P-type $\delta$-doping with Diborane on Si(001) for STM Based Dopant Device Fabrication

TL;DR

This paper demonstrates a method for fabricating p-type nanostructures in silicon using STM-based hydrogen resist lithography combined with gas-phase boron doping, achieving high-resolution patterning and functional device prototypes.

Contribution

It introduces a novel process integrating STM lithography with gas-phase doping for precise p-type silicon nanostructures and demonstrates functional device fabrication at the nanoscale.

Findings

Achieved sheet resistivities as low as 300 Ω.

Demonstrated 2 nm lithographic resolution.

Fabricated a functional 100 nm pn junction with diode-like behavior.

Abstract

Hydrogen resist lithography using the tip of a scanning tunneling microscope (STM) is employed for patterning p-type nanostructures in silicon. For this, the carrier density and mobility of boron $\delta$-layers, fabricated by gas-phase doping, are characterized with low-temperature transport experiments. Sheet resistivities as low as $300\thinspace\Omega$ are found. Adsorption, incorporation and surface diffusion of the dopants are investigated by STM imaging and result in an upper bound of 2\,nm for the lithographic resolution which is also corroborated by fabricating a 7.5\,nm wide p-type nanowire and measuring its electrical properties. Finally, to demonstrate the feasibility of bipolar dopant device fabrication with this technique, we prepared a 100\,nm wide pn junction and show that its electrical behavior is similar to that of an Esaki diode.