Diamond-like carbon generation from graphene oxide by ion irradiation

Graphene oxide (GO) thin foils were deposited on silicon and aluminum substrates and then irradiated in vacuum with 300 keV helium and argon ion beams at room temperature and at fluences ranging between 5 x 10(14) ions/cm(2) and 10(16) ions/cm(2). Attenuated total reflectance (ATR) coupled to the Fourier-transform infrared (FTIR) spectroscopy, & mu;-Raman spectroscopy, X-ray diffraction (XRD) and other analyses, such as Rutherford backscattering (RBS) of alpha particles, energy-dispersive X-ray (EDX) fluorescence, elastic recoil detection analysis (ERDA), scanning electron microscopy (SEM) and contact angle measurements, were used to study the effect of ion irradiation in GO. Such analytical techniques have indicated that the Ar ion implantation at high fluence may induce diamond-like-carbon (DLC) phases in the superficial irradiated layers. ATR-FTIR spectroscopy has evinced a partial removal of the oxygen functional groups with the ion fluence, indicating a GO reduction, and the presence of C=C chemical bonds when Ar irradiation is employed. Raman spectra analysis has pointed out a different behavior of GO by changing the type of ion. In fact, irradiation with 300 keV He ions induced a gradual GO reduction which increased with fluence, while the 300 keV Ar ions implantation also produced DLC, whose formation was promoted by the high energy release into GO from the Ar ions. The presence of some diamond-like crystalline phases onto the surface of the GO foil irradiated with 300 keV Ar+ ions at a fluence of 10(16) ions/cm(2) is also indicated by XRD spectra. RBS and EDX analyses confirm the beam-induced GO reduction from the C/O atomic ratio deduced value that grows with the He and Ar irradiations and assumes, at the same beam fluence, the highest value with the Ar+ ions. The highest carbon concentration in the Ar-irradiated rGO surface is also indicated by SEM images. The minor presence of hydrogen in the reduced GO foils has been evinced by ERDA spectrometry according to which this reduction is stronger for the Ar ion irradiation. At the highest irradiated Ar+ fluence, drastic changes on the GO surface properties have been also observed by means of wettability measurements in agreement with the suggested presence of DLCs.