Narrow Results

The Cd${}_x$Zn${}_{1-x}$O thin films have been deposited on glass and Si substrates at room-temperature with different Cd contents (x = 0, 2%, 4% and 6 wt.%) by pulsed laser deposition (PLD) technique. X-ray diffraction (XRD) analyses evidenced that the films possess polycrystalline and a hexagonal ZnO crystal structure for x = 0, 2% and 4% with a preferred orientation in the a-axis (101) direction, while films with a mixed hexagonal and cubic structure was revealed for x = 6 wt.%. Electrical measurement presented that the resistivity decreased with increased temperature and concentration of Cd. The deliberated activation energy was reduced was from 0.224 to 0.113 eV with increase doping concentration. Current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the fabricated Cd${}_x$Zn${}_{1-x}$O/p-Si heterojunction varied with the applied bias and the Cd concentration. The results of the values of built-in potential (V${}_{\mathrm{\text{bi}}}$) and the ideality factor (n) increased with raising Cd concentration.

In this work, the structure, elastic and thermodynamic properties of Ti₂GaC at high pressure (P) and high-temperature (T) are studied based on the density functional first-principles. The lattice parameters and elastic constants are well consistent with some theoretical data and experimental results. The elastic constant of Ti₂GaC increase monotonously with the increase of pressure (P), which demonstrates the mechanical stability of Ti₂GaC at the pressure (P) from 0 to 200 GPa. Mechanical properties including Poisson’s ratio ($\delta$), Young’s modulus (E), shear modulus (G) and bulk modulus (B), which are obtained from elastic constants C${}_{ij}$. The ratio B/G value shows that Ti₂GaC is a brittle material, but its enhancing ductility significantly with the elevate of pressure (P). The Grüneisen parameters ($\gamma$), thermal expansion coefficient ($\alpha$), heat capacity (C${}_v$), elastic constant (C${}_{ij}$), bulk modulus (B), energy (E) and volume (V) with the change of temperature (T) or pressure (P) are calculated within the quasi-harmonic Debye model for pressure (P) and temperatures (T) range in 1600 K and 100 GPa. Besides, densities of states and energy band are also obtained and analyzed in comparison with available theoretical data.

Nanocrystalline SnO₂ and SnO₂:Cu thin films derived from SnCl${}_2\cdot 2$H₂O precursors have been prepared on glass substrates using sol–gel dip-coating technique. The deposited film was $300\pm 20$nm thick and the films were annealed in air at 500${}^{\circ }$C for 1h. Structural, optical and sensing properties of the films were studied under different preparation conditions, such as Cu-doping concentration of 2%, 4% and 6wt.%. X-ray diffraction studies show the polycrystalline nature with tetragonal rutile structure of SnO₂ and Cu:SnO₂ thin films. The films have highly preferred orientation along (110). The crystallite size of the prepared samples reduced with increasing Cu-doping concentrations and the addition of Cu as dopants changed the structural properties of the thin films. Surface morphology was determined through scanning electron microscopy and atomic force microscopy. Results show that the particle size decreased as doping concentration increased. The films have moderate optical transmission (up to 82.4% at 800nm), and the transmittance, absorption coefficient and energy gap at different Cu-doping concentration were measured and calculated. Results show that Cu-doping decreased the transmittance and energy gap whereas it increased the absorption coefficient. Two peaks were noted with Cu-doping concentration of 0–6wt.%; the first peak was positioned exactly at 320nm ultraviolet emission and the second was positioned at 430–480nm. Moreover, emission bands were noticed in the photoluminescence spectra of Cu:SnO₂. The electrical properties of SnO₂ films include DC electrical conductivity, showing that the films have two activation energies, namely, $E_{a1}$ and $E_{a2}$, which increase as Cu-doping concentration increases. Cudoped nanocrystalline SnO₂ gas-sensing material has better sensitivity to CO gas compared with pure SnO₂.