# Optical identification using imperfections in 2D materials

## TL;DR

This paper introduces an optical method to identify 2D materials by detecting nanometer-scale imperfections through photoluminescence, offering a potential security measure against counterfeiting.

## Contribution

The paper presents a simple optical technique to read unique defect signatures in 2D materials for authentication purposes, verified by microscopy.

## Key findings

- Spatial variations in photoluminescence correlate with imperfections
- A straightforward optical setup captures complex defect maps
- Method can reliably distinguish unique 2D material signatures

## Abstract

The ability to uniquely identify an object or device is important for authentication. Imperfections, locked into structures during fabrication, can be used to provide a fingerprint that is challenging to reproduce. In this paper, we propose a simple optical technique to read unique information from nanometer-scale defects in 2D materials. Flaws created during crystal growth or fabrication lead to spatial variations in the bandgap of 2D materials that can be characterized through photoluminescence measurements. We show a simple setup involving an angle-adjustable transmission filter, simple optics and a CCD camera can capture spatially-dependent photoluminescence to produce complex maps of unique information from 2D monolayers. Atomic force microscopy is used to verify the origin of the optical signature measured, demonstrating that it results from nanometer-scale imperfections. This solution to optical identification with 2D materials could be employed as a robust security measure to prevent counterfeiting.