摘要:

Josephson tunnel junctions with Pb counterelectrodes have been fabricated on magnetron‐sputtered Al5 Nb3X(X=Al,Ge) thin films using a CF4plasma cleaning process (CFCP) in conjuction with standard photolithographic processing. The fabrication conditions necessary to produce optimized junctions and their tunneling properties have been investigated. The junction quality rapidly decreases with the increase in the discharge cathode self‐bias voltage (VCSB) during the plasma oxidation as well as the CF4cleaning. The optimum voltage for the cleaning necessary to obtain high‐quality junctions with a uniform current distribution is common to both compounds and exists in the narrower range of 120–140 V than for Nb/Pb junctions. Nevertheless, high‐quality Nb3X/Pb junctions withVm>20 mV can be highly reproducibly fabricated for a wide range of the critical current density (1–103A/cm2). Such junctions show high barrier height values of 0.8–1.0 eV and good aging stability, which is also the case for the Nb/Pb junctions fabricated using CFCP. X‐ray photoelectron spectroscopy (XPS) and ellipsometric measurements on the CF4‐cleaned base electrode surface indicate the presence of an ultrathin fluoride overlayer which is composed of Nb‐F and X‐fluorides. The former also show that the tunnel barrier is a mixture of Nb2O5, Nb‐F‐O, and X‐F‐O. These results, in addition to those for barrier height measurements, suggest that F atoms prevent the defect creation in the barrier and the selective Nb oxidation. They, thus, play an important role in the formation of the highly insulating barriers as well as a nearly ideal barrier‐electrode interface without a substantial proximity layer.

ISSN:0021-8979    

DOI:10.1063/1.335778

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Ferroelectric thin films of antimony sulphoiodide (SbSI) have been grown by flash evaporation in the thickness range of 0.1–1.5 &mgr;m. Annealing the films in a sulphur atmosphere at 100 °C for 10–12 min improved their stoichiometry and crystallinity. Structural studies revealed that films deposited normal to the substrate have a tendency to grow with thecaxis oriented at 6° to the substrate. The refractive index and band gap estimated from the optical transmission curves for 1.0‐&mgr;m‐thick films were found to be 4 and 1.97 eV, respectively. The measured relative dielectric constant (&egr;’) for a 1.0‐&mgr;m thick film at 100 KHz, 300 K was ∼73. Reproducible ferroelectric‐to‐paraelectric phase transitions were observed for films thicker than 0.2 &mgr;m.

ISSN:0021-8979    

DOI:10.1063/1.335779

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Time‐zero and time‐dependent dielectric breakdowns for thermally grown 60‐ through 70‐A˚ SiO2films were studied in two kinds of Si‐gate metal‐oxide‐semiconductor (MOS) capacitors, where Al/polycrystalline silicon (poly‐Si) connecting contact hole was formed over the thin gate oxide (type A) and the thick field oxide (type B). Almost the same time‐zero dielectric breakdown was obtained in types A and B MOSs annealed at 450 °C for metal sintering. In type A samples, however, pinholes increased for the higher sintering temperature. Time‐dependent dielectric breakdown on a type‐A MOS depended on the sintering anneal temperature and four orders of magnitude shorter lifetime than that for type‐B MOS was observed under 450 °C annealed samples. Auger measurements for a type‐A MOS yielded that (i) Al precipitated at the poly‐Si/SiO2interface, caused by Al diffusion through poly‐Si film at the Al/poly‐Si connecting contact hole area during low temperature anneal for metal sintering, and (ii) Al precipitates were extremely enhanced at the contact hole edge. Unannealed type‐A samples showed almost the same good reliability as for type‐B MOS. The inferior reliability in a type‐A MOS with a metal sintering anneal was concluded to be caused by the Al precipitates at the poly‐Si/SiO2interface.

ISSN:0021-8979    

DOI:10.1063/1.335753

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We have investigated the optical‐pumping properties ofn‐type GaAs and the modification of these results produced by compensation of the crystal by diffusion of copper acceptors. The rate of circular polarization and its decrease as a function of a transverse magnetic field have been measured for the various luminescence lines. We obtain the values of lifetime &tgr; and spin‐lattice relaxation timeT1of conduction electrons. WhereasT1does not change upon copper introduction, &tgr; is found to be decreased by two orders of magnitude because copper acts as a killer center. The compensation of the crystal can be characterized in a straightforward manner from the study of the luminescence polarization as a function of energy in the vicinity of the band gap. Finally, the inhomogeneities of the crystal and the local strains can be investigated respectively from the measure of the nonlorentzian tail of the depolarization curve in a transverse magnetic field and of the polarization of acceptor‐related luminescence. All these results show that optical‐pumping techniques can allow simple nondestructive characterization of semiconductors.

ISSN:0021-8979    

DOI:10.1063/1.335728

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A structural analysis of the luminescence spectra of molecular‐beam‐epitaxy grown GaAs layer, in the energy range 1.5040–1.5110 eV (g‐vlines) is reported. At least two distinct recombination processes are distinguished from the selectively excited photoluminescence, not the excitation spectra and the luminescence polarization measurements. The relation of several lines in this emission band with oriented complex defects is established and suggested acting as isoelectronic centers.

ISSN:0021-8979    

DOI:10.1063/1.335729

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Electroluminescence emission from indium‐tin‐oxide (ITO) and indium oxide films incorporated in a Si‐rich SiO2‐SiO2‐ITO (In2O3) multiple‐layer structure is reported. The light emitted has a peak at approximately 3.3 eV for ITO and at 2.6 eV for In2O3. The intensity of the light is found to depend on the applied electric field.

ISSN:0021-8979    

DOI:10.1063/1.335730

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Preparation of amorphous silica doped with organic dye molecules, 1,4‐dihydroxyanthraquinone, and the observation of the amorphous structure of this system by photochemical hole burning using the dye molecules as a spectral probe are reported. The various kinds of organic molecule‐doped inorganic glassy materials are obtained with the alcoholate method. The appearance of the photochemical hole in this system shows the molecular dispersion of the dye molecules in the matrix without cracking or decomposition. The burning yield, 1.2×10−4, is the same as that observed in organic glasses. The intrinsic holewidth, 0.9 cm−1at zero burning time limit, the burning‐time dependence and the annealing effects on the hole profile were observed and compared with those in the alcoholic organic glass. It is suggested that the nearest‐neighbor structures around quinizarin molecules consist of some hydroxyl groups. The matrix cages seem to be fairly tight and rigid in comparison with those of the alcoholic glass. The possibility that the quinizarin molecule or molecules are embedded within the pore of amorphous SiO2with some amount of solvent molecules, mainly ethanol or water, seems to be excluded. The annealing effects of the burned hole indicate that there exist two kinds of mechanisms which dominate the temperature dependence of the holewidth in the present system. One is already dominant below about 27 K which gives rise to the reversible behavior in the holewidth with temperature, and the other becomes effective above 27 K and is irreversible with temperature cycling. Some discussions are given on the origin of these relaxation mechanisms in this system which are inherent in the structure of amorphous materials.

ISSN:0021-8979    

DOI:10.1063/1.335731

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The negative hydrogen ion formation process on a cesiated W(110) surface is studied by scattering a proton beam from such a surface. The primary energy ranges from 50 to 3000 eV. The angle of incidence with respect to the surface normal is 45° or 70°. A maximum negative‐ion formation probability of 0.67 is measured. This quantity does not depend on the angle of incidence. However, it is strongly influenced by the time the surface has been exposed to the beam. This effect is attributed to hydrogen implantation.

ISSN:0021-8979    

DOI:10.1063/1.335732

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A pulsed ArF excimer laser has been used to deposit thin conductive films of titanium silicide on silicon and silicon oxide substrates. The films are deposited from a gas mixture of titanium tetrachloride and silane by initiating photochemical reactions near the heated substrate. The resistivity, composition, crystal structure, and morphology of the films vary as a function of gas composition and substrate temperature. Films deposited at 400 °C, with SiH4/TiCl4mole ratios of ∼2, have resistivities of 300 &mgr;&OHgr; cm, which drop to 20–30 &mgr;&OHgr; cm on annealing at 650–700 °C. At higher deposition temperatures (450–550 °C) the films have resistivities of ∼110 &mgr;&OHgr; cm and show similar annealing behavior. The as‐deposited films are a mixture of amorphous and a metastable Ti‐Si crystalline phase. On annealing they convert to polycrystalline TiSi2. Films deposited at 400–450 °C are smooth and show conformal step coverage. The film roughness increases at higher deposition temperatures.

ISSN:0021-8979    

DOI:10.1063/1.335733

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Thin films of tungsten have been prepared by radio frequency (rf) diode sputtering and a saddle field ion beam source. The microstructure and electrical properties of the ion‐beam sputtered films are comparable to those of rf sputtered films deposited at low‐deposition rates. rf sputtered films deposited at high rates have larger grains and consist of &bgr;‐W. They also have lower sheet resistances. An x‐ray photoelectron spectroscopy analysis revealed that all of these films contained a considerable proportion of oxygen, the ion beam sputtered films containing more. Ion beam sputtering offers no advantages over low‐rate rf sputtering of tungsten.

ISSN:0021-8979    

DOI:10.1063/1.335734

出版商:AIP    

年代:1985

数据来源: AIP