  Origin of room temperature visible photoluminescence (PL) from defect free
germanium (Ge) nanoparticles have been discussed here. The Ge nanoparticles
produced by laser-induced etching technique show broad visible PL around 2.0 -
2.2 eV at room temperature. Size dependent PL peak shift in Ge nanoparticles
has been explained in terms of quantum confinement. Theoretical calculations of
radiative lifetime using oscillator strength, which is closely related to the
size of the nanostructures, suggests that the PL is originating from a
radiative recombination process in quantum confined Ge nanostructures.
