摘要:

Field emission from a single level surface state is modelled and numerically estimated. Field emission current from the surface state is dominant at low fields while field emission current from the conduction band is dominant at high fields due to not enough electrons being supplied for the surface state. The field emission Fowler–Nordheim plot shows no linearity. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365304

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electrochemical conditions for the direct electroplating of Ni–Fe Permalloy (19&percent; Fe, 81&percent; Ni) thin films onto Si(111) surfaces were determined. The film composition, structure, and magnetic properties were examined by various techniques involving Auger electron spectroscopy depth profiles analysis, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and magneto-optic Kerr effect measurements. The Permalloy films consisted of 10–50-nm-diam Ni/Fe nanocrystallites. It was found that the coercivity decreased with increased film thickness. Moderate annealing of the films below 200 °C released stress in the films and led to a decrease in coercivity. Interfacial diffusion occurred after the annealing of films above 300 °C. The Ni–Fe films exhibited bulk properties after the completion of electrodeposition of a buffer layer of thickness>20 nm;below this thickness, the films were discontinuous and consisted of separated clusters or islands on the Si surface. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365305

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Wet thermal oxidation of AlAsSb was investigated. The oxidation kinetics was studied as a function of temperature and oxidation duration. An expression to allow accurate determination of the oxide depth for any temperature and time was established. Secondary ion mass spectrometry profiles and x-ray diffraction were used to demonstrate that an interfacial layer, composed of pure Sb and As and textured on InP, is formed during the oxidation process. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365335

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

As-grown Fe-doped semiconducting InP wafers (residual carrier concentration ⩽1015 cm−3,estimated iron concentration5–8×1015 cm−3) were converted to semi-insulating, with high resistivity and good mobility, when annealed under appropriate conditions. This fact is very interesting, since it permits the preparation of semi-insulating InP with an Fe content substantially lower than that of standard as-grown material. In this article, we report the annealing parameters, together with the results of an extensive characterization (Hall effect,C–V,infrared absorption, and photoinduced current transient spectroscopy) of the treated samples. The onset of the semi-insulating regime seems to be primarily due to an annealing-related loss of shallow donors. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365336

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Atomic hydrogen from plasma discharges dissolves in silicon previously amorphized by ion implantation(aSi)in the form of Si–H bonds, giving rise to infrared (IR) absorption at∼1990 cm−1and causing partial activation of implanted dopants. Passivation ofaSidoes not affect the rate at which the material subsequently undergoes solid phase epitaxy. Exposure giving rise to[H]>6 at. &percent;causes the appearance of an additional IR absorption band at∼2080 cm−1and coloration of the layer. Despite annealing, the Si–H defects, normal solid phase epitaxy does not occur during subsequent heat treatment. The structural modification by H-plasma exposure coincides with etching of the layer. The observations can be understood in terms of void formation inaSiresulting from the clustering of Si–H. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365337

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Defect chalcopyrite thin films ofCu(In,Ga)2Se3.5were prepared by rf sputtering from stoichiometricCuInxGa1−xSe2(x=0.6)and Na mixture target. The composition of the thin films fabricated in the ratio of[Na]/[Cu(In,Ga)Se2]above 5&percent; was changed from the stoichiometric composition ofCu(In,Ga)Se2to Cu-poor one, and identified asCu:(In+Ga):Se=1:2:3.5.From the results of x-ray diffraction, the lattice parameters of these thin films were slightly smaller than that ofCu(In,Ga)Se2and, besides the peaks appearing for chalcopyrite structureCu(In,Ga)Se2,the additional peak was observed. The optical band gap is increased from 1.24 to 1.36 eV with increasing the[Na]/[Cu(In,Ga)Se2]ratio from 0&percent; to 10&percent; in the target. These films showedn- orp-type conduction. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365338

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Carbon diffuses into metal and recrystallizes as graphite, which is termed graphitization of carbon by metal. This study has revealed that the temperature at which this graphitization occurs depends on the initial state of the carbon. The lowest temperatures at which graphitization by Ni occurs for diamond, diamondlike amorphous carbon, graphite, and graphitelike amorphous carbon were 700, 500, 900, and 700 °C, respectively. It is shown that the temperature ranges at which graphitization by Ni occurs are correlated to the temperature ranges at which graphite can be formed on Ni by chemical vapor deposition using organic substances as starting materials. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365339

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The performance of ⟨indium-tin-oxide (ITO)/silicon oxide/n-Si(100)⟩ junction solar cells is improved by immersing Si wafers in a potassium cyanide solution before the ITO deposition. It is found from x-ray photoelectron spectroscopy measurements that about 3&percent; monolayer cyanide(CN−)ions are present on the Si surface after the cyanide treatment. The temperature dependence of the current–voltage curves shows that the band bending inn-Si is increased by the cyanide treatment. The increase in the band bending is attributed to an upward Si band edge shift caused by the presence ofCN−ions at the oxide/Si interface and/or in the oxide layer. Conductance–voltage measurements show that the density of trap states considerably decreases after the cyanide treatment. The conductance decrease is attributed to the passivation of interface states by the adsorption ofCN−ions on Si dangling bonds. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365340

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Three kinds of important properties of the solar cell were calculated: short-circuit current density, open-circuit voltage, and conversion efficiency. Two equations which show the relationship between the minority-carrier diffusion length and the grain size or the etch pit density were used for the calculation. The dependence of the properties on the cell thickness were estimated as a function of grain size and etch-pit density. The effect of the internal reflectance with varying minority-carrier diffusion length was also examined. The results show that thin film polycrystalline silicon solar cells have the potential to attain an efficiency of 17&percent; even at a film thickness of 2 &mgr;m if the grain size is bigger than 10 &mgr;m and the etch-pit density of less than1×106 cm−2.The principal requirement is to achieve efficient light trapping. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365341

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the detection of individual optical and ultraviolet photons using a different approach to photon detection based on a superconducting tunnel junction. A20×20 &mgr;m2junction, employing a 100 nm niobium film and operated at a temperature of∼0.4 K,has been used to detect individual photons with inherently high quantum efficiency(>45&percent;)over a broad wavelength range (between 200 and 500 nm), yielding high temporal (sub-ms) resolution, spatial resolution determined by the junction size, under conditions of minimal dark current, and in the absence of read noise. The quantum efficiency is limited by surface reflection, and could be improved by the deposition of antireflection coatings. The theoretical wavelength response range continues into the far UV and soft x-ray region, and is presently limited beyond 500 nm largely by the available signal processing electronics. The device intrinsically functions at very high incident photon rates—with count rates of order∼10 kHzor higher being feasible and again currently limited primarily by the signal processing electronics—thus providing a correspondingly enhanced dynamic range by several orders of magnitude compared with previous panoramic photon counting detectors. The measured charge output from the device is highly linear with photon energy resulting in an optical photon detection system with intrinsic spectral resolution, related to the critical temperature of the junction material and, in the current device, providing a limiting spectral resolution of about 50 nm. It is realistic in the future to envisage that these devices could be packaged into arrays, with the resulting system characteristics offering advantages over detectors based on semiconductors. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365342

出版商:AIP    

年代:1997

数据来源: AIP