摘要:

Two new electron paramagnetic resonance centers are reported, Si‐L8 and Si‐L9, which are identified with the stable and one of the four metastable configurations, respectively, of a multistable defect recently discovered by deep level transient capacitance spectroscopy in electron‐irradiated phosphorus‐doped silicon. Resolved31P hyperfine interactions and stress‐induced alignment effects are detected in the spectra which serve to confirm the identification as a Ci‐Pspair and lead to a model for the atomic structure in the stable configuration.

ISSN:0003-6951    

DOI:10.1063/1.104987

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A new test structure has been developed to identify unambiguously the main mechanism which determines the profiles of thin films deposited by low‐pressure chemical vapor deposition (LPCVD) in structures such as steps, trenches, and via‐holes. The two mechanisms considered are reemission due to a low surface reaction probability and surface diffusion. Experimental results using silane, diethylsilane (DES), tetraethoxysilane (TEOS), and tetramethylcyclotetrasiloxane (TMCTS) as the silicon sources for oxide deposition by LPCVD show that indirect deposition from reemission is the major contributing factor in determining the step coverage.

ISSN:0003-6951    

DOI:10.1063/1.104988

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Selective growth of GexSi1−xon Si is demonstrated for the first time using a pulsed laser induced epitaxy technique, combined with either standard oxide or liftoff patterning processes. Two different dimensions of Ge0.12Si0.88/Si lateral wells are formed, 3.5 &mgr;m wide by 1700 A˚ deep, and 6 &mgr;m wide by 1300 A˚ deep. High‐resolution transmission electron microscopy, combined with energy‐dispersive x‐ray imaging, reveals a well‐defined two‐dimensional (2D) Ge redistribution profile with no significant line or surface defects observed. The 2D Ge well distribution profiles, governed by heat and mass transport during the laser processing, are discussed.

ISSN:0003-6951    

DOI:10.1063/1.104989

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A systematic study of the change in structural quality of as‐grown GaAs layers deposited at temperatures between 180 and 210 °C by molecular beam epitaxy was performed using transmission electron microscopy, double‐crystal x‐ray rocking curves, and particle‐induced x‐ray emission. We found that the crystal quality was correlated strongly with growth temperature near 200 °C. The lattice parameter and the amount of As incorporated in the layer were observed to increase at lower growth temperatures. After exceeding a certain growth‐temperature‐dependent layer thickness, large densities of pyramidal‐type defects are formed, which at lowest growth temperature result in the breakdown of crystallinity and in columnar polycrystalline growth. The lattice expansion is ascribed to the excess As in the layers. The mechanisms of breakdown of crystallinity are discussed.

ISSN:0003-6951    

DOI:10.1063/1.104990

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Ultrafast graded double‐heterostructure GaInAs/InPp‐i‐nphotodiodes grown by gas source molecular beam epitaxy have been fabricated on an InP semi‐insulating substrate. The graded band‐gap layers and the double heterostructure reduce carrier trapping effects and diffusion current and the resulting response of a 5 &mgr;m×5 &mgr;m device was measured by electro‐optic sampling to be 5 ps full width at half maximum (FWHM). The deconvolved impulse response is 3.8 ps FWHM.  

ISSN:0003-6951    

DOI:10.1063/1.104991

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A highly strain tolerant family of conductors has been developed for the high‐temperature superconductor Bi2Sr2Ca1Cu2O8−&dgr;by fabricating a microfilamentary composite in which discontinuous filaments of the superconductors are separated from one another by very thin layers of Ag. The Ag provides a region of plastic flow and the strain tolerance. The Ag also provides barriers to supercurrent flow and to overcome these barriers, long slender filaments of Bi(2212) are arranged to have enormous overlap areas perpendicular to the direction of average current flow. This requires filament length to diameter ratios of about 10 000 to 1 and Ag barrier thicknesses on the order of 20 nm. This permits highJcvalues even though the sample has a dense array of barriers. At 4.2 K and 0.3 T, critical current densities typically fall smoothly from 1000 to 800 A/cm2as the strain increases from 0 to 1.6%.

ISSN:0003-6951    

DOI:10.1063/1.104992

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Coherent emission has been generated by two‐dimensional arrays of SIS Josephson junctions and detected in a junction coupled to the array through a dc‐blocking capacitor. The detector junction exhibits Shapiro steps at frequencies corresponding to the voltage across single array junctions and ranging from 60 to 210 GHz. The maximum power coupled to the detector junction occurs at 150 GHz and is estimated to be 0.9 &mgr;W, based on simulations of the detector circuit. Possible mechanisms for coherent emission from two‐dimensional arrays are discussed.

ISSN:0003-6951    

DOI:10.1063/1.104993

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have prepared epitaxial (100)CeO2thin films on LaAlO3, sapphire, and yttria‐stabilized zirconia using pulsed laser deposition. It is demonstrated in this letter that the CeO2films are chemically and structurally compatible to the high‐temperature superconductor YBa2Cu3O7−&dgr;(YBCO). Epitaxial YBCO films on CeO2/LaAlO3had a zero resistance temperature and critical current density in a zero field of 90 K and 5.9×106A/cm2at 75 K, respectively. Furthermore, epitaxial multilayers of CeO2/YBCO were prepared. This work demonstrated that CeO2is an excellent buffer layer material for the high‐temperature superconductors.

ISSN:0003-6951    

DOI:10.1063/1.104994

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We demonstrate that two distinctly different in‐plane epitaxial states ofc‐axis oriented YBa2Cu3O7−&dgr;(YBCO) films on (100) yttria‐stabilized ZrO2(YSZ) single‐crystal substrates can be produced independently, namely, YBCO [100]//YSZ [100] or YBCO [100]//YSZ [110]. Both in‐plane epitaxial relationships can be modeled by matching YBCO and YSZ oxygen sublattices at the film‐substrate interface. High critical current densities (Jc), ∼5×105–1×106A/cm2at 77 K, are achieved when ≳90 vol % of either orientation is present.Jccan be degraded nearly four orders of magnitude in films with mixed orientation.

ISSN:0003-6951    

DOI:10.1063/1.104995

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The lengths and spacings of twins in YBa2Cu3O7−&dgr;thin films deposited onto MgO substrates have been measured by transmission electron microscopy as a function of film thicknesst, fortranging from 50 to 1400 nm. The twin length is linear int, while the twin spacing follows at1/2dependence. This form for the twin spacing is consistent with the prediction of a simple free energy expression for the twinning transformation.

ISSN:0003-6951    

DOI:10.1063/1.104996

出版商:AIP    

年代:1991

数据来源: AIP