Electronic structure of (Ga₅₅In₄₅)₂S₃₀₀ and (Ga_54.59In_44.66Er_0.75)₂S₃₀₀ single crystals

We report on studies of the X-ray photoelectron core-level and valence-band spectra for pristine and Ar⁺-ion bombarded surfaces of (Ga₅₅In₄₅)₂S₃₀₀ and (Ga_54.59In_44.66Er_0.75)₂S₃₀₀ single crystals grown by solution-melt technique. The (Ga₅₅In₄₅)₂S₃₀₀ and (Ga_54.59In_44.66Er_0.75)₂S₃₀₀ single crystals were found to be very rigid with respect to Ar⁺-ion bombardment. In particular, such a treatment did not cause any significant changes of values of the binding energies of core-level electrons as well as of the shapes of the XPS core-level and valence-band spectra of (Ga₅₅In₄₅)₂S₃₀₀ and (Ga_54.59In_44.66Er_0.75)₂S₃₀₀ single crystal surfaces. We measured for the (Ga₅₅In₄₅)₂S₃₀₀ compound the X-ray emission bands representing the energy distribution of mainly the valence S p and Ga p states and compared them on a common energy scale with the XPS valence-band spectrum. The comparison allows us for concluding that the S 3p and Ga 4p states contribute mainly at the top and in the central portion of the valence band of (Ga₅₅In₄₅)₂S₃₀₀, respectively. In addition, we have also detected at ambient conditions a strong photoluminescence of the (Ga_54.59In_44.66Er_0.75)₂S₃₀₀ single crystal with a maximum at 810 nm for the excitation wavelength of 532 nm. Our results indicate that the (Ga_54.59In_44.66Er_0.75)₂S₃₀₀ single crystal is a very promising material for its application in optoelectronic technologies.