Search

Article

x

Vol. 29, No. 1 (1980)

1980-01-05
CONTENT
THE CHARACTERISTICS OF EPITAXIAL p-n JUNCTIONS GROWN BY METHOD OF SILICON CARBIDE CRYSTALS SUBLIMATION
FENG XI-QI, LUO BIN-ZHANG
1980, 169 (1): 1-10. doi: 10.7498/aps.29.1
Abstract +
Measurements of the voltage-current characteristics and space-charge capacitance have been made on the epitaxial p-n junctions grown by method of silicon carbidt crystals sublimation. An analysis of the forward voltage-current and voltage-capacitance charateristics shows that the structures of the p-n junction may vary over a quite wide range, from typical p-i-n junctions to nearly linear graded junctions resulted from different epitaxial growth parameters, but most of them have intermidiate structures. The effect of epitaxial growth parameters on structures of p-n junctions is briefly discussed.In addition, The brightness-current characteristics, the spectral distribution of electroluminescence of forward biased epitaxial p-n junctions, and their performance under pulse and a.c. excitions are also described.
ON THE FACETS AND TWIN FORMATION IN THE GROWTH OF InSb SINGLE CRYSTALS
YU ZHEN-ZHONG, JIN GANG, CHEN XIN-QIANG, MA KE-JUN
1980, 169 (1): 11-18. doi: 10.7498/aps.29.11
Abstract +
The observations of solid-liquid interface morphology of InSb single crystals pulled by using various oriented seeds is described. Experimental results indicate that the external forms of crystals as well as the formation of growth twin are closely related to the development and properties of {111} facets on the solid growth surface. The various experimental phenomena can all be interpreted successfully according to a {111} plane octahedron or two-octahedron model of the zinc-blende structure.
ANOMALOUS IMPURITY SEGREGATION IN InSb SINGLE CRYSTALS
YU ZHEN-ZHONG, JIN GANG, CHEN XIN-QIANG, MA KE-JUN
1980, 169 (1): 19-24. doi: 10.7498/aps.29.19
Abstract +
The impurity distributions on the cross-section of Te-doped and non-doped InSb single crystals are determined by means of Hall technique and mass-spectrum analysis. Results of measurements show clearly that the impurity segregation is anomalous on the facets. These phenomena are discussed in connection with the mechanism of the facet effect. An explicit expression based on thermodynamic considerations is derived and applied to explain the observed anomalous segregation phenomena.
A CRYSTALLOGRAPHIC INVESTIGATION ON THE ONE-DIMENSIONAL TRANSITION PHASE β2 IN AN AGED Mg-Zn ALLOY
SU QIAN-WU, XU SHUN-SHENG
1980, 169 (1): 25-34. doi: 10.7498/aps.29.25
Abstract +
The co-existence of two transition phases β′1 and β′2 at the initial stage of 165℃ aging of a Mg-5% Zn alloy was shown by means of X-ray diffraction method. The one-dimensional diffraction phenomena of the thin rod-like transition phase β′2 were investigated in detail. This transition phase has a hexagonal lattice structure, its long axis is the 6-fold symmetry axis [0001](β′2). The lattice constants of β′2 and its orientational relationship with the magnesium matrix are found as follows:a(β′2)=13.2?,c(β′2)=5.25?,[0001](β′2)∥[0001]M,(β′2)∥M. The problem concerning the lattice distortion of the matrix by precipitation of the β′2 phase has been discussed.
QUANTITATIVE DETERMINATION OF SPECTRAL PURITY OF X-RAY TUBES FOR DIFFRACTION ANALYSIS
GUO CHANG-LIN
1980, 169 (1): 35-45. doi: 10.7498/aps.29.35
Abstract +
In this paper, a method for quantitative determination of spectral purity of X-ray tubes for diffraction analysis is presented. The instrument used for this purpose was a home-made diffractormeter with a monochrometer of quartz crystal plate which is used as the analyzer. The experimental values of the X-ray intensities of various wavelengths must be expressed in terms of intensities just emitted from the X-ray tube window. Theoretical analysis of the various factors affecting intensity was made in detail, and the conversion factors for the reduction of intensities corresponding to different target elements and impurities was summarized in a table. The intensity of major characteristic spectrum line of the target element was attenuated by Cu or Al absorption foils, so as to avoide the errors caused by counting loss. Using this method, the spectral purity of a number of X-ray tubes was determined.
ENHANCED PLASMA-FREQUENCY RADIATION IN TOKAMAKS
ZHOU RU-LING, WU C. S., KANG SHOU-WAN, XIA MENG-FEN, CAI SHI-DONG
1980, 169 (1): 46-53. doi: 10.7498/aps.29.46
Abstract +
This paper is concerned with the phenomenon of enhanced plasma-frequency radiation in Tokamaks which has attracted much attention recently. Experimental results indicate that the radiation is associated with high energy runaway electrons. However the emission mechanism has not been completely understood. In this paper we review and discuss two possible processes which can explain the observed enhanced radiation. One is an induced emission process which is due to an anomalous cyclotron resonance of the runaway electrons with waves. The other is a spontaneous radiation process mainly due to Cherenkov resonance. The former requires higher energies of the runaway electrons than that required in the latter. Thus the theory of the spontaneous emission is more appealing and deserve more attention. Extensive numerical calculations of the emissivity have been performed over a broad range of parameters. The discussion is also extended to the case in which the electron plasma frequency is higher than the cyclotron frequency, a situation may be reached by Alcator.
SPECTRAL PROPERTIES OF Nd3+ IN GLASS
CHEN SHU-CHUN, QI CHANG-HONG, DAI FENG-MEI
1980, 169 (1): 54-63. doi: 10.7498/aps.29.54
Abstract +
This paper analyses stark splittings of Nd3+ in glasses. The experimental method of determining fluorescence levels is described and the experimental results of stark splittings of the metastable states and ground states for four types of Nd3+-doped silicate glasses are given. In addition, the radiative and non-radiative transition rate of the 4F3/2 state, the stimmulative emission cross-section σ, the radiative quntum efficiency η, the fluorescence branching ratio β and the lifetime τ are also determined experimentally for thirteen types of Nd-doped glasses with different compositions. On the basis of experimental results, the relation between non-radiative transition rate and compositions of the hosts is discussed.
STRUCTURE AND STABILITY OF POLYTROPIC FLUID SPHERES WITH NEGATIVE INDEX WITHIN THE GENERAL RELATIVISTIC THEORY
CHU YAO-QUAN, CHEN FU-ZHEN, FANG LI-ZHI
1980, 169 (1): 64-72. doi: 10.7498/aps.29.64
Abstract +
Based on the general relativistic theory, an investigation on the polytropic fluid spheres with negative index is made. The difference between classical gravitational theory and the relativistic one is measured by a parameter σ, which is the ratio of pressure to density at the center of the sphere. The relativistic Emden functions for ned* increases with the value of σ.
THE LONG TIME ASYMPTOTIC BEHAVIOUR OF THE CORRELATION FUNCTIONS——THE INFLUENCES OF THE WAVES ON THE RELAXATION PROCESSES
HUO YU-PING
1980, 169 (1): 73-92. doi: 10.7498/aps.29.73
Abstract +
Based on the general theory of the non-equilibrium statistical mechanics, we have discussed the influences of waves on the relaxation processes in macroscopic systems, especially. about the non-exponential asymptotic behaviour of the correlation functions.Because, how to select the representation is important for discussing the dissipative processes in non-equilibrium statistical mechanics, it is desirable to start from the elementary excitation representation. Using the Basic idea of C* algebra theory, we have developed a method for operator expansion, and employed it to express the flow operators in second quantized elementary excitation representation. Taking the residual interaction between the elementary excitations as perturbation in the calculation of the resolvent of the Liouville operator, and using the method of projection operator, a general expression of the non-exponential decaying part of the correlation functions have been obtained.By analysing the procedure of treating the elementary excitation spectrum, we devided the residual interaction into two parts. For pure dissipative mode, taking into account the linear interaction, the main terms of the non-exponential decaying part(t(-d/2) term) were obtained. Detailed analysis shows that, the non-linear interaction (mode-mode coupling) is very small, and leads to a relatively faster decaying process (t(-d) or so), hence it can be neglected.This article emphasizes that, for the wave processes, the local fluctuation correlation, the particle self-correlation and the transport processes are different in nature. Their relative magnitudes (relative to the corresponding quasi-particle parts) may also be quite different.With these general results, we have analysed briefly the relaxation processes in liquid, and made some discussion about the so called mode-mode coupling theory.
THE DIFFUSION THEORY OF OUTGASSING OF SOME NON-CRYSTAL MATERIALS IN VACUUM
GAO BEN-HUI, XUE DA-TONG
1980, 169 (1): 93-105. doi: 10.7498/aps.29.93
Abstract +
In the early works of Dayton, Schram and Jaeckel, the hypothesis or the model of theory on the outgassing process of material in the Vacuum was given. So far, these conclusions have been accepted as the base for research on outgassing process.But it has already been found that the experimental results of outgassing rates of some non-crystal-line materials (for example, rubber, plastics etc.) are not in agreement with the above mentioned theories. In 1964, we suggested two theoretical models, i.e., "twofold over lapping diffusion" and "non-uniform concentration diffusion". We found that all the abnormal phenomena observed in the experiments can be thoroughly explained by these diffusion mechanisms.We have improved the method of experiment in outgassing rate measurement.
BRIEF REPORT
THE FREE BOUNDARY SOLUTION TO THE EQUATION OF PLASMA MAGNETOHYDRODYNAMIC EQUILIBRIUM WITH AXISYMMETRY AND NON-CIRCULAR CROSS-SECTION
QING CHENG-RUI, ZHOU YU-MEI
1980, 169 (1): 106-110. doi: 10.7498/aps.29.106
Abstract +
A generized method of iteration is developed for solving the equation of plasma MHD equilibrium with free boundary in axial-symmetric tori with non-circular cross-section and conducting shell. The plasma current distributions may be peaked at the center of the plasma or have various forms of skin distributions. The conditions under which this method can effectively be used are also discussed.
HOLOGRAPHIC CONCAVE GRATING MONOCHROMATOR
JIANG YA-GUANG, SONG CONG-LONG
1980, 169 (1): 111-116. doi: 10.7498/aps.29.111
Abstract +
This monochromator is specially designed for the F/3 holographic concave grating. Having taken into first consideration the simplicity of mechanical structure, a new kind of optical path has been designed to increase the focussing precision as much as possible. Based on Seya-Namioka Mounting and Johnson Mounting, the new design is characterized by choosing a more suitable position of the rotation axis and selecting two wavelengths for spectrum correction. The method employed is similar to that of the three point ganged tuning. The new mounting is named JS-Ⅱ Concave Grating Monochromator. So far, the results obtained have proved that the new mounting is an improvement over the Seya-Namioka and Johnson mountings. The monochromator functions within the range of 2500?→ 10000?, the loss of resolution due to defocussing being less than 1? within the range of 3500? → 6500?.
FLUX GROWTH OF GGG CRYSTALS AND DETERMINATION OF THE NUCLEATION TEMPERATURE
LIU JI-ZHE, JIN TONG-ZHENG, LIU GONG-QIANG
1980, 169 (1): 117-121. doi: 10.7498/aps.29.117
Abstract +
Flux-growth of the GGG crystal has been investigated. Experiments showed that in PbO -PbF2 flux system the composition range of the solution for the crystallization of GGG is quite wide, the growth is quite stable, and the density of dislocations is relatively low. The nucleation temperature of crystallization was determined by the technique of induced striations.
A PRELIMINARY STUDY ON THE RELAXATION OF Si(111) SURFACE ATOMS
ZHANG KAI-MING, YE LING
1980, 169 (1): 122-126. doi: 10.7498/aps.29.122
Abstract +
In this paper the Extended Hucker Method is adopted and the Cluster model is used to calculated the surface relaxation of the Si (111) plane. The calculation shows that the surface atoms will be displaced inward with respect to their "ideal" positions by an amount of 0.10?. This expectation is in better agreement with the experimental results than previous empirical evaluations and theoretical calculations.
SUPERCONDUCTING CRITICAL FIELDS OF TYPE A AND TYPE B SUPERCONDUCTORS
ZHANG YU-HENG, CAO XIAO-WEN
1980, 169 (1): 127-130. doi: 10.7498/aps.29.127
Abstract +
In this paper, the experimental data of thermodynamical critical magnetic field Hc at T = OK are analysed. The conclusion arrived here is that Hc(O) is increasing with λ for type A, and with λ2> for type B superconductors.
ANOMOLOUS PATTERNS OF TUNGSTEN SAMPLES OBSERVED WITH SCANNING ELECTRON MICROSCOPE
LIAO QIAN-CHU, WANG YUN, WANG HONG-JUN, LAN FEN-LAN
1980, 169 (1): 131-137. doi: 10.7498/aps.29.131
Abstract +
On recording a number of SACP's of tungsten specimen successively tilted -to different orientations, some anomolous patterns superimposed on the general SACP's were observed at the exact positions of direction, direction, and direction. These anomolous patterns are similar to Kossel patterns observed with transmission electron microscope. Moreover, the present patterns have two additional important characteristics. First, the intensity distribution of patterns changes with the electron energy (the electron accelerating voltage). Second, the geometric feature of the patterns can be used to represent some characters of the internal structure of the crystal. Finally, from the view points of the anomolous scattering effect, and the parameter a, which represents the interaction strength between the crystal potential. and the incident electron, the origin of the contrast of these patterns was explained qualitatively.