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Ge–SiO2 thin films were prepared by the RF magnetron sputtering technique on p-Si substrates from a Ge–SiO2 composite target. The as-deposited films were annealed in the temperature range of 300–1000 °C under nitrogen ambience. The structure of films was evaluated by X-ray diffraction, X-ray photoemission spectroscopy and Fourier transform infrared absorption spectroscopy. Results show that the content of Ge and its oxides in the films change with increasing annealing temperature (Ta), the photoluminescence (PL) characteristics are closely dependent on the contents of Ge and its oxides in SiO2 matrix. The dependence observed strongly suggests that the PL peak at 394 nm is related to the existence of GeO and 580 nm to that of Ge nanocrystal (nc-Ge) in the films. [Copyright &y& Elsevier]

Abstract: Piezomodulated reflectance (PzR) spectra at 77 and 300K have been measured for InAs/In0.15Ga0.85As dots-in-a-well and a conventional InAs/GaAs quantum dots. The optical features of both samples were well resolved and confirmed by photoluminescence results. Numerical calculations are in good agreement with the experimental results. The transitions in sandwiched structure formed by InAs wetting layer and In0.15Ga0.85As/GaAs quantum well supports the model of strain-driven alloy decomposition. The abnormal intensity between heavy-hole-type and light-hole-type transition of such sandwiched structure in PzR spectra has been discussed in terms of increased hydrostatic strain in In0.15Ga0.85As/GaAs quantum well. [Copyright &y& Elsevier]

Abstract: Signatures associated with electronic states confined in two strained In x Ga1–x As/GaAs single quantum wells have been observed in its piezomodulated (PzR) and photomodulated (PR) reflectivity spectra. One comparison of the relative intensity between 11H and 11L signatures in PzR of GaAs/In0.14Ga0.86As SQW emphasizes the contribution of strain dependence of energies of the confined states; the other comparison of corresponding confined states between PzR and PR spectra in both samples has been introduced to interpret the discrepancy of the relative intensity in term of modulated strength, and the calculated ratio of energy shifts induced by strain to that of produced by surface electric field agree with the experimental observation. [Copyright &y& Elsevier]