Effect of rf power on the properties of magnetron sputtered CeO2 thin films

Abstract

Cerium oxide (CeO 2 ) thin films were prepared by rf magnetron sputtering (PVD) technique onto glass substrates at a pressure of 3 9 10 -4 mbar of Ar ? atmosphere. The thickness of deposited CeO 2 films ranges from 380 to 590 nm. X-ray diffraction studies on the films showed that the films are polycrystalline in nature. The crystallite size (D), dislocation density (d) and micro-strain (e) were evaluated from XRD patterns. The obtained micro-strain and dislocation density of the films were found to be *10 -3 and *10 16 lines/m 2 respectively, along with a marginal increase in crystallite size from *6 to *9 nm. The experimental diffraction values of the films agreed with the standard values. The optical properties of cerium oxide films were studied in the wavelength range 325-900 nm. Optical absorption, extinction coefficients, refractive index and optical conductivity were evaluated from optical measurements. The films are found to be highly transparent in visible region and exhibits low reflectance in the ultraviolet region. The optical band gap of the films was found to decrease from 3.53 to 3.45 eV, with the increase of film thickness. The defects were found to increase with the increase of rf power. Emission bands like UV, weak blue, blue, blue-green and green bands were observed from PL spectra of CeO 2 thin films. Raman active mode (F 2g ) of CeO 2 thin films was observed at 466 cm -1 and films deposited at higher rf power show increased line width as well as peak intensity in Raman spectra. Rf power induced formations of flower like morphology were observed in SEM images. The surface roughness of CeO 2 thin films was increased from 2.9 to 7.7 nm with the increase of rf power as ascertained from AFM images and the results are discussed.

The influence of substrate temperature on the optical and micro structural properties of cerium oxide thin films deposited by RF sputtering

“…This is attributed to poor crystallinity and large disorder in the films [19]. It is reported that CeO 2 films with smaller crystallite show poorer luminescence, which is attributed to non radiative relaxation through surface states [36].…”

“…Figure 7 These Raman active modes are attributed to a symmetrical stretching mode of Ce-8O vibrational unit, and therefore, they are very sensitive to any disorder in oxygen sub lattice that resulted from thermal, doping, or grain size [19,[38][39][40][41]. The effect of microstructure of CeO 2 on the shape of the Raman spectra was observed by broadening the line and by increasing its asymmetry, which are attributed to the reduction in phonon lifetime in the nanocrystalline regime [42][43][44].…”

“…Several methods have been proposed to prepare CeO 2 thin films such as molecular beam epitaxy (MBE) [13], chemical vapor deposition (CVD) [14], pulsed laser deposition [15], dip coating [16], spray pyrolysis [17], spin coating [18] and radio frequency (RF) magnetron sputtering [19]. Among these techniques RF sputtering method has many attractive advantages which include better film growth control, repeatability, low temperature deposition, large scale stability and uniform film properties.…”

Fabrication and characterization of double‐shelled CeO2‐La2O3/Au/Fe3O4 hollow architecture as a recyclable and highly thermal stability nanocatalyst

“…As observed in Figure B(f), the matching IR spectra gave a similar absorption band around 1380 cm ‐1 assigning to the characteristic vibration mode of CeO 2. In Figure A(f), after the H‐CLACF MCs were calcined at 550 °C (H‐CLACF‐550), the amorphous La 2 O 3 crystallites still remains amorphous, not appearing crystal structure transformation . The peak at 33.2° corresponding to the (104) crystal planes of a‐Fe 2 O 3 confirms that a small portion of Fe 3 O 4 transfers into the α‐Fe 2 O 3 .…”

Room temperature ferromagnetism of Ni doped cerium oxide single crystalline thin Films deposited by using rf magnetron sputtering

“…The details of the target preparation and coating procedures are described elsewhere [6]. Argon was used as the plasma generation gas.…”