摘要:

Langmuir probe measurements of electron density and temperature are made in the plume of a dc arcjet reactor. A dc arc is struck in an argon or argon/hydrogen mixture at 6 atm pressure and expands through a converging/diverging nozzle into the reactor with a pressure of 25 Torr. Methane and methane/nitric oxide are added in the diverging nozzle, and diamond film grows on a substrate in the gas plume. Electron temperatures of 1–2 eV are significantly hotter than the neutral gas temperature in the plume. Electron densities range from 1010to 1013cm−3, well above the Saha equilibrium for the gas temperature and pressure and well below the equilibrium for the electron temperature. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363852

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The refractive index profile ofnaof ion-implanted potassium niobate (KNbO3) planar waveguides is evaluated for waveguides fabricated with ion energies between 2.0 and 3.5 MeV and doses between 7.5×1014cm−2and 3.0×1015cm−2. The measured mode index values are fitted to a quantitative model that correlates the index profile with the irradiation parameters. The reconstructed profile ofnais compared to the profiles ofnbandncwhich have been determined previously. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363853

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Nanocrystalline samples with grains in the range of 12–94 nm were synthesized via thermal crystallization of the amorphous alloy. High-resolution electron microscope observations show that the nanocrystalline Ni33Zr67sample is composed of many “orientation regions.’’ Each orientation region consists of a high density of well-defined microtwin domains. Positron annihilation spectroscopy reveals that two types of defects are present in the Ni33Zr67samples. With the increase of annealing temperature up to 973 K, the two types of defects show remarkable change while microhardness changes slightly. The contributions of the microtwin domain and the nature of constituent phases to microhardness in the present alloy system are discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363984

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Preferential alignment is produced for the NL8 thermal double donors (TDDs) when uniaxial stress is applied during their formation at∼450 °C. The recovery kinetics reveal that they can reorient readily on the time scale of their lifetime and their individual alignments therefore reflect the strain fields that each introduces into the lattice. Analysis reveals that each of the donor cores produces large compressional strain along its C2v[001]′axis, the magnitude of which decreases monotonically with increase in the TDD species series, suggesting strain relief as the mechanism for nearby oxygen accumulation. The rate and activation energy for the reorientation suggests that the process is limited by the diffusion motion of the nearby interstitial oxygen atoms, with∼5 jumps being required for TDD3, the third in the series, and progressively more for the subsequent ones. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363854

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Proton irradiation damage of InPn+-pspace solar cells has been examined over a wide range of energy (0.015–10 MeV) and at high fluence (∼1013cm−2). Although the usual red spectral response degradation of InP cells has been observed under lower fluence proton irradiation, radiation testing has revealed an anomalous spectral response in the blue part of the spectrum. We propose a model to explain this phenomenon by considering conductivity-type conversion fromp-InP inton-InP in a defect-induced region, determined by the proton range, of thep-InP base layer due to high fluence proton irradiation. This is confirmed by measurements of conductivity-type conversion ofp-InP crystals by high fluence (⩾1016cm−2) 1 MeV electron irradiation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363855

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The lattice parameter of undoped and boron doped polycrystalline diamond films has been measured up to 8×1020B cm−3. It varies slightly according to the three crystallographic directions [111], [220], and [311] investigated here. The cell parameters for the undoped films are within the published values for synthetic crystal and thin films. For the boron doped films, the cell parameter has a high expansion coefficient versus boron incorporation, with a mean value of&Dgr;a/a=3×10−24[B], ([B] in cm−3), and a variation law in the [220] direction in striking agreement with a Russian work. The simplest Vegard model predicts a smaller variation, while both the deformation potential (but with a high deformation potential on the boron impurity band of +19.5 eV) and a defect model might explain the experimental results. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363856

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The microstructure of 5 MeV ion implanted silicon at room temperature has been investigated in detail by means of cross-sectional transmission electron microscopy. Buried amorphous layers were observed in the specimens obtained by ion doses of 1×1017and 2×1017/cm2with abrupt amorphous-to-crystal interfaces. Damaged layers adjacent to the amorphous layers included many dislocation loops and the concentration increased toward the amorphous region. Microdiffraction patterns and high-resolution images showed that this damaged region is defective crystalline silicon, suggesting that homogeneous amorphization occurs due to an accumulation of defects. The atomistic structure of the damaged regions was analyzed by comparing high-resolution electron microscopy images with those calculated on the basis of a model for amorphization processes proposed previously [T. Motooka, Phys. Rev. B49, 16 367 (1994)]. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363857

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The total concentration of ionized impurities in silicon implanted GaAs was estimated from carrier concentration and mobility values obtained by Hall effect measurements together with published compensations. We have demonstrated that the calculated profiles(ND++NA−)are in good agreement with that of the silicon atomic distributions obtained by secondary-ion-mass spectroscopy. We have observed that a large concentration of gallium vacancies are injected into the sample during a 900 °C anneal for 1000 s using a Si3N4cap. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363858

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The reorientation behavior of nematic liquid crystal molecules induced by an electric pulsed field was investigated by means of time-resolved optical waveguide spectroscopy (TROWS) which was developed to observe transient changes in dielectric constants and to measure the thickness of a thin dielectric medium. Time evolution of the waveguide mode patterns was successfully obtained by using TROWS, which records the reflectivity as both functions of the incident angle of laser light and the time from switching-on or -off of the external electric field. The transient dielectric tensor profile in the 4′-pentyl-4-cyanobiphenyl (5CB) layer both after switching-on and -off of the electric field could be precisely determined in a three-dimensional coordinate system by using Deuling’s theory which treats the orientational deformation induced by an external electric field. Theoretical analysis of TROWS data clearly indicated that half of the 5CB molecules rotate clockwise in the plane defined by the rubbing direction and the substrate normal, and the other half rotates counter-clockwise in the same plane. The counter rotation compensates the effect of birefringence observed in the direction parallel and perpendicular to the rubbing direction and the reorientation kinetics could be well described by the Ericksen–Leslie equation. Relaxation behavior from homeotropic to planar orientation could be treated as an orientation diffusion process by applying a Gaussian distribution function to the maximum tilting angle at the middle of the cell. We report the usefulness of TROWS which provided more detailed information about the dynamics of the 5CB molecules. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363859

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The nature of amorphization and crystallization of Si brought about by 50 keV Zn ion implantation within the dose range 2×1017–1×1018cm−2is studied. The structures are evaluated in the as-implanted state by transmission electron microscopy, transmission electron diffraction, reflection high-energy electron diffraction, selected-area electron diffraction, x-ray energy-dispersive analysis, and Rutherford backscattering spectrometry. It is found that, contrary to the theoretical predictions, the Zn concentration profile does not reach saturation even at a dose as high as 1×1018cm−2. A common feature of the microstructure of these high-dose implants is the formation of a continuous amorphous layer and concurrent crystallization of Zn and Si in small crystalline clusters. Microscopic beam-heating effects are also believed to play an appreciable role in the development of the specific morphologies observed. The results are interpreted in terms of two recent models proposed in the literature and the concept of critical dose ranges. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363904

出版商:AIP    

年代:1997

数据来源: AIP