• Mohney, Suzanne
• Walter, Timothy
• Oliver, Nailah

Abstract

<jats:title>Abstract</jats:title><jats:p>Metal contacts to two-dimensional layered semiconductors are crucial to the performance of field-effect transistors (FETs) and other applications of layered materials in nanoelectronics and beyond. In this work, the wetting behavior of very thin Au films on exfoliated MoS<jats:sub>2</jats:sub> flakes was studied and evaluated as a nanoscale, self-assembled dry etch mask. Etching nanoscale pits into MoS<jats:sub>2</jats:sub> flakes prior to metallization from the top of the flake forms edge sites that contribute some fraction of edge contacts in addition to top contacts for additional carrier injection and lower contact resistance. The morphology and thickness of Au islands and MoS<jats:sub>2</jats:sub> were studied with scanning electron microscopy and atomic force microscopy before and after etching with low-power plasmas. A Cl<jats:sub>2</jats:sub> plasma etch of 10 s with a Au island mask of 6 nm (nominal) showed the best resulting morphology among the plasma conditions studied. Back-gated MoS<jats:sub>2</jats:sub>-based FETs on SiO<jats:sub>2</jats:sub>/<jats:italic>p</jats:italic><jats:sup>+</jats:sup>-Si with Ti/Au contacts were fabricated using a Cl<jats:sub>2</jats:sub> etch of only the contact regions, and they yielded devices with ON currents of 100s <jats:italic>µ</jats:italic>A/<jats:italic>µ</jats:italic>m, ON/OFF ratios ⩾10<jats:sup>6</jats:sup>, and contact resistance &lt;10 kΩ <jats:italic>µ</jats:italic>m. The best set of devices had a very low contact resistance of ∼1 kΩ <jats:italic>µ</jats:italic>m with almost no dependence of contact resistance on gating. Using nanoscale etch masks made from metal islands could be highly customizable and shows promise for engineering FETs with low contact resistance.</jats:p>

Topics

• scanning electron microscopy
• atomic force microscopy
• semiconductor
• layered
• etching
• two-dimensional
• field-effect transistor method