Correlation of Structural and Optical Properties of Sputtered FeSi₂Thin Films

Abstract

Iron-disilicide films were sputter deposited on Si(100) wafers to 300–400 nm, at substrate temperatures ranging from room temperature to 700 °C. As-deposited films were amorphous at deposition temperatures up to 200 °C, and crystalline β-FeSi 2 at 300–700 °C. Amorphous films were heat-treated after deposition at 300–700 °C. They remained amorphous up to 400 °C, and transformed to crystalline β-FeSi 2 at 500–700 °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 ×10 4 cm -1 for amorphous films to 1.2 ×10 5 cm -1 for the samples deposited at 700 °C. The films crystallized by heat-treatment had a markedly different and irregular structure, resulting in their lower optical absorption.