The Optical Behavior of FeS2 Synthetic Pyrite Single Crystals

• Main Authors: Chen Shinn Horng, 陳信宏
• Other Authors: Mr. Huang Ying Sheng
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/64042071566423060774

碩士 === 國立臺灣科技大學 === 工程技術研究所 === 82 === The optical behavior of synthetic iron disulphide (pyrite) has been investigated. Single crystals of iron disulphide with mirror-like surfaces have been grown by an osillating chemical vapor transport method, using iodine trichlorine, dibromine, nitrogen quadrihydrogen bromine as the transport agent. The photoconductivity and optical absorption study is reported over a temperature range from 20K to 300K. At lower temperatures, several features which occur below absorption curve. The origin of sharpest peak is identified as the transition between the top of valance band and positive trivalent chromium ion trapping center through comparsion of the results with that of the photo-electron paramagnetic resonance (photo-EPR) measurements. The nature of other weaker features are discussed. The existence of these features prevents us from determining the band gap of iron disulphide at low temperatures by fitting the optical absorption data to the form of (.alpha.. plcnst..nu.) in direct proportion to the n power of (.plcnst.. nu.-E0). Therefore the energy gap of iron disulphide at low temperature is estimated by adding the thermal ionization energy of the shallow acceptor states to the photo ionization energy between the negative divalent sulphide-chlorine imputity states and the bottom of the conduction band. The band gap of various temperatures are determined and its temperature dependence is analyzed by an empirical expression proposed by O' Donnell et al. [Appl. Phys. Lett. 58, 2924 (1991)]. The parameters that describe the temperature dependence of Eg of the material are evaluated and discussed.