We studied Ge nanocrystals (nc-Ge) formed by bombarding Ge(100) surface with N-2(+) gas followed by rapid thermal annealing (RTA). After initial N-2(+) implantation, near-edge x-ray absorption fine structure and x-ray photoelectron spectroscopy (XPS) data showed formation of molecule-like N-2 species and chemically metastable Ge nitrides (GeNx) The RTA transformed these into hemispherical nc-Ge of 10-25 nm in the diameter as clearly seen in transmission electron microscope images. XPS confirmed that the surface of the nc-Ge was covered with Ge3N4 layer and underlying layer is also mostly likely Ge3N4 This simple process of forming isolated nc-Ge with Ge3N4 surrounding layer can be useful in non-volatile memory applications. (C) 2010 Elsevier B.V All rights reserved.