Vol. 36, No. 7 (1987)
1987-04-05
CONTENT
1987, 36 (7): 829-837.
doi: 10.7498/aps.36.829
Abstract +
The roughness at the Si-SiO2 interface has been determined by the ellipsometric spectroscopy. Several geometric forms have been used to simulate the surface irregularities. The dielectric properties of the rough layer are modelled in the effective-medium approximation by dividing the rough layer into a number of sub-layers with equal thickness. The asperity height H (normal to surface) and the correlation length L (along the surface) can be defined by best fit of the theoretically calculated multiphase reflective ellipsometric parameters ψcal, △cal to the measured ellipsometric parameters ψexp, △exp. It is found that the trend of the electric properties of the sample is consistent with the variance of its roughness. It is also found that the dielectric function of Si has some anisotropic properties at the interface.
1987, 36 (7): 838-846.
doi: 10.7498/aps.36.838
Abstract +
A new model used to interpret the phenomena of dielectric breakdown is proposed over the whole range of applied field. There are two main mechanisms that one of which is the avalanche breakdown, so-call intrinsic type, and the other is the filament heating transport leading to the destructive breakdown exist in the breakdown process. The theoretical analysis and the experimental data indicate that the field strength of intrinsic breakdown depends on the band gap and the thickness of film, but the filament heating transport which induces a destructive breakdown depends on the properties of film. In particular, the defect is the main origin leading to the occurrence of destructive breakdown. In addition, the effect of various physical parameters, testing conditions and process factors on the breakdown are discussed briefly.
1987, 36 (7): 847-854.
doi: 10.7498/aps.36.847
Abstract +
The relationship between average velocity of phase and/or domain interface V and the effective phase transformation (PT) driving force in the process of diffusionless (DL) PT △G＇ (the difference between PT driving force AG and the resistence △GR, △G＇=△G - △GR) can be expressed as V = φ(△G - △GR). Consider a monodirectional varying external field (intensity is ξ and varying rate is ξ) exerted on a DLPT system, the phase interface moves and then the DLPT takes place when △G provided by the external field increases to a critical value △GR. If a hamonic external stress σ = σ0 sin ωt which can interact with the moving interface exerts on the system and the coupling factor is n,an expression between dynamic relation of interface V = φ(△G - △GR) and the internal friction in the DLPT process Q-1, related modulus defect △M/M, PT rate dF/dξ and the PT strain ε0 can be derived as d lnφ(△G＇)/d△G＇= Q-1ω/n2M(dF/dξ) = (△M/M)ω/nMε0(dF/dξ)ξ, or and (△M/M)Q-1=ε0/n. where ω is frequency of hamonic stress, M is modulus related to vibration mode. A gerenal solution of the interface dynamic equation can be obtained as V = ∑(±n)/(α≠-1) Aα exp[((△G - △GR)/△Gα*)α+1/(α+ 1)] +∑(m)/(β0) Aβ(△G-△GR)/△Gβ*)β where Aα,Aβare coefficient, △Gα* and △Gβ* are resistance parameters related to the high velocity interface. The specific solution and the value of △GR can be determined by the experimental data of the internal friction in the DLPT with diffrent ξ. The equation of (△M/M )/Q-1 can be used to determine whether the soft mode contributes in the process of DLPT.
1987, 36 (7): 855-861.
doi: 10.7498/aps.36.855
Abstract +
On the basis of our previous work [1] on commercially pure aluminum, the change of internal friction peak of grain bound- (Ke peak) in commercially pure copper has been studied in the course of creep. Creep experiments were conducted under different conditions: (a) high temperature and low stress; (b) medium temperature and medium stress; (c) low temperature and high stress; which lead to intergranular, mixed type and transcrystalline rupture respective'y. From the changes of grain boundary peak under different creep conditions, it can be deduced that the strength of grain boundaries is changed little during creep at high temperature and low stress; somewhat increased at medium temperature and medium stress; and considerably increased at low temperature and high stress. The present work indicates that the strength of grain boundaries is changeable during creep. The extent of strengthening of grain boundaries is different under different creep conditions, which is believed to be an important roie to lead to different type of creep rupture. This provides a modification and complement of the idea of "equicohesive temperature".
1987, 36 (7): 862-869.
doi: 10.7498/aps.36.862
Abstract +
The hydrogen storage capacities and pressure-composition isotherms of TiFe + La and TiFe + Mm alloys were measured by exhausting water method. The effect of La and Mm on the activation characteristics of the alloys was studied. It was shown that the activation characteristics of the alloys could be improved greatly and the alloys were activated near the room temperature when the quantities of La or Mm in the alloys were greater than 4 wt% under our experimental conditions. However, La or Mm did not enter the crystal lattice of TiFe. They presented in the alloys in the form of a second phase to purify the alloys. The hydrogen storage mechanism mainly depends upon the intermetallic compound TiFe. The formation enthalpies of the hypothetical hydrides TiFeLayH1.0, were also calculated after Miedema's formulae and compared with the experimental results.
1987, 36 (7): 870-880.
doi: 10.7498/aps.36.870
Abstract +
The dispersion relation for weak relativistic inhomogeneous plasma in general magnetic field configurations is derived from the relativistic gyrokinetic equations, which is valid for arbitrary frequencies. In the derivations the singular integrations with the quadratic denominator are represented by the drift plasma dispertion functions. This dispersion relation can be used to study the various micro instabilities driven by gradient and curvature of B, weak relativistic effects, and/or gyrofrequency shift. Extending the results to the nonequilibrium case such as loss-cone distribution is simple and straight forward. For demonstration, we apply it to investigate the lower hybrid drift instability. Using this dispersion relation we can recover the re-suits of Drake et al. in a straight forward and much more transparent way.
1987, 36 (7): 881-891.
doi: 10.7498/aps.36.881
Abstract +
In lower-hybrid current drive Tokamak, the waves can drive radial resonant electron flow, which is composed of an average flow and a diffusion flow. The characteristics and the effects of the radial flow are discussed.
1987, 36 (7): 892-901.
doi: 10.7498/aps.36.892
Abstract +
The ground state properties of the Sm-based valence fluctuation compounds are discussed by introducing an indirect on-site hybridization mediated by phonons, as the direct on-site hybridization is forbidden by inversion symmetry. The Hamihonian including this indirect hybridization is transformed into an effective Hamihonian of a "small polaron" type by means of a. canonical transformation. A self-consistent field approximation is used, a non-zero energy gap and the noninteger occupation of the f level have been given. The results obtained can be used to explain the small energy gap and the valence fluctuation phenomena observed in SmB6 and SmS.
1987, 36 (7): 902-908.
doi: 10.7498/aps.36.902
Abstract +
The Mossbauer spectra of amorphous alloys Fe80B20-xMx (M = P, C) at room temperature and 4.2 K have been measured. It is found that the mean values of the hyperfine field and the isomer shift vary linearly when M (P, C) substitutes for B. Two structure models of amorphous alloys, microcrystal model and Bernal-Polk model, have been compared using these results and that of their crystalline counterparts. The study suggests that there do not exist a microcrystalline short range order and corresponding transition in amorphous alloys TM-M as in the crystalline counterparts. For describing the microstructure of amorphous alloys TM-M the Bernal-Polk model is preferable to the microcrystal model.
1987, 36 (7): 909-914.
doi: 10.7498/aps.36.909
Abstract +
In this paper, lkeda equation for a nonlinear optical ring cavity is studied by numerical method. It is found that the topological structure, the way of bifurcation and its convergence rate and the period-window-structure depend on the parameters B and φ0 in long delay time limit. In short delay time limit, some anomalous period-windows and nonperiod-doubling bifurcations are revealed, and it is also discovered that the self-similar structure in chaotic bands is blurred in the short time limit.
1987, 36 (7): 915-923.
doi: 10.7498/aps.36.915
Abstract +
In this paper, the periodic Anderson Hamiltonian has been used to study the heavy-fermion behavior in the Rare-Earth and Actinide compounds. The mean-field approximation has been applied to the Coulomb correlation term between the f electrons and a self-energy term has been introduced to represent the effect of the many-body interaction. The single-site approximation has been used for the self-energy term. The properties of the systems have been discussed in a quasi-particle picture. The effective mass of the quasi-particles has been obtained through the self-consistent calculation of the average occupation number of the f electrons. The conditions necessary for the presence of the heavy fermions and the corresponding change of the magnetic properties have been discussed and numerical computation has been carried out. The calculated results have been compared with recent experiments.
1987, 36 (7): 924-929.
doi: 10.7498/aps.36.924
Abstract +
By using X-ray differaction, SEM and the measurement of sheet resistance, the effect of annealing of a-Ge/c-Ag bilayer were studied. Sheet resistance of the bilayers were measured in the range 80-300 K. The relation between sheet resistance at room temperature and annealing temperature was presented. A new diffusion mechanism was found. As the temperature increased, amorphous germanium crystallize. In the meantime, a part of Ge diffuse into Ag. When the temperature went on increasing, the germanium which diffused into silver would separate out again. The activation energy of diffusion was estimated to be 0.15 eV by means of measuring the sheet resistance of bilayer.
BRIEF REPORT
1987, 36 (7): 930-934.
doi: 10.7498/aps.36.930
Abstract +
In this paper, we present a new transformation in the solution space of the Ernst equation and investigat the relationship between the solutions of the Ernst equation and our transformation. We show that the Ernst equation is invariant under such a transformation, i.e., our transformation can be used to generate the new solutions of the Ernst equation from the old ones. Finally, we discuss the relationship between the Virasoro algebra and this transformation.
1987, 36 (7): 935-939.
doi: 10.7498/aps.36.935
Abstract +
In the symmetric gauge with vector potential the one-body wave functions of two-dimen sional electron in a strong magnetic field have been obtained analytically. Based on the diseussing of two non-interacting electrons, we get a relation of the wave functions in two representations. This relation is useful in considering the interactions between the electrons.
1987, 36 (7): 940-944.
doi: 10.7498/aps.36.940
Abstract +
Expenrimental results of Jc(B) in high magnetic fields for diffusion and CVD Nb3Sn tapes and MF Nb3Sn wires have been analysed by using regression analysis, the empirical rules for Jc(B) and FP(B) in high magnetic fields were obtained. The rules are different from Kramer scaling law. There is a need for a new model of flux pinning mechanism to explain the empirical rules.
1987, 36 (7): 945-950.
doi: 10.7498/aps.36.945
Abstract +
In this work, the dependence of the planar Hall votage and the magnetoresistance on composition, temperature, and the applied magnetic field has been studied. All the measurements were made by the six probe method. From the results, the planar Hall votage and the magnetoresistance are shown to satisfy the phenomenological formula simultaneously: Vy = p0M2sin2θ and △ρ = cM2cos2θ, and we obtain an equation Vy = cρ2M2sin2θ. Morever, the change of the planar Hall votage of Co90Zr10 and Fe70 Co20Zr10 after their crystallization are just opposite, that is, the above-mentioned value of the Co-rich one increases, but that of the later one decreases.
1987, 36 (7): 951-955.
doi: 10.7498/aps.36.951
Abstract +
Brillouin scattering of light from certain crystal plane of polished single crystal spheres was measured. From the obtained data of sound velocity anisotropy, all the elastic and piezoelectric parameters of the single crystals of Fe and Cr doped LiNbO3 were deduced. The results were compared with pure LiNbO3. Discussion indicated that the sign uncertainty of some elements of the elastic tensor was due to the choice of the coordinates.
1987, 36 (7): 956-959.
doi: 10.7498/aps.36.956
Abstract +
In this paper, we present the Raman spectra of [Al-O-P]- groups in Na2O-Al2O3-P2O5 glasses. We attribut the regular shift of high frequency peak in the Raman spectra to the decrease in the glass network polymerization.
1987, 36 (7): 960-964.
doi: 10.7498/aps.36.960
Abstract +
Nal(Tl) scintillation detector and Si(Au) surface barrier semiconductor detector are used to measure X-ray fluctuations in the HT-6B Tokamak device. The hard X-ray emission and sawtooth oscillations have been observed. The experiment shows hard X-ray fluctuations are due to MHD disturbances in the frequency range of 2-25 kHz.
