摘要:

CO2laser interferometry was used to determine electron density profiles in copper vacuum arcs just before and after the transition from the low‐voltage quiescent mode to the high‐voltage mode associated with anode‐spot formation. Just before transition, the electron‐density profiles are peaked on axis, with maxima of 9×1014cm−3and 6×1014cm−3in the cathode and anode regions, respectively. At about 0.1 ms after transition, the electron‐density profile in the cathode region remains unchanged, while the central electron density near the anode drops be a factor of about 2. No constriction in the density profile was observed at any axial position. Previously reported anode surface temperature measurements are used to attribute the sudden drop in electron density near the anode just after transition to a local increase in the electron‐ion recombination rate caused by a sudden influx of relatively cold neutral atoms from the anode surface. The implications of these observations with regard to a mechanism for transition are discussed.

ISSN:0021-8979    

DOI:10.1063/1.326040

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Radiation‐induced conduction in polyethylene‐terephthalate under high electric field (1×106to 1.6×108V/m) has been studied. At field strengths below 1×108V/m, the induced current reaches its initial steady‐state value (primary component) soon after irradiation is initiated, then monotonically decreases with time thereafter. This decrease of current is due to a ’’polarization’’ effect. Above 1×108V/m, the induced current decreases for a while then increases again to reach the equilibrium value (secondary component). This secondary component is due to the electron injection, enhanced by the fixed positive space‐charge accumulation near the cathode. The radiation‐induced conductivity of the primary component increases with electric field strength between 1×106and 1×108V/m and then shows a saturation tendency above 1×108V/m. This may be due to geminate recombination in the carrier generation process. The primary component in the 50‐&mgr;m‐thick specimen is deduced to be dominated by a deep‐trapping‐limited process. The primary component of the induced current in a 6‐&mgr;m‐thick specimen is demonstrated to attain saturation above 1.2×108V/m.

ISSN:0021-8979    

DOI:10.1063/1.326041

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The defect structure of degraded Ga1−xAlxAs double‐heterostructure (DH) light‐emitting diodes (LED’s) was investigated by electroluminescence (EL) topography and transmission electron microscopy (TEM). Two types of dark‐line defects (DLD’s), ⟨100⟩ DLD’s and ⟨110⟩ DLD’s, and dark‐spot defects (DSD’s) were observed in EL patterns of degraded LED’s. Dislocation dipoles or large zigzag‐shaped dislocation loops were associated with DSD’s and ⟨100⟩ DLD’s. The dipoles had Burgers vectors of the type (a/2) ⟨011⟩ inclined at 45° to the (001) junction plane or (a/2) ⟨110⟩ parallel to the junction plane and were extrinsic in character. The zigzag‐shaped dislocation loops had Burgers vectors of the type (a/2) ⟨011⟩ and were extrinsic in character. On the other hand, multiple stacking faults which lay in ⟨110⟩ directions or half dislocation loops which also lay in ⟨110⟩ directions and had Burgers vectors of the type (a/2) ⟨011⟩ inclined at 45° to the junction plane or (a/2) ⟨110⟩ parallel to the junction plane were associated with ⟨110⟩ DLD’s.

ISSN:0021-8979    

DOI:10.1063/1.326042

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The elastic field of a line force oriented in the ⟨111⟩ direction in a cubic crystal is analyzed, based on anisotropic elasticity theory. Closed‐form expressions for the stress components are presented. The characteristics of the stress field are strongly affected by elastic anisotropy. In the case where the line force is parallel to the singular line, a dilatation field exists but it vanishes when isotropy is approached.

ISSN:0021-8979    

DOI:10.1063/1.326043

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The formation of a phosphorus or boron impurity peak in silicon has been observed following irradiation with monoenergetic protons. In this study we used a sample temperature of 700 °C, proton‐beam energies of 50–140 keV, proton‐beam current densities of ∼1 &mgr;A/cm2, and proton‐bombardment times of 3 min to 3 h. The resultant impurity profiles were obtained using Schottky‐barrier differentialC‐Vtechniques.

ISSN:0021-8979    

DOI:10.1063/1.326044

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Short‐duration high‐intensity pulsed electron beams have been used to anneal ion‐implantation damage in silicon and to electrically activate the dopant species. Lattice regrowth and dopant activation were determined using4He+backscattering, SEM, TEM, and device performance characteristics as diagnostic techniques. The annealing mechanism is believed to be liquid‐phase epitaxial regrowth initiating from the substrate. The high‐temperature transient pulse produced by the electron beam causes the dopant to diffuse rapidly in the region where the liquid state is achieved.

ISSN:0021-8979    

DOI:10.1063/1.326045

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The transition to single crystal of ion‐implanted amorphous Si and Ge layers is described in terms of a liquid‐phase epitaxy occurring during pulsing‐laser irradiation. A standard heat equations including laser light absorption was solved numerically to give the time evolution of temperature and melting as a function of the pulse energy density and its duration. The structure dependence of the absorption coefficient and the temperature dependence of the thermal conductivity were accounted for in the calculations. In this model the transition to single crystal occurs above a well‐defined threshold energy density at which the liquid layer wets the underlying single‐crystal substrate. Experiments were performed in ion‐implanted amorphous layers of thicknesses ranging between 500 and 9000 A˚. The energy densities of theQ‐switched ruby laser ranged between 0.2 and 3.5 J/cm2; time durations of 20 and 50 ns were used. The experimental data are in good agreement with the calculated values for the amorphous thickness–energy−density threshold. The model deals mainly with plausibility arguments and does not account for processes occuring in the near‐threshold region or below the melting temperature.

ISSN:0021-8979    

DOI:10.1063/1.326046

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An analysis is presented to determine the characteristics of the radiation from planar channeled positrons. This radiation has interesting properties as a source for the keV photon energy range, and may also be used to investigate the behavior of channeled particles and to characterize the channeling crystal. Several important aspects of this problem are considered, such as line‐broadening mechanisms, dependence of the radiation on the properties of the incident particle beam, and effects of anharmonicity in the crystal field potential. The emission has a full width at half‐maximum (FWHM) ?13%, is an order of magnitude brighter than bremsstrahlung, is tunable, is linearly polarized, and is highly directional.

ISSN:0021-8979    

DOI:10.1063/1.326047

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The dependences of diffusion coefficient of As,DAs, upon total As concentration,CT, and the relationships betweenCTand resistivity &rgr; for several diffusion temperatures are experimentally obtained for the As diffusion intop‐type Si from doped polycrystalline‐Si sources in the temperature range 850–1050 °C. It is found that the relationship betweenCTand &rgr; is dependent upon diffusion temperature forCTabove 1020cm−3. The relationship betweenCTand electrically active As concentration at diffusion temperature,CA, i.e.,CT=CA+(3.2×10−6/n3i)C4Acan be obtained, assuming that only electrically active As is mobile and is diffused by the single‐level vacancy mechanism, and using the experimental result that the dependence ofDAs/Di(Diis the intrinsic diffusion coefficient of As) uponCT/ni(niis the intrinsic electron concentration) is not influenced by diffusion temperature. Using the above equation, it is found that the relationship betweenCAand &rgr; is independent of diffusion temperature, even forCAabove 1020cm−3, and can be approximated forCAabove 1020cm−3by an empirical equation: &rgr;=8.7×104C−2/5A.

ISSN:0021-8979    

DOI:10.1063/1.325993

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Profiles of S+and S+2ions implanted at 60 and 120 keV were studied using Auger electron spectroscopy. The maximum sulfur concentration of unannealed samples was found to be 86 nm below the GaAs surface for the 120‐keV S+with a total dose of 2×1016cm−2, whereas it was 40 nm for the 120‐keV S+2with a dose of 1016cm−2. These depths compare favorably with the calculated LSS ranges of 89 and 45 nm, respectively. Outdiffusion of sulfur has been observed in sulfur‐implanted Cr‐doped GaAs following annealing. The absolute sulfur concentrations were obtained by comparing the relative heights of Auger peaks between the implanted sulfur and the sulfur in ZnS and CdS crystals. Limits of detectability for the implanted sulfur were measured to be ∼1019cm−3.

ISSN:0021-8979    

DOI:10.1063/1.326048

出版商:AIP    

年代:1979

数据来源: AIP