STM nanopatterning on pristine Nb-doped SrTiO3 surfaces
The surface morphology of modified Nb:STO surfaces.
By using different electric
pulse conditions, holes of
different sizes and depths
are created on a ~500-nm atomic-flat
terrace. The sizes of the holes are ~10 to ~20 nm.
Collaborative users from the Advanced Photon Source, working with the Electronic & Magnetic
Materials & Devices Group, have found a controllable way to modify
the surfaces of pristine Nb-doped SrTiO3 (Nb:STO) at the nanoscale. For
decades, most of the work on noncleavable STO focused on heavily treated
surfaces (chemical etching, sputtering/annealing). This is the first
scanning tunneling microscope (STM) work on how the tip can interact
with pristine Nb:STO surfaces created by in situ fracturing.
By fracturing Nb:STO at ~50 K, ~500-nm atomically flat TiO2 terraces
with a random covering of SrO molecules are attained. Using a pulsed
sample-tip bias, the SrO clusters can be removed and redeposited reversibly
from surface to STM tip. This work demonstrates the interaction between
the STM tip and oxide surfaces, and it offers a pathway to creating nanoscale
objects on single-crystal oxide surfaces.
T. Chien, T. Santos, M. Bode, N. Guisinger, J. Freeland, Appl. Phys. Lett. 95, 163107 (2009).