Vol. 47, No. 1 (1998)
CLASSICAL AREA OF PHENOMENOLOGY
1998, 47 (1): 1-8. doi: 10.7498/aps.47.1
Starting from the Frantz-Nodvik equation and Huygens-Fresnel diffraction integral and using the fast Fourier transform and successive iteration method, we studied the inverse problem of a laser amplifier system containing a spatial filter, i-e-, to find the initial input temporal pulse profile, am-plitude and phase distributions from the required output temporal, spatial pulse profile and fluence, as well as the given amplifier and spatial filter parameters-
1998, 47 (1): 9-18. doi: 10.7498/aps.47.9
This paper presents a theoretical model for erbium-doped fiber lasers, which are passively mode-locked by a semiconductor saturable waveguide acting as a slow saturable absorber and a nonlinear fast saturable absorber- The influences of semiconductor saturable waveguide, fiber self-phase modulation and self-amplitude modulation on mode-locking pulse width and chirp have been analyzed-
1998, 47 (1): 19-26. doi: 10.7498/aps.47.19
The problem of propagation of (2+1)-dimensional optical pulse with time-space asymmetry in a saturable Kerr medium is discussed-That pseudo-momentum and energy of the optical pulse keep conservative along propagation is obtained by using variational method-The impacts of initial asymmetry,saturable strength and coupling strength on pulse width and beam width are studied by using numerical method-
1998, 47 (1): 27-34. doi: 10.7498/aps.47.27
Using the “spring” model for a weak interface and the wave equations in cylindrical composite structures, we derive the generalized frequency equation for axisymmetric guided waves in a two-layered cylindrical composite structure with a weak interface- Numerical computations are made for dispersion characteristics of the axisymmetric guided waves in two-layered composite tubes(with or without water in hollow) and clad rods with rigid or slip interfaces- The influence of the shear stiffness of the weak interface on the lower order guided wave modes is studied-
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1998, 47 (1): 35-39. doi: 10.7498/aps.47.35
The result of experimental studies of stimulated Raman scattering (SRS) was report in this paper- When the disk target was irradiated by low-energy laser, the plasma density scale length was short, and the SRS threshold intensity was very high, SRS only occurred in those local ranges where electron density was homogeneous- Multi-material targets and filamentation will produce more those local range, these will increase SRS light-
1998, 47 (1): 40-46. doi: 10.7498/aps.47.40
X-ray reemission from gold disk targets,which were heated by intense soft X-ray radiation((2—6)×1012W·cm-2),had been observed with two time-related soft X-ray spectrometers-The spectra of X-ray reemission were “softer” than those of irradiating X-ray-Temporal evolution of the X-ray reemission was analyzed in terms of a time-modified self-similar solution for the ablative heat wave-
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1998, 47 (1): 47-52. doi: 10.7498/aps.47.47
Hg loss of B+-implanted HgCdTe with and without a ZnS film under rapid thermal annealing(RTA) has been analysed by secondary ion mass spectroscopy and Auger electron spectroscopy in detail- The temperatures for RTA are 300, 350 and 400℃, and the duration is 10s- The thickness of ZnS film is 160nm- Results obtained show that the surface layer of HgCdTe with a ZnS film does not show Hg loss after RTA (300℃,10s)- The procedure of RTA for B+-implanted HgCdTe forming N+-P junction has been optimized- It was shown that RTA carried out after the lithography of the metal electrode can improve the junction characteristics-
1998, 47 (1): 53-59. doi: 10.7498/aps.47.53
Its electric conductivity,spectral transmisivity and color change markly when V2O5 amorphous film is irradited by 308nm laser pulse if the fluence is over the threshold-The films before and after being irradited is surveyed with XRD,XPS and SEM methods, etc-It can be determined that the change of the film is due to irradiation by high fluence excimer laser pulse,the film temperature rises and melts quickly,and then the temperature lowers and the film resolidifies quickly- The quick melting and resolidifying procedure leads to oxygen deficiency in the film,so its stoichiometry changes-
1998, 47 (1): 60-67. doi: 10.7498/aps.47.60
The pendant drop technique has been used to compress and expand the monolayer film,both the surface density of surfactant molecules and surfactant orientation on the surface of a pendant drop can be determined with polarized fluorescent image for the surfactant molecules which has a chromophore-The experiment on octadecyl Rhodamine B(ODRB) molecules shows that:(1) The surface density of ODRB follows the formula σ/σ0=(D0/D)2 in the compressing process-(2) The ODRB molecules are absorbed on the surface of pendant water drop in the way of lying flat-(3) The pendant drop method is a reliable and convenient technique for compressing the surface density of surfactant molecules-
1998, 47 (1): 68-74. doi: 10.7498/aps.47.68
Synchrotron radiation photoelectron spectroscopy (SRPES) combined with scanning electron microscopy (SEM) and gravimetric method is used to study the neutralized (NH4)2S-passivated GaAs(100) surfaces- Compared to the conventional (NH4)2S alkaline solution treatment, a thicker Ga sulfide layer and stronger Ga—S bonding on GaAs surface can be formed by dipping GaAs in neutralized (NH4)2S solution- Gravimetric data show that the etching rate of GaAs in neutralized (NH4)2S solution is about 15% lower than that in the conventional (NH4)2S solution- From SEM observation, only fewer number of etching pits with smaller size on the neutralized (NH4)2S treated GaAs surfaces can be found-
1998, 47 (1): 75-82. doi: 10.7498/aps.47.75
A 200nm Ti film was deposited on a polished AlN ceramic substrate at 200℃ by electron beam evaporation under high vacuum conditions and annealed in a vacuum furnace.X-ray diffraction measurement and secondary ion mass spectrometry,Rutherford backscattering spectrometry,Auger electron energy spectroscopy were used to investigate the solid phase reactions between the titanium thin film and the AlN ceramic substrate during annealing from room temperature to 850℃.Experimental results showed that after annealing beyond 600℃,diffusion and reaction took place at the interface of Ti/AlN obviously and the reaction was enhanced with increasing temperature.The titanium aluminides and titanium nitrides as reaction products at the interfaces have been found.The titanium aluminides consist of Ti-Al binary and Ti-Al-N ternary compounds,in which Ti2AlN is dominant after 4h annealing at 850℃.The results have been explained in terms of extended Ti-Al-N ternary phase diagram given by Bhansali et al.
The a-C∶H(N) films was deposited from the mixture of C2H2 and N2 by rf-dc plasma enhanced chemical vapor deposition. The influence of N2 percentage in the mixture on the composition and structure of a-C∶H(N) films was studied by XPS. As the N2 percentage in the feed gas was increased from 0% to 75%, up to 9.09% N was incorporated in the film. The results of analysing C1s and N1s core level indicated that a-C∶H(N) films are consisted of stoichiometry C3N4 phase and CHx matrix which is identified as predominantly sp2 bonded structure. The N/C ratio of C3N4 phase is near 4/3. The N atoms incorporated in the films is useful to increase the content of C3N4 phase and sp3/sp2 ratio.
1998, 47 (1): 89-93. doi: 10.7498/aps.47.89
We have grown two-layer InAs structures spaced by 6.5nm GaAs. Self-assembled InAs quantum dots (QDs) occur in the first layer with 2.5ML InAs coverage due to S-K growth mode. The second layer changes from 2D to 3D growth when the thickness of InAs is 1.5ML, which is obviously smaller than the critical thickness (1.7ML) of single InAs layer structures. Transmission electron microscopy shows that two-layer QDs with different heights have been obtained according to the mechanism of a vertically correlated arrangement. But only one photoluminescence peak related with large QD ensemble has been observed as a result of strong electronic coupling in InAs QD pairs.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1998, 47 (1): 94-101. doi: 10.7498/aps.47.94
The self-trapped exciton in polymers under the electric field has been studied using a tight-binding model including the electric field, symmetry-breaking term te and electron-lattice interaction simultaneously. It is discovered that the electric field will polarize the self-trapped exciton in polymers. The polarization depends on the electric field E and te. When te≤0.1eV，self-trapped biexciton in polymers shows the characteristic of the reverse polarization, i.e., electrons move along the direction of E; however, plus charges move along the minus direction of E. The cause of the polarization has been discussed.
1998, 47 (1): 102-106. doi: 10.7498/aps.47.102
Within the effective mass approximation, the energy spectra of the three-electron system in two-dimensional quantum dots subjected to different confinement potential are calculated by using the method of few-body physics. The results show that the appearance of magic angular momentum arises from the quantum mechanical symmetry, the size of confinement potential and the strength of magnetic field.
1998, 47 (1): 107-111. doi: 10.7498/aps.47.107
By use of the method of few-body physics, we study the relations between the energy of ground state and the thickness of three-electron quantum disk in a magnetic field. As the thickness increases, the magic number angular momentum states of three-electron(i.e., the states of fractional quantum Hall effect) will be destroyed. The results show the thicknesses of quantum disks whose magic number angular momentum is destroyed decrease as the magnetic fields increase.
EFFECTS OF STRUCTURAL TRANSITION ON THE ELECTRICAL AND MAGNETIC PROPERTIES IN LIGHTLY DOPED La1-xSrxMnO3 PEROVSKITE
1998, 47 (1): 112-116. doi: 10.7498/aps.47.112
A structural transition from rhombohedral to cubic phase occurred in the lightly doped La1-xSrxMnO3 under high temperature and high pressure. The samples changed from an insulated (polaron ordering) state to metallic state after the phase transition. At the same time, the long-range ferromagnetic ordering of the spins of localized Mn ions collapsed into the spin glass state with only short-range ordering when the temperature decreased. The change of properties was due to the variation of Mn—O—Mn bond angle and Mn—O bond length during the structural transition.
1998, 47 (1): 117-123. doi: 10.7498/aps.47.117
The ZnWO4∶Sm3+ single crystal (Sm2O3=0.1wt%) has been grown by the Czochraiski technique. Absorption spectra were measured. The up-conversions at 448,471,505 and 533nm were observed by exciting with a He-Ne laser at 632.8nm wavelength, using a laser Raman spectrometer.
1998, 47 (1): 124-130. doi: 10.7498/aps.47.124
Some porous silicon, which were formed on n-type c-Si under illumination during the anodization,show blue photoluminescence after a long period of storage in an atmospheric environment at room temperature. Experiments of photoluminescence and infrared transmission and reflection indicate that samples, which were anodized under strong Ar+ 488 nm laser illumination, have an oxidation layer of better quality, in which there are less stress, less amorphous and a more completely cross-linked Si-O-Si network. And this kind of oxidation is favorable to the blue emission of porous silicon.
INTENSITY RELATIONSHIP BETWEEN EXCITATION AND THE STEADY-STATE PHOTOLUMINESCENCE OF FREE EXCITONS IN SEMICONDUCTOR QUANTUM WELLS
1998, 47 (1): 131-138. doi: 10.7498/aps.47.131
The photoluminescence (PL) intensity of free excitons in a GaInAsSb/GaAlAsSb quantum well (QW) laser structure is investigated as a function of excitation intensity and lattice temperature.The relationship between PL intensity of free excitons and excitation intensity as well as lattice temperature in the steady-state PL measurements was developed for the quantitative descriptions of the experimental data.Calculations show that the variation of exciton relative population with excitation intensity has strong influence on the relationship between PL intensity of free excitons and excitation intensity. It is found that the linear coefficient I/I0 is actually the characterization of the exciton photoluminescence efficiency. According to our model,the background density of the quantum well material as well as the scattering time constant of the QW,in addition to the excitonic binding energy and activation energy, is also obtained by fitting the Arrhenius plot of PL intensity.
HIGH-FIELD ELECTRON TRANSPORT OF AMORPHOUS SiO2 AS ACCELERATING LAYER IN THE LAYERED OPTIMIZATION TFEL
1998, 47 (1): 139-145. doi: 10.7498/aps.47.139
Amorphous SiO2 is used as the accelerating layer in the layered optimization thin film electroluminescent devices. In this paper we discuss the effects of high electric fields on the transport of electrons in amorphous SiO2. The energy differences between two localized states in the vicinity of the Fermi level or in the tail of the conduction band are lowered due to high electric fields. Therefore, electron transport in these localized states is in the form of thermally-assisted hopping conduction strengthened by electric fields. Based on the experimental data we calculate the average mobility value of electrons in the conduction band, the minimum metal conductivity and the densities of states near the Fermi level and the mobility edge.
1998, 47 (1): 146-153. doi: 10.7498/aps.47.146
A systematic investigation of different types of lattice defects in intentionally doped or impurity substituted piezoelectric ceramics was carried out by using positron annihilation.La3+ doped PbTiO3,Sr2+,Cd2+,and La3+ doped Pb (Mg1/3Nb2/3)0.375Ti0.375Zr0.25O3;Ca2+ doped BaTiO3; and Nb5+ doped SrTiO3 were chosen as testing materials.It was found that positrons can be traped by cation vacancies,oxygen vacancies,as well as defects associated with lattice deformations,but with different dynamic specific trapping rates and annihilation characteristics.A new possible method for determining the defect species in perovskite structured piezoelectric ceramics is presented.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1998, 47 (1): 154-159. doi: 10.7498/aps.47.154
CNx films deposited on Si substrates with microwave plasma chemical vapor deposition method are measured and analyzed using Raman scattering,X-ray photoelectron spectrum,X-ray diffraction and scanning electron microscopy techniques.The result of Raman spectrum shows the amorphous graphite peak around 1600cm-1 with the flow ratio of CH4 and N2 below 1∶8.As the flow ratio is equal to 1∶8,a characteristic peak around 2190cm-1 exists,which represents C≡N bond.According to the XPS results,the binding pattern of C and N are seen to be of C—N bond and C≡N bond.There is no diffraction peaks corresponding to β-C3N4 phase in the XRD pattern.The gas pressure has influence on the deposited rate of the film.
1998, 47 (1): 160-167. doi: 10.7498/aps.47.160
A new theoretical model for SrTiO3 physisorption and chemisorption has been developed to quantitatively analyze the effect of relative humidity on electrical conductivity of the amorphous porous SrTiO3 film.This model may also be applied to other type of porous semiconductor ceramics.In this paper,the SrTiO3 film is deposited on SiO2/Si substrate by using the argon-ion beam plating technique,and then formed a planar resistor structure on SrTiO3 film. The experimental results show that, at room temperature,the current decreases slowly when relative humidity changes from 12% to 53%, and then increases rapidly with the increase of relative humidity from 53% to 92%.The current and its rate of change increase with increasing test frequency.The response time of water adsorption is longer than desorption.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
1998, 47 (1): 168-176. doi: 10.7498/aps.47.168
In this paper,we deal with three kinds of characteristic surfaces of a uniformly rectilinearly accelerating Kerr black hole whose mass is varying.i.e., the event horizon,the apparent horizon,and the time-like limit surface (the infinite red-shift surface). It is pointed out that the three kinds of characteristic surfaces no longer coincide with one other when the black hole mass is varying (accreting or evaporating).