Manipulation of Transition Metal Dichalcogenides: Nanomachining 2D PtSe2 using AFM
Katie O'Neill a, Cormac Ó Coileáin a, Jason Kilpatrick b, Max Prechtl c, Niall McEvoy a, Georg S. Duesberg c
a CRANN/AMBER, School of Physics, Trinity College Dublin, Ireland
b Adama Innovations Ltd., CRANN, Trinity College Dublin, Ireland
c Institute of Physics, Universität der Bundeswehr München, Germany
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#MapNan19. Mapping Nanoscale Functionality with Scanning Probe Microscopy
Berlin, Germany, 2019 November 3rd - 8th
Organizer: Stefan Weber
Oral, Katie O'Neill, presentation 302
Publication date: 16th July 2019

For the realisation of 2D-material-based electronic devices, two things in particular are needed; good gate control and low contact resistance. Current issues with realising such devices stem from bulk metal contacts which form poor interfaces with 2D materials leading to high contact resistances. We propose a solution to these issues by way of ‘self-contacting’ 2D-material-based field effect transistors (FETs), resulting in seamless interfaces and low contact resistance.

2D layered materials, such as transition metal dichalcogenides (TMDs), have been heavily studied due to their exciting physical properties and high potential for use in a wide range of future nanoelectronic devices.[1] The band structure of many TMDs changes drastically with thickness. In the case of PtSe2, a little-studied TMD, it goes from semimetallic in bulk to semiconducting in mono and bilayer. [2] This makes PtSe2 a strong candidate for a one-material device, consisting of a thin mono/bilayer channel seamlessly contacted by multilayer regions.

By using novel manipulation techniques, such as nanomachining with an atomic force microscope (AFM), we demonstrate that TMDs can be incrementally machined down, altering their electrical properties. Using Kelvin probe (KPFM) and conductive AFM (C-AFM), the change in surface potential and conductivity can be characterised/monitored. Furthermore, nanomachining of contacted TMD channels is performed while monitoring the device performance with each layer removal down to the monolayer. This paves the way for `self-contacted' devices through the creation of a semiconducting channel via nanomachining, leading to high mobility, low contact resistance and low power. [3]

Figure 1: SEM of nanomachined thermal-assisted conversion (TAC) films of PtSe2

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