Effect of hydrothermal and chemical treatment on the optical and electrical properties of reduced graphene oxide deposited on ITO glass

In this work, the effect of hydrothermal and chemical treatment on the optical and electrical properties of reduced graphene oxide (RGO) was investigated. Reduced graphene oxide was synthesized by both hydrothermal route using a locally fabricated Teflon lined autoclave and chemical method using hydrazine monohydrate. The thin film was obtained by depositing RGO on Indium Tin Oxide (ITO) glass via spray pyrolysis technique. In RGO hydrothermal, the Raman spectroscopy analysis showed greater restoration of the conjugated networks in graphene sheet. The optical transmittance of RGO hydrothermal and RGO hydrazine decreased after the reduction methods unlike in highly oxidized graphene oxide (HOGO) where eighty percent transmittance was observed at 600 nm and above. For RGO hydrothermal and RGO hydrazine; the optical analysis gave an energy band gap value of 2.1 eV and 2.4 eV respectively, while the resistivity were calculated to be 0.3 Ω m and 0.09 Ω m respectively. This research showed a correlation between the band gap value of RGO and the electrical conductivity. This finding can improve the functionality of RGO as sensing materials. The improved electrical and optical properties of RGO hydrothermal makes it suitable in fiber-optic and opto-electronic applications.http://iopscience.iop.org/2053-1591am2021Physic

Preparation of nanocrystalline ZnO/CoxOyand CNT/CoxOybilayers for photoabsorption potential: XPS and some surface structural characterization

Zinc oxide and carbon nanotubes (CNT) have been separately grown atop cobalt oxide (CoxOy) thin film to form bilayer structures. The structures were characterized by some surface probing techniques. Surface morphology shows that particles of the underlying CoxOy film are evenly distributed across substrate, its average size increases between 60 and 73 nm with deposition voltage. A transparent layer of ZnO completely laminated the CoxOy film in the first set of bilayer sample. Thickness of overgrown CNT on CoxOy is about 16 nm. Dispersion of CoxOy crystallites along the path of the adsorbed CNT was also observed. Optical studies indicated that both the CoxOy film and the ZnO/CoxOy bilayers are fairly transparent to visible light. Values of their energy band gap were estimated in the range between 2.0 and 2.14 eV. Photoemission and crystallographic studies revealed possible interaction between particles of CoxOy and ZnO films but not with the substrate. The study suggests that both the laminated II-VI bilayer and the CNT enhanced structures could be a recipe for effective charge harvesting and separation in nanostructured photovoltaic device

Friction and wear behavior of nitrogen-doped ZnO thin films deposited via MOCVD under dry contact

Most researches on doped ZnO thin films are tilted toward their applications in optoelectronics and semiconductor devices. Research on their tribological properties is still unfolding. In this work, nitrogen-doped ZnO thin films were deposited on 304 L stainless steel substrate from a combination of zinc acetate and ammonium acetate precursor by MOCVD technique. Compositional and structural studies of the films were done using Rutherford Backscattering Spectroscopy (RBS) and X-ray Diffraction (XRD). The frictional behavior of the thin film coatings was evaluated using a ball-on-flat configuration in reciprocating sliding under dry contact condition. After friction test, the flat and ball counter-face surfaces were examined to assess the wear dimension and failure mechanism. Both friction behavior and wear (in the ball counter-face) were observed to be dependent on the crystallinity and thickness of the thin film coatings

Single solid source precursor route to the synthesis of MOCVD Cu-Cd-S thin films

Bis-(morpholinodithiato-s,s')-Cu-Cd was synthesized from appropriate reagents as a single solid source precursor and characterized using particle induced x-ray emission (PIXE), Fourier transform infrared (FTIR) spectroscopy and differential thermal analysis (DTA). Cu-Cd-S thin films were deposited on sodalime glass substrate using MOCVD technique at temperatures in the range 360 °C–450 °C. The films were further characterized using Rutherford backscattering spectroscopy (RBS), x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy and four-point probe technique. PIXE revealed that the synthesized precursor contained the expected elements which led to the successful deposition of the Cu-Cd-S thin films. FTIR ascertained that the organic ligand actually attached to the metals. DTA analysis showed that the synthesized precursor was thermally stable and could pyrolyzed around 300 and 500 °C. RBS of the deposited films showed that the stoichiometry and the thickness depended on deposition temperature. XRD analysis revealed that the films deposited at 360 and 380 °C are amorphous while those deposited at 400 °C to 450 °C showed peaks, which supported the possible co-existence of CuS and CdS as Cu-Cd-S, with an improvement in the crystallinity as substrate temperature increased. SEM showed that the films are uniform and crack-free, in which the morphology strongly depended on substrate temperature. Optical analysis revealed that the films have high absorbance in the UV region and high transmittance in the visible and near infrared region, in which direct band gap energy of 2.36 to 2.14 eV was obtained as deposition temperature increased. Other optical parameters such as Urbach energy, refractive index, extinction coefficient, dielectric constant also increased as the deposition temperature increased. Electrical analysis showed that resistivity is temperature dependent as it reduced as deposition temperature increased.http://iopscience.iop.org/journal/2053-15912020-09-13hj2020Physic