Structural Defect Analysis of Graphene Nanoplatelets under Sub-kGy Gamma Irradiation for Dosimetric Applications

Abstract

In the present work, an investigation has been conducted on the structural alterations and defect formation in tailor-made graphene nanoplatelets when exposed to 60Co gamma irradiation, with absorbed doses ranging from 0 to 200 Gy. In this experiment, graphene nanoplatelets, namely few-layer graphene (FLG) and multi-layer graphene (MLG) were fabricated using hot wire chemical vapor deposition (HWCVD). The vibrational spectra of irradiated graphene nanoplatelets samples were determined using a 532 nm and a 325 nm laser Raman and photoluminescence (PL) spectrometer, respectively. The intensity ratios of defects (D) to graphite (G), represented as ID/IG, closely matched the oscillatory pattern is seen in graphene. This ID/IG ratio was used to further characterize the dose-dependent defects in the graphene materials. From PL measurements, the average energy band gap values for the FLG and MLG samples were found to be 1.115 ± 0.01 eV and 1.112 ± 0.01 eV, indicating that these materials behave like direct bandgap semiconductors. In addition to this, X-ray photoelectron spectroscopy (XPS) spectra were obtained using Al Kα sources (hv ∼1400 eV), and carbon KLL Auger peaks were acquired with 50 eV Pass Energy. At these relatively low doses, alteration in the order-disorder structure are evident, with defect generation and internal annealing competing as the dominant effects throughout the dose range.