Vol. 37, No. 7 (1988)
1988-04-05
CONTENT
1988, 37 (7): 1053-1058.
doi: 10.7498/aps.37.1053
Abstract +
The properties of Si-H bonds and H-induced defects in single crystal silicon were investigated by means of photoluminescence, nuclear magnetic resonance and electron spin resonance. The results of photoluminescence indicate that the Si-H bonds induced a lot of non-radiative centers. The relation of average thickness of samples to electron spin resonance measurement was observed and discussed.Our work overcomes the difficulties in association with diffusion of H through the surface during annealing in vacuum and with ESR measurement when the thickness of the samples was over 1.00 mm or less than 0.85 mm. in comparing the ESR results for single crystal silicon grown in hydrogen and that in argon atmosphere, we got the amount of hydrogen to be 4×l016cm-3 and the activation energy to be about 0.1 eV. The former agrees quite accurately with references [6] , [10] . The later is one order lower than the activation energy of precipitation reported in reference [11] .
1988, 37 (7): 1059-1064.
doi: 10.7498/aps.37.1059
Abstract +
In this paper, we first investigated some important properties of high temperature ESR of doped (B and P) and undoped a-Si1-xCx:H and a-Si1-xNx:H alloy films. The ESR measurements were continuously performed in high temperature annealing process. Our experimental results show that: (1) For B-doped a-Si1-xCx:H and a-Si1-xNx:H films, a ESR absorption line can be decomposed to a broad (g1 = 2.005) and a narrow (g2 = 2.010) ESR absorption lines, g1 and g2 correspond to the contributions of Si dangling bonds and of holes in the valence band tail states, respectively. (2) The drop of hole density in the valence band tail states is faster than Si30 with rising temperature. The hole density in the valence band tail states is further larger than Si30 when temperature is low. However, the contribution of Si30 is the main one when temperature is very high.
1988, 37 (7): 1065-1071.
doi: 10.7498/aps.37.1065
Abstract +
The temperature dependence of magnetization at H=0.1-7T for amorphous SmxT1-x (T = Fe, Co) thin films was investigated in the range of 1.5 to 300 K. It was found that there was a maximum magnetization in the σ(T) curves, measured in the temperature rising process, for the SmxCo1-x thin films (x=0.46, 0.48, 0.54, 0.65). For the Sm-Co alloys, the temperatures, corresponding to σmax, are about 25-28 K and are independent of the composition. But the Sm-Fe amorphous alloys are different from the Sm-Co alloys, in the former the temperature corresponding to σmax depends on both the field and the composition of the alloys. In addition, it was found that there was σmin (or a repaid variation) at T≈6 K, and σ(T) decreased very slowly near room temperature. It was suggested that the thermomagnetic effect for the Sm-Co thin films at high field may be caused by the contribution of Sm moment to the magnetization, though the magnetic moment of Sm atoms is very small (≈0.1μB), and the random local anisotropy is strong at low temperatures and changes signicantly between 20-30 K. But the thermomagnetic effect of the Sm-Fe amorphous alloys may be caused by the dispersion of the Fe moments. The σmin at T≈6 K and the slow decrease of σ(T) near room temperature may be caused by fluctuation of composition in these alloys.
1988, 37 (7): 1072-1082.
doi: 10.7498/aps.37.1072
Abstract +
A complete set of symmetry-adapted product operator was introduced to analyse multipulse FT-NMR experiments for spin-1/2 I2S and I3S systems. General cyclic commutation relations exist among the symmetrized product operators. These commutation relations govern the evolution rules of different order coherences under the action of the Hamiltonian in various stage of pulse sequence. The use of symmetry-adapted product operator algebra simplified the analysis of experiments and revealed more evident physical meaning. The procedure was demonstrated by the treatment of DEPT experiment performed on spin-1/2 I2S and l3S systems.
1988, 37 (7): 1083-1088.
doi: 10.7498/aps.37.1083
Abstract +
According to IRD theory, we considered the infrared divergence response in the supe-rionic glasses, resulting from mang-body interactions caused by the presense of disorder. On the basis of studying a new relaxation mechanism, we revised the rate equation of anelasric strain, and then using Boltzmann superposition principle, the formula of ultrasonic attenuation with IRD is derived. From this, the power law dependence of ultrasonic attenuation on frequency α∝ωn at low temperature side and an apparent activaion energy EA+ are obtained. They are in agreement with experimental data for superionic glasses (Agl)x(Ag2O·nB2O3)1-x.
1988, 37 (7): 1089-1095.
doi: 10.7498/aps.37.1089
Abstract +
We have measured the superconducting transition temperature Tc and resistivity ρ(T) (from Tc onset to 300 K) of the reactive sputtered MoNx thin films. The X-ray diffraction, Rutherford back scattering (RBS), Auger and XPS technique were used for exmination of these specimens. The results showed that Tc and ρ(T) change with the concentration of nitrogen in thin films obviously. For Bl structure or nitrogen-rich samples, Tc is lower than 4.2 K. dρ/dT is negative as temperature is higher than Tc onset. Auger analysis indicated that the existence of oxygen and carbon could be also the reason for very low Tc and semiconducting behaviour in ρ(T) of this kind of thin films.
1988, 37 (7): 1103-1109.
doi: 10.7498/aps.37.1103
Abstract +
Electron Stimulated Desorption (BSD) of O+ from polycrystal Ni surface was studied. The ESD O+ was measured after the Ni sample was annealed at 700℃ for two hour and then exposed to 20-60 L O2 at room temperature and 500℃ respectively. Two kinds of ESD O+ had been found with different electron energy thresholds (29 eV and 23 eV). It was concluded that the two O+s were due to Auger induced desorption and the two thresholds corresponded to O(2s) electron ionization energy and excitation energy respectively. The process of excitation, ionization and de-excitation was also discussed.
1988, 37 (7): 1110-1118.
doi: 10.7498/aps.37.1110
Abstract +
The effective elastic constant of the GaAs-GaAlAs kind semiconductor superlattice has been obtained by means of the mathod of Green's function in the long Wave approximation. The results show that the effective elastic constant is not greater than that of either kind of the matter which are the components of the superlattice. In the limit of b = 0 and b = a, where a is the period of the superlattice and b is the width of one of the component, the te-sult reduces to the elastic constant of one single medium.
1988, 37 (7): 1119-1123.
doi: 10.7498/aps.37.1119
Abstract +
A new class of a-Si:H/doped a-SiNx:H superlattices with fixed sublayer thicknesses and NH3/SiH4 ratio, but varying gaseous doping level in a-SiNx:H sublayers, has been sythesized by using equipped shutter deposition system. It is shown that the position of the Fermi level in superlattices can be controlled through doping in a-SiNx:H sublayers, that means that a-Si:H/a-SiNx:H superlattices can be changed from n-type to p-type depending on the B doping level in a-SiNx:H sublayer. However, the trasport property of a-Si:H/a-SiNx:H super-lattices is not affected very much by the P doping in a-SiNx:H sublayers.
1988, 37 (7): 1124-1130.
doi: 10.7498/aps.37.1124
Abstract +
The single-particle electronic states of group-IB impurities, Cu, Ag and Au, in silicon are calculated by use of the self-consistent field scattered-wave Xα method. The clusters XSi4Si＇12 and XSi10Si＇16, which have been used in some pioneer works and in our earlier successfully treatments of the 4d transition-metal impurities in silicon, are taken to simulate the silicon crystals locally perturbed by substitutional and tetrahedral interstitial group-IB impurities X, respectively. We find that the substitutional impurities introduce a t2 type level in the band gap. This state is by no means (d-lik, but rather mostly dangling bond-like on the silicon neighbors. The interstitial impurities introduce an a1 type level in the gap. In the case of Si:Au, this state is close to the bottom of conduction band and is rather delocalized. In addition, a hyperdeep s-like level just below the bottom of the valence band is obtained. The trends in the electronic properties of group-IB impurities in silicon have been discussed also.
1988, 37 (7): 1131-1136.
doi: 10.7498/aps.37.1131
Abstract +
Using a detection system with high resolution, backscattering spectra for 1-2 MeV 4He+ incident along Al (100) and Si(l00) and (110) planes are measured at a variety of entrance (θin) and exit (θout) angles. The energy intervals between the peaks in the energy spectra are plotted as a function of cosθin/cosθout Half wavelength and stopping power for 1-2 MeV 4He+ in these three channeling planes are obtained. The experimental half wavelength is in agreement with the calculated value within the limit of error and the planar channeled stopping power is slightly greater than the random stopping power.
1988, 37 (7): 1137-1143.
doi: 10.7498/aps.37.1137
Abstract +
We measured SERS intensities of pyridine on Pt and Pd deposited as overlayers on several silver island films, obtained the damping curve of SERS intensities versus Pt and Pd thickness. The results were compared with the electromagnetic damping theory proposed by Murray. We concluded that the short range damping play a very important role. Moreove, a new mode related to Pt and Pd overlayers were also discovered.
1988, 37 (7): 1144-1149.
doi: 10.7498/aps.37.1144
Abstract +
The coupling coefficient of two laser beams with different frequencies at their resonant point in an inhomogeneous plasma is studied. The effect of this coefficient on plasma beat-wave heating and its dependences on the frequency ratio of the two laser beams and the scale length of plasma are calculated.
1988, 37 (7): 1150-1156.
doi: 10.7498/aps.37.1150
Abstract +
A method to determine the electron temperature and density from the time resolved spectra of hydrogen atoms left in a pulsed laser plasma is described. The temporal behavior of electron temperature and density in a CuBr laser is obtained by employing this method.
1988, 37 (7): 1157-1166.
doi: 10.7498/aps.37.1157
Abstract +
We propose a model for internal friction at low frequency in fec alloys due to extended dislocations is proposed, in order to explain the internal friction peak around 210 K in heavily cold-worked concentrate Cu-Al and Cu-Zn alloys with measuring frequency of about 1 Hz.The motion of extended dislocations under the action of applied stress is divided into the relative motion (the relative displacement between two partial dislocations) and the overall motion (the displacement of the centre of extended dislocations). In addition to the restoring force due to the interaction between two partials and the restoring force due to the line tension of dislocations, the restoring force due to long range interaction among neighbouring dislocations is introduced. It is demonstrated that the last restoring force only influences the overall motion of extended dislocations, but does not influence their relative motion.The relative motion and the overall motion of extended dislocations each give rise to its internal friction peak respectively. The two peak temperatures are close to each other. The observed internal friction peak is a superposition of these two peaks. The predictions of the model in the present paper are in agreement with the experimental results.
1988, 37 (7): 1196-1102.
doi: 10.7498/aps.37.1196
Abstract +
AES and ESCA has been applied to the analysis of the superconducting Nb-Ge film which were deposited onto sapphire substrate by a low-energy sputtering technique. The results of surface analysis and depth profiles showed that there are impurities such as C, O and Al etc. contained in the Nb-Ge film, and O being especially effective impurity which determines Tc. The segregation of Ge at surface has not been found. The concentration retio of Nb/Ge in the film decreased from 3.1 to 2.26 from the surface to the substrate interface. XPS depth profiles showed that the photoelectron spectrum of Nb, Ge, C and O exhibited apparant chemical shifts and variations of the peak shape, i.e. the properties and the chemical states of these elements are complicated and varing along the depth profiles. It may be estimated that Nb probably stabilize the growth of A15 Nb3Ge phase during sputtering deposition.
BRIEF REPORT
1988, 37 (7): 1167-1171.
doi: 10.7498/aps.37.1167
Abstract +
Low temperature electrical transport properties of metallic glasses (Cu1-xNix)33Zr67 series has been investigated in the present work. In the wide temperature range of 2-273 K, the resistivity is in accordance with Mooij correlation. The theoretical results in the two level tunnelling model agree with the experimental data (TD) satisfactorily.
1988, 37 (7): 1172-1176.
doi: 10.7498/aps.37.1172
Abstract +
In this paper, we have studied systematically the l-V characteristic of the superconducting metallic glass Zr78Co22 without applied magnetic fields. It is observed that the transition from superconducting states to normal states is completed in steps as the current increasing. The properties of steps are localized and depend on current scanning rate. It is shown that the occurence of resistive steps is because of the inhomogenity of materials which leads to the ap-pearence of hot-spots. The equation of one-dimensional thermal flow may be used to described the localized resistive state of superconducting metallic glass Zr78Co22, in case of considering the effecs of interaction between hot-spots, selfabsorbing-heat of the sample itself, and so on.
1988, 37 (7): 1177-1179.
doi: 10.7498/aps.37.1177
Abstract +
Using the Anderson lattice Hamiltonian, We have explained the changes of superconducting critical temperature of Ba-Y-Cu-O with pressures in the framework of electron-electron mechanism which was proposed by the authors.
1988, 37 (7): 1180-1182.
doi: 10.7498/aps.37.1180
Abstract +
Through analysing the condition of the formation of bipolarons, we point out that the bipolaronic explanation for high temperature superconducting ternary metal oxide, given by Ref. [1] is doubtful.
1988, 37 (7): 1183-1187.
doi: 10.7498/aps.37.1183
Abstract +
Using X-ray crystal spectrograph, light probing and X-ray pin-hole camera, we have measured the distributions of high and low ionizing ions of plasma in the three-dimensional space. We have found the spaces in which the high and low ionizing ions occupied were of conical forms, but overlapped each other and the directions of the cones were opposite. in addition, we have also obtained two distrbutions of ion densities.
1988, 37 (7): 1188-1191.
doi: 10.7498/aps.37.1188
Abstract +
The recent experimental work on the ferromagnetic resonance of cylindrcal domain lattice at action of arbitrary magnetic field is reported. The device used in the experiments is a microwave microstrip transmission line placed between the poles of a electromagnet. Based on the experimental results, the present theories on the bubble mode resonance is analysed and some significant results are achieved.
1988, 37 (7): 1192-1196.
doi: 10.7498/aps.37.1192
Abstract +
When the ferrofluid is magnetized with biasing field, it's dielectric characteristics shows a magnetoelectric directive effect, i.e., the dielectric constant depend on not only the magnetic field, but also the relativf direction between the electric field and the magnetic field.In experiments, it has been observed that the magnetic particles in the ferrofluid are of spherical shape, and when magnetized with biasing field, they take a long-chain type distribution.In this paper, we analyze experimental results mentioned above and explain the magne-toelectric directive effects with long-chain model. The theoretical results are in agreement with experimental work.
1988, 37 (7): 1197-1202.
doi: 10.7498/aps.37.1197
Abstract +
We have discussed EL2 metastable mechanism combining with the theoretical calculations for the EL2 metastable "actuator" performed by Baraff and Schluter. On the basis of the experimental data for the Electronic Paramagnetic Resonance (EPR) "AsGa" photoquench-ings performed by Goltzene et al., we suggest that the AsGaVAsVGa atomic model, in which VAs and VGa are situated in the 1st and 2nd neighboring layers around AsGa antisite atom respectively, can be used for interpreting not only the capacitance but also the EPR "AsGa" photoquenching. This model seems more reasonable than AsGaVGaVAs, in which VGa and VAs are situated in the 2nd and 3rd neighboring layers around AsGa antistite atom respectively, as suggested by Wager and Van Vechten. In addition, our discussion has further supported the identification of the EPR "AsGa" defect ia n-irradiated GaAs as an isolated AsGa antisite atom, and has also shown a slight difference between EL2 defect configurations in LEC and HB GaAs crystals, which would be associated with the EL2 family phenomenon.
1988, 37 (7): 1203-1208.
doi: 10.7498/aps.37.1203
Abstract +
The characterization and thermal annealing behavior of deep-level defects in 1 MeV neutron irradiated VPE n-GaAs layers have been studied. The results indicate that the majority of induced defects are associated with displacement of two or more neighboring atoms. In addition, a new defect level E5(Ec-0.73 eV) emerges, as the H1 level anneals out, It is found that the changes of GaAs MESFET parameters are mainly due to the carrier removal.
1988, 37 (7): 1209-1212.
doi: 10.7498/aps.37.1209
Abstract +
The hydrogen evolution and IR absorption spectroscopy experiments are used to investi-gate the content and configuration of hydrogen in the amorphous carbon films(a-C:H).The results show that: with ilacreasing of the substrate temperature Ts, 1)the configuration of hydrogen in a-C:H changes from a two-phase structure to a single phase structure;2)the hydrogen content in a-C:H decreases monotonically;3)the ratio of sp3 bonds tO sp2 bonds ina-C:H increases monotonically.
1988, 37 (7): 1213-1216.
doi: 10.7498/aps.37.1213
Abstract +
Superionic conductors exhibit non-Debye behavior of solid dielectrics at low frequencies (f9Hz). Based on the characteristic of superionic conductors and a physical picture of Ngai's infrared divergent theory, we consider the fast ion transport as a non-Markovian process and analyze the alternating current properties of superionic conductors. The theory predicts that the admittance diagram is a line the curvature of which is less than one at higher frequencies. The discrepancy between theory and experiments at lower frequencies is due to interfacial effects.
1988, 37 (7): 1217-1220.
doi: 10.7498/aps.37.1217
Abstract +
The intercalation compound Li1+xV3O8 has been prepared successfully and investigated by X-ray powder diffraction and quantitative element analysis. The compound was also studied with 7Li NMR (on line width) in temperature range 298-400K by using SXP4-100 NMR spectrometer at a frequency f = 35.03 MHz. The active energy of Li+ion, Ea = 0.18eV, is derived from the line width of the motional narrowing. The conductivity is 10-3Ω-1·cm-1 at room temperature.
1988, 37 (7): 1221-1226.
doi: 10.7498/aps.37.1221
Abstract +
In this paper, the shifts of 5DJ and 7FJ energy levels of Eu3+ ion caused by crystal field effect, are calculated in 25 hosts containing Eu3+ ions. The relation between the calculated shifts and experimental values are analysed. The correct order on nephelauxetic effect shifts in these hosts is given.
