摘要:

Characteristics of a phosphorus liquid‐metal ion source (LMIS) for use in focused ion beam systems was investigated because of its potential as ann‐type dopant for integrated circuit device fabrication. A continuous lifetime of more than 33 h was recorded as a part of the source stability measurement. Short‐term stability measurements indicated a very stable beam emission during its operation. Three different emitter tip radii of 2.5, 5.0, and 10 &mgr;m were selected to examine phosphorus beam emission characteristics. Mass spectrum measurements were used to examine phosphorus ion content and beam stability by repeat scanning. Steep current‐voltage characteristics were observed for 5.0‐ and 10‐&mgr;m emitter tip radii. The beam purity was characterized with Auger electron spectroscopy and a scanning electron microprobe by analysis of the deposited beam on a flat silicon substrate. Microstructure analysis by optical metallography indicated no liquid‐metal corrosion on the emitter tip. A thorough analysis was carried out on beam purity and metallurgical aspects of LMIS in order to develop a more reliable phosphorus liquid‐metal ion source.

ISSN:0021-8979    

DOI:10.1063/1.340099

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Channeled-substrate buried heterostructure (CSBH) lasers which were purged from populations undergoing high reliability qualification have been studied in detail. Gradual and rapid degradation mechanisms leading to accelerated aging failure modes have been analyzed by transmission electron microscopy, convergent beam electron diffraction, electroluminescence, energy dispersive x-ray analysis, and chemical etching. The gradual degradation mode of CSBH lasers is characterized by (1) a gradual increase in room-temperature threshold current; (2) a decrease in external quantum efficiency, typically a drop in peak value ofdL/dIgreater than 25%; (3) a drop in forward voltage at low current, indicating a change in junction characteristics; (4) a large peak inI(dV/dI) below threshold (at around 3 mA); and (5) an enhancement in the peak inI2(d2V/dI2) at laser threshold. A defect mechanism associated with the gradual degradation begins with a nucleation of extrinsic dislocation loops along the V-groove {111}p-n–type sidewall interfaces between the Cd-diffusedp-InP and liquid-phase-epitaxial-grownn-InP buffer inside the groove. These dislocation loops subsequently grow out of the interfaces into then-InP buffer region in the direction of minority-carrier injection, indicating a nonradiative recombination-assisted defect growth process. For those loops which enter the quaternary active region near the tip of the active crescent, the growth rate along the (001) and (010) planes is greatly enhanced and the loops eventually cut across the active stripe and become dark-line defects, as confirmed by electroluminescence. Nucleation of dislocation loops is not observed along the {111}p-p–type sidewall interfaces above the active stripe. The fact that the dislocation loops are all extrinsic in nature implies that the {111} sidewall interfaces as well as the quaternary active region contain a high density of interstitials. The possible causes for the generation and growth of the dislocation loops and the high density of point defects are discussed. The rapid degradation mode of the CSBH laser is characterized by a sudden drop in light intensity during the aging process. The associated defect mechanism starts with localized melting at the mirror facet or inside the lasing cavity. A metal-rich droplet subsequently forms which propagates along the center of the active stripe in the direction towards the cavity center via a meltback-regrowth process; i.e., material melts in front of the droplet and regrows after it propagates by. The nonideal condition of regrowth results in the formation of a wormlike defect composed of a cylinder of defective materials bounded by an off-stoichiometric interface. The wormlike defect is dark under electroluminescence. Complicated dislocation structures can also be grown from the wormlike defect under a nonradiative recombination-assisted defect growth process. These phenomena are presented and discussed.

ISSN:0021-8979    

DOI:10.1063/1.340100

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We theoretically analyze a two‐wave mixing interaction in photorefractive Bi12SiO20crystals in which the amplitude of the signal beam is time modulated at high frequency. Calculations of the photoinduced space‐charge field are derived for a sinusoidal modulation of the input signal. Due to the time‐integrating properties of the nonlinear crystal, the transmitted signal exhibits a differential gain when the modulating frequency is much greater than the inverse of the material response time. Application to coherent homodyne detection of wave fronts carrying spatial and temporal information is also presented.

ISSN:0021-8979    

DOI:10.1063/1.340101

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Losses and near and far field intensity distributions of unstable resonators with equivalent Fresnel numbers in the range up to three have been investigated both experimentally and theoretically. The losses were determined absolutely using a new method for loss measurement. Intensity distributions of lowest loss modes were recorded by means of an image‐processing system and compared to numerical solutions of Kirchhoff ’s integral equation of the empty cavity. The experiments were performed with a pulsed Nd‐YAG system.

ISSN:0021-8979    

DOI:10.1063/1.340102

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A detailed experimental analysis of Ag+‐Na+ion exchange in glass using Ag films as ion sources for the fabrication of planar optical waveguides has been performed. The refractive index profiles of the waveguides have been measured and compared to the theoretical Ag+concentration profiles. The theoretically predicted special characteristics of the process are verified and the material parameters of the used substrate glass (Corning 0211) are evaluated.

ISSN:0021-8979    

DOI:10.1063/1.340103

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A novel photoacoustic measurement technique is introduced, which is based on the phase perturbation of an external acoustic wave that propagates through a region of material irradiated by an optical beam. The mechanism of the perturbation is the local change in acoustic velocity due to heating of the irradiated sample. Because the acoustic phase perturbation may be calibrated directly, it is found that the absolute optical absorption coefficient of the irradiated sample may be determined using the technique. Both the experimental phase detection system and a theoretical analysis of the acoustic perturbation are discussed. Finally, an experiment is described in detail, where the measurement technique is used to determine the absolute optical absorption coefficient of a liquid.

ISSN:0021-8979    

DOI:10.1063/1.340104

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report on an investigation of the optogalvanic effect in the cathodic region of a glow discharge. Analysis of the spatial behavior of the fluorescence intensity enabled us to obtain detailed information on the laser‐unperturbed discharge. A description of the discharge maintenance mechanisms through the secondary electron emission from the cathodic surface by the impact of ions, metastable atoms, and VUV photons has been used to describe the current‐voltage tube discharge characteristics. The laser‐induced perturbation of the secondary emission has been understood as the main mechanism responsible for optogalvanic production in our discharge configuration.

ISSN:0021-8979    

DOI:10.1063/1.340052

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An approach to determination of populations of the excited lithiumlike ions C iv, N v, O vi, and Ne viiiin stationary nonequilibrium plasmas is presented. Each of these ions produces several dipole‐allowed spectral lines so that the number of the available line intensity ratios is large. Consequently, the electron density and temperature can be determined by comparing some of the measured intensity ratios with their calculated values. The populations of several ionic levels, electronic partition functions, and the intensity ratios for 3 2D→2 2P/2 2P→2 2S, 3 2P→2 2S/2 2P→2 2S, 3 2S→2 2P/2 2P→2 2S, 3 2D→2 2P/3 2P→2 2S, 3 2D→2 2P/3 2S→2 2S→2 2P, and 3 2P→2 2S/3 2S→2 2Ptransitions are calculated in a broad range of electron density and temperature. The approach is especially useful for diagnostics of systems where nonintrusive spectroscopic techniques must be used (e.g., astrophysical and fusion plasmas).

ISSN:0021-8979    

DOI:10.1063/1.340053

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The Townsend model of electric breakdown in gases is considered for the case in which the field along the breakdown path may vary in an arbitrary way, corresponding to arbitrary electrode configuration. The common approximations are made that the first Townsend ionization coefficient &agr; depends only on the field, and the second coefficient &ggr; is a constant. It is also assumed that the dependence of &agr; on field is such that the Stoletow constants are uniquely determined. This assumption is satisfied by a number of semiempirical approximations to &agr; that have been suggested. It can then be shown that the breakdown voltage, regardless of electrode configuration, cannot be less than that which obtains for planar electrodes.

ISSN:0021-8979    

DOI:10.1063/1.340054

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The gases released by surface flashovers on alumina ceramics, glass, and quartz, using 20‐&mgr;s voltage pulses, were investigated using an ion‐pumped metal vacuum system. Appreciable quantities of gas were measured (approximately 10−6Torr liter or 1013molecules). The composition of this gas differed significantly from the background gas. The dominant species in the surface flashover gases were CO2, CO, and H2; a modest amount of CH4was observed, along with lesser quantities of N2and H2O. The dominant gas in the system background was nitrogen, accompanied by (in decreasing amounts) H2, H2O, CO/CO2, Ar, CH4, and He. We concluded that the gas released by flashovers on the surface of the insulators was not adsorbed system background gas, but was gas adsorbed during the handling and processing of the insulator.

ISSN:0021-8979    

DOI:10.1063/1.340055

出版商:AIP    

年代:1988

数据来源: AIP