Nils Goedecke: Contacts to 2D materials with vanishing Schottky barriers by NanoFrazor lithography

Tero S. Kulmala1, Nils Goedecke1, Xiaorui Zheng2, Edoardo Albisetti2, Elisa Riedo2 1 SwissLitho AG Technoparkstrasse 1, Zurich, Switzerland 2Tandon School of Engineering, New York University, New York, NY, USA. Forming high-quality electrical contacts is a key issue in fabricating high-performance 2D material electronic devices. However, predominant fabrication processes (i.e. electron beam lithography followed by metal evaporation and lift-off) typically yield poor quality non-ohmic metal contacts with high Schottky barriers and large contact resistances [1]. Here, we show that NanoFrazor (thermal scanning probe) lithography that relies on thermal decomposition of polymer resists [2] can be used to pattern high-quality metal contact electrodes to monolayer MoS2 with high reproducibility, sub-10-nm resolution, and a throughput comparable to high-resolution electron beam lithography [3]. The approach offers simultaneous in situ imaging and patterning as well as superior markerless alignment accuracy [4] and does not utilize high-energy charged particle beams. We developed a variety of lift-off metallization processes with different resists and solvents achieving gaps between metal electrodes below 10nm. Using this technique, we have patterned both top-gated and back-gated field-effect transistors with metal electrodes in direct contact with monolayer MoS2. These devices exhibit vanishing Schottky barrier heights (around 0 meV, Figure 1), record-high on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64 mV per decade without the use of negative capacitors or hetero-stacks. Nils is a trained biophysicist with a Master’s Degree from Humboldt University Berlin (1999) and a Ph.D. in Analytical Chemistry from Imperial College London (2005). Throughout his scientific career he applied microsystem and surface engineering to a broad range of technical development projects with biological context. In that capacity he developed lab-on-a-chip devices for DNA forensics at MIT (2003-2005) as well as microfluidics for single-cell analysis at ETH Zurich (2005-2011). His research at University Hospital Balgrist (2012-2017) focused on sensor arrays for measuring cell mechanics. Nils joined SwissLitho in summer 2018, where he is part of the sales team trying to identify new customers and applications for the NanoFrazor technology.