Correlation of Structural and Optical Properties of Sputtered FeSi2 Thin Films

Iron-disilicide films were sputter deposited on Si(100) wafers to 300-400 nm, at substrate temperatures ranging from room temperature to 700 degrees C As-deposited films were amorphous at deposition temperatures up to 200 degrees C, and crystalline beta-FeSi2 at 300-700 degrees C Amorphous films were heat-treated after deposition at 300-700 degrees C They remained amorphous up to 400 degrees C, and transformed to crystalline beta-FeSi2 at 500-700 degrees C Optical absorption measurements showed that the band gap of all films is direct in nature, ranging from 0 88 to 0 93 eV The deposition temperature was seen to affect the crystallinity of the as-deposited films and to vary their optical properties significantly The photoabsorption coefficient, measured at 1 eV, increased from 5 6 x 10(4) cm(-1) for amorphous films to 1.2 x 10(5) cm(-1) for the samples deposited at 700 degrees C The films crystallized by heat-treatment had a markedly different and irregular structure, resulting in their lower optical absorption (C) 2010 The Japan Society of Applied Physic