摘要:

A scheme for the production of a thin layer of dense lithium plasma is outlined, and the results of a proof‐of‐principle experiment are presented. Our objective is to produce a thin layer of lithium plasma for the anode plasma of an intense ion beam diode, such as the one being designed for inertial confinement fusion experiments with the Particle Beam Fusion Accelerator II. Minimum requirements for the lithium anode plasma density, thickness, and purity are developed. Production of a lithium vapor layer by pulsed evaporation, and plasma formation by laser ionization based on resonant saturation (LIBORS) of the vapor are described. Lithium was evaporated, by ohmic heating with a two step capacitor discharge, from a thin layer of lithium silver alloy deposited on a tantalum foil. A two‐photon pumped fluoresence technique was developed and used to characterize the density and thickness of the vapor layer. A peak vapor density near 1×1016cm−3with a thickness of a few millimeters was observed. The electron density of the final plasma was inferred from broadening of the 460.3 nm lithium line, and agreed with the lithium neutral density within experimental uncertainty, for several different lithium densities.

ISSN:0021-8979    

DOI:10.1063/1.336693

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This paper addresses problems associated with thermal annealing andn‐type andp‐type doping in CuInS2. The results of incorporating impurities like Zn and P in CuInS2single crystals by different methods are reported. Some evidence has been provided to explain the formation of precipitates being the limiting factor to exhibit the shallow acceptor property. The electron beam annealing of phosphorus‐implanted CuInS2has been shown for the first time to be an effective way forp‐type conductivity control by extrinsic impurities in any I‐III‐VI2ternary chalcopyrite.

ISSN:0021-8979    

DOI:10.1063/1.336694

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Experiments ona‐Si prepared by vapor deposition or ion bombardment exhibit anomalies which are most readily explained not by a continuous random network but by arrays of morphologically oriented paracrystalline clusters with 3% unreconstructed surface atoms. The effects of hydrogenation on the cluster dimensions are small compared to the effects of deposition or annealing temperature. Substantial morphological reorientation can be induced either by substrate‐driven strain or by thermal annealing. Further experiments to study cluster morphological transitions are proposed.

ISSN:0021-8979    

DOI:10.1063/1.336640

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Ion beam induced atomic mixing at Fe‐Mo interface has been studied by using the technique of conversion electron Mo¨ssbauer spectroscopy (CEMS). Use has been made of a thin (∼50 A˚) layer of Fe57isotope (enriched to 95.4%) at the interface to obtain the Mo¨ssbauer information selectively from this region. A noninterface sensitive measurement has also been performed to reveal the magnetic hyperfine interactions in the entire region of the iron overlayer. It is shown that a deposition induced reaction between the molybdenum substrate (having a thin coating of native oxide) and the Fe57layer renders a graded nature to the interface, which is transformed upon ion bombardment (100‐keV Kr+, dose ∼1016ions/cm2) into a disordered alloy. The dominant nonmagnetic component corresponding to the interface of the ion beam mixed sample happens to be a quadrupole doublet, which represents the presence of Fe57atoms in Fe2+charge state. The appearance of this contribution is attributed to formation of an oxygen coordinated ternary compound in the interface layer during ion bombardment. On the basis of the comparison of the results of the interface‐sensitive and non‐interface‐sensitive studies it is established that the inclusion of oxygen in the ion mixed sample is mainly confined to the near interface region and that the region of the overlayer contains a metastable alloy of the binary Fe‐Mo system. The influence of thermal annealing at various temperatures between 200 °C and 500 °C on the ion beam mixed state has also been studied by monitoring the changes in the hyperfine interaction parameters. It is shown that the oxygen‐incorporated regions of the disordered alloy retain the nonmagnetic Fe2+charge state subsequent to annealing at 500 °C, while other regions lead to precipitation of &agr;‐Fe and Fe2Mo phases.

ISSN:0021-8979    

DOI:10.1063/1.336641

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Undoped Ga0.5In0.5P has been successfully grown by organometallic vapor‐phase epitaxy on GaAs substrates with a free‐electron concentration of 1016cm−3and a mobility of 1050 cm2/V s in nominally undoped material. The distribution coefficient of indium in the growth of Ga0.5In0.5P is nearly to unity. Bothn‐ andp‐type carrier concentrations of up to 1019cm−3have been obtained in the present study. Diethyltelluride and silane are used asn‐type dopants. Dimethylzinc is used as thep‐type dopant. Te is a very efficient dopant with a distribution coefficientkTe=54. The photoluminescence (PL) intensity increases with Te doping level to a maximum atn=2×1018cm−3. The silicon distribution coefficient is temperature dependent, due to the incomplete pyrolysis of silane at the growth temperature. Si‐doped Ga0.5In0.5P has a lower PL efficiency than Te‐doped samples and is not strongly correlated with carrier concentration. The incorporation efficiency of Zn is low, withkZn=3.8×10−3, due to the high vapor pressure of Zn at the growth temperature. The PL intensity of Zn‐doped Ga0.5In0.5P also increases with Zn doping level to a maximum atp=2×1018cm−3and is comparable to the optimum Te‐dopedn‐type Ga0.5In0.5P. Only a single band‐edge PL peak is observed in all cases.

ISSN:0021-8979    

DOI:10.1063/1.336642

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The standard discrete atomic jump model of the relaxation of point defect‐solute pairs is augmented by a dynamic continuum model reflecting the effect of the surroundings of the complex. Effective‐medium theory is used to derive the response characteristics of this continuum. In this way the effect of dissociation and association of solute‐defect pairs on the anelastic behavior of a solid is described quantitatively. The model leads to the prediction of an additional very low‐frequency internal friction peak when experiments are carried out at fixed temperature. The relaxation is identified with the ‘‘reaction mode’’ discussed earlier by Nowick. It is investigated in some detail for doped oxide materials. However, the emphasis here is directed less towards extensive comparison with experiment than towards an exposition of the new methodology. For this reason only nearest‐neighbor binding between defect and solute is considered and only the trigonal pair in cubic materials is analyzed. However, the generalizations that are necessary in order to remove these restrictions are described.

ISSN:0021-8979    

DOI:10.1063/1.336643

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Thermal time constants of semiconductor lasers (‘‘test lasers’’) are measured by transient heating of test laser chips by use of another laser (‘‘pump laser’’). Pump laser emission impinging on the test laserpcontact generates local heating. Thus, current‐independent thermal responses are studied. Thermal time constants of 5.6 and 7.2  &mgr;s are measured and tend to confirm heat diffusion as the mechanism governing transient laser thermal behavior for times in the several microsecond range.

ISSN:0021-8979    

DOI:10.1063/1.336644

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The photochemical properties of Mo(CO)6adsorbed on Si(100) were investigated using temperature programmed desorption (TPD) and Auger spectroscopy. TPD experiments indicate that Mo(CO)6physisorbs on silicon and desorbs at 210–230 K. At 150 K, KrF laser radiation (248 nm) partially decomposes the adsorbed Mo(CO)6releasing gas‐phase CO in the process and TPD experiments after irradiation show that additional CO desorbs at 335 K. However, Auger analysis indicates that one CO molecule per molybdenum atom dissociates, leaving the molybdenum overlayer heavily contaminated with carbon and oxygen. The cross section for photodecomposition was measured to be 5±3×10−17cm2. Decomposition of the excited molecule must compete strongly with energy relaxation to account for the magnitude of this cross section.

ISSN:0021-8979    

DOI:10.1063/1.336645

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Electrical and microstructural changes of coevaporated Ir50Si50have been studied as a function of temperature from room temperature to 970 °C.Insituresistivity measurements,insituannealing and transmission electron microscopy, Rutherford backscattering spectroscopy and Seeman–Bohlin glancing angle incidence x‐ray diffraction were applied. In the as‐deposited state the alloy film is amorphous and exhibits semiconducting behavior. A two‐stage phase transformation occurs in the process of heating. The first transition from amorphous to crystalline IrSi is nucleation controlled. It is accompanied by an abrupt decrease in resistivity and was found to be dependent on the heating rate and chemical composition. The second crystalline‐to‐crystalline transformation is controlled by nonstoichiometry of the alloy film. An excess of Ir atoms leads to formation of Ir2Si at ∼640 °C while an excess of Si atoms leads to formation of IrSi3at ∼710 °C. The second transition is independent of the heating rate. The formation of both Ir2Si and IrSi3decreases the electrical resistivity. The isothermal transformation from amorphous to crystalline structure follows a sigmoidal function. The apparent activation energy of this process is about 1.32 eV. The kinetic behavior implies random nucleation and interface‐controlled two‐dimensional growth of the crystalline phase.

ISSN:0021-8979    

DOI:10.1063/1.336646

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Formation of a surface layer was studied in pure yttrium iron garnet (YIG) by annealing in H2atmosphere at temperatures above 450 °C. Double‐crystal x‐ray diffraction from the surface layer shows interference fringes in analogy with the ion‐implantation case. From an analysis of the fringes based on the kinematical theory, the strain profile was determined. It appears that the surface layer has a well‐defined negative lattice mismatch with respect to the underlying film bulk, and that a transition region exists with a decreasing absolute value of mismatch. Analogies and differences with respect to the ion implantation are pointed out.

ISSN:0021-8979    

DOI:10.1063/1.336647

出版商:AIP    

年代:1986

数据来源: AIP