The electronic structures and optical properties of Y-doped ZnO are calculated using first-principles calculations.It is found that the replacement of Zn by the rare-earth element Y presents a shallow donor,and the Fermi level moves into the conduction band(CB).The high dispersion and s-type character of CB is expected to result in an increase in conductivity.Moreover,the absorption spectrum of the Y-doped ZnO system exhibits a slight blue shift with an increase of Y concentration,and a higher transparency in visible light is expected.Therefore,the Y-doping in ZnO would enhance the mobility and hence increase the electrical conductivity without sacrificing the optical transparency,which is essential for the improvement of ZnO's behavior and its performance in extension applications.
ZnO film with claviform structure was synthesized on quartz substrates through a hydrothermal method at 90℃.The microstructure of the film is composed of clusters of submicrometer rods,which therefore endues the film with good superhydrophobicity.Meanwhile,the film with such tanglesome structure also shows highly crystalline quality testified by a strong ultra-violet (UV) emission and very low deep-level emission observed on the photoluminescence (PL) spectrum as well as high transparence of about 89% transmittance in visible light range.
Nanocrystalline Cu with average grain sizes ranging from ～ 24.4 to 131.3 nm were prepared by the electric brushplating technique.Nanoindentation tests were performed within a wide strain rate range,and the creep process of nanocrystalline Cu during the holding period and its relationship to dislocation and twin structures were examined.It was demonstrated that creep strain and creep strain rate are considerably significant for smaller grain sizes and higher loading strain rates,and are far higher than those predicted by the models of Cobble creep and grain boundary sliding.The analysis based on the calculations and experiments reveals that the significant creep deformation arises from the rapid absorption of high density dislocations stored in the loading regime.Our experiments imply that stored dislocations during loading are highly unstable and dislocation activity can proceed and lead to significant post-loading plasticity.
Nanocrystalline Cu film with a mirror surface finishing is prepared by the electric brush-plating technique. The asprepared Cu film exhibits a superhydrophilic behavior with an apparent water contact angle smaller than 10o. A subsequent increase in the water contact angle and a final wetting transition from inherent hydrophilicity with water contact angle smaller than 90o to apparent hydrophobicity with water contact angle larger than 90o are observed when the Cu film is subjected to natural aging. Analysis based on the measurement of hardness with nanoindentation and the theory of the bond-order-length-strength correlation reveals that this wetting variation on the Cu film is attributed to the relaxation of residual stress generated during brush-plating deposition and a surface hydrophobization role associated with the broken bond polarization induced by surface nanostructure.
Optical and electronic properties of Zn_(1−x)Mg_(x)O ternary alloys of wurtzite structure are calculated by using first-principles based on the framework of generalized gradient approximation to density functional theory with the introduction of the on-site Coulomb interaction.The use of the𝑈parameter on Zn-3d𝑑and O-2p𝑝orbits is obviously crucial,which can improve the GGA to predict the electronic properties and bandgap of the Zn_(1−x)Mg_(x)O(0≤𝑥≤0.25)system reasonably.It is further demonstrated that the bandgap widens with an increasing Mg concentration from 3.217 eV of ZnO to 3.877 eV of Zn0.75Mg0.25O.Therefore,the theoretical results show that Zn_(1−x)Mg_(x)O ternary alloys are potential candidates for optoelectronic materials,especially for UV photon emitters and detectors.
