Non-invasive Scanning Raman Spectroscopy and Tomography for Graphene Membrane Characterization

TL;DR

This paper introduces a fast, non-invasive Raman spectroscopy method combined with tomography for large-scale, in-line characterization of graphene membranes, enabling detailed analysis of their structure and composition in NEMS devices.

Contribution

It develops a novel Raman tomography technique for three-dimensional, non-invasive characterization of graphene membranes, enhancing quality control in NEMS fabrication.

Findings

Effective differentiation between freestanding and supported graphene.

Successful 3D Raman tomography of graphene membranes.

Automated data analysis for in-line device monitoring.

Abstract

Graphene has extraordinary mechanical and electronic properties, making it a promising material for membrane based nanoelectromechanical systems (NEMS). Here, chemical-vapor-deposited graphene is transferred onto target substrates to suspend it over cavities and trenches for pressure-sensor applications. The development of such devices requires suitable metrology methods, i.e., large-scale characterization techniques, to confirm and analyze successful graphene transfer with intact suspended graphene membranes. We propose fast and noninvasive Raman spectroscopy mapping to distinguish between freestanding and substrate-supported graphene, utilizing the different strain and doping levels. The technique is expanded to combine two-dimensional area scans with cross-sectional Raman spectroscopy, resulting in three-dimensional Raman tomography of membrane-based graphene NEMS. The potential of Raman tomography for in-line monitoring is further demonstrated with a methodology for automated data analysis to spatially resolve the material composition in micrometer-scale integrated devices, including free-standing and substrate-supported graphene. Raman tomography may be applied to devices composed of other two-dimensional materials as well as silicon micro- and nanoelectromechanical systems.