Charge Fluctuations in Pairs of Silicon Dangling Bonds

Several non-contact atomic force microscopy (nc-AFM) techniques have arisen in recent years to study and manipulate atomic species with single electron sensitivity. Thus far, however, this suite of techniques has relied upon the use of thin insulating films to stabilize the charged species and the application of large perturbative fields to control charge. By engineering charge configurations from silicon dangling bonds, which are mid-gap states, and performing all experiments with zero applied bias we bypass these difficulties. Crucially, we find both the contact potential difference and the image charge induced in the tip are required to explain the total tip induced band bending at the semiconductor surface. By employing a series of nc-AFM measurements at different heights, amplitudes, and scan speeds we elucidate the strong distance dependence of these interactions. We demonstrate that with carefully chosen tip-sample separations we can monitor the charge states of dangling bond structures nearly non-perturbatively, revealing surprisingly long sticking times on the order of minutes.
[1] T.R. Huff et al., ACS Nano 11 (9), 8636–8642 (2017). [2] W. Vine et al., arXiv:1709.10091 (2017).