Substrate-dependent optical absorption characteristics of titanium dioxide thin films

Abstract

We used the electron-beam evaporation method in various oxygen partial pressure environments to deposit TiO(2) thin films on various glass substrates at 300 degrees C. We found the threshold oxygen partial pressures above which the film is transparent are different for films on various substrates. Below the threshold oxygen partial pressure, the refractive index and the extinction coefficient of the films varied from substrate to substrate. The films on substrates with higher threshold oxygen partial pressure were associated with a higher extinction coefficient and a higher growth rate. These phenomena are correlated with the appearance of rutile phase in the anatase phase, which is also correlated with variations in the Al(2)O(3) and Na(2)O content in the substrates. The Al(2)O(3) content in the substrate tends to enhance the formation of rutile phase in the film and to give a higher extinction coefficient for the film, while the Na(2)O content in the substrate tends to retard the rutile formation in the film and to give a lower extinction coefficient for the film.

Analysis of nanostructured porous films by measurement of adsorption isotherms with optical fiber and ellipsometry

“…1,2 Cross sections of micrographs from scanning electron microscopy and transmission electron microscopy have provided direct information about the nanostructure of the multilayer systems, although many other techniques have been utilized to characterize films ͑x-ray diffraction, electron diffraction, Auger electron spectroscopy, x-ray fluorescence, etc.͒. It is currently known that most evaporated films are formed by a nanostructure composed of nanometric-size columns, amorphous or crystalline.…”

Influence of the Oxygen Partial Pressure on the Composition and Optical Properties of Electron-beam Evaporated TiOx Films

“…Recently, a variety of techniques has been used for the preparation of TiO 2 films [1][2][3][4]. For instance, Bennett et al [5] and Chen et al [6] have reported that the optical properties of the TiO 2 films deposited by electronbeam evaporation, such as refractive index, extinction coefficient and scattering losses, are strongly process-dependent and are especially sensitive to oxygen partial pressure. So, the determination of the oxygen content of TiO 2 films deposited by electron-beam evaporation at different oxygen partial pressures is relevant.…”

Atomic Layer Deposition of Titanium Oxide from TiI4 and H2O2

“…Various properties of the extensively studied metal oxide TiO 2 have been of interest, including deposition process control, [1] crystal structure, [2] phase stability, [3±5] optical quality, [6,7] (electro)luminescence, [8] photosensitivity, [9] microhardness, [6] epitaxial growth, [10] permittivity, [11,12] and leakage current. [5,12,13] With reference to factors affecting the physical properties, an interesting aspect in TiO 2 growth has been the stability of various crystallographic phases such as anatase and rutile.…”

“…At the same time, pure anatase is optically less absorbent than rutile. [7] As a metastable polymorph of TiO 2 , anatase is often first to form at relatively low processing temperatures, especially in fine-grained form. [2,3,14] Possibly the lowest reported in-situ processing temperature of pure rutile has been 300 C in laser ablation, [15] or rutile mixed with anatase in films evaporated at 300 C and above.…”

“…[1,4,12,14,17] The composition of the substrate may also have an influenceÐit has been noted that, at rather low temperatures (around 300 C), high Al 2 O 3 and Na 2 O contents in the substrate material favor the formation of rutile and anatase phases, respectively. [7] Recently, rutile TiO 2 has been produced by low-pressure CVD from titanium-tert-butoxide on SnO 2 (of rutile structure) substrates at temperatures as low as 290 C and on glass at 322 C. [4] Anatase and rutile thin films have been obtained by physical methods such as reactive sputtering [6,13] and electron beam evaporation, [5] or by various chemical methods such as ambient air hydrolysis of metal precursors, [9] hydrolysis in aqueous medium, [2,8] chemical beam epitaxy (CBE), [10] and CVD. [ sors have been used in CVD, including b-diketonate complexes, [1,18] TiCl 4 , [9,16,19] Ti(NO 3 ) 4 , [14] Ti(OC 2 H 5 ) 4 , [12] or Ti(OC 3 H 7 ) 4 .…”