Exploring Flatlands:  Characterizing 2D Materials with Atomic Force Microscopy (AFM)
 

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Overview

Dr. Andras Kis of EPFL Institute of Electrical Engineering and Keith Jones, Asylum Research's nanoelectrical characterization specialist, are your hosts. They discuss the integral role of AFM in 2D materials research and present tools and techniques to successfully characterize a variety of 2D materials used for device manufacturing, energy storage and optoelectronics. Learn about AFM modes for mapping physical properties and see how they can evaluate local electrical, mechanical and functional response. They also discuss how AFM can now be used to accurately determine the thickness of single or multiple layers of a 2D material, challenging a common misconception.
 

Included, results on the following studies:

  • Molybdenum disulfide (MoS2) and graphene
  • Measurements of mechanical properties
  • Kelvin probe imaging (KPFM) of operating transistors
  • Electrical characterization

Detailed discussions of these modes:

  • KPFM
  • Piezoresponse force microscopy (PFM)
  • Conductive AFM
  • Scanning microwave impedance imaging (sMIM)

 

 
Presenters
Andras Kis discusses Exploring Flatlands: Characterizing 2D Materials with atomic force microscopy

Prof. Andras Kis

EPFL, STI-IEL-LANES

Andras Kis is an Associate Professor at Ecole Polytechnique Federale de Lausanne (EPFL), School of Engineering (STI), Institute of Electrical Engineering (IEL) with a research focus in developing 2D materials.  His group demonstrated the first transistor based on a 2D semiconductor. He has more than 16 years of AFM experience, including 63 peer-reviewed papers, more than 50 invited talks at scientific meetings, and participation in organization committees for numerous 2D materials and graphene conferences. He has also been the editor-in-chief for Nature Partner Journal, “2D Materials and Applications”.

Prof. Kis received his PhD from EPFL and did his post doc at Univ. of California Berkeley, Zettl Lab. 

Keith Jones electrical characterization expert

Keith Jones

Asylum Research Applications scientist, Specializing in nanoelectrical characterization

Keith Jones is an Application Scientist at Oxford Instruments Asylum Research (12 years). He has more than 18 years of SPM experience specializing in nanoelectrical characterization and was instrumental in developing and applying electrical AFM techniques, such as dopant profiling and scanning microwave impedance microscopy. Keith is also a co-inventor on a patent for scanning impedance microscopy and has co-authored 34 published papers.

Keith received his M.S. in Physics at Virginia Commonwealth University. 

 

 

 

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mapping local electrical properties across grain boundaries in monolayer MoS2

Mapping the local electrical properties across grain boundaries in large-area monolayer MoS2. (a) Local potential map (upper panel) and line scan across the red line (lower panel) showing the potential drop over the conductive channel of a biased field-effect transistor based on two merged MoS2 single crystals with the same lattice orientation. In this case, no grain boundary is expected. The smooth potential drop indicates the absence of abrupt changes of potential that would indicate the presence of an electrically resistive grain boundary. (b) Local potential map and line scan over two merged triangles with a 60 misorientation angle. This configuration is expected to result in a twin grain boundary. Its presence does not introduce an extra potential drop, indicating that it does not degrade the electrical conductivity of the material. (c) Local potential map and line scan over two merged triangles with a 30 misorientation angle. The presence of the grain boundary does not introduce an extra potential drop in the channel. Insets in line scan plots indicate relative orientations of MoS2 single crystals.

 

From the paper: Exploring Flatlands, characterizing 2D materials with atomic force microscopy. Single crystal of MoS2 on sapphire

AFM topography image of a CVD-grown single crystal of MoS2 on sapphire. Adapted from  ACS Nano, 2015, 9 (4), pp 4611–4620. 
 

Kelvin probe image of a transistor device

Kelvin probe image of a transistor device with two grains of MoS2 and a resistive grain boundary in the middle.

 


More resources on AFM Electrical Characterization

Measuring Nanoelectrical Properties