摘要:

Misfit dislocation glide velocities have been measured in Si/Si1−xGex/Si heterostructures. Si capped single Si1−xGexalloy layers and multiple quantum well geometries were investigated and no difference was found between dislocation kinetics in these structures and the equivalent alloy layer of the same average composition. Velocities in the range 25 nm s−1to 2 nm s−1were determined from the length ofa/2⟨110⟩ 60° type misfit dislocation segments after annealing in the temperature range 450–950 °C, for times between 5 and 2000 s. Two dislocation mechanisms were observed; a single misfit array at the first Si1−xGex/Si interface was found in multiple quantum wells and alloy layers while paired misfit segments were observed at both strained interfaces in Si capped Si1−xGexalloy layers. An expression for the effective stress, &tgr;eff, for single and paired misfit dislocation propagation is presented which accommodates variation in the unstrained Si cap thickness. The mean activation energy for misfit disclocation glideQvfor Si1−xGex/Si heterostructures with 0.035<x<0.25 was found to be 2.25±0.05 eV andQvwas independent of &tgr;eff. For all geometries and for &tgr;effin the range 100–750 MPa the misfit dislocation glide velocity can be defined byV(mm s−1)= (4±2)×1014(&tgr;eff/&mgr;)2 exp−(2.25/kT).

ISSN:0003-6951    

DOI:10.1063/1.103457

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Laser‐assisted atomic layer epitaxy (LALE) is used to locally deposit device‐quality material for the first time, as demonstrated by successfully fabricating broad‐area lasers with a GaAs quantum well grown in this way. By hybridizing LALE with conventional metalorganic chemical vapor deposition epitaxy, heterostructures are grown which allow characterization of material quality by photoluminescence and capacitance‐voltage measurements. In addition, graded‐index separate‐confinement heterostructure lasers with threshold current densities of 650 A/cm2for 580‐&mgr;m‐long devices were made using the LALE quantum well deposit, while devices made away from the deposit did not lase.

ISSN:0003-6951    

DOI:10.1063/1.103363

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report a study of the saturated light‐induced defect densityNs,satin 37 hydrogenated (and in part fluorinated) amorphous silicon [a‐Si:H(F)] films grown in six different reactors under widely different conditions.Ns,satwas attained by exposing the films to light from a krypton ion laser (&lgr;=647.1 nm).Ns,satis determined by the constant photocurrent method and lies between 5×1016and 2×1017cm−3.Ns,satdrops with decreasing optical gapEoptand hydrogen contentcH, but is not correlated with the initial defect densityNs,annor with the Urbach tail energyEu. We discuss our results within the framework of existing models for light‐induced defects.

ISSN:0003-6951    

DOI:10.1063/1.103364

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Previous work has shown that germanium oxynitride films grown on Ge substrates by thermal oxidation followed by nitridation provide a passivating dielectric which can be used to fabricate metal‐oxynitride‐semiconductor field‐effect transistors. We have investigated the interfacial microstructure of this semiconductor‐dielectric system with high‐resolution transmission electron microscopy (TEM) and show that 21‐nm‐thick germanium oxynitride films grown using this technique are uniform in thickness and interfacially smooth on a scale of ±0.5 nm over lateral peak‐to‐peak distances on the order of 100’s of nm. The germanium oxynitride was seen to be electron beam sensitive with significant damage to both the oxynitride and the semiconductor‐insulator interface being observed after exposure for 15 s to 200 keV electrons at a current density of 2.250 A/cm2at the specimen.

ISSN:0003-6951    

DOI:10.1063/1.104123

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Heteroepitaxial films of InSb on GaAs (100) grown by metalorganic magnetron sputtering have been studied by transmission electron microscopy. The elastic strain in the InSb films has been measured using Moire´ fringe analysis. Dilational lattice strain was found to decrease with increasing film thickness. The measured strains are in general agreement with a simple strain energy criterion for elastic accommodation. The application of a coincidence site lattice model for heteroepitaxy is also discussed.

ISSN:0003-6951    

DOI:10.1063/1.103365

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

CdTe (111)Bfilms with a 5 in. diameter have been grown on Si (100) substrates. They were characterized byinsituelectron diffraction, x‐ray diffraction, and low‐temperature photoluminescence. The layer thickness was measured across two diameters with infrared transmission, and a standard deviation of 2.3% is obtained. This demonstrates the possibility of producing CdTe layers with a 5 in. diameter with excellent uniformity in terms of thickness and crystalline quality. Moreover, this demonstrates the potential for molecular beam epitaxial growth of other materials on large‐area substrates. In fact, these are the largest monocrystalline layers of a II‐VI semiconductor material ever grown by any technique.

ISSN:0003-6951    

DOI:10.1063/1.103366

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using an inductively coupled rf plasma operated at atmospheric pressure, superconducting thin films of Y1Ba2Cu3O7−xhave been growninsituon single‐crystal yttria‐stabilized zirconia [100] from an aerosol precursor. X‐ray diffraction and rocking curve results indicate that the films are highlyc‐axis oriented normal to the substrate with a lattice constant of 11.67–11.68 A˚. The full width at half maximum of these films ranges from 0.55° to 1.0°. The films have typicalTc’s of 86 K andJc’s in excess of 105A/cm2at 77 K and zero field; magnetic measurements reveal an anisotropy of 3:1 at 69 K. The dependence of the processing parameters on the transport properties of the superconducting films is discussed.

ISSN:0003-6951    

DOI:10.1063/1.104124

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Zone melting has been used to produce texture in extruded YBa2Cu3O6+xwires. Highly aligned microstructures are produced witha‐bplanes oriented along the axis of the wires. Microstructural observations show that changes in alignment orientation can occur, and can result in the inability to carry a transport current. Pulsed transportJcmeasurements on oriented samples indicate a zero field critical current density greater than 4×104A/cm2.

ISSN:0003-6951    

DOI:10.1063/1.104125

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Phase decomposition of a bulk Y2Ba4Cu8O16superconductor has been studied. The microstructure of the sample is heavily faulted and contains many stacking defects, including a new ‘‘125’’ structure. It is likely that these fine‐scale (10–30 A˚ thick) stacking defects are responsible for the significantly improved flux pinning in the phase‐decomposed sample. It is proposed that the decomposition process begins with the reaction ‘‘248’’ 0><fv/0 ‘‘123’’+‘‘125’’, which could possibly occur by a spontaneous, short‐range diffusion reaction. Further decomposition involves gradual removal of the extra CuO chains by long‐range diffusion to produce a mixture of ‘‘123’’+CuO.

ISSN:0003-6951    

DOI:10.1063/1.104126

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Tl2Ca1Ba2Cu2O8+xhighTcsuperconductors were developed using a new alkoxide sol‐gel system. Barium‐, calcium‐, thallium‐methoxyethoxide and Cu(II) ethoxide precursors were used for the formation of homogeneous sols. Solubility of the Cu(II) ethoxide was aided by using a 2‐methoxyethanol/methyl ethylketone/toluene solvent system. The sols were characterized by small‐angle x‐ray scattering and transmission electron microscopy. The average particle size was 50 nm and the fractal dimension of these particles was 1.8. Powders were produced by rotary evaporation followed by thermal treatment in a closed container with excess thallium at 900 °C for various calcination times. Powders were characterized by x‐ray diffraction, resistivity, and magnetic susceptibility measurements, and chemical analysis. Samples exhibited transition temperatures between 100 and 110 K depending upon the processing conditions.

ISSN:0003-6951    

DOI:10.1063/1.103367

出版商:AIP    

年代:1990

数据来源: AIP