摘要:

The dynamics of nanoparticle formation, transport, and deposition by pulsed laser ablation ofc-Siinto 1–10 Torr He and Ar gases are revealed by imaging laser-induced photoluminescence and Rayleigh-scattered light from gas-suspended 1–10 nmSiOxparticles. Two sets of dynamic phenomena are presented for times up to 15 s after KrF-laser ablation. Ablation of Si into heavier Ar results in a uniform, stationary plume of nanoparticles, while Si ablation into lighter He results in a turbulent ring of particles which propagates forward at 10 m/s. Nanoparticles unambiguously formed in the gas phase were collected on transmission electron microscope grids forZ-contrast imaging and electron energy loss spectroscopy analysis. The effects of gas flow on nanoparticle formation, photoluminescence, and collection are described. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121516

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The optical properties of homoepitaxial GaN layers deposited by organometallic vapor phase epitaxy on stripe-patterned GaN films on 6H-SiC substrates have been investigated. Analysis of the spatially-resolved Raman scattering spectra indicate an improvement in material quality of the overgrown region. Room-temperature color cathodoluminescence imaging and low-temperature photoluminescence measurements indicate that a donor and an acceptor, different from those detected in the underlying GaN/AlN/SiC substrate, have been incorporated in the epitaxial layer. Detailed photoluminescence studies of the near-band-edge emission strongly suggest that Si is the additional donor detected in the homoepitaxial GaN layer. Its occurrence, along with that of an acceptor-related defect which is primarily found in the laterally overgrown region, is discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121517

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Real time spectroellipsometry and a two-layer optical analysis have been applied to obtain alloy composition(x)and optical gap(Eg)depth profiles with ∼3 Å resolution and sensitivities better than ±0.01 inxand ±0.02 eV inEgfor graded amorphous semiconductor alloy thin films prepared by plasma-enhanced chemical vapor deposition. Graded amorphous silicon–carbon alloy(a-Si1−xCx:H)layers incorporated at thei–pinterfaces ofa-Si:Hn-i-psolar cells have been studied using these methods, and the layer characteristics have been related to improvements in solar cell performance. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121518

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Ion-assisted deposition is suitable for the formation of epitaxial Si films at high deposition rate and low substrate temperature. We demonstrate epitaxial deposition of Si films on (100)-oriented Si wafers using deposition rates up to 0.3 &mgr;m/min at deposition temperatures in the range of 500–650 °C. Hall-effect measurements show a majority carrier mobility of200 cm2/V sat a hole concentration of1.4×1017 cm−3in our films. A minority carrier diffusion length of 4.5 &mgr;m is determined from quantum efficiency measurements in the epitaxially grown Si films. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121519

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The areal densities of oxygen and nitrogen incorporated into ultrathin films of silicon dioxide during rapid thermal processing in nitric oxide, as well as the regions where these incorporations took place, were determined by combining nuclear reaction analysis and narrow nuclear resonance depth profiling with isotopic enrichment of the processing gas. Oxygen is seen to incorporate in the near-surface and near-interface regions of the oxynitride films, whereas nitrogen is incorporated only in the near-interface regions. The growth of the oxynitride film is very moderate as compared to that of aSiO2film in dryO2.The thermal oxynitridation of ultrathinSiO2films takes place by two mechanisms in parallel: the major part of the NO molecules, which react with the silica, decompose in the near-surface region, the O atoms being exchanged for O atoms preexistent in this region of theSiO2films; a minor portion of the NO molecules diffuse through the silica film in interstitial sites, without reacting with it, to react at the oxynitride/Si interface. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121520

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Interference between single-photon and two-photon absorption is investigated theoretically to demonstrate coherent control of the emission of THz radiation from semiconductor double wells. Variation of the relative phase between the two concurrent pump pulses controls both the final density of photogenerated electron-hole pairs, predominantly excitons, and the intensity of microwave emission associated with coherent charge oscillations in the double well. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121521

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The effects of pore size distribution in porous glasses on the photoluminescence of nanosized Si clusters and of the humidity on the sample dimensions have been investigated. Increase of the pore size brings about the blueshift of the emission peak. In the spectra, geminate and distant components of the emission have been resolved. The humidity influences the dimensions of the samples due to the competing of chemical bonding forces and capillary forces. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121522

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Accelerator mass spectrometry (AMS) is now widely used in over 30 laboratories throughout the world to measure ratios of the abundances of long-lived radioisotopes such as10Be, 14C, 36Cl,and127Ito their stable isotopes at levels as low as10−16.Trace-element AMS (TEAMS) is an application of AMS to the measurement of very low levels of stable isotope impurities. Copper concentrations as low as 1 part per billion have been measured in silicon wafers. In this letter, we demonstrate the use of TEAMS to measure previously unknown copper concentration depth profiles in As-implanted Si wafers at a few parts per billion. To verify the TEAMS technique, the samples from the same wafer were measured with secondary ion mass spectrometry, which showed the same profiles, albeit plateauing out at a concentration level six times higher than the TEAMS measurement. The ability to measure at these levels is especially significant in light of the recent moves towards the use of copper interconnects in place of aluminum in integrated circuits. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121523

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The electrical activation of B in Si after ion implantation in the energy range between 5 and 160 keV and rapid thermal annealing processes is investigated. It is found that it critically depends on the purity of the substrate as well as the distance from the surface. In particular, while in very pure epitaxial Si layers (where O and C contents are below∼1×1015/cm3)typically the total B content is electrically active, in Czochralski Si (containing∼1×1018 O/cm3and∼1×1017 C/cm3)the active fraction is very small at doses of1×1012/cm2and increases with increasing dose. For very shallow B implants (∼5 keV), the electrical activation in Czochralski Si further decreases to a few percent of the total amount. These results are interpreted in terms of the formation of boron-impurity complexes deactivating the dopant, the dose effect being a result of trap saturation. Vacancies can eventually dissolve some of the inactive complexes. However, close to the surface an enhanced vacancy annihilation process reduces the dissolution probability producing the observed dramatic effects on the electrically active profiles. Finally, at very low energies (∼5 keV), also in epitaxial Si layers, part of the dopant can be electrically inactive due to B–B interactions, the process being negligible at low doses and increasing with dose. The implications of these results on the formation of ultrashallow junctions are discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121524

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report room temperature delamination of chemically vapor deposited diamond films on a Si substrate due to 1.5 MeVHe+ion bombardment. The delamination of films has been studied by scanning electron microscopy. The threshold fluence at which the delamination takes place has been determinedin situby monitoring the hydrogen signal with the help of elastic recoil detection analysis. Micro Raman measurements show the presence of residual stress (1.19 GPa) in the as-prepared films and its relaxation at the peripheri of the delaminated regions. It is proposed that enhancement of the residual stress duringHe+ion bombardment leads to stress saturation conditions which result in the delamination of the brittle diamond films from the film/substrate interface. These findings lead to the possibility of creating ion-beam induced channels in diamond films for device isolation by suitable choice of film/substrate combination. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121525

出版商:AIP    

年代:1998

数据来源: AIP