Manipulating Ge quantum dots on ultrathin SixGe1-x oxide films using scanning tunneling microscope tips

Germanium quantum dots (QDs) were extracted from ultrathin SixGe1-x oxide films using scanning tunneling microscope (STM) tips. The extraction was most efficiently performed at a positive sample bias voltage of +5.0V. The tunneling current dependence of the extraction efficiency was explained by the electric field evaporation transfer mechanism for positive Ge ions from QDs to STM tips. Ge QDs (7nm) were formed and isolated spatially by extracting the surrounding Ge QDs with an ultrahigh density of > 1012cm-2. Scanning tunneling spectroscopy of the spatially-isolated QDs revealed that QDs with an ultrahigh density are electrically-isolated from the adjacent dots.