Melioration of Electrical and Optical Properties of Al and B Co-Doped ZnO Transparent Semiconductor Thin Films

Undoped, Al-doped and Al-B co-doped ZnO transparent semiconductor thin films were deposited on glass substrates by sol-gel method and spin coating technique. This study investigated the influence of Al (2 at.%) doping and Al (2 at.%)-B (1 or 2 at.%) co-doping on the microstructural, surface morphological, electrical and optical properties of the ZnO-based thin films. XRD analysis indicated that all as-prepared ZnO-based thin films were polycrystalline with a single-phase hexagonal wurtzite structure. The substitution of extrinsic dopants (Al or Al-B) into ZnO thin films can significantly degrade the crystallinity, refine the microstructures, improve surface flatness, enhance the optical transparency in the visible spectrum and lead to a shift in the absorption edge toward the short-wavelength direction. Experimental results showed that the Al-doped and Al-B co-doped ZnO thin films exhibited high average transmittance (>91.3%) and low average reflectance (<10%) in the visible region compared with the ZnO thin film. The optical parameters, including the optical bandgap, Urbach energy, extinction coefficient and refractive index, changed with the extrinsic doping level. Measured results of electrical properties revealed that the singly doped and co-doped samples exhibited higher electron concentrations and lower resistivities than those of the undoped sample and suggested that 2 at.% Al and 1 at.% B were the optimum dopant concentrations for achieving the best electrical properties in this study.

Recyclable Graphene Sheets as a Growth Template for Crystalline ZnO Nanowires

Recent advances in nanoscience have opened ways of recycling substrates for nanomaterial growth. Novel materials, such as atomically thin materials, are highly desirable for the recycling substrates. In this work, we report recycling of monolayer graphene as a growth template for synthesis of single crystalline ZnO nanowires. Selective nucleation of ZnO nanowires on graphene was elucidated by scanning electron microscopy and density functional theory calculation. Growth and subsequent separation of ZnO nanowires was repeated up to seven times on the same monolayer graphene film. Raman analyses were also performed to investigate the quality of graphene structure along the recycling processes. The chemical robustness of graphene enables the repetitive ZnO nanowire growth without noticeable degradation of the graphene quality. This work presents a route for graphene as a multifunctional growth template for diverse nanomaterials such as nanocrystals, aligned nanowires, other two-dimensional materials, and semiconductor thin films.

Influence of surface morphology on electrophysical properties of PbTe: Sb films

The electrophysical properties of polycrystalline doped semiconductor thin films PbTe: Sb deposited on mica and sital (glass based ceramic) substrates are considered. The thickness dependencies of carrier mobility, of Hall coefficient and of Seebeck coefficient, and the correlations between these parameters for films deposited on different substrate materials were studied. The peculiarities of growth of thin films and their structural parameters are analyzed taking into account the features of the ‘substrate – film’ boundary section.