Polymorphous Si is a nanostructured form of hydrogenated amorphous Si that contains a small fraction of Si nanocrystals or clusters. Its thermally induced transformations such as relaxation, dehydrogenation, and crystallization have been studied by calorimetry and evolved gas analysis as a complementary technique. The observed behavior has been compared to that of conventional hydrogenated amorphous Si and amorphous Si nanoparticles. In the temperature range of our experiments (650–700 °C), crystallization takes place at almost the same temperature in polymorphous and in amorphous Si. In contrast, dehydrogenation processes reflect the presence of different hydrogen states. The calorimetry and evolved gas analysis thermograms clearly show that polymorphous Si shares hydrogen states of both amorphous Si and Si nanoparticles. Finally, the total energy of the main Si–H group present in polymorphous Si has been quantified.

Rapid quenching during flame spray synthesis of Pt/TiO2 (0–10 wt% Pt) is demonstrated as a versatile method for independent control of support (TiO2) and noble metal (Pt) cluster characteristics. Titania grain size, morphology, crystal phase structure, and crystal size were analyzed by nitrogen adsorption, electron microscopy and x-ray diffraction, respectively, while Pt-dispersion and size were determined by CO-pulse chemisorption. The influence of quench cooling on the flame temperature was analyzed by Fourier transform infrared spectroscopy. Increasing the quench flow rate reduced the Pt diameter asymptotically. Optimal quenching with respect to maximum Pt-dispersion (∼60%) resulted in average Pt diameters of 1.7 to 2.3 nm for Pt-contents of 1–10 wt%, respectively.

Intensity variation of 1.5 μm light emission at room temperature from Er-doped epitaxial and polycrystal ZnO films depending on annealing temperature (773–1373 K) was studied. As-grown Er-doped epitaxial ZnO film emitted 1.5 μm photoluminescence(PL) higher than as-grown Er-doped polycrystal ZnO. It was found that the annealing in air increases PL intensity and the maximum PL intensity was obtained by annealing at optimal temperature (1073 K). Spectrum shape and intensity of 1.5 μm PL of Er-doped epitaxial ZnO after annealing at 1073 K resembled those of Er-doped polycrystal ZnO after annealing at 1073 K. X-ray diffraction measurement demonstrated that annealing improves crystal quality of Er-doped ZnO film. We assumed that the process of 1.5 μm light emission is dependent on local area placement of Zn and O atoms around Er as well as crystal quality of ZnO.

The properties of nanocomposite tantalum carbide/amorphous hydrocarbon (TaC/a-C:H) thin films depend closely on reactive magnetron sputtering deposition process conditions. The chemical composition and structure trends for TaC/a-C:H films were obtained as a function of three deposition parameters: acetylene flow rate, applied direct current (dc) bias voltage, and substrate carousel rotation rate. Films were deposited according to a 23 factorial experimental design to enable multiple linear regression modeling of property trends. The Ta/C atomic ratio, hydrogen content, total film thickness, TaC crystallite size, and Raman spectra were statistically dependent on acetylene flow rate, applied dc bias voltage, or both. Transmission electron microscopy revealed a nanometer-scale lamellar film structure, the periodicity of which was affected mostly by substrate carousel rotation rate. The empirical property trends were interpreted with respect to hypothesized growth mechanisms that incorporate elements of physical vapor deposition and plasma-enhanced chemical vapor deposition.

The GexGa5Se(95−x) glasses, where x = 20, 22.5, 25, 27.5, 29.17, 30, 32.5, and 35, all doped with 0.05 mol% Dy3+ were prepared and studied. Thermal stabilities, optical properties, and 1.3 μm emission properties of the glasses were investigated. Strong fluorescence centered at 1.34 μm with a bandwidth of 92 nm was observed. Three phenomenological intensity parameters were obtained: Ω2 =12.64 × 10−20, Ω4 =2.94 × 10−20, and Ω6 =1.48 × 10−20 cm2 by Judd–Ofelt analysis. A new method estimating lifetime of overlapping energy level was introduced. Lifetimes of 520 μs were measured for the 1.3 μm transition, and the quantum efficiency was 36.8% according to the new method.