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Here, glancing angle deposition is employed to synthesize the undoped GeO2 and Mg-doped (0.4 and 0.8 at. %) GeO2 nanowires (NWs) on a Si substrate. The microscopic images show the formation of the NW-like morphology of the grown materials. The gradual decrease in the average ratio of length to diameter depicts the worsening of the formation of NWs with the incorporation of Mg into the GeO2 host lattice. This also affects the crystallinity characteristics of the materials, which have been demonstrated from the selected area electron diffraction (SAED) pattern of the materials. The polycrystallinity nature of undoped GeO2 NWs changes to amorphous due to the introduction of Mg, which has been confirmed from both the obtained SAED and x-ray diffraction patterns of the samples. The presence of Mg was confirmed from the obtained broad bands at 473 and 437 cm−1 in the Fourier transmission spectrum of the doped samples. The increasing conductance with the temperature of Au/undoped GeO2 devices can be explained by the thermionic emission process, whereas the Mg-GeO2 device shows an overall decrease in conductance with increasing temperature. We have ascribed the origin of this abnormal conductance as the positive temperature coefficient of resistance, which is one of the first reports, due to the generation of random grain boundaries and enormous electron trapping at the Au/Mg-GeO2 NW junction. Furthermore, the undoped GeO2 NW device shows good temperature-dependent conductivity as well as stability compared to the doped one. [ABSTRACT FROM AUTHOR]

Sol-gel synthesis route was adopted to prepare undoped and 2 at. % Ce doped ZnO (CZO) nanoparticles (NPs). Distinct characteristic absorption peaks at 520 and 524 cm–1 are seen in FTIR spectra of NPs, which generally correspond to Zn–O stretching mode. This confirmed the formation of ZnO in the samples. Other peaks at 628 and 631 cm–1 were also observed corresponding to Zn–O–Zn antisymmetric vibrations. UV-Vis transmission spectra revealed absorption dips at 370 and 364 nm respectively for undoped ZnO and CZO NPs and the corresponding band gap values were estimated to be 3.34 and 3.41 eV. The photoluminescence (PL) emission spectra of undoped ZnO NPs had one major peak at 391 nm (UV) along with feeble visible peaks at 467, 480 and 492 nm. The UV peak observes a continuous rise in intensity with reduction in temperature ranging from 50 ºC to – 10 ºC. The UV peak also blue-shifted slightly with temperature lowering. The temperature dependent PL spectra of CZO NPs too had similar peaks but a very feeble change in the intensity with temperature was noticed and the blue-shift of the UV peak occurred at negative temperature. The temperature dependent PL properties and band gap enhancement in CZO NPs may have potential applications in optoelectronics. [ABSTRACT FROM AUTHOR]

We report the formation of sol-gel spin coated TiO2 films on corning glass substrates. The XRD spectra revealed the predominance of anatase phase in the films with annealing temperature from 250 to 450 °C. The FE-SEM studies showed dense distribution of nanocrystallites in the deposited films. Elemental analysis by EDAX measurement also confirmed the formation of TiO2 films. Most interestingly, annealing at 250 to 450 °C for 1 h in air produced a red shift in the absorption edge from 353 to 374 nm. This red shift was attributed to annealing-induced reduction in carrier confinement linked to enhancement in nanocrystallite sizes in the annealed films. [ABSTRACT FROM AUTHOR]