Scanning tunneling microscopy detection of individual dopant atoms on wet-prepared Si(111):H surfaces

We have performed scanning tunneling microscopy (STM) observation of individual acceptor and donor atoms on hydrogen-terminated Si(111)-1×1 surfaces prepared by wet etching in a NH4F aqueous solution. Separate measurements of p- and n-type substrates showed that acceptors appear as protrusions in filled-state images and as depressions in empty-state images, while for donors the topography is reversed in both filled- and empty-state images. The same relation between the bias polarity and the dopant appearance is preserved for codoped substrates. These results demonstrate that the STM on the Si(111):H surface can detect acceptors and donors distinguishably, enabling us to measure dopant profiles across codoped areas such as p-n junctions.