Nanometer scale islands were observed in air on CdSe/ZnSe surfaces grown by molecular beam epitaxy. Measurements by atomic force microscope revealed that the aspect ratio of the island increased first and then decreased with time. Surface analyses by Auger electron spectroscopy indicated clearly that the island was composed in large part of oxides and the outer shell of the island was Zn-enrichcd and Cd-depletcd. These islands showed sharp emissions as quantum dots. This work demonstrates that the islands were formed mainly due to the oxidation of the surface and that it grew in a way similar to that generated from a strained film. III addition, intermixing of ZnSe and Zn segregation during the island Formation occurred.