摘要:

Current‐voltage, capacitance‐voltage, and photoresponse measurements have been reexamined on the polar Ga‐(111)Aand P‐(∼(111))Bsurfaces ofn‐GaP for reactive (Al) and nonreactive (Ag) metals. Using a chemical etching/invacuodesorption cleaning sequence, nearly oxide‐freeAandBfaces could be obtained. For diodes formed on such surfaces, the intrinsic, face‐dependent variation inAandBSchottky barrier heights was less than 30 meV.

ISSN:0021-8979    

DOI:10.1063/1.336231

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The capacitive response of deep Fe acceptors in a semi‐insulatingn‐type Fe‐doped InP Schottky barrier has been investigated. The capacitance‐voltage (C‐V) and conductance‐voltage (G‐V) characteristics over the frequency range 0.06–100 kHz are measured at 300, 317, and 335 K. Great frequency dispersion is observed inCandG. The reverse bias dependencies ofCand (G−G0) are shown to be very weak at high frequencies, whereG0is the dc conductance. As measuring frequency is lowered, (G−G0) decreases butCincreases considerably. At low frequencies, the bias dependencies ofCand (G−G0) are observed and measured 1/C2versus reverse bias curves are found to be straight lines. It is shown that at low frequencies,Cand (G−G0) take maxima near zero bias and rapidly decrease in a forward bias region. As temperature increases, the frequency region in which such low‐frequency characteristics are found extends more widely into a high‐frequency range. Theoretical calculations ofCand (G−G0) are also carried out. The results are compared with experimental ones. Observed variations ofCandGwith frequency, bias voltage, and temperature are well explained in terms of the delayed response of deep Fe acceptors.

ISSN:0021-8979    

DOI:10.1063/1.336232

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The trapping characteristics of thin oxynitride films obtained by the oxidation of a thermally nitrided silicon surface were studied under both tunneling and hot electron injection. Comparison with standard oxide layers yields the following differences: No net positive charge generation is observed in the investigated layers, and the rate of surface states generation is about one order of magnitude smaller. The electron trap density is estimated to be ∼6×1017cm−3with a capture cross section of ∼10−17cm2.

ISSN:0021-8979    

DOI:10.1063/1.336233

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Superconducting tunnel junctions have been prepared with NbN‐base electrodes, oxidized Al or Mg tunnel barriers, and NbN or Pb counterelectrodes. The tunnel barriers were formed either by thermal oxidation at room temperature or by subjecting the thin overlayers of Al or Mg to a low‐energy ion beam in an argon‐5% oxygen background. High‐quality junctions with Pb counterelectrodes were produced by either method. However, for junctions with NbN counterelectrodes deposited at room temperature, the thermal oxidation resulted in shorts and the ion‐beam oxidation resulted in low‐leakage junction. X‐ray photoelectron spectroscopy measurements of the NbN artificial‐oxide bilayers showed that the ion‐beam treatment increased the aluminum oxide thickness by the minimum detectable increment, approximately 0.2 nm, and increased the MgO thickness by 1 nm. The superconducting energy gap inferred for NbN counterelectrodes was typically half as large as the gap of the NbN base. Limitations on the gap values of NbN counterelectrodes grown on these barriers were established by measuring the energy gap of films as thin as 7.5 nm.

ISSN:0021-8979    

DOI:10.1063/1.336234

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Thin films of niobium nitride with superconducting transition temperature (Tc) of 15.7 K have been deposited on a variety of amorphous as well as crystalline substrates including glass, glazed ceramic, fused quartz, and sapphire, maintained at room temperature, by dc reactive magnetron sputtering in a mixture of Ar and N2gases. The effects of the deposition conditions, particularly the carrier gas pressure and composition, on the film crystal structure, orientation, and resistivity have been studied in an effort to maximize the superconducting transition temperature. A study of the variation of nitrogen consumption with nitrogen injection pressures for constant background argon pressures is conducted and found to be an absolute indicator of the NbN formation systematics. Initially, the consumption increases linearly with the injection pressure but beyond a certain threshold, it shows a distinct drop. The desired highTc NbN with B1 crystal structure is formed in the vicinity of this turning point of the reactive gas consumption‐injection characteristic. HighTcfilms possess B1 (fcc, NaCl‐type) crystal structure as revealed by their x‐ray diffraction patterns. An initial increase in the injection pressure of the reactive gas (N2) results in a remarkable increase in the (111) diffraction line intensity along with an increase in the filmTc. This trend continues up to the turning point of consumption‐injection characteristic, beyond which the crystal structure distorts into the substoichiometric tetragonal phase with a consequent reduction in the transition temperature. A general protocol for studying the formation systematics of transition metal nitrides has thus emerged.

ISSN:0021-8979    

DOI:10.1063/1.336235

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A classical (Y Sm Lu Ca)3(Fe Ge)5O12bubble garnet, supporting 1.8‐&mgr;m bubbles, has been implanted with 1.5×1016D+2cm2at 60 keV either directly or through a predeposited 100‐A˚‐thick silica layer. Nuclear techniques such as D (3He, &agr;)pnuclear reaction and Rutherford backscattering combined with channeling measurements were used to determine the implant and damage profiles, respectively. Double‐crystal x‐ray diffraction was used to measure the maximum strain and magnetic properties were obtained from ferromagnetic resonance. The evolution of these parameters has been studied as a function of annealing treatments. It follows that, as compared to hydrogen, deuterium also interacts at damage‐level inducing within the garnet new magnetic phenomena. A higher annealing temperature is required for bubble memory applications. The silica overlayer which is useful for increasing the anisotropy field change, somewhat affects the magnetic properties of the implanted layer.

ISSN:0021-8979    

DOI:10.1063/1.336236

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The influence of thermal expansion on thermally stimulated currents has been studied by means of model calculations based on the bistable model of Fro¨hlich, considering especially the case of materials characterized by expansion coefficients markedly different above and below the relaxation range. A good qualitative and quantitative agreement has been obtained between theory and experiment in elastomeric materials (styrene‐isoprene‐styrene and isoprene‐styrene‐isoprene block copolymers) showing that thermal expansion is the main factor responsible for the appearance of current reversals in thermally stimulated polarization processes.

ISSN:0021-8979    

DOI:10.1063/1.336237

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Infrared (IR) absorption and Raman spectra are measured for glow‐discharge‐produced, wide‐optical‐gap binary Si:H alloys containing a number of polysilane (SiH2)ngroups (polysilane alloys). The highly resolved IR stretching band revealed double peaks, at 2100 and 2122 cm−1, which correspond to an exterior SiH2and an interior SiH2, respectively, in a 3/4 Si(SiH2)nSi 3/4 group. This result provides evidence for the existence of (SiH2)n(n≥3) groups. Nonlinearity of the (SiH2)nwagging absorption strength with the number of SiH2units in the alloy is observed in the IR spectra. This is related to a change in the polymerization degree of a (SiH2)nchain. Raman scattering intensity in the 50–400 cm−1range is lower than that for conventional hydrogenated amorphous silicon alloys, suggesting a reduction in the number of Si loops arising from (SiH2)nchain formations. The change in the polymerization degree as a function of substrate temperature during deposition and the annealing temperature are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.336238

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Cryobaric (11–100 K and 300 K, 0–65 kbar) measurements of photoluminescence in GaAs/AlxGa1−xAs multiquantum well structures are described. Results on a narrow‐well (38 A˚ wide) structure exhibitingbothquantum well and bulk GaAs emission (from a thick buffer region) allow direct comparison of the two for the first time. We find that transitions between &Ggr;‐derivedn=1 confined levels have the same pressure coefficient, within ±0.2 meV/kbar, as the bulkE0gap, 11.4 meV/kbar. An interaction betweenn=1 electron states and a state 35–40 meVbelowtheX‐conduction minima is observed within the pressure‐induced &Ggr;‐Xcrossover region for our narrow‐well sample. The proposed origin of the latter state is residual interface impurities.

ISSN:0021-8979    

DOI:10.1063/1.336239

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Linear electro‐optic effects in zincblende semiconductors are theoretically analyzed by means of a microscopic simple model without any fitting of parameters. Faust–Henry, second harmonic generation, and linear electro‐optic coefficients are obtained from the calculation of the derivatives of the susceptibility with respect to electric fields and ionic displacements. Our results for GaP, GaAs, InP, ZnSe, and ZnTe are in satisfactory agreement with the available experimental information.

ISSN:0021-8979    

DOI:10.1063/1.336240

出版商:AIP    

年代:1985

数据来源: AIP