Tunable transport measurement on single donors performed by a scanning tunneling microscope

In devices like the single-electron transistor (SET) the detailed transport properties of a nanostructure can be measured by tuning its energy levels with a gate voltage. The scanning tunnelling microscope (STM) in contrast usually lacks such a gate electrode. We demonstrate th capability of tuning of the levels of a donor in a STM without a third electrode. Single donors in ZnO(0001) were investigated and the chemical nature was identified [1,2]. Furthermore, we realized the manipulation of the subsurface atom by STM tip [3]. In the further research, the potential and the position of the STM tip are used to locally control band bending. Conductance maps in this parameter space reveal Coulomb diamonds known from three-terminal data from single-electron transistors and provide information on charging transitions, binding energies and vibrational excitations. The analogy to SET data suggests anew way of extracting these key quantities without making any assumptions about the unknown shape of the STM tip [4].[1] H. Zheng, J. Kröger, and R. Berndt, Phys. Rev. Lett. 108, 076801 (2012)[2] H. Zheng, M. Gruyters, E. Pehlke, and R. Berdnt, Phys. Rev. Lett. 111, 086101 (2013)[3] H. Zheng, A. Weismann, and R. Berndt, Phys. Rev. Lett. 110, 226101(2013)[4] H. Zheng, A. Weismann, and R. Berndt, Nature Communication 5, 2992 (2014)