Thermomechanical nanocutting of 2D materials using thermal scanning probe lithography

The rapidly evolving field of 2D materials has developed a plethora of emerging micro/nano devices where atomically-thin materials play a fundamental role. In most cases, this implies the need of nanostructuring them, but due to their delicate nature, conventional lithographies using electrons or ions can deteriorate their performance. Thermal scanning probe lithography (t-SPL) is an advanced direct-write method that uses a heated nanotip for 2D and 3D subtractive/additive manufacturing [1]. The creation of patterns by t-SPL is accomplished by consecutive indentation of the sample with the heated nanotip while simultaneously scanning the sample. We extend the application of t-SPL beyond polymers and demonstrate the direct cutting of different 2D materials using a heated scanning nanotip [2]. To do so, a 2D material flake is transferred onto a substrate covered by polyphthalaldehyde (PPA), a dedicated polymer that unzips into smaller volatile monomers at around 150 °C, as shown in Figure 1(a). When the tip indents the 2D material, the applied force, together with the heat, induces the rapid sublimation of the PPA and breaks the chemical bonds of the thin flake without damaging the rest of the material. In this way, we created different test structures in the 2D material, i.e. nanoribbons as shown in Figure 1(b). A resolution down to 20 nm is achieved for monolayered MoTe2; yet many other 2D materials, multilayers, and even heterostructures can be patterned. Raman spectroscopy is used to validate the removal of the 2D materials in the cut areas and electrical characterization shows that clean cuts have been achieved. In the future, this high-resolution nanocutting process can be of benefit to scientists and engineers as a fast prototyping technique to fabricate 2D material nanodevices by a clean, one-step thermo-mechanical technique. References [1] S.T. Howell, A. Grushina, F. Holzner, J. Brugger, Microsyst. Nanoeng.,6 21 (2020). [2] X. Liu, S.T. Howell, A. Conde-Rubio, G. Boero, J. Brugger, Adv. Mater. (2020). doi:10.1002/adma.202001232