摘要:

We have introduced hydrogen into single crystal InP:Fe by implanting samples with 2 MeV protons and/or deuterons at fluences between 1×1016and 5×1017cm−2. This results in the creation of four local vibrational modes (LVMs) in infrared absorption which are all due to the stretching vibration of bonds formed between phosphorous and the implanted atom with various lattice defects or impurities at nearest‐neighbor sites. Our implant‐created LVMs are much sharper than those reported by previous workers and we observe two additional well separated peaks. The two main LVMs show a strong fluence dependence and are probably associated with lattice defects. The two weakest LVMs are not as fluence‐dependent and may be associated with impurities. Two samples were implanted with both protons and deuterons in an attempt to observe the formation of complexes containing both isotopes, but no evidence of such complexes could be found.

ISSN:0021-8979    

DOI:10.1063/1.350621

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The maximum growth rate (MGR) principle is discussed in connection with the morphological stability of growing particles. It is suggested that the MGR principle may be applicable to the growth of a platelike particle when there is no sidebranching. The suggestion is based on a stability analysis indicating that MGR principle would hold at least approximately unless the supersaturation is too large. For large supercooling, the stability analysis breaks down, but the MGR principle still presents reasonable values.

ISSN:0021-8979    

DOI:10.1063/1.350622

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The role of dislocation‐dislocation interactions on the relaxation behavior of biaxially stressed semiconductor thin films is considered by including interaction terms in an energy minimization. Both parallel and crossing interactions are considered and energies are calculated for orthogonal arrays of equally spaced 60° misfit dislocations, and it is shown that the parallel interactions can be either attractive or repulsive. The equilibrium misfit dislocation density is shown to be a function of the ‘‘cutoff’’ distance for dislocation interactions in these structures.

ISSN:0021-8979    

DOI:10.1063/1.350623

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The thermal relaxation of SiGe films deposited by ultrahigh‐vacuum chemical vapor deposition was studied by annealing the films for times up to 21/2 h at a temperature of 950 °C. Strain relaxation was determined by misfit dislocation density obtained by planar‐view transmission electron microscopy and by double‐crystal x‐ray diffractometry. When the relaxation process requires relatively few dislocations (≲2 &mgr;m), the films relax to a remnant strain which is in agreement with previous experimental measurements; however, when higher densities of misfit dislocations were generated, substantially larger remnant strains were observed. This is interpreted as resulting from energetic interactions among the dislocations and analyzed in terms of the theory developed previously. It is found that the cutoff distance for dislocation interactions is substantially greater than the film thickness and a value of 1.4±0.5 &mgr;m is determined for 75–150‐nm‐thick films. Limited data from the literature also indicate a cutoff distance that is substantially in excess of the film thickness. In addition, as the annealing time is increased, a marked propensity for dislocation banding is observed, attesting to the mixed nature (attractive and repulsive) of the interactions.

ISSN:0021-8979    

DOI:10.1063/1.350624

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A model is presented which describes the properties of a sheet polarizer under oblique incident light. Experimental evidence indicates that the model describes the polarizer adequately when we take the index of the active (absorbing) layer asn=1.3. In the second part of the paper we present an analytical expression for the transmission of a nontwisted nematic sample (electrically controlled birefringence cell) under oblique incident light and as a function of externally applied electric fields. We obtain the expression by separate integration of phase and amplitude contributions to the final transmission. Combination of this model with the description of the sheet polarizer yields a satisfactory agreement with the experimental results. The speed of calculation using the above model is about 20 times that of a traditional fast 4×4 matrix calculation.

ISSN:0021-8979    

DOI:10.1063/1.350625

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The damage generation and its annealing behavior in GaAs/(Ga,Al)As quantum wells after Ga+implantation at room temperature is investigated by transmission electron microscopy. Its relations with the disordering of the layered structures is explored by low temperature photoluminescence spectroscopy. We find that at low doses the intermixing is activated during annealing through the diffusion of point defects, while at high doses the disordering is produced by cascade mixing. A strong segregation of the defects in the GaAs layers is observed. During implantation of a GaAs/Ga0.65Al0.35As single quantum well, the GaAs quantum‐well layer accumulates damage more rapidly than the Ga0.65Al0.35As barriers. At high dose this leads to a differential amorphization of the two compounds. Using the critical damage energy density model, the amorphization thresholds of GaAs and Ga0.65Al0.35As are estimated around 26 eV/molecule and 960 eV/molecule, respectively, in our conditions of implantation. The influence of barriers in AlAs is studied. AlAs is more resistant to amorphization than Ga0.65Al0.35As and delays the amorphization of the GaAs quantum‐well layer. This effect is attributed to thein siturecombination of point defects during irradiation in AlAs material as well as to some intermixing of the layers. After annealing it appears that defects can easily diffuse in Al rich materials but are trapped in GaAs. It is concluded that the ability of AlAs to prevent damage accumulation in GaAs quantum wells and to drain off the defects during annealing can be exploited for device applications. The general trends for an optimized GaAs/GaAlAs quantum well dedicated to mixing applications such as the fabrication of quantum‐well wires by masked implantation is finally proposed.

ISSN:0021-8979    

DOI:10.1063/1.350626

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Molecular beam epitaxy GaAs films on Si, with thicknesses ranging from 0.9–2.0 &mgr;m, were implanted with Si ions at 1.2–2.6 MeV to doses in the range 1015–1016cm−2. Subsequent rapid infrared thermal annealing was carried out at 850 °C for 15 s in a flowing N2atmosphere. Crystalline quality was analyzed by using Rutherfold backscattering/channeling technique and Raman scattering spectrometry. The experimental results show that the recrystallization process greatly depends on the dose and energy of implanted ions. Complete recrystallization with better crystalline quality can be obtained under proper implantation and subsequent annealing. In the improved layer the defect density was much lower than in the as‐grown layer, especially near the interface.

ISSN:0021-8979    

DOI:10.1063/1.350627

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The time dependence of catastrophic optical mirror damage (COMD) is investigated for cw operation of AlGaAs‐GaAs quantum well lasers. The apparent Arrhenius parameters (i.e., the activation energy and pre‐exponential factor) for the rate process leading to COMD are determined. In particular, we compare the rate process for various cleaved facets with and without a subsequent plasma oxidation step. Analysis of the experimental Arrhenius parameters indicates that surface reactions on the corroded facets are responsible for facet degradation accompanied by heating. A tentative model of the facet heating that ultimately leads to COMD is presented.

ISSN:0021-8979    

DOI:10.1063/1.350628

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The deactivation of electrically active ion‐implanted arsenic in silicon during cooling‐down, following rapid thermal annealing, has been studied. Chemical and carrier‐density profiles were measured as a function of annealing temperature and cooling rate. It is found that the cooling rate has a pronounced effect on the maximum carrier concentration which can be obtained at a given temperature. It is further demonstrated that the equilibrium carrier concentration at a given temperature is higher than the previously accepted values.

ISSN:0021-8979    

DOI:10.1063/1.350629

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The effect of most usual kinds of mechanical treatment on marble, such as drilling, grinding, and polishing, has been systematically investigated with electron‐paramagnetic‐resonance (EPR) spectroscopy. Two different major effects have been observed: the decrease of Mn2+and the creation of several kinds of lattice defects. Drilling can cause a drop in the intensity of Mn2+by 50% and at the same time create a high concentration of lattice defects. The most characteristic is a defect, with a pair of peaks atg=2.0003 and 1.9997, created and filled with electrons simultaneously. The causes, nature, stability, and sensitivity to &ggr; irradiation of the two effects have been investigated. For the filling of the above defects with the mechanical action a model has been proposed. This involves another, EPR‐silent, defect that stores electrons by ionizing radiation during the geological age of marble and transfers a number of them by the mechanical treatment to the newly created defects. Another pair of defects (g=2.0069 andg=2.0059) has also been observed to be mechanically induced but not filled by the mechanical action. These are filled only by ionizing radiation. The reduction in the Mn2+signal is caused by the pressure exerted on the grains during the mechanical treatment, destroying the crystal symmetry and probably causing jumping out of Mn2+ions from their normal crystal symmetry sites. The decrease of the Mn2+sextet with drilling causes great concern to provenance studies of ancient marble artifacts that are based on the intensity of the Mn2+peaks. Finally, the polished surfaces of a number of ancient artifacts have been investigated for possible detection of absorbed radiation.

ISSN:0021-8979    

DOI:10.1063/1.350630

出版商:AIP    

年代:1992

数据来源: AIP