Demonstration of gating action in atomically controlled Si:P nanodots defined by scanning probe microscopy

We study the low temperature electrical characteristics of planar, highly phosphorus-doped nanodots. The dots are defined by lithographically patterning an atomically flat, hydrogenated Si(1 0 0):H surface using a scanning-tunneling-microscope (STM), phosphorus δ-doping and low temperature molecular beam epitaxy in an ultra-high vacuum environment. Ohmic contacts and a surface gate structure are aligned ex-situ using electron beam lithography. We present electrical transport measurements of a 25×21nm2 Si:P nanodot at 4 K containing about 1000 P atoms. We find significant gating action within a gate range of -2 to 7 V. From the stability diagram, we observe a large conductance gap and the existence of electron resonances near threshold which can be modulated with the top gate. Our results show promise for the fabrication of planar quantum dots using this technique.