title: Effect of thermal annealing on the phase evolution of silver tungstate in Ag/WO₃ films.
abstract: Silver/tungsten oxide multi-layer films are deposited over quartz substrates by RF magnetron sputtering technique and the films are annealed at temperatures 200, 400 and 600°C. The effect of thermal annealing on the phase evolution of silver tungstate phase in Ag/WO3 films is studied extensively using techniques like X-ray diffraction, micro-Raman analysis, atomic force microscopy and photoluminescence studies. The XRD pattern of the as-deposited film shows only the peaks of cubic phase of silver. The film annealed at 200°C shows the presence of XRD peaks corresponding to orthorhombic phase of Ag2WO4 and peaks corresponding to cubic phase of silver with reduced intensity. It is found that, as annealing temperature increases, the volume fraction of Ag decreases and that of Ag2WO4 phase increases and becomes highest at a temperature of 400°C. When the temperature increases beyond 400°C, the volume fraction of Ag2WO4 decreases, due to its decomposition into silver and oxygen deficient phase Ag2W4O13. The micro-Raman spectra of the annealed films show the characteristic bands of tungstate phase which is in agreement with XRD analysis. The surface morphology of the films studied by atomic force microscopy reveals that the particle size and r.m.s roughness are highest for the sample annealed at 400°C. In the photoluminescence study, the films with silver tungstate phase show an emission peak in blue region centered around the wavelength 441 nm (excitation wavelength 256 nm).
authors: Department of Optoelectronics, University of Kerala, Kariyavattom, Thiruvananthapuram, Kerala 695581, India.
authors: R Jolly
authors: RJ
authors: Bose
authors: Department of Optoelectronics, University of Kerala, Kariyavattom, Thiruvananthapuram, Kerala 695581, India.
authors: R Sreeja
authors: RS
authors: Sreedharan
authors: Department of Optoelectronics, University of Kerala, Kariyavattom, Thiruvananthapuram, Kerala 695581, India.
authors: R Resmi
authors: RR
authors: Krishnan
authors: UGC - DAE Consortium for Scientific Research, Khandwa Road, Indore 452017, Madhyapradesh, India.
authors: V R
authors: VR
authors: Reddy
authors: UGC - DAE Consortium for Scientific Research, Khandwa Road, Indore 452017, Madhyapradesh, India.
authors: Mukul
authors: M
authors: Gupta
authors: UGC - DAE Consortium for Scientific Research, Khandwa Road, Indore 452017, Madhyapradesh, India.
authors: V
authors: V
authors: Ganesan
authors: Department of Optoelectronics, University of Kerala, Kariyavattom, Thiruvananthapuram, Kerala 695581, India.
authors: S K
authors: SK
authors: Sudheer
authors: Department of Optoelectronics, University of Kerala, Kariyavattom, Thiruvananthapuram, Kerala 695581, India.
authors: V P Mahadevan
authors: VPM
authors: Pillai
mesh_terms: D049449:Luminescence; D018625:Microscopy, Atomic Force; D010087:Oxides / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014414:Tungsten / Q000737:chemistry*; D017973:Tungsten Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D010087:Oxides; D017973:Tungsten Compounds; D012834:Silver; C511604:tungsten oxide; C045951:tungstate; D014414:Tungsten
keywords: Micro-Raman; Phase evolution; Photoluminescence; Silver tungstate; Thermal annealing; XRD