Structural investigation of pristine and annealed nanocrystalline TiO₂ thin films by X‐ray diffraction and Raman spectroscopy

Abstract

Nanocrystalline anatase TiO 2 films were prepared from colloidal suspensions using particles with a nominal size of 12 nm. Their structure was examined by Raman spectroscopy and X-ray diffraction (XRD). The as-prepared specimens exhibit exclusively features due to the anatase phase of TiO 2 (e.g., the E g , B 1g and A 1g vibration modes in Raman spectroscopy and the characteristic diffraction peaks in XRD). Isochronal annealing of the films in air at temperatures of up to 1320 K effected clear structural changes, observed both in Raman and XRD: the crystallite size increases from ~13 nm to ~125 nm between 470 K and 1220 K, with the crystallites remaining in the anatase phase. A phase transition to the rutile phase of TiO 2 occurs gradually in the temperature range 1220 -1320 K and the average crystallite size increases to ~160 nm. The E g vibration in anatase films reveals a blue shift and an asymmetric peak broadening towards higher frequencies for smaller particle size/lower annealing temperatures. A power-law dependence between the Raman peak width and the inverse of the crystallite size is found.

Red shifts of the Eg(1) Raman mode of nanocrystalline TiO2:Er monoliths grown by sol–gel process

“…7 displays the FWHM of the E g(1) Raman phonon versus R. The FWHM decreases as R also decreases (observe the direction of arrow), like cubic CeO 2 nanoparticles where FWHM diminishes as R decreases [26]. But, actually, this result is contrary to the tendency expected in most peak line-width versus R data [8,[27][28][29], where FWHM increases when R decreases. Besides, the inset of Fig.…”

“…The Raman spectrometry technique has been a useful and important tool and there have been a variety of publications that interpret of different manners the behavior of the vibrational modes of a Titania matrix as the radius of nanoparticles changes due to the incorporation of different types of ions. Among these interpretations are phonon confinement, non-stoichiometry or internal/stress surface tension effects [7][8][9][10][11][12].…”

Thickness dependence of the growth of magnetron-sputtered TiO2 films studied by Raman and optical transmittance spectroscopy

“…Half width of the E g peak vs. crystallite size as deduced from XRD, including results from the literature. 4,18,27,28,35,36 thickness obtained from the simulation of the transmittance data are close to that obtained by profilometry (see Fig. 7).…”

“…Orendorz et al 36 also observed that the prominent E g 144 cm À1 mode of their nanocrystalline anatase TiO 2 films is blueÀshifted and the FWHM varies as a power of the inverse of crystallite size. These films were prepared from colloidal suspensions using particles of 12 nm size and their crystallite sizes were varied from $13 to $125 nm upon annealing at higher temperatures without any phase transformation.…”

Symmetrically substituted phenothiazine as prospective candidate for UV responsive dye sensitized solar cells

“…The structural properties of such films are subject to several publications [19] [20] [21] [22] [23]. The DTPT was prepared following the synthesis as described in [9] and [10].…”