Spontaneous formation of Ge nanocrystals with the capping layer of Si3N4 by N2+ implantation and rapid thermal annealing

We studied Ge nanocrystals (nc-Ge) formed by bombarding Ge(100) surface with N2+ gas followed by rapid thermal annealing (RTA). After initial N2+ implantation, near-edge x-ray absorption fine structure and x-ray photoelectron spectroscopy (XPS) data showed formation of molecule-like N2 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.