摘要:

High‐resolution optical emission spectroscopy has been used to measure Doppler profiles of Ar and Ar+transitions in a divergent magnetic field electron cyclotron resonance (ECR) source, yielding average translational energies between 0.1 and 0.6 eV (Ar), and 1.0 and 2.5 eV (Ar+). ECR magnetic field configuration strongly affects Ar+energies, although little variation with Ar pressure (0.1–1.5 mTorr) is found. The average Ar energy increases slightly with pressure. These observations suggest that thermal ion and neutral excitation primarily results from collisional degradation of directed downstream ion energies arising from the unique ambipolar potential created in ECR sources.

ISSN:0003-6951    

DOI:10.1063/1.101739

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A method has been developed for time‐resolved Raman measurements under shock loading to examine the first‐order Raman line of diamond (&ohgr;0=1333 cm−1). The diamond samples were subjected to uniaxial strain along the [110] direction to a longitudinal stress of 121 kbar. The observed spectral changes are consistent with frequency shifts calculated according to a phenomenological model used to describe stress effects on the zone center phonons of cubic materials.

ISSN:0003-6951    

DOI:10.1063/1.101740

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We deposited Ni‐Zr thin‐film multilayers by electron beam evaporation onto polished alumina substrates. The multilayers were annealed at a constant heating rate, andinsituresistance measurements made to derive the growth kinetics of amorphous NiZr alloy at the Ni/Zr interfaces. Using a simple model that relates resistance change to amorphous‐layer thickness, we derive the apparent diffusivity of nickel in amorphous Ni50Zr50,DNi=2.5×10−5 exp[−1.01(eV)/kT] cm2 s−1.

ISSN:0003-6951    

DOI:10.1063/1.101747

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The interface between the (001) surface of GaAs and a CoGa layer grown by molecular beam epitaxy has been characterized using transmission electron microscopy in plan view and cross‐sectional view. The interface is found to consist primarily of a network of edge dislocations with Burgers vectorsa[100] anda[010] (abeing the lattice parameter of the CoGa). The occurrence of these Burgers vectors indicates that these misfit dislocations are nucleated in the CoGa during growth. It is clearly shown that the threading dislocations in the CoGa originate at the misfit dislocations at the interface, while the GaAs layer underneath is free of dislocation.

ISSN:0003-6951    

DOI:10.1063/1.101748

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A self‐consistent approach is proposed for the first time to describe the fracture in viscous plastic media taking into account the energy dissipation near the crack tip. The conditions are found under which slow heat‐ and stress‐stimulated crack propagation occurs. It is found that cracks of small size are unstable with respect to thermal and mechanical disturbances. It is shown that stick‐slip fracture instability due to the energy exchange between mechanical and thermal modes can take place at a certain stage of crack propagation. An estimation is obtained for the number of slips in the course of discontinuous fracture.

ISSN:0003-6951    

DOI:10.1063/1.101749

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The chemical reduction of metal oxides by mechanical alloying with a strong reducing element has been investigated. Using x‐ray diffraction to follow the reaction it was found that the mechanical alloying of CuO and Ca using toluene as a processing lubricant resulted in the formation of Cu. The mechanical alloying of CuO and ZnO together with Ca resulted in the formation of &bgr;’brass.

ISSN:0003-6951    

DOI:10.1063/1.101750

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

By using a thermodynamical approach to the ensemble of interface traps of insulator‐semiconductor interfaces, it is demonstrated that the entropy properties of the traps may have a considerable influence on measured energy distributions. Because experimentally obtained distributions are given on a free‐energy scale, thermodynamics must be utilized when comparing with theoretical distributions of eigenenergy scales. Both the U‐shaped energy distributions profiles, normally found for silicon–silicon dioxide structures, and the peaks, obtained in these distributions for samples being exposed to radiation or bias stress, would occur for reasonable entropy distributions even if the interface state distribution on an eigenenergy scale were constant.

ISSN:0003-6951    

DOI:10.1063/1.102389

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A simultaneous reduction of interface roughness and of impurity and trap incorporation in GaAs/AlGaAs quantum wells is observed for a decrease of the molecular beam epitaxy growth rate below its standard value 1 &mgr;m/h, down to 0.1 &mgr;m/h, at a substrate temperature of 620 °C. Thus, layer quality is drastically improved at low, nonstandard growth rates. Incorporation of impurities from the background is observed to induce a transition from two‐ to three‐dimensional growth. The conclusions are based on a detailed study and line shape analysis of quantum well luminescence.

ISSN:0003-6951    

DOI:10.1063/1.101751

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report the first observation of a lateral junction formed in an alloy due to an abrupt transition from segregated to random AlGaAs alloy compositions. Al0.25Ga0.75As epilayers were grown by molecular beam epitaxy on [011¯] oriented grooves in a nonplanar (100) GaAs substrate. A quasi‐periodic modulation of the aluminum concentration occurs spontaneously in material grown on the (111) facets of the groove, with a period of 50–70 A˚ along the [111] direction. The compositional modulation is associated with a reduction of the band gap by 130 meV, with respect to the random alloy. While segregation of the AlGaAs alloy has been seen previously, this is the first observation of segregation of AlGaAs grown on a (111) surface. The compositional modulation terminates abruptly at the boundaries of the (111) facet, forming abrupt lateral junctions in the AlGaAs layers grown on a groove.

ISSN:0003-6951    

DOI:10.1063/1.102263

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Reactive ion etching of InP with CH4/H2mixtures leads to hydrogen passivation of near‐surface Zn acceptors but not S donors. Secondary‐ion mass spectrometry (SIMS) measurements of CH4/D2etched samples show deuterium diffuses to a depth of 2000 A˚ inp‐InP (1.5×1018cm−3) when etching at a rate of 520 A˚/min and a temperature of about 80 °C. Acceptor passivation occurs to the same depth. Forn‐InP, no donor passivation is observed, even though SIMS shows deuterium diffusion to a depth of 7000 A˚. Annealing at 350 °C for 1 min restores carrier concentrations to near pre‐etched levels.

ISSN:0003-6951    

DOI:10.1063/1.101752

出版商:AIP    

年代:1989

数据来源: AIP