Investigation of the local density of states in self-assembled GeSi/Si(001) nanoislands by combined scanning tunneling and atomic-force microscopy

The local density of states in self-assembled GeSi/Si(001) nanoislands is investigated for the first time by combined tunneling and atomic-force scanning microscopy. Current images and tunneling spectra of individual GeSi/Si(001) islands are obtained. These measurements yield the spatial and energy distributions of the local density of states in GeSi islands, respectively. The tunneling spectroscopy data demonstrate that uncapped Ge_0.3Si_0.7/Si(001) islands behave as type-I heterostructures.