Nanostencil Lithography for Atomic-Scale Fabrication Scale-Up

In this project the student will develop ultrahigh vacuum (UHV) nanostencilling techniques [1] for integration with
atomically-precise scanning probe microscopy (SPM) lithographies. Hydrogen resist lithography is a fabrication
technique in which dopant atoms are incorporated into a silicon lattice, with atomic precision, using the tip of a
scanning tunnelling microscope (STM) to pattern a single atomic layer of hydrogen providing a masking layer for
dopant incorporation [2]. This is the only fabrication technique capable of producing deterministic, atomically-precise
electronic devices. As such, it promises significant impact on future integrated circuit technologies and may lead to
advances in exotic device architectures such as quantum computers [3]. In order to achieve this promise, pathways
to scale-up of atomic-scale device fabrication must be developed.
UHV nanostencil shadow mask patterning is compatible with UHV-STM based fabrication, and can facilitate scale-up
of atomic-scale fabrication by parallel patterning all but the finest details of a device, thus providing a contact
framework within which the scanning probe can operate. In order to integrate nanostencil patterning with STM
fabrication, compatible materials and processes must be developed. This requires engineering nanostencilling tools,
and studying the surface and materials science of patterned structures. In this project, nanostencil shadow masks will
be designed and fabricated using standard cleanroom microfabrication techniques (electron beam lithography (EBL),
Focused ion beam (FIB), etc) and then used to pattern devices in a UHV-STM system. As an integral part of the
development process, layered and patterned structures fabricated at UCL will be characterised regularly using SPM
at UCL and secondary ion mass spectrometry (SIMS) at Imperial, and less frequently using a variety of advanced and
novel characterization techniques at partner institutions [4], thus allowing development of both the fabrication
processes and the measurement techniques.
[1] A. Linklater and J. Nogami, Nanotech., 19, 285302 (2008).
[2] T.J.Z. Stock, et. al., ACS Nano, 14, 3316 (2020).
[3] C. D. Hill et. al., Sci. Adv., 1, e1500707 (2015).
[4] N. D'Anna et. al., Adv. Electron. Mater., 2201212 (2023)