Low-temperature sputtering of crystalline TiO{sub 2} films
- Department of Physics, University of West Bohemia, Univerzitni 22, 30614 Plzen (Czech Republic)
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 T{sub surf} necessary to form crystalline TiO{sub 2} 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 Ti{sub 5}O{sub 9} 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 T{sub surf} using thermostrips pasted to the glass substrate. It was found that (1) T{sub surf} is considerably higher (approximately by 100 deg. C or more) than the substrate temperature T{sub s} measured by the thermocouple incorporated into the substrate holder and (2) T{sub surf} strongly depends on the substrate-to-target distance d{sub s-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 TiO{sub 2} films depends not only on T{sub surf} but also on the total pressure p{sub T} of sputtering gas (Ar+O{sub 2}), partial pressure of oxygen p{sub O{sub 2}}, the film deposition rate a{sub D}, and the film thickness h (2) crystalline TiO{sub 2} films with well developed anatase structure can be formed at T{sub surf}=160 deg. C and low values of a{sub D}{approx_equal}5 nm/min (3) the crystalline structure of TiO{sub 2} film gradually changes from (i) anatase through (ii) anatase+rutile mixture, and (iii) pure rutile to x-ray amorphous structure at T{sub surf}=160 deg. C and p{sub T}=0.75 Pa when p{sub O{sub 2}} decreases and a{sub D} increases above 5 nm/min, and (4) crystallinity of the TiO{sub 2} films decreases with decreasing h and T{sub surf}. Interrelationships between the structure of TiO{sub 2} film, its roughness, T{sub surf}, and a{sub D} are discussed in detail. Trends of next development are briefly outlined.
- OSTI ID:
- 20777184
- Journal Information:
- Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films, Vol. 24, Issue 3; Other Information: DOI: 10.1116/1.2187993; (c) 2006 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1553-1813
- Country of Publication:
- United States
- Language:
- English
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