摘要:

Transient enhanced diffusion (TED) from implantation of5 keV B10H14and 0.5 keV B ions has been quantified and compared for nominal boron doses of1014and1015 cm−2.Boron diffusivity during annealing was extracted from secondary ion mass spectroscopy depth profiles of diffused marker layers in boron doping-superlattices and the actual implanted B dose was independently measured by nuclear reaction analysis. Comparable enhancements were observed from both ions. Transmission electron microscopy analysis revealed that both boron- and decaborane-implanted samples were amorphized at a nominal1015 cm−2 Bdose. A comparison with data from low energy Si implants revealed a similar dependence of diffusivity enhancement on implant dose. These findings are consistent with the understanding that TED is caused by the interstitial supersaturation resulting from a number of excess interstitials approximately equal to the number of implanted atoms which can become substitutional in the silicon lattice. Accordingly, no contribution to TED is expected from the hydrogen in theB10H14ions and none is observed. Furthermore, there is no detectable effect in the diffusion profiles which can be attributed to a difference in the ion damage produced by the decaborane molecule and the boron atom. In both cases the reduction in diffusivity enhancement is due only to proximity of the implantation-induced excess interstitials to the wafer surface. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122353

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

GaN decomposition is studied at metallorganic vapor phase epitaxy pressures (i.e., 10–700 Torr) in flowingH2.For temperatures ranging from 850 to 1050 °C, the GaN decomposition rate is accelerated when theH2pressure is increased above 100 Torr. The Ga desorption rate is found to be independent of pressure, and therefore, does not account for the enhanced GaN decomposition rate. Instead, the excess Ga from the decomposed GaN forms droplets on the surface which, for identical annealing conditions, increase in size as the pressure is increased. Possible connections between the enhanced GaN decomposition rate, the coarsening of the nucleation layer during the ramp to high temperature, and increased GaN grain size at high temperature are discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122354

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The use of anodic oxidation as a post-treatment of porous silicon has been investigated to enhance the external quantum efficiency of electroluminescence from a device based on a thin transparent indium tin oxide contact on porosifiedn+-type silicon. Enhancement in external quantum efficiency of three orders of magnitude has been obtained. We report here an external quantum efficiency of 0.21&percent;. The treatment also greatly improves the stability of the device. Results can be explained by the fact that anodic oxidation considerably reduces leakage current flowing via nonconfined silicon. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122355

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Hole trap levels in a Mg-doped GaN grown by metalorganic vapor phase epitaxy (MOVPE) are studied with deep level transient spectroscopy (DLTS). The Mg concentration of the sample was4.8×1019 cm−3,but the hole concentration was as low as1.3×1017 cm−3at room temperature. The DLTS spectrum has a dominant peakD1with activation energy of0.41±0.05 eV,accompanied by two additional peaks with activation energies of0.49±0.09 eV(D2)and0.59±0.05 eV(D3).It was found that the dominant peakD1consists of five peaks, each of which has different activation energy and capture cross section. A relevant model for these levels is presented in relation to the Mg–N–H complexes. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122356

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Low-energy ion scattering spectrometry (LEISS) and x-ray photoelectron spectroscopy (XPS) have been employed to quantifyin situthe near-surface composition of strainedSi1−xGexepitaxial thin films grown on Si(100) substrates usingGeH4andSi2H6as sources. The use of LEISS reveals the Ge concentration in essentially the first monolayer, whereas XPS is sensitive to several monolayers. We find that the extent of Ge surface segregation implied by each technique follows the trend:LEISS-Ge&percent;≫XPS-Ge&percent;≫bulk-Ge&percent;.A two-site model (involving surface and bulk states) cannot account for both the XPS and LEISS results, rather a model invoking Ge enrichment in the subsurface layers is required to explain the data. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122357

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have studied the formation of Cu clusters from Cu atoms deposited onto a Si (111) surface patterned with (2–5 &mgr;m width) lines of photoresist. In addition to a thin Cu layer on the exposed Si surface, large (∼150 nm) clusters nucleate at the boundary between the Si and the resist strips, which remain after removal of the resist by dissolution. The results show how it is possible, using the resist to collect deposited atoms, to assemble nanoscale cluster structures with a precision (∼150 nm feature size) which is much better than the resolution of conventional optical lithography (∼&mgr;m linewidth). ©1998 American Institute of Physics.&hthinsp;

ISSN:0003-6951    

DOI:10.1063/1.122358

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Lattice-matchedn-nZnSe/In0.04Ga0.96Asheterojunctions were studied by means of current densityversusvoltage (J–V) and capacitanceversusvoltage (C–V) measurements. The resulting characteristics indicate that the behavior of thisn-nheterostructure can be explained by a back-to-back double Schottky diode model. The value of conduction band discontinuity(&Dgr;Ec)is found to be 0.10–0.12 eV. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122560

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report mechanical detection of ferromagnetic resonance (FMR) signals from microscopic Co single layer thin films using a magnetic resonance force microscope (MRFM). Variations in the magnetic anisotropy field and the inhomogeneity of were clearly observed in the FMR spectra of microscopic Co thin films 500 and 1000 Å thick and∼40×200 &mgr;m2in lateral extent. This demonstrates the important potential that MRFM detection of FMR holds for microscopic characterization of spatial distribution of magnetic properties in magnetic layered materials and devices. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122359

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Ac conductivity measurements were carried out on polycrystalline samples of a ferrimagnetic spinel(Zn0.44Mn0.56Fe2O4)and a ferroelectric perovskite(Sr0.25Bi4Ti3.25O12.75),in the temperature range 20–160 and 20–660 °C, respectively, and in the frequency range 5 Hz–13 MHz. The impedance response in both cases could be resolved into two contributions, associated with the bulk (grains) and the grain boundaries. An analysis by means of the ac conductivity power law showed evidence of a critical temperature of 132 and 536 °C, for the ferrimagnetic and the ferroelectric samples, respectively, which corresponds to the Curie temperature for each type of material. These results are interpreted in terms of the disorder increase approaching the phase transition. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122360

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using microdiffraction techniques at the Advanced Photon Source, we have found evidence for local molecular alignment within the mesoscopic fibers of DNA–cationic membrane complexes, a system originally conceived as gene delivery vectors. Furthermore, these mesoscopic structures can be manipulated by using lithographically patterned microchannel arrays, so that the optical axes of individual fibers are aligned parallel to the channels. These observations suggest that DNA–membrane complexes may have additional technological applications, such as active electrophoretic media and templates for the fabrication of semiconductor superlattices and nanoporous materials with tunable pore sizes. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122361

出版商:AIP    

年代:1998

数据来源: AIP