Individual flakes and films of graphene oxide patterned by laser using Raman spectroscopy and atomic force microscopy

L. PÉREZ; F. FIORAVANTI; NOELIA BAJALES LUNA; G. LACCONI

Simposio; Virtual Raman Imaging Poster Summit 2020; 2020

WITec Wissenschaftliche Instrumente und Technologie GmbH

Raman spectroscopy was used for quality control and identification of graphene oxide (GO) flakes, but it is able to generate a laser-induced reduction process during the spectroscopic characterization. However, only few recent reports have advised about potential changes induced by laser irradiation, even at low power, during the measurements of such systems. Thus, an overview of this phenomenon is urgently required because it leads to new alternatives for obtaining hybrid surfaces of thin two-dimensional materials, which are useful for diverse applications. Individual flakes and films of GO were deposited on silicon oxide and exposed to visible laser radiation during characterization by micro-Raman spectroscopy. Noticeable topography modifications on both GO individual sheet and film surfaces were observed in the optical image,recorded after spectroscopic measurements. These surface morphology modifications together with an apparent thickness change were induced by the visible radiation in the graphene-based coating. Likewise, chemical changes of the oxygen functional groups (sp3 carbon defects in the GO structure) were recognized, identifying the decrease of the oxygen content by means of X-ray photoelectron spectroscopy, which evidenced the formation of reduced graphene oxide (rGO) in the trace generated by the laser, when a sample movement control is available. Differences of characteristics between components GO and rGO in the hybrid were supported also by SEM, dark field microscopy and NSOM images. Comparison between laser-induced effects in supported GO films and GO flakes, as well as a correlation with changes observed in Raman spectra and temporal evolution were performed. This study contributes to the quality control of supported GO flakes and films because it provides information about physical damage produced by the laser radiation during Raman measurements. In addition, the combined AFM-Raman spectroscopy research strategy here employed, introduces a simple lithographic method to obtain GO-rGO hybrid materials by usinga continuous visible laser to pattern GO flakes and films