Subsurface imaging of two-dimensional materials on the nanoscale
Authors: Dinelli F., Pingue P., Kay N.D., Kolosov O.V.
Autors Affiliation: 1. CNR, Istituto Nazionale di Ottica (INO), via Moruzzi 1, 56124 Pisa, Italy
2. Laboratorio NEST – Scuola Normale Superiore, and Istituto Nanoscienze – CNR, Piazza San Silvestro 12, I-56127 Pisa, Italy
3. Physics Department, Lancaster University, Lancaster, LA1 4YB, UK
Abstract: Scanning probe Microscopy (SPM) represents a powerful tool that, in the past thirty years, has allowed one to investigate material surfaces in unprecedented ways at the nanoscale level. However, SPM has shown very little power of depth penetration, whereas several nanotechnology applications would require it. Subsurface imaging has been achieved only in a few cases, when subsurface features influence the physical properties of the surface, such as the electronic states or the heat transfer. Ultrasonic Force Microscopy (UFM), an adaption of the contact mode Atomic Force Microscopy (AFM), can dynamically measure the stiffness of the elastic contact between the probing tip and the sample surface. In particular, UFM has proven highly sensitive to the near surface elastic field in non-homogeneous samples.
In this paper, we present an investigation of two-dimensional (2D) materials, namely flakes of graphite and molybdenum disulphide placed on structured polymeric substrates. We show that UFM can non-destructively distinguish suspended and supported areas and localize defects, such as buckling or delamination of adjacent monolayers, generated by residual stress. Specifically, UFM can probe small variations in the local indentation induced by the mechanical interaction between the tip and the sample. Therefore, any change in the elastic modulus within the volume perturbed by the applied load or the flexural bending of the suspended areas can be detected and imaged. These capabilities of investigation are very promising in order to study the buried interfaces of nanostructured 2D materials such as in graphene-based devices.
Volume: 28 Pages from: 085706 to: 085713
KeyWords: SPM; UFM; 2D Materials; Subsurface; Elastic propertiesDOI: 10.1088/1361-6528/aa55e2Citations: 6data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2020-02-23References taken from IsiWeb of Knowledge: (subscribers only)