Scanning tunneling microscopy of buried dopants in silicon: images and their uncertainties

The ability to determine the locations of phosphorous dopants in silicon is crucial for the design, modelling, and analysis of atom-based nanoscale devices for future quantum computing applications. Recently, several papers showed that a metrology of scanning tunnelling microscopy (STM) imaging combined with atomistic tight-binding simulations could be used to determine coordinates of a dopant buried close to a Si surface. We identify effects which play a crucial role in the simulation of STM images and have to be precisely modelled for STM imaging of buried dopants and multi-dopant clusters to provide reliable position information. In contrast to previous work, we demonstrate that a metrology combining STM imaging with tight-binding simulations may lead to pronounced uncertainty due to tip orbital model, effects of dangling bonds and choice of local atomic basis for the tight-binding representation. Additional work is still needed to obtain a reliable STM metrology of buried dopant position.