A study on structural, optical, electrical and microstructural properties of thin TiOx films upon thermal oxidation: Effect of substrate temperature and oxidation temperature

作者：Sreemany Monjoy^*; Bose Ankita; Sen Suchitra

来源：Physica B: Condensed Matter , 2010, 405(1): 85-93.

DOI：10.1016/j.physb.2009.08.031

• RF magnetron sputtering
• TiOx thin films
• Thermal oxidation
• Scanning electron microscopy
• Optical and electrical properties

Influences of both substrate temperature, T-s (similar to 305, 473 K) and oxidation temperature, T-a(similar to 623-973 K) on the structural, optical, electrical and microstructural properties of thin TiOx (x <= 2) films obtained by thermal oxidation of sputtered titanium thin films have been investigated. T-s is found to be an important parameter that affects both the as deposited film morphology and phase evolution of TiOx films during oxidation. As deposited and oxidized films processed at T-a similar to 623 K exist in TiO form. Formation of anatase (TiO2) phase takes place at T-a similar to 723 K. As the T-a increases above 723 K, degree of crystallinity of the film improves and rutile (TiO2) phase appears along with anatase phase at T-a similar to 873 K. Further increase in the T-a enhances the contribution of rutile phase at the expense of anatase contribution. Apparent crystallite size, L, and refractive index of the TiOx (x approximate to 2) films increase with T-a but band gap energy, E-g decreases from similar to 3.4 to 3.35eV. Scanning electron microscopic study reveals that both film densification and grain size improve with T-a. As the T-a increases above 873 K, rutile phase contribution as well as grains of the oxidized films deposited at a lower T-s grow at a faster rate than that of the TiOx films prepared at a higher T-s. Room temperature resistivity of the as deposited films is found to be dependent on T-s. Film-resistivity increases with oxidation temperature and at T-a similar to 723 K, resistivity of the film increases drastically. Temperature coefficient of resistivity (TCR) for all the as deposited and oxidized films processed at T-a similar to 623 K is found to be negative and lie between similar to 1.2 x 10(-3)-2.1 x 10(-3) K-1. Thermal activation energy, E-a, of the as deposited and oxidized (T-a similar to 623 K) TiOx (x approximate to 1) films is estimated to vary over the range similar to 0.015-0.027 eV. Observed change in the film electrical properties with T-a is discussed in the light of oxygen incorporation in the TiOx structure.

• 出版日期2010-1-1