2023 Volume 58 Issue 2 Pages 76-79
In the pursuit of exploratory nano- or atomic-scale devices, there is great demand for characterization of extremely small one- and two-dimensional structures. Imaging, fabricating, and measuring of local electronic properties of these structures can be performed with a one-probe scanning tunneling microscope (1P-STM). Yet, assessing the electrical conduction properties lateral to the surface demands two-probe (2P-) and four-probe (4P-) STM. The conductance measurement with 4P-STM is generally preferred over 2P-STM as it can eliminate the uncertainty in the probe-to-surface contact resistance that are derived from Schottky barrier. However, if we can solve the issue of the high resistive contact resistance with 2P configuration, we would be able to measure surface state conduction with the minimum number of probes, reducing arduous tasks in this field. In this report, we report the refinement of 2P-STM for surface state conduction measurements by Ohmic contact between probe and surface. We also utilized STM lithography to create electronically isolated regions from the otherwise surface area, finding that we can measure their conduction properties correctly by the Ohmic 2P-STM. Since the probe-to-probe distance can be reduced down to 30 nm, the present method will be useful in a wide range of fields of material sciences.
