Post-deposition Annealing Controlled Structural And Optical Properties Of RF Magnetron Sputtered MoO3 Films

Abstract

MoO3 films were deposited on Corning glass and silicon substrates held at room temperature (303 K) by RF magnetron sputtering of metallic molybdenum target at a fixed oxygen partial pressure of 4x10 -4 mbar and sputter pressure of 4x10 -2 mbar. The as deposited films were annealed in air at different temperatures in the range 473 -673 K. X-ray diffraction studies suggest that the as-deposited and the films annealed at 473 K were amorphous in nature, while those annealed at 573 and 673 K were polycrystalline with mixed phases of αorthorhombic and βmonoclinic MoO3. Scanning electron microscope images of the films annealed at 573 and 673 K exhibited nanoflower like and nanodisk like structures due to improvement in the crystallinity. Fourier transform infrared studies showed the characteristic vibrations of MoO3 with shift in the vibrational modes of Mo = O and Mo -O -Mo with increase of annealing temperature. The optical absorption edge of the films shifted towards lower wavelengths side with increase of annealing temperature. Optical band gap of as-deposited films was 2.98 eV with refractive index 2.01, while those annealed at 673 K showed the optical band gap of 3.15 eV and refractive index of 2.08. The MoO3 films annealed at 673 K were of nanocrystalline with crystallite size of 39 nm with optical band gap of 3.15 eV and refractive index of 2.08 were favorable for electron blocking and hole-selective layers in bulk-heterojuction solar cells.

Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

“…The present optical band gap data are well matched with those reported in literature for different oxidation state of vanadium oxide505152 as well as molybdenum oxide5053. Further, the data presented in Table 2 confirmed that the optical band gap decreased with the increase in VO-MO film thickness.…”

Photochromic Response and Steady‐State Photoconductivity of Fibrous‐Reticulated α‐MoO3 Thin Films Prepared by Modified Spray Pyrolysis Technique

“…It can be observed from Figure that the transmission values are relatively low in the visible region for all the α‐MoO 3 thin films, which may be attributed to the heat treatment at low temperature (350 °C). In this respect, Subbarayudu et al . have reported that the low transmission in the MoO 3 thin films thermally treated at low temperatures is due to the presence of oxygen vacancies, whereas these vacancies can scatter the light photons.…”

22.2: Invited Paper: Sputtered Molybdenum‐Oxide for Anti‐Reflection Layers in Displays: Optical Properties and Thermal Stability

“…For sputtered MoO 3 thin films, post annealing at temperatures of 300-400 °C gives rise to the formation of orthorhombic α-phase and monoclinic β-phase crystalline structure [12] depending on the annealing temperature. The crystalline size and quality increases with annealing temperature, which at some point also changes optical properties.…”