# Reducing the metal-graphene contact resistance through laser-induced defects

**Authors:** Vikas Jangra, Satender Kataria, Max C. Lemme  
**arXiv:** [2402.07151](https://arxiv.org/abs/2402.07151)  
**Date:** 2024-02-11  
**Summary page:** https://www.summarizepaper.com/en/paper/2402.07151v1/

## Key points

- Graphene's exceptional properties make it promising for electronic and optoelectronic applications
- High contact resistance between metal and graphene is a challenge for efficient charge carrier injection
- Laser irradiation method proposed by Vikas Jangra, Satender Kataria, and Max C. Lemme aims to reduce specific contact resistance in nickel-contacted devices
- Laser with a wavelength of λ = 532 nm used to induce defects at contact regions of graphene, monitored using micro-Raman spectroscopy
- Significant reduction in contact resistance observed in laser-treated devices, with reduction scaling with laser power
- Lowest contact resistance achieved was approximately 250 Ωμm for devices treated with 20 mW laser power compared to 900 Ωμm for untreated devices
- Reduction in contact resistance attributed to increase in defect density induced by laser treatment, facilitating enhanced charge carrier injection from metal into graphene
- Laser irradiation shown as scalable technology for reducing contact resistance in graphene-based devices, potentially applicable to other two-dimensional materials

## Summary

Graphene has emerged as a promising material for various electronic and optoelectronic applications due to its exceptional properties. One of the challenges in utilizing graphene for these applications is the high contact resistance between metal and graphene, which can hinder efficient charge carrier injection. In this study by Vikas Jangra, Satender Kataria, and Max C. Lemme, a scalable method based on laser irradiation of graphene is proposed to reduce the specific contact resistance (R{_C}) in nickel-contacted devices. The researchers utilized a laser with a wavelength of {\lambda} = 532 nm to induce defects at the contact regions of graphene, which were monitored in real-time using micro-Raman spectroscopy. Physical damage at the contact sites was further analyzed through ex-situ atomic force and scanning electron microscopy. The transfer line method (TLM) was employed to extract R{_C} from back-gated graphene devices with and without laser treatment under both ambient and vacuum conditions. Significant reduction in R{_C} was observed in devices where the contacts were laser irradiated, with the reduction scaling with the laser power used. The lowest R{_C} achieved was approximately 250 {\Omega} {\mu}m for devices treated with a laser power of 20 mW, compared to 900 {\Omega} {\mu}m for untreated devices. This decrease in contact resistance was attributed to an increase in defect density induced by the laser treatment, leading to the formation of crystallite edges and in-plane dangling bonds that facilitated enhanced charge carrier injection from the metal into the graphene. Overall, this study highlights the potential of laser irradiation as a scalable technology for reducing contact resistance in graphene-based devices. It offers insights that could be applicable to other two-dimensional materials as well. By addressing this critical issue of contact resistance, this research contributes towards advancing the practical implementation of graphene in electronic and optoelectronic applications.