Fabrication of Transparent Superhydrophobic Surface from ZnO Nanorods

A transparent superhydrophobic surface was fabricated from ZnO nanorods grown on Si and glass substrates in a thermal furnace for industrial applications such as surface coating. Two types of glasses were used for the substrates: slide glass and Corning glass. The ZnO nanorods were then coated with PTFE using existing sputtering technology and then grown on the glasses. The optical transparency and processing temperature of the nanorods on the substrates with and without a ZnO buffer layer were investigated, for comparison. The superhydrophobic surface formed on Corning glass with a 50-nm-thick ZnO buffer layer exhibited a transparency of 80% or higher and a water contact angle of 150° or higher in the visible light region. High optical transmittance of the superhydrophobic surface was achieved by controlling the size and growth direction of the nanorods. X-ray diffraction and scanning electron microscopy images showed that the nanorods on the glass substrates were thicker than those on Si, and the nanorods predominantly grew in the vertical direction on the buffer layer. However, the growth direction did not affect the wettability of the surface. Vertically grown nanorods can still affect optical transmittance because they facilitate the propagation of light. In the case of Corning glass, superhydrophobic surfaces with contact angles of 150° and 152.3° were formed on both samples with buffer layers of 50 nm and 100 nm, respectively. Therefore, a buffer layer thickness in the range of 50–100 nm is suitable for realizing a transparent superhydrophobic surface on a glass substrate.

Self-Catalysed Vapor-Liquid-Solid Growth Mechanism of ZnO Nanowires Grown on Silicon Substrate Pre-Coated with ZnO Buffer Layer

The present article reports the growth mechanism of zinc oxide (ZnO) nanowires grown on silicon substrate pre-coated with ZnO buffer layer by thermal evaporation method. ZnO nanowires are grown for different growth time of 0, 30, 90 and 120 mins with controlled supply of Ar and O2 gas at 650 °C. The structural, morphological and crystallinity properties of ZnO nanowires are analyzed by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). FESEM images infers that, the nanowires growth is driven by self-catalysed vapor-liquid-solid mechanism, where the buffer layer serve as nucleation site. EDX spectra show the uniform composition and purity of ZnO nanowires. A strong (002) peak is detected in XRD spectra which indicates that the preferred growth orientation of the nanowires is toward the c-axis with a hexagonal wurtzite structure. The HRTEM microscopic graphs confirm the growth of nanowire along the preferred [0001] axis. Based on the analysis of grown ZnO nanowires, the probable growth mechanism is schematically presented.

Numerical Simulation for Enhancement of the Output Performance of CZTS Based Thin Film Photovoltaic Cell

The performance of CZTS thin film photovoltaic cell has been simulated using SCAPS-1D (Solar cell capacitance simulator). The thickness of CZTS absorber layer, ZnO buffer layer and ZnO doped with Al window layer have been varied to optimize the overall output performance of CZTS based thin film photovoltaic cell. Simulation show the favorable result which can help to prove the feasibility of highly efficient CZTS thin film photovoltaic cell.

Investigation on the Deposition of an AlN-ZnO/ZnO/AlN-ZnO Double Heterojunction Structure Using Radio Frequency Magnetron Cosputtering Technology

A symmetric AlN-ZnO/ZnO/AlN-ZnO double heterojunction structure was consecutively deposited onto silicon substrate using cosputtering technology and then annealed at 700 °C under vacuum ambient for 30 min. The crystalline quality of the ZnO film in the heterojunction structure was significantly improved as verified by X-ray diffraction (XRD) and photoluminescence (PL) measurements. Improvement on the crystalline structure was ascribed to the stress in the ZnO active film, which was effectively buffered by the underlayered AlN-ZnO layer. Native oxygen vacancies in the ZnO film also were effectively suppressed due to a little diffusion of the Al atoms from the cosputtered AlN-ZnO layer, and led to an increase in the carrier concentration. Such ZnO film deposited onto the homogeneous AlN-ZnO buffer layer emitted an intense near-band-edge emission, and the deep level emission was absent. The ultraviolet emission was further enhanced by covering an AlN-ZnO barrier laye, which was a consequence of the improvement on the carrier confinement. Accordingly, single ultraviolet emission with a quality ZnO crystalline structure, which is very promising for application in short-wavelength optoelectronic devices, was realized from the ZnO film sandwiched by the homogeneity of the cosputtered AlN-ZnO layers.