Large transparent tetrahedral CuX (X =CI, Br) single crystals with over 6 mm on an edge were grown by the temperature reduction method at the range of 40-50 degrees C. Aqueous HX (X=C1, Br) were used as solvents. Solubility curves of CuX in 3 mol L-1 HX acid solutions were measured by indirect weight analysis. The crystals were further characterized by X-ray powder diffraction (XRD) measurement, thermal analysis (DTA/TG), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflection spectrum (UVDRS). The results indicate that CuX single crystals have cubic structures with a nearly standard ratio of Cu/X and wide direct band gaps (Eg(cuci) =3.21 eV, Eg(cuBR) Br=2.95 eV). (C) 2014 Elsevier B.V. All rights reserved.