This article reports on the investigation of reactive magnetron sputtering of transparent, crystalline titanium dioxide films. The aim of this investigation is to determine a minimum substrate surface temperature Tsurf necessary to form crystalline Ti O2 films with anatase structure. Films were prepared by dc pulsed reactive magnetron sputtering using a dual magnetron operating in bipolar mode and equipped with Ti(99.5) and ceramic Ti5 O9 targets. The films were deposited on unheated glass substrates and their structure was characterized by x-ray diffraction and surface morphology by atomic force microscopy. Special attention is devoted to the measurement of Tsurf using thermostrips pasted to the glass substrate. It was found that (1) Tsurf is considerably higher (approximately by 100 °C or more) than the substrate temperature Ts measured by the thermocouple incorporated into the substrate holder and (2) Tsurf strongly depends on the substrate-to-target distance ds-t, the magnetron target power loading, and the thermal conductivity of the target and its cooling. The main result of this study is the finding that (1) the crystallization of sputtered Ti O2 films depends not only on Tsurf but also on the total pressure pT of sputtering gas (Ar+ O2), partial pressure of oxygen p O2, the film deposition rate aD, and the film thickness h, (2) crystalline Ti O2 films with well developed anatase structure can be formed at Tsurf =160 °C and low values of aD ≈5 nmmin, (3) the crystalline structure of Ti O2 film gradually changes from (i) anatase through (ii) anatase+rutile mixture, and (iii) pure rutile to x-ray amorphous structure at Tsurf =160 °C and pT =0.75 Pa when p O2 decreases and aD increases above 5 nmmin, and (4) crystallinity of the Ti O2 films decreases with decreasing h and Tsurf. Interrelationships between the structure of Ti O2 film, its roughness, Tsurf, and aD are discussed in detail. Trends of next development are briefly outlined.
|Number of pages||8|
|Journal||Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films|
|Publication status||Published - 23 May 2006|
ASJC Scopus subject areas
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films