Study of ion implanted Al0.25Ga0.75As/GaAs by Raman spectroscopy

This paper reported the effect of the weak damage in the Al_0.25Ga_0.75As/GaAs epitaxial layer induced by 0.8 MeV Si ions implantation with ion dose from 1 × 10¹⁴ to 5 × 10¹⁵ cm^-2. The Raman spectra measured on these samples showed that there were two kinds of phonon modes existing in the epitaxial Al_0.25Ga_0.75As films. The strains induced in the implanted layer and the corresponding lattice parameters were also evaluated as a function of the implanted dose. In addition, the Rutherford backscattering spectrometry/channeling (RBS/C) was also measured on these samples. These two measurement techniques all confirmed that the implantation only induced weak damage in the material.     

Photoelectric behaviour of lattice-matched GaAs/Al x Ga1- x As quantum well electrodes

The photoelectric properties of the lattice-matched GaAs/A1 _x Ga_l - _x As quantum well electrodes and the influence of the electrode structure such as well width, the thickness of outer barrier and the number of period were studied in a nonaqueous electrolyte. A new kind of structure of multiple quantum well electrode with varied well width, possessing the quantum yield three times that of GaAs bulk materials, was designed and fabricated. Project supported by the National Natural Science Foundation of China.     

Study of indium complexes by solvent extraction and ion exchange

Complexes of indium with hydroxy carboxylic acids like glycollic, mandelic and thioglycollic acids have been investigated by the method of competitive reactions using HTTA as the auxiliary ligand. An ion exchange study has been made in some cases to confirm the results. An ion exchange study of indium fluoride complexes has also been made. The data have been analysed for the stability constants of the indium complexes.     

Investigation on quality of cubic GaN/GaAs(100) by double-crystal X-ray diffraction

Cubic GaN was grown on GaAs (100) by low pressure metal organic chemical vapor deposition (MOCVD). X-ray diffraction, scanning electron microscope (SEM) and photoluminescence (PL) spectra were performed to characterize the quality of the GaN film. The PL spectra of cubic thin films being thicker than 1.5 μm were reported. Triple-crystal diffraction to analyze orientation distributions and strain of the thin films was also demonstrated.     

Thermodynamic equilibrium studies of nanocrystallite SrTiO3 grain boundaries by high temperature photoelectron spectroscopy

Nanostructured strontium titanate (SrTiO₃) thin films are studied by high temperature photoelectron spectroscopy and thermal gravimetric analysis. The results indicate that ion migration and redistribution as well as transformation between lattice oxygen and gas phase oxygen take place near the grain boundaries during thermodynamic equilibrium process, which lead to obvious variation of the surface composition with temperature. The lattice oxygen ions migrate from bulk to grain surface with temperature rising up; meanwhile Ti ions also migrate to grain surface and combine with oxygen ions forming Ti-0 complex. An opposite process takes place during temperature falling down, but the latter process is much slower than the former one. A primary model is proposed to explain this phenomenon.     

Influence of SiO2 in SiCp on the microstructure and impact strength of Al/SiCp composites fabricated by pressureless infiltration

The effect of SiO₂ in SiC_p and the following processing parameters on the microstructure and impact strength of Al/SiC_p composites fabricated by pressureless infiltration was investigated: Mg content in the aluminum alloy, SiC particle size, and holding time. Preforms of SiC_p in the form of rectangular bars (10 × 1 × 1 cm) were infiltrated at 1150°C in an argon→nitrogen atmosphere for 45 and 60 min by utilizing two aluminum alloys (Al-6 Mg-11 Si and Al-9 Mg-11 Si, wt.%). The results obtained show that the presence of SiO₂ in SiC affects the microstructure and impact strength of the composites significantly. When Al₄C₃ is formed, the impact strength decreases. However, a high proportion of SiC to SiO₂ limits the formation of the unwanted Al₄C₃ phase in the composites. Also, a higher content of Mg in the Al alloy lowers the residual porosity and, consequently, increases the composite strength. The impact strength grows with decrease in SiC particle size and increases considerably when the residual porosity is less than 1%. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 401–418, May–June, 2006.