Optical characterization of filtered vacuum arc deposited zinc oxide thin films

Abstract

ZnO thin films, 100-250 nm thick, were deposited on microscope glass slides and UV fused silica (UVFS) substrates using a filtered vacuum arc deposition (FVAD) system, operating at room temperature (RT) and 200 A for 60 s. The cathode was prepared from 99.9% pure Zn metal and the oxygen background pressure during deposition was in the range 0.67-0.93 Pa. The films were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), optical transmission and spectroscopic ellipsometry. As-deposited ZnO films were found to be polycrystalline with c-axis orientation. The atomic concentration ratio of Zn to O in the film as determined by XPS analysis was stoichiometric. Film transmission in the visible was 70-90%. The maximum and minimum values of the refractive index n and the extinction coefficient k in the visible, for all samples, were 2.23 to 1.90 and 0.6 to approximately 0, respectively. The type of inter-band electron transition was found to be direct transition with optical band gap in the range of 3.25-3.42 eV.

Structural and optical properties of Cr-doped ZnO thin films

“…27 An increase in the values of the refractive index and extinction coefficient was observed with the chromium doping concentration. The increase in the refractive index can be due to the high density of the films and a reduction in the grain size, 28 which is consistent with XRD and FE-SEM measurements. High optical scattering and optical losses also induce the increase in the extinction coefficient values.…”

Hybrid ZnO:polystyrene nanocomposite for all‐polymer photonic crystals

“…The bare PS extinction coefficient (k) is negligible over the whole spectral range and its refractive index shows the well-known dispersion with values in agreement with literature data [13,60]. The n and k spectra of NC thin films loaded with 2.5% (v/v) of ZnO NPs were calculated by the effective medium model [57] using literature data [61] for crystalline ZnO and compared with those of bare PS. The NC k spectrum shows a clear absorption peak below 400 nm, with a correspondent counterpart in the n spectrum [61].…”

“…The n and k spectra of NC thin films loaded with 2.5% (v/v) of ZnO NPs were calculated by the effective medium model [57] using literature data [61] for crystalline ZnO and compared with those of bare PS. The NC k spectrum shows a clear absorption peak below 400 nm, with a correspondent counterpart in the n spectrum [61]. These well-defined peaks are not observed in ellipsometric measurements, which anyway account for broader structures in the same spectral range of comparable intensity.…”

Growth and characterization of nanocrystalline SrTiOxfilms: room temperature deposition using RF sputtering system in a pure argon environment

“…Near the absorption edge (~380-400 nm), which is also presented in figure 3, the refractive index has a well-defined maxima for both films. However, the maxima are slightly shifted to longer wavelengths after annealing, indicating change in the optical band edge as confirmed by band gap calculations [31]. Furthermore, in the VIS range, the refractive indices of nanocrystalline STO films are found to be 2.36 and 2.31 (@550 nm) for as-deposited and annealed films, respectively.…”