摘要:

Ion beam induced epitaxial crystallization of amorphous NiSi2is reported. Epitaxial NiSi2layers on (111) Si substrates were implanted at ∼−196 °C with low‐energy Si ions to form an amorphous surface layer. The recrystallization of amorphous NiSi2was induced at 13–58 °C by irradiating with high‐energy Si or Ne ions. Recrystallization proceeded in a layer‐by‐layer manner from the original amorphous/crystalline interface with an activation energy of 0.26±0.07 eV.

ISSN:0003-6951    

DOI:10.1063/1.102989

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin films of silicon oxide and oxynitride were prepared by rapid thermal processing. Under optimum conditions (e.g., nitridation at 1100 °C for 4 s followed by reoxidation at 1150 °C for 60 s), their electrical properties (charge trapping, low‐field leakage, and charge to breakdown) were significantly improved over those of the starting oxide. Values ofQbdas high as 260 C/cm2for a positive current density of 200 mA/cm2were obtained. Yet, the improvement was much smaller for negative than positive stress. This difference is ascribed to the asymmetrical role of nitridation on the prevention of interface trap generation at high fields and is consistent with models of the generation of interface traps described in the literature.

ISSN:0003-6951    

DOI:10.1063/1.103234

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Phase coherence lengthL&fgr;of on‐facet quantum wires is determined at temperatures down to 50 mK by three methods: magnetoresistance, conductance fluctuation amplitude, and the conductance fluctuation correlation field. It is found thatL&fgr;saturates below about 0.4 K. This saturation is identified as due to spin‐orbit interaction, which has no temperature dependence. This result is supported by positive magnetoresistance under a weak magnetic field.

ISSN:0003-6951    

DOI:10.1063/1.102990

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Epitaxial thin films of the semiconducting transition metal silicide, beta‐FeSi2, were grown on (001) silicon wafers. The observed matching face relationship is FeSi2(100)/Si(001), with the azimuthal orientation being FeSi2[010]‖‖Si⟨110⟩. This heteroepitaxial relationship has a common unit mesh of 59 A˚2area, with a mismatch of 2.1%. There is a strong tendency toward island formation within this heteroepitaxial system.

ISSN:0003-6951    

DOI:10.1063/1.103235

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A thermally stable, low‐resistance PdIn ohmic contact ton‐GaAs has been developed based on the solid phase regrowth mechanism [T. Sands, E. D. Marshall, and L. C. Wang, J. Mater. Res.3, 914 (1988)]. Rapid thermal annealing of a Pd‐In/Pd metallization induces a two‐stage reaction resulting in the formation of a uniform single‐phase film of PdIn, an intermetallic with a melting point greater than 1200 °C. A thin (∼5 nm) layer of average composition In0.4Ga0.6As uniformly covers the interface between the PdIn layer and the GaAs substrate. Specific contact resistivities and contact resistances of ∼1×10−6&OHgr; cm2and 0.14 &OHgr; mm, respectively, were obtained for samples annealed at temperatures in the 600–650 °C range. The addition of a thin layer of Ge (2 nm) to the first Pd layer extends the optimum annealing temperature window down to 500 °C. Specific contact resistivities remained in the low 10−6&OHgr; cm2range after subsequent annealing at 400 °C for over two days.

ISSN:0003-6951    

DOI:10.1063/1.102993

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new source of cadmium diffusion in In0.53Ga0.47As has been developed. Langmuir–Blodgett (LB) deposited monolayers of cadmium arachidate have been used as a source of cadmium. The LB film has been characterized by grazing incidence infrared spectroscopy and Auger electron spectroscopy. Acceptor profiles obtained by differential Hall technique are presented. Highly doped (NA=2×1019cm−3) shallow (xj≊0.1–0.4 &mgr;m),p+‐njunctions are obtained. Mesa‐typep‐i‐ndiodes with 125 &mgr;m diameter, ideality factor =1.3,Idark=5 nA at 20 V reverse bias, andVbreakdown=30 V have been fabricated.

ISSN:0003-6951    

DOI:10.1063/1.102994

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have prepared new highTcsuperconducting thin films of (Tl,Bi)‐Sr‐Ca‐Cu‐O by combining low temperature (500 °C) rf sputtering of Bi‐Sr‐Ca‐Cu‐O precursor films and thallium diffusion. A typical film hasTc(onset)=80 K,Tc(midpoint)=79 K, andTc(zero)=50 K. X‐ray diffraction and energy dispersive spectroscopic studies were carried out to determine the composition and crystal structure of the superconducting phase within the film. We identified a material with the chemical composition of (Tl0.7Bi0.3)Sr2CaCu2Oyand tetragonal symmetry (a=3.795 A˚ andc=12.095 A˚), and propose that this phase is responsible for superconductivity around 80 K. The film also has a highly preferred orientation with thecaxis perpendicular to the surface of the (100)MgO substrate.

ISSN:0003-6951    

DOI:10.1063/1.103236

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have investigated the microstructure of epitaxial YBa2Cu3O7−xthin films on SrTiO3(100), LaGaO3(100), and LaAlO3(100) with particular emphasis on how the final microstructure is developed. Cross‐sectional transmission electron microscopy as well as plan‐view transmission electron microscopy combined with sputter depth profiling were used to study the change in microstructure with the increase in film thickness. For a thin film or near the substrate/film interface of a thick film, the YBa2Cu3O7−xfilm is composed primarily of grains oriented withcaxis normal to the substrate surface and a small volume fraction of grains withcaxis parallel to the substrate surface. As the film grows thicker, thec‐axis parallel grains increase in size and grow over the top of thec‐axis normal grains. The volume fraction ofc‐axis parallel grains increases rapidly as the film thickness increases and eventually the entire film surface is covered byc‐axis parallel grains. However, the number density of thec‐axis parallel grains remains constant throughout the whole film thickness. A growth model is proposed to explain the observed microstructure. Based on this model, a computer simulation is carried out. The simulated microstructure agrees well with the experimental result.

ISSN:0003-6951    

DOI:10.1063/1.103237

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Flexible Li‐doped Bi‐Sr‐Ca‐Cu‐O superconducting whiskers have been prepared by heating a glassy melt‐quenched plate in a stream of O2gas. The whiskers show a resistance drop at 110 K with a zero resistance at 81 K. These values are higher than those of the Pb‐doped Bi‐Sr‐Ca‐Cu‐O whiskers by 5 and 11 K, respectively. The doping of Li is effective to raiseTcfor both the 2212 phase and the 2223 phase. TheJcvalues of the Li‐doped whiskers are 30 000 A/cm2at 77 K and 300 000 A/cm2at 66 K in a zero magnetic field.

ISSN:0003-6951    

DOI:10.1063/1.103238

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Experimental demonstration of reduction in the number and size of particulates formed in the laser ablation deposition of YBa2Cu3O7−&dgr;thin films is obtained by the use of a second laser which further heats and fragments the blowoff material in the plume formed by the first laser. This results in a smoother film with higher critical current density as compared to that obtained without the second laser irradiation of the plume.

ISSN:0003-6951    

DOI:10.1063/1.103239

出版商:AIP    

年代:1990

数据来源: AIP