Over the last three years we have demonstrated key milestones in the fabrication of buried nano-scale devices in silicon using an ultra-high vacuum scanning tunnelling microscope (STM) and silicon molecular beam epitaxy (MBE). Recently we have achieved the final step of connecting the STM-patterned buried phosphorus devices to the outside world to perform electrical measurements. The results of our low temperature magnetotransport measurements highlight the potential of this approach for the creation of atomic-scale devices.
The control of feature sizes down to the atomic scale made possible with STM based hydrogen lithography allows unprecedented accuracy in the control of the number and distribution of dopant atoms in devices. We present a detailed STM study of the adsorption of PH<sub>3</sub> on STM-patterned H:Si(001) surfaces for the controlled placement of P dopants in Si. In particular we characterise the effect of the orientation of lithographic line features relative to the surface dimer rows on phosphine adsorption and the scaling of dopant density feature size down to single atom lithography.