Albert Juma

Meyer-Neldel rule for Cu (I) diffusion in In2S3 layers

The nature of barriers for atomic transport in In2S3 layers has been varied by addition of chlorine. Diffusion of Cu(I) from a removable CuSCN source was used to probe the variation of the barriers. The Meyer-Neldel (compensation) rule was observed with a Meyer-Neldel energy (EMN) and a proportionality prefactor (D00) amounting to 40 meV and 5 × 10−14 cm2/s, respectively. D00 shows that the elementary excitation step is independent of the specific mechanism and nature of the barrier including different densities of Cl in In2S3. The value of EMN implies that coupling of the diffusing species to an optical-phonon bath is the source of the multiple excitations supplying the energy to overcome the diffusion barriers.

Effect of Zr doping on the structural and electrical properties of spray deposited TiO2 thin films

Doping is an effective material re-engineering technique, which provides a possibility of improving properties of materials for different applications. Herein, a Zr-doped TiO2 thin film was deposited applying the chemical spray pyrolysis method and the influence of varying zirconium dopant concentrations on the properties of the film was studied. Morphological studies showed that the Zr–TiO2 films were homogeneous with smaller grain sizes compared to the undoped TiO2 films. Asdeposited Zr–TiO2 films were amorphous while the undoped TiO2 films were crystalline with anatase structure as revealed by both X-ray diffraction and Raman spectroscopy studies. The optical band gap of the Zr–TiO2 film was higher (3.44 eV) than that of the undoped TiO2 films (3.13 eV) showing a strong dependence on the phase composition. As revealed by energy dispersive spectroscopy analysis, the Zr/Ti ratio in the film increased from 0.014 to 0.13 as the doping concentration in the spray solution was increased from 5 to 40 mol%. The current–voltage (I–V) characteristic revealed a reduction of the leakage current in the Zr-doped TiO2 film (6.06 × 10 A) compared to the undoped TiO2 films (1.69 × 10 A) at 1 forward bias voltage. The dielectric relaxation response at the oxide–electrode interface dipole was strongly influenced by the Zr doping concentration in the film.