Study of EUV induced defects on few-layer graphene

Defects in graphene greatly affect its properties1-3. Radiation induced-defects may reduce the long-term survivability of graphene-based nano-devices. Here, we expose few-layer graphene to extreme ultraviolet (EUV, 13.5nm) radiation and show there is a power-dependent increase in defect density. We also show that exposure to EUV radiation in an H2 background increases graphene's dosage sensitivity. This may be due to reactions caused by the EUV induced hydrogen plasma. The nature of the defects was studied with X-ray photoelectron spectroscopy (XPS), which showed that the sp3 bonded carbon and oxide fractions increase with exposure. The experimental results are important for understanding the defect-creating mechanisms upon photon interaction as well as designing graphene-based components for EUV lithography systems. Graphene samples grown on 25x25mm2 Ni/Si substrate by CVD were obtained from Graphene Laboratories, Inc. Each sample had 1 to 7 layers, with a spatial average of 4. The samples were exposed to EUV, and for comparison purposes, hydrogen radicals, under conditions summarized in table 1. Raman spectroscopy and XPS were used to study the defects in graphene. Fig. 1 shows the Raman spectra of the five samples. The spectrum for the sample exposed to EUV in a hydrogen background (SEUV+H2) has the highest D peak intensity. The spectra for the samples exposed to atomic hydrogen (SH) and EUV irradiation (SEUV) show slightly lower D peak intensities. The pristine sample (Sref), and the one exposed to molecular hydrogen (SH2) have the lowest D peak intensities. An increased D peak intensity indicates increased defect density.