摘要:

The reactions of Co‐Mo, Co‐Ta, and Ni‐Ta amorphous films with Si substrates and Al overlayers were analyzed by a combination of backscattering spectrometry, transmission electron microscopy, and x‐ray diffraction measurements. When the alloy is in contact with Si, the reaction temperature lies between 550 and 650 °C and phase separation is generally observed with near noble silicides formed next to the Si substrate and refractory silicides formed on the surface. When the alloy is in contact with Al, the reaction occurs at temperatures of ∼450 °C with a two‐layer structure in the final product. The crystallization temperature of an amorphous alloy is generally higher than its reaction temperature and there is no correlation between the two parameters. The reaction takes place when the annealing temperature reaches the value at which compounds can be formed with both constituents of the alloy.

ISSN:0021-8979    

DOI:10.1063/1.336343

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This work outlines an optimized seed selection through ion channeling (SSIC) process for enhancing the grain size and {110} texture of polycrystalline Si films grown by low‐pressure chemical vapor deposition on SiO2. These films, 0.44 &mgr;m thick, were self‐implanted at normal incidence to various doses (1–20 × 1014cm−2) and subsequently recrystallized at 600 °C. An enhanced average grain diameter resulted after implantation and annealing, ranging from 0.10 to 2.0 &mgr;m (versus the as‐deposited 0.080 &mgr;m) and increasing with the implant dose. The grain size versus implant dose behavior may be explained by a previously proposed stochastic model. An enhanced {110} texture was also observed after processing for implant doses of 6–14 ×1014cm−2. The optimal dose was 11 × 1014cm−2, for which the {220} diffracted x‐ray intensity was 30 times the as‐deposited value, and the ⟨110⟩ directions were confined to within ±4° (versus the as‐deposited ±20°) of the surface normal. This experiment demonstrates the effectiveness of SSIC in growing strong {110}‐textured polycrystalline Si films on amorphous insulators.

ISSN:0021-8979    

DOI:10.1063/1.336344

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Phase transformations in coevaporated amorphous vanadium‐silicon thin alloy films and bilayer vandium/silicon films have been studied as a function of heat treatment byinsituelectrical resistivity measurement together with Rutherford backscattering spectrometry, Seeman–Bohlin glancing angle incidence x‐ray diffraction, and scanning and transmission electron microscopy. In the as‐deposited state the amorphous alloy films were silicon rich, having an atomic ratio of 1:3 for vanadium and silicon, respectively. Upon heat treatment a sharp decrease in resistivity occurs at approximately 250 °C, which has been determined to be a transformation from the amorphous to crystalline VSi2phase. The kinetics of the transformation have been obtained by isothermal treatment over the temperature range of 184–220 °C. The transformation is described by a Johnson–Mehl–Avrami‐type equation with an apparent activation energy of 1.30±0.06 eV. Subsequent heat treatment causes a gradual decrease in resistivity up to 850 °C. Upon cooling, a monotonic decrease in resistivity was observed. Heat treatment at high temperatures (900 °C) promotes the growth of nonuniformly distributed silicon grains. For the bilayer vanadium/silicon films, the sheet resistance increases gradually upon heat treatment up to 500 °C, then a sharp decrease is observed, which is due to the formation of VSi2. Further heat treatment at higher temperatures (850 °C) promotes a monotonical decrease in the resistance. The cooling behavior is similar to that of the crystallized alloy specimens except for having a slightly lower resistivity value. In a model for the two thin films connected electrically in parallel, the growth kinetics of VSi2in the bilayer films has been found to be linear in time over the temperature range of 500–535 °C with an activation energy of 2.23±0.09 eV. The microstructure of films at various stages of annealing have been studied by x‐ray diffraction and transmission electron microscopy. Correlation between the resistivity and microstructure is given and discussed.Insituresistivity of annealed films below room temperature has been measured. Crystalline VSi2thin films do not become superconductive down to 2 K.

ISSN:0021-8979    

DOI:10.1063/1.336345

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We formulate a two‐dimensional ordering model for a finite‐level system of adatoms on a crystalline surface. The placement of steps in the two surface directions obeys Markovian disorder. Steps in the two directions are weakly correlated due to the restriction that the system occupies only a finite number of levels in the vertical dimension. In particular, we derive the surface atom pair correlation function and the diffracted intensity for the two‐level system and obtain a closed‐form solution. We discuss the effect of the weak correlation of the two surface directions. This is perhaps the simplest two‐dimensional model that can describe the molecular‐beam epitaxy measurements of Si/Si(111) reported by Gronwald and Henzler [Surf. Sci.117, 180 (1982)]. The results of our calculation are also compared to our previous one‐dimensional and fully correlated two‐dimensional model calculations.

ISSN:0021-8979    

DOI:10.1063/1.336346

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The usefulness of cw laser irradiation for semiconductor surface processing is evaluated. While perfect surface cleaning has not yet been obtained, surface annealing of silicon by this technique equals and even beats classical techniques or pulsed‐laser irradiation. cw laser ‘‘writing’’ of fine surface patterns is also demonstrated.

ISSN:0021-8979    

DOI:10.1063/1.336347

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The InxGa1−xAs/InyGa1−yAs strained‐layer superlattices can be grown lattice matched to an InP substrate if proper compositions and thicknesses are chosen. Such structures were grown by molecular‐beam epitaxy. The wavelength range covered by this material is from 1.65 &mgr;m to beyond 2 &mgr;m. Structural (double x‐ray diffraction) and optical (absorption) characterizations were performed and quantitatively interpreted; they show the excellent properties of these structures.

ISSN:0021-8979    

DOI:10.1063/1.336348

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A high‐resolution optical study was carried out on GaAs crystals grown by horizontal Bridgman and liquid‐encapsulated‐Czochralski methods. An excellent correlation was found between the intensity of the 1.039‐eV no‐phonon line and the characteristic absorption of EL2, the major deep donor level in GaAs. A correlation was also found between the characteristic optical absorption of EL2 and its concentration as determined by junction capacitance measurements. The presence of EL0, another midgap level contained in heavily oxygen‐doped crystals at concentrations always less than those of EL2, had no effect on the optical spectra, but altered the capacitance measurements. Accordingly, an accurate calibration for the determination of EL2 by optical absorption was obtained from capacitance measurements on crystals containing only EL2; in this way the uncertainties introduced by other midgap levels were eliminated.

ISSN:0021-8979    

DOI:10.1063/1.337013

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A numerical technique has been used to solve the carrier transport equations for several (Hg,Cd)Te photodiode configurations, namelyn+pp+,n+np, andpin. Of particular interest are the fundamental recombination mechanisms of radiative and Auger. Results clearly demonstrate the importance of Auger type 1 and 7 mechanisms on thenandpsides of the junction, respectively, in limiting carrier lifetimes. For example, it was found that for defect‐free Hg1−xCdxTe alloys withx=0.2 and hole concentration less than 4×1014cm−3adjacent to the depletion region, the Auger recombination rate can be reduced below the radiative rate. An analysis of the spatial dependence of the electron mobility shows that the presence of high carrier concentrations and electric field strengths can reduce the mobility and consequently have an effect on the sensitivity and temporal response of the photodiode.

ISSN:0021-8979    

DOI:10.1063/1.337014

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Hole transport properties of resistive hydrogenated amorphous silicon (1012&OHgr; cm) are studied by a pulsed photoconductivity technique. Transit time is analyzed by the Scher–Montroll plotting method. Estimation of mobility is done with photocurrent measurement under a space‐charge‐limited condition, and it is confirmed that the mobility value measured under this condition agrees with the calculated value found from space‐charge‐limited current. With no space‐charge effect, temperature dependence and electric field dependence of transit time is represented by &tgr;=&tgr;0 E−1/&agr;’ exp(&Dgr;/kT).

ISSN:0021-8979    

DOI:10.1063/1.337015

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The sputter deposition of Au onp‐silicon has been studied by means of forward and reverse current voltage characteristics. Barrier heights have been determined from Fowler plots and from activation energies. The observed increase of the barrier height with respect to evaporated contacts is mainly dependent on features of the discharge like the sputtering voltage, deposition time, gas composition, and pressure. It is for the most part independent of the semiconductor pretreatment before deposition or on the thickness of an insulating thin (<10 nm) layer. For low sputter voltages (<1 kV) there is an increase of the barrier height with increasing sputter voltage. Sputter voltages exceeding 1 kV result in a fixation of the barrier height at 0.60–0.65 eV. This fixation is due to the presence of sputter‐induced traps in a thin surface layer of about 10 nm.

ISSN:0021-8979    

DOI:10.1063/1.336992

出版商:AIP    

年代:1986

数据来源: AIP