Zn0.40Mn0.60Se thin films were grown on GaAs (100) substrate by hot-wall epitaxy. The grown films had both NaCl structure and zincblende structure. Energy-dispersive X-ray analysis revealed that the Mn composition ratio of the grown ZnMnSe thin films was approximately 0.60 and this Mn composition ratio had no relation to the increase of the substrate temperature. However, it was found that the surface state and the crystal structure of Zn0.40Mn0.60Se thin films were changed with increasing substrate temperature. These results were confirmed through examination of the surface morphology using atomic force microscopy and the change of the imaginary part epsilon(2)(E) peak of the dielectric function measured by spectroscopic ellipsometry. (c) 2005 Elsevier B.V. All rights reserved.