Electron Spin Resonance Studies of Fe in CuGaS2


Katsuaki Sato , Yuji Katsumata and Takao Nishi

Proc. 12th Int. Conf. Ternary and Multinary Compounds, Hsinchu, Taiwan, March 13-17.2000, Jpn. J. Appl. Phys. Supplement (2000) to be published

Abstract
ESR spectra (X band) were measured in single crystals of CuGaSe2 prepared by traveling heater method (THM) and iodine transport (IT) technique. In the THM-crystal an anisotropic signal around 200-300 mT, which is completely quenched by H2-annealing, is assigned to Fe3+. On the other hand, two types of ESR spectra were observed in IT-crystals. In the type-1 spectrum, nearly isotropic lines were found at 110-130, 400 and 890-950 mT. The spectral features are similar to that of Fe3+ in CuInSe2. On the contrary, in the type-2 spectrum, strongly anisotropic resonance lines were observed and were assigned to Fe2+ states. Annealing in Se vapor completely quenches the type-2 signal but results in appearance of the type-1 spectrum. This finding may be explained by an assumption that the Fermi level is lowered below the Fe2+/Fe3+ demarcation level by reduction of Se-vacancy brought about by the Se- vapor anneal. KEY WORDS: CuGaSe2 single crystals, electron spin resonance, iron impurity