Abstract
Thin films in the Cr-Ti-O system were atomic layer deposited from CrO<sub>2</sub>Cl<sub>2</sub>, TiCl<sub>4</sub>, and CH<sub>3</sub>OH on Si(1 0 0), fused SiO<sub>2</sub>, and <i>a</i>-Al<sub>2</sub>O<sub>3</sub>(0 1 2) substrates at 420 <sup>o</sup>C. The proportion between Ti and Cr resulted from the ratio of the CrO<sub>2</sub>Cl<sub>2</sub>/CH<sub>3</sub>OH and TiCl<sub>4</sub>/CH<sub>3</sub>OH pulsing. The films were grown up to the thickness of about 70 nm. Annealing of the films was performed in O<sub>2</sub> at 1000 <sup>o</sup>C. A notable dependence of their microstructure, conductance, and conductometric response to CO, H<sub>2</sub>, and CH<sub>4</sub> in dry air on the substrates, Ti content, and annealing has been demonstrated. The films were polycrystalline on Si and SiO<sub>2</sub>, and epitaxial on <i>a</i>-Al<sub>2</sub>O<sub>3</sub>. At temperatures above 400 <sup>o</sup>C, the films had a conductance, advantageous from the point of view of semiconductor gas sensors. In response to a 30-ppm CO exposure at 450 <sup>o</sup>C, an annealed film on the <i>a</i>-Al<sub>2</sub>O<sub>3</sub>(0 1 2) substrate, distinguished by a relatively high Ti/Cr atomic ratio, showed a 16-% conductance decrease in 20 s, with a 120-s recovery.
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