摘要:

The technique of cross‐sectional transmission electron microscopy has been applied to study the nature of the radiation damage in GaAs bombarded with 300 keV protons to total doses of 1015and 5×1015protons cm−2. The results indicate that upon annealing at temperatures of 500 °C and above, the precipitated damage becomes visible in the form of hydrogen platelets (i.e., hydrogen‐filled edge vacancy loops) on the {110} cleavage planes of GaAs.

ISSN:0021-8979    

DOI:10.1063/1.337789

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We determined the chain segment lengths involved in the &ggr; process of low‐density polyethylene by introducing linear alkanes of different chain lengths into the polymer. These alkanes possess at one end of the chain an electric dipole constituted by an ester group. Their influence on the &ggr; relaxation of low‐density polyethylene was observed by thermostimulated depolarization measurements. We found a correlation between the &ggr; temperature peak position and the alkane chain length, while the activation parameters distributions determined by the thermal sampling technique were only slightly modified. This was explained by considering that the distribution in activation parameters is partly induced by a distribution in the chain segment length of the relaxing species. Adding a linear alkane to the polyethylene modifies the population of the mobile chain segments of a given length. We deduced that the &ggr;1subrelaxation is induced by the motion of chain segments having approximately between 10 and 20 carbon atoms. A compensation law was evidenced in the &ggr; process of all samples studied. The slight modifications of the preexponential factor of relaxation time and the variation of compensation temperature with the alkane chain length are discussed considering a local order in the amorphous phase of low‐density polyethylene.

ISSN:0021-8979    

DOI:10.1063/1.337335

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The effects of a moderate concentration of noninteracting dislocations on the axial channeling radiation due to MeV positrons are analytically calculated. The axial potential due to all the six strings surrounding a ⟨110⟩ axial channel in diamond structure is first obtained which is exact up to quartic terms in distance from the central axis of the channel. The particle oscillation period and hence the radiation frequency depends upon the oscillation amplitude. The effects of dislocations are manifested through the modification in the oscillation amplitude of the channeled particle. We have suggested some suitable experiments to test the results.

ISSN:0021-8979    

DOI:10.1063/1.337336

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Be+/O+‐ion implantation is performed in GaAs/AlGaAs heterojunction wafers. Secondary ion mass spectroscopy analysis shows that the oxygen profile is in good agreement with the theoretical profile (LSS) and that the beryllium profile is still deeper than the theoretical one. The electrical properties of the ion‐implanted heterojunctions are studied by means of current‐voltage (I‐V) and capacitance‐voltage (C‐V) measurements and are found to strongly depend on the isochronal annealing temperature. A low‐temperature anneal (≤400 °C) produces a high‐resistivity isolation layer of about 0.4 &mgr;m thick in the heterojunctions. At annealing temperatures above 400 °C, the data indicates a pronounced decrease in the carrier concentration in AlGaAs regions as compared with their original doping, but a good recovery after a high‐temperature anneal (800 °C).

ISSN:0021-8979    

DOI:10.1063/1.337337

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The two‐beam dynamical theory of electron diffraction has been used to calculate transmission electron microscope image profiles for small dislocation loops in GaAs. It is shown that the method of matching computed and experimental image profiles of loops is useful in the determination of their Burgers vectors. The results also indicate that the isotropic elasticity theory may be used to a good approximation for GaAs.

ISSN:0021-8979    

DOI:10.1063/1.337338

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The influence is described of several device parameters, i.e., the total director twist, the pretilt angle, and anchoring energy, on the director pattern in highly twisted samples with nonzero boundary tilt. A difference compared with previous approaches is the inclusion of a finite anchoring energy coefficient in the continuum equations. The results indicate a pronounced influence of the surface anchoring on the hysteresis in the midplane tilt angle as a function of an applied voltage.

ISSN:0021-8979    

DOI:10.1063/1.337339

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Deep level transient spectroscopy ofp–njunctions, Schottky barriers, or metal‐oxide‐semiconductor (MOS) capacitors is widely used to obtain the concentrations of defects and their profiles in semiconductors. The use of this technique for profiling presents several difficulties, some of which have not been taken into account in the works previously published. The aim of this paper is to describe the exact analysis which should be performed to obtain correct profiles. The analysis is tested on a constant defect profile, induced by electron irradiation inn‐GaAs, in order to illustrate the effect of each correction. It is then applied to defect profiling of a silicon MOS capacitor and on the EL2 defect in annealed GaAs.

ISSN:0021-8979    

DOI:10.1063/1.337340

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Ion‐beam‐induced microstructure of the iron‐rich end of the Fe–Ti and Fe–Ti–C systems was studied by using multilayered thin‐film samples with a linearly varying composition of the metallic constituents. The ion bombardment was carried out using Xe++ions at 600 keV. A mixing of iron and titanium in binary samples was complete after a bombardment with 8×1015ions/cm2whereas Fe–Ti–C samples were only partially mixed after the fluence of 1.8×1016ions/cm2. Transmission electron microscope studies revealed that the microstructure of Fe–Ti samples was amorphous or amorphous and crystalline iron over a wide range of the compositions investigated. In the case of Fe–Ti–C, the microstructure consisted of crystalline iron and titanium together with a very little amorphous phase.

ISSN:0021-8979    

DOI:10.1063/1.337341

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Kinetics of dry oxidation of silicon after implantation of fluorine in the oxide layer are investigated. It appeared that implanted fluorine can result in negative values of the linear oxidation rate constant. Fluorine profiles obtained by the nuclear reaction analysis (NRA) method using a resonant19F(&agr;, p)22Ne nuclear reaction will be presented. At 1200 °C the fluorine moves to the interface of Si and SiO2, both in dry oxidizing and inert atmospheres. Based on these findings, a model is presented that explains quantitatively the observed anomalous behavior of the linear oxidation rate constant.

ISSN:0021-8979    

DOI:10.1063/1.337342

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The metallurgical examination of solid‐state reaction between nickel thin films and single‐crystal GaAs substrates and the resultant electrical properties of the contacts are reported. Annealing at 100–300 °C in forming gas led to formation of a metastable hexagonal phase Ni2GaAs which was stabilized due to its epitaxial growth on (001) and (111) GaAs substrates, as follows: (101¯1)Ni2GaAs∥(001)GaAs and (0001)Ni2GaAs∥(111)GaAs. Nickel atoms were found to be the dominant diffusing species during the ternary phase growth. Ni2GaAs is stable on (111)GaAs up to at least 600 °C, compared to 350 °C on (001)GaAs. The larger stability on (111) is explained by the better epitaxial match found in this case. Reaction on (001)GaAs in the temperature range of 350–550 °C resulted in decomposition of Ni2GaAs by NiAs precipitation. After annealing at 600 °C the reacted film was composed of two phases: NiGa and NiAs. The electrical properties of the contacts were correlated to the phase interfacing the substrate. The Ni2GaAs formed rectifying contact with a barrier height of 0.84 eV, whereas when NiGa and NiAs were at the interface an ohmic behavior was observed.

ISSN:0021-8979    

DOI:10.1063/1.337343

出版商:AIP    

年代:1986

数据来源: AIP