Electronic Control of Silicon Surface Atomic Structures with Two-Probe Scanning Tunneling Microscopy

Dangling bonds (DBs) on the H-terminated Si(100) surface have stimulated much interest in exploring atomic-scale devices. Although multiprobe scanning tunneling microscope (STM) can be utilized as an ideal tool to characterize DB architectures, studying these on low conductive Si substrates remains a challenge since the effects such as large screening length and long mean-free path for carriers can emerge during measurements. Here, we report the effects of minority carrier (hole for n-type Si) injection on DBs with two-probe STM. While one STM probe was used to characterize the surfaces, another one was placed in the distance to inject holes into the Si substrates. We found that in steady state, migrating holes can negate band bending at the STM imaging areas and that the average charge states of DBs can be controlled by the amount of injected holes. We also investigated a DB island crafted on the H-terminated Si surface, which, as a result of hole injection, shows image features not ordinarily seen at the applied bias, confirming that the hole injection induces a shift of the STM apparent imaging bias and additional gap states in I-V measurements. These findings are important for understanding atomic-scale devices on low conductive substrates.