A Dependence of Crystallinity of In2O3 Thin Films by a Two-Step Heat Treatment of Indium Films on the Heating Atmosphere
A difference in crystallinity of In2O3 thin films on sapphire substrates by heat treatment of indium films was reported. Indium films were heated in an inert atmosphere or in air until they reached a specified temperature and then oxidized in air at much higher temperatures. Crystallinity of the In2O3 thin film which was heat-treated in air from room temperature was quite poor. On the other hand, narrow X-ray rocking curves of the In2O3 films were obtained when the temperature was increased in an inert atmosphere to a specified tem-perature.
High mobility and size dependent carrier concentration in CdTe nanoparticles synthesized by single injection hydrothermal method for device applications
Abstract Single Injection Hydrothermal (SIH) method is employed to synthesize high mobility CdTe nanoparticles (NPs). The hexagonal CdTe NPs are typified for different durations of synthesis and found to have linear dependence on size as a function of time, as revealed by the Powder-X ray Diffractometer (P-XRD) studies. Transmission Electron Microscopic (TEM) image clearly depicts regular fringe like pattern for the CdTe NPs except at few free space grain boundary defects. From the van der Pauw measurements of Hall parameters, it is found that there is a linear dependence between particle size and the carrier concentration; however the linear variation of p-type carrier concentration is found to impede mobility and conductivity. Smaller sized CdTe NPs are found to possess higher mobility. Interestingly, p-type conductivity has been found to get transformed in to n-type with the increase in electrons as majority carriers, in phase with increasing duration of synthesis. Synthesis of such high mobility CdTe NPs tuneable to the desired type of conductivity can be promising for the device fabrication such as photovoltaic cells.
Influences of In2O3 Crystal Grains Formed by Annealing on Characteristics of Hexagonal InN Crystalline Films Grown on Si(111) Substrates
We investigated the influences of In2O3 crystal grains formed by annealing in N2 atmosphere mixed with O2 (O2 concentration: 10%) on the characteristics of hexagonal InN crystalline films grown on Si(111) substrates. (111) cubic (β)-In2O3 CuKα1 X-ray diffraction was observed from α-InN films with In droplets on their surfaces after annealing at temperatures higher than 400°C. The annealed films exhibited relatively strong, uniformly broad orange photoluminescence (PL) emissions at approximately 1.9 eV under 325 nm He-Cd laser excitation although they were not observed under 514.5 nm Ar+ ion laser excitation. The reactivity of In droplets on the film surface with oxygen atoms is higher than that of the InN films and the In droplets easily transform into wide-band-gap β-In2O3 crystal grains by annealing.