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

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