation group manifold) to the n-dimensional sphere. Physical interpretations can be made about the pull-back of the map.
An explicit expression for any higher cocycles in translation group is given by means of Kronecker mapping from the n-dimensional flat space (translation group manifold) to the n-dimensional sphere. Physical interpretations can be made about the pull-back of the map.