Films of SiGe nanocrystals (NCs) in oxide have the advantage of tuning the energy band gap by adjusting SiGe NCs composition and size. In this study, SiGe-SiO2 amorphous films were deposited by magnetron sputtering on Si substrate followed by rapid thermal annealing at 700, 800 and 1000 °C. We investigated films with Si:Ge:SiO2 compositions of 25:25:50 vol.% and 5:45:50 vol.%. TEM investigations reveal the major changes in films morphology (SiGe NCs with different sizes and densities) produced by Si:Ge ratio and annealing temperature. XPS also show that the film depth profile of SiGe content is dependent on the annealing temperature. These changes strongly influence electrical and photoconduction properties. Depending on annealing temperature and Si:Ge ratio, photocurrents can be 103 times higher than dark currents. The photocurrent cutoff wavelength obtained on samples with 25:25 vol% SiGe ratio decreases with annealing temperature increase from 1260 nm in SWIR for 700 °C annealed films to 1210 nm for those at 1000 °C. By increasing Ge content in SiGe (5:45 vol%) the cutoff wavelength significantly shifts to 1345 nm (800 °C annealing). By performing measurements at 100 K, the cutoff wavelength extends in SWIR to 1630 nm having high photoresponsivity of 9.35 AW−1.
Zn-ferrite (ZnFe2O4) thin films were deposited by rf-magnetron sputtering on glass substrates at room temperature (RT) in pure oxygen environment. The as-deposited films were investigated by x-ray diffraction to show that single phase nanocrystalline spinel patterns belong to zinc ferrite. The magnetization shows ferrimagnetic behavior, and it strongly depends on oxygen working pressure. The maximum magnetization of 230 emu/cm3 (42 emu/g) at RT is obtained for the film deposited at 27 mTorr of oxygen pressure. The oxygen vacancy concentration and random distribution of Zn2+ and Fe3+ on both tetrahedral and octahedral sites are the possible reasons of high magnetization due to rapid cooling of sputtered vapors to form solid state film. The optical properties of the films show 85% transparency above 550 nm wavelength. The estimated values of direct and indirect band gaps are 2.5 and 1.9 eV, respectively.
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