摘要:

Raman scattering has been used to investigate the optical phonons in thick compositionally uniform epilayers of In1−xAlxSb (x<0.65) grown by magnetron sputter epitaxy on (001)InSb. An analysis of the stress‐induced changes in the frequencies of the two optical phonon modes found in the epilayers was performed, and the stress factors and phonon mode behaviors for bulk material were evaluated. It was found that some epilayers with lowxvalues were coherently strained, even though their thicknesses far exceeded the mechanical‐equilibrium critical thickness limit.

ISSN:0021-8979    

DOI:10.1063/1.355091

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A simplified model of the gas‐surface chemistry occurring during chemical‐vapor deposition of diamond thin films is presented. The model results in simple scaling relations, useful for process scale‐up and optimization, for growth rate and defect density in terms of the local chemical environment at the substrate. A simple two‐parameter expression for growth rate is obtained, which with suitable parameter choices reproduces the results of more detailed mechanisms and experiment over two orders of magnitude in growth rate. The defect formation model suggests that the achievable growth rate at specified defect density scales approximately quadratically with the atomic hydrogen concentration at the substrate.  

ISSN:0021-8979    

DOI:10.1063/1.355063

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Scaling relations are developed to allow estimation of the atomic hydrogen concentration at the substrate during diamond chemical‐vapor deposition for both diffusion‐dominated and convection‐dominated reactors. In the convection‐dominated case, it is shown that there exists an optimal Mach number which maximizes the H concentration delivered to the substrate. In addition, when homogeneous recombination is taken into account, there exists an optimal operating pressure. This analysis shows that a sonic flow of highly dissociated hydrogen at a pressure near atmospheric is optimal for rapid growth of high‐quality diamond.

ISSN:0021-8979    

DOI:10.1063/1.355064

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We used consolidation (hot pressing) and deformation (die upsetting) techniques to produce magnetically anisotropic permanent magnets from melt‐spun PryCo100−y−xCxalloys. The primary phase in these magnets (16≤y≤24 at. %) was the hexagonal PrCo5phase. The greatest alignment was obtained for low‐carbon compositions (0≤x≤2 at. %); in particular, Pr18Co81C produced a remanence of ∼8.7 kG and an energy product of 16.9 MG Oe. The addition of 1 at. % carbon enhanced the coercivity (Hcl≊5.9 kOe) by nearly 80% compared to the carbon‐free composition (Hcl≊3.3 kOe). Higher carbon levels (x≥4 at. %) resulted in even larger coercivities (Hcl≥10 kOe) but were accompanied by significantly lower remanences (Br≊6 kG).

ISSN:0021-8979    

DOI:10.1063/1.355336

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The material properties of 2‐&mgr;m‐thick InxGa1−xAs epilayers grown on GaAs with 0.28≤x≤1 were investigated. It was found that forx≥0.5, the material quality of the larger lattice‐mismatched heterojunction recovers, as evidenced by cross‐sectional transmission electron microscopy (XTEM) and double‐crystal x‐ray diffraction (DXRD). Magnetophotoconductivity measurements were performed on InxGa1−xAs epilayers with 0.75≤x≤1. The dependence of both the cyclotron resonance linewidth and the carrier relaxation time on the material quality is consistent with the XTEM and DXRD results. The transport properties of InxGa1−xAs epilayers with 0.75≤x≤1 were studied using temperature‐dependent van der Pauw measurements. It was found that the electron mobility in the low‐temperature range is determined by a combination of ionized impurity and dislocation scatterings. The contribution of dislocation scattering to ternary InGaAs epilayers is larger than that to InAs, although InAs has a larger lattice mismatch with respect to GaAs. These four different measurement techniques confirm that the growth mode rather than lattice mismatch determines the density of dislocation for the heteroepitaxy of highly mismatched InxGa1−xAs on GaAs.

ISSN:0021-8979    

DOI:10.1063/1.355065

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Boron carbide thin films of several B/C ratios have been deposited on Si(111) using plasma‐enhanced chemical vapor deposition fromnido‐pentaborane(9) (B5H9) and methane (CH4). X‐ray diffraction studies of boron carbide thin films on Si(111) exhibited characteristic microcrystalline diffraction lines. Soft x‐ray emission spectroscopy was used to verify that the local electronic structure and composition of each sample corresponded to a homogeneous solid solution boron carbide phase.  

ISSN:0021-8979    

DOI:10.1063/1.355066

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A small‐angle neutron scattering (SANS) study of the structure of II‐VI semiconductor crystallites in a semiconductor‐doped glass is presented. The scattered intensityI(k) exhibits a peak at a nonzero scattering vector and decreases to zero askgoes to zero. The data are interpreted with a simple phenomenological model, based on local mass conservation, which describes a dilute gas of crystallites surrounded by depletion zones. We show that SANS allows a quick and accurate measurement of the average size and of the volume fraction of the crystallites, and we give values of both quantities for a commercial series of glasses.

ISSN:0021-8979    

DOI:10.1063/1.355067

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Effects of the substrate temperature and ion incident energy on silicon surface cleaning and hydrogen penetration caused by irradiation with a hydrogen plasma have been investigated using x‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. A silicon native oxide and a hydrocarbon‐contaminated layer were removed only on the condition that the silicon substrate was struck with hydrogen ions having proper kinetic energies of less than 40 eV at temperatures from room temperature to 400 °C. However, the silicon oxide grew either at temperatures below room temperature or at no ion incidence onto the substrate. This oxidation phenomenon was attributed to residual H2O in the vacuum system. On the other hand, hydrogen penetration occurred only on the condition of hydrogen ion bombardment. The amount of penetrated hydrogen increased with substrate temperature and ion incident energy. The amount of penetrated hydrogen was found to be drastically reduced under the condition of ion incident energy of less than 5 eV and a substrate temperature of about room temperature. It is concluded that an oxideless clean surface without hydrogen penetration into silicon bulk is obtained by means of irradiation with a hydrogen plasma having a low ion incident energy (≤5 eV) at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.355042

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

This paper presents a numerical simulation of the gas‐phase chemistry in diamond deposition processes. The simulation shows that the concentration of the two potential growth species CH3and C in the boundary layer near the diamond film substrate are sensitive to these species’ concentration in the bulk gas. The concentrations in the bulk gas depend, in turn, on the physical arrangement of the reactor, and in particular on the time provided for the gas mixture to reach chemical equilibrium. With sufficient equilibration time, simulations of both a hot‐filament reactor and a plasma torch reactors show that the concentration of atomic carbon at the substrate surface can be much higher than the concentration of CH3.

ISSN:0021-8979    

DOI:10.1063/1.355043

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The time‐of‐flight (TOF) measurements for ions in the expanding plume during laser ablation of Y1Ba2Cu3Oxare performed. The TOF spectra consist of peaks of only the monatomic ions. The drift velocities for these ions are revealed to be (2–4)×106cm/s at the laser fluence of 2.0 J/cm2and an oxygen pressure of 10−3Torr. These velocities are affected by the ablation conditions, and are found to increase with increasing laser fluence and decrease with increase of oxygen pressure. The velocity distributions for the ions at high oxygen pressure are described by the supersonic expansion model with a distribution width narrowing with decreasing oxygen pressure.

ISSN:0021-8979    

DOI:10.1063/1.355044

出版商:AIP    

年代:1993

数据来源: AIP