摘要:

The effect of thermal annealing on the interface quality in undoped, AlAs/GaAs multiple quantum well (MQW) structures grown at a low substrate temperature (310 °C) by molecular beam epitaxy has been investigated using chemical lattice imaging and high resolution x‐ray diffraction. The low‐temperature‐grown MQW is of high crystalline quality comparable to the standard‐temperature‐grown MQW. However, significant interface roughening and intermixing occurs at the quantum well heterointerface when the structures are annealed beyond 700 °C. The effective activation energy for interdiffusion is estimated as 0.24±0.07 eV. The structural properties observed here suggest that the excess arsenic associated with the low‐temperature growth substantially enhances the diffusion of column III vacancies across an interface, which leads directly to intermixing of Al and Ga. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115257

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Epitaxial thin films of lanthanum‐deficient LaxMnO3−&dgr;(0.67≤x≤1) have been grown on (100) SrTiO3substrates by pulsed laser deposition. The as‐deposited films exhibit a ferromagnetic transition at temperatures ranging from 115 to 240 K, with the transition temperature (Tc) increasing with higher La deficiency. A sharp drop in resistivity and negative magnetoresistance is observed close toTc, a behavior similar to that observed in divalent substituted La1−xMxMnO3−&dgr;(M=Ba, Sr, Ca, Pb) films. Postannealing the films in O2reduces the resistivity and raises theTcto values close to room temperature. A magnetoresistance value of 130% (&Dgr;&rgr;/&rgr;H) has been obtained at 300 K at 4 T for a post‐annealed film withx=0.75. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115258

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We studied both the resistivity and the Hall resistivity of cosputtered granular Ni–SiO2films with the metal volume fractionxin the range of 0.5–1.0. Near the metal‐insulator transition, orxof about 0.53–0.61, the saturated value of the Hall resistivity was up to 2×10−4&OHgr; cm. This value is almost 4 orders of magnitude greater than that of pure nickel. Both the resistivity and the Hall resistivity varied weakly with temperature, throughout the range of 5–300 K. We suggest that the percolating ferromagnetic granular metal films can be an alternative candidate material for high sensitivity Hall sensors. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115259

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The kinetics of the oxidation of Si in a microwave excited O2plasma have been studied at temperatures in the range of 260–390 °C. The substrate was positively biased and the total electron and O−ion current maintained constant by application of an electric field ∼5 MV cm−1across the growing oxide. This field was established for thicknesses ≥10 nm. Total current densities were 2–6 mA cm−2while the O−current was estimated to be 0.02–0.04 mA cm−2. Oxide growth kinetics are discussed in terms of a recent physical model. Chemical etch rates and refractive indices were measured and although similar to those of thermal oxide, infrared absorption spectra suggest that the internal network structure is not the same. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115260

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Single‐crystalline and single‐domain PbTiO3films with thickness of 3000 A˚ have been prepared by metalorganic chemical vapor deposition (MOCVD), using metalorganic precursors of tetra‐ethyl‐lead and iso‐propoxide titanium. The nature of single‐crystalline epitaxy and single domain of as‐grown films was characterized by x‐ray diffraction (XRD), synchrotron radiation (SR), and Rutherford backscattering (RBS). Using atomic force microscopy (AFM), the evidence of layer‐by‐layer growth was observed. The growth steps on the surface may be attributable to the formation of single‐crystalline and single‐domain PbTiO3film with 3000‐A˚ thickness. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115261

出版商:AIP    

年代:1995

数据来源: AIP