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Pb1-xSrxTe thin films with different strontium (Sr) compositions are grown on BaF2(111) substrates by molecular beam epitaxy (MBE). Using high resolution x-ray diffraction (HRXRD), we obtain Pb1-xSrxTe lattice constants, which vary in the range 6.462-6.492A. According to the Vegard law and HRXRD data, Sr compositions in Pb1-xSrxTe thin films range from 0.0-8.0%. The Pb1-xSrxTe refractive index dispersions are attained from infrared transmission spectrum characterized by Fourier transform infrared (FTIR) transmission spectroscopy. It is found that refractive index decreases while Sr content increases in Pb1-xSrxTe. We also simulate the Pb1-xSrxTe transmission spectra theoretically to obtain the optical band gap energies which range between 0.320 eV and 0.449 eV. The simulated results are in good agreement with the FTIR data. Finally, we determine the relation between Pb1-xSrxTe band gap energies and Sr compositions (Eg = 0.320+0.510x-0.930x2 + 184x3 (eV)).

Single crystal PbTe thin films have been grown on BaF2 (111) by using solid source molecular beam epitaxy. The studies of evolution of the surface morphology with the increasing growth temperature from 375 to 525 degrees C by AFM show that PbTe epilayers exhibit smooth surface morphologies with atomic layer scale roughness and are crack free. It is found that for PbTe grown at 475 degrees C, the morphology is dominated by triangles and the rms roughness is 3.987 nm. Compared to the rms roughnesses of 0.432 nm and 0.759 nm for the samples grown at 375 and 525 degrees C respectively, the surface of the PbTe layer grown at 475 degrees C is much rougher. This roughening transition is due to the interaction between the elastic relaxation and the plastic relaxation during the strain relaxation process. In contrast to the result of the morphology that the PbTe epitaxial layer grown at 375 degrees C has most smooth surface, as observed from the line width of x-ray diffraction curves at higher growth temperature improves the crystal quality of the single-crystalline PbTe layer.

Cubic ZnMgO thin films in the (100) orientation were grown on Si (111) substrates by reactive electron beam evaporation at low substrate temperature. X-ray photoelectron spectroscopy (XPS) analyses show that Mg content as high as 75 at.% in the cubic ZnMgO film can be obtained. Secondary ion mass spectroscopy (SIMS) measurement indicates the evidence of Mg richness in the interface between the ZnMgO film and the Si substrate, and it is probably the primary reason to form the MgO-like cubic ZnMgO structures rather than the wurtzite one. The optical band gap of cubic ZnMgO is estimated to be 5.76 eV, which was measured by the transmission spectrum of the cubic ZnMgO film grown on the sapphire substrate under the same growth condition with that on Si (111). The band gap is of 2.39 eV blueshifted compared with that of ZnO (3.37 eV), which should render applications in the fabrication of ZnMgO-related heterostructures.