Synthesis, structure, physical properties, and electronic structure of KGaSe2

The ternary gallium selenide KGaSe2 has been synthesized by solid-state reactions and good quality crystal has been obtained. KGaSe2 crystallizes in the monoclinic space group C2/c with cell dimensions of a = 10.878(2) Å, b = 10.872(2) Å, c = 15.380(3) Å, and β = 100.18(3)°. In the structure, adamantane like [Ga4Se10]8− units are connected by common corners forming two-dimensional [GaSe2]− layers which are separated by K+ cations. KGaSe2 exhibits congruent-melting behavior at around 965 °C. It is transparent in the range of 0.47–20.0 μm and has a band gap of 2.60(2) eV. From a band structure calculation, KGaSe2 is a direct-gap semiconductor. The band gap is mainly determined by the [GaSe2]− layer.

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► A single-crystal structural analysis of KGaSe2 was carried out for the first time.
► Adamantane-like [Ga4Se10]8− are connected to generate two-dimensional layers.
► KGaSe2 is transparent in the range of 0.47–20 μm and melts congruently at 965 °C.
► KGaSe2 is a direct-gap semiconductor according to the band structure calculation.