摘要:

Raman spectroscopy is found to be a powerful tool to determine the structural phase boundary between cubic (Fm3m) and tetragonal (P42/nmc) phase in arc‐melted Zr1−XYXO2−X/2(0.08≤X≤0.24) solid solution. The Raman peak intensity characteristic of the tetragonal phase at about 470 cm−1decreases with the YO1.5contentXand becomes 0 aroundX=0.18.  

ISSN:0021-8979    

DOI:10.1063/1.354989

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A scheme is presented for producing a high gain recombination x‐ray laser in hydrogen like oxygen by irradiating 7‐&mgr;m‐diam fiber targets with picosecond high‐power laser pulses. The lasing gain coefficient for the O viiiBalmer &agr; transition at 10.2 nm is predicted to be over 100 cm−1. The optimized electron density and temperature are 8.8×1019cm−3and 22 eV, respectively, at the time when the lasing gain reaches its maximum. Significant improvement in gain performance of recombination x‐ray lasers is indicated for picosecond pulse drivers, which might be a route towards saturated recombination x‐ray layers.

ISSN:0021-8979    

DOI:10.1063/1.355280

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The alternate capture and emission of electrons at an individual defect site generates discrete switching in resistance, referred to as a random telegraph signal (RTS). Recent experiments indicate that some defects might have two mutually exclusive emission modes with distinct emission rates, which result in the anomalous RTS: a rapid‐switching RTS modulated in time by a slow‐switching RTS of the same amplitude. The spectrum is calculated of the anomalous RTS by assuming that the emission mode for a captured electron is determined at the moment of capture of the electron, and the probability for a given mode is a constantpin each event of capturing. It is shown that a distribution inpmight lead to a 1/fspectrum.

ISSN:0021-8979    

DOI:10.1063/1.354962

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

SiC diode operating at high avalanche breakdown current has been fabricated. The 6H‐SiCp‐nstructure was grown by liquid phase epitaxy. The diodes displayed avalanche breakdown at ∼80 V. The breakdown current density of 60 kA/cm2and the input power density of 9 MW/cm2were achieved at a current pulse duration of 60 ns. For the first time, the temperature coefficient of avalanche breakdown voltage of SiCpnjunction was studied at high current density. It was found that the avalanche breakdown voltage of the diodes decreases with temperature from 300 to 750 K and increases from 750 to 900 K.

ISSN:0021-8979    

DOI:10.1063/1.354963

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Porous Si (PS) layers are prepared by stain etching in a HF/NaNO2solution on bothp‐ andn‐type crystal Si substrates, and are characterized by photoluminescence (PL), electron paramagnetic resonance (EPR), and infrared absorption (IR) spectroscopy. The PL spectra under 488 nm laser excitation exhibit a strong peak at 680–720 nm for various samples of different substrate parameters and remain stable upon aging in air or &ggr; irradiation; as‐etched (∼20 min in air before measurement) and aged (for up to six months) samples show no detectable EPR signal but the &ggr;‐irradiated samples show an isotropicg=2.006 signal of peak‐to‐peak linewidth of 1.1 mT supporting an amorphous Si structure; the IR spectra show both hydrogen and oxygen related IR modes in the as‐etched samples and the former decreases with aging time in air while the latter increases. Comparing our results with those of anodically etched PS samples we conclude that: (1) the PL peak position of the stain PS seems to be unique and stable as compared with that of the anodic PS varying in 620–830 nm; (2) the isotropic EPR signal of the stain PS reflects no crystallinity, in contrast with the anisotropic signal of the anodic PS; and (3) obvious oxidation in the as‐etched stain PS is also in contrast with the nonobservation of oxygen‐related IR modes in the as‐etched anodic PS. We discuss the results in terms of structural properties and PL mechanism of PS.

ISSN:0021-8979    

DOI:10.1063/1.354940

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We report on a modified Kroemer’s analysis [Appl. Phys. Lett.36, 295 (1980)] for the determination of the band offset &Dgr;Ecof a single quantum well from a carrier profile obtained by capacitance‐voltage measurement. The procedure is applied to a pseudomorphic GaAs/InGaAs/GaAs strained layer structure.

ISSN:0021-8979    

DOI:10.1063/1.354941

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The temperature characteristics of 1.3 &mgr;m InGaAsP/InP buried heterojunction lasers are investigated using a fully self‐consistent two dimensional numerical model. Devices operating at 1.3 &mgr;m are very temperature sensitive and therefore the model includes for the first time coupled solutions to the thermal as well as the electrical and optical equation sets. Good agreement is found with experimental results, including the temperature dependence of the threshold current and the prediction of a break‐point temperature.

ISSN:0021-8979    

DOI:10.1063/1.354942

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The binding energies of hydrogenic donor in both finite and infinite GaAs‐(Ga,Al)As spherical quantum dots are calculated as a function of the donor position for different radii within the effective‐mass approximation. It is observed an enhancement of the binding energy of donors in quantum dots when compared to results in quantum wells and quantum‐well wires, which is an expected consequence of the higher geometrical electronic confinement in these systems. The density of impurity states as a function of the donor binding energy was also calculated. As a general feature it presents structures associated with special impurity positions that may be important in the understanding of the absorption and photoluminescence experiments of doped quantum dots.

ISSN:0021-8979    

DOI:10.1063/1.354943

出版商:AIP    

年代:1993

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.355348

出版商:AIP    

年代:1993

数据来源: AIP