CuAl2S4 single crystals were grown with the constituent elements coppe
r, aluminium and sulphur (purity 6N) as the starting material by the c
hemical transport reaction method using iodine as a transport agent. L
ayer-type colourless transparent single crystals were obtained, and th
e crystal structure of the single crystals was found to be cubic with
the lattice constant a = 9.954 Angstrom. The energy bandgap of the CuA
l2S4 single crystal was revealed to be direct bandgap, and the optical
energy gap was found to be 4.10 eV at 10 K.