Immobilization of Reduced Graphene Oxide on Hydrogen-Terminated Silicon Substrate as a Transparent Conductive Protector

Abstract

Silicon is a promising electrode material for photoelectrochemical and photocatalytic reactions. However, the chemically active surface of silicon will be easily oxidized when exposed to the oxidation environment. We immobilized graphene oxide (GO) onto hydrogen-terminated silicon (H-Si) and reduced it through ultraviolet (UV) and vacuum-ultraviolet (VUV) irradiation. This acted as an ultrathin conductive layer to protect H-Si from oxidation. The elemental evolution of GO was studied by X-ray photoelectron spectroscopy, and it was found that GO was partially reduced soon after the deposition onto H-Si and further reduced after UV or VUV light irradiation. The VUV photoreduction demonstrated ca. 100 times higher efficiency compared to the UV reduction based on the irradiation dose. The saturated oxygen-to-carbon ratio (R) of the reduced graphene oxide (rGO) was 0.21 ± 0.01, which is lower than the photoreduction of GO on SiO substrate. This indicated the H-Si played an important role in assisting the photoreduction of GO. No obvious exfoliation of rGO was observed after sonicating the rGO-covered H-Si sample in water, which indicated rGO was immobilized on H-Si. The electrical conductivity of H-Si surface was maintained in the rGO-covered region while the exposed H-Si region became insulating, which was observed by conductive atomic force microscopy. The rGO was verified capable to protect the active H-Si against the oxidation under an ambient environment.

Chemical Etching of Silicon Assisted by Graphene Oxide in an HF–HNO3 Solution and Its Catalytic Mechanism

“…It has been reported that epoxide moieties, which are also found on CGO sheets, react with hydrogen-terminated silicon surfaces and that CGO sheets on hydrogen-terminated silicon are partially reduced. 29,30 We also found that CGO sheets are reduced by immersion in an HF solution for 4 min (Figure S2). These results suggest that the oxygen functionalities on CGO have little influence on its capacity to promote the etching reaction and that the CGO sheets function as catalysts, not reactants, for the silicon etching reaction.…”

Effect of Electrolytic Medium on the Electrochemical Reduction of Graphene Oxide on Si(111) as Probed by XPS

“…The oxygen-to-carbon ratio (R O/C ) was determined as an additional independent test of the GO reduction extent, considering that a decrease in R O/C corresponds to a more efficient reduction. In this work, the R O/C were calculated using the C 1s curve-fitting results according to the procedure previously described in [ 86 , 87 ] (see the SM for details). The obtained R O/C values for the erGO aq and erGO non-aq samples are depicted in Figure 7 .…”

Catalytic Properties of Chemically Modified Graphene Sheets to Enhance Etching of Ge Surface in Water

“…Figures b–d show the change in C 1s XPS spectra of single sheets of GO, hyd -rGO, and amm -rGO on the Ge surface by etching, respectively, which was conducted in hot water at 58 °C for 3 h. Compared with the aggregated GO on SiO 2 in Figure b, the epoxide (C–O–C) peak in GO decreased even before etching in Figure b. Tu et al reported that GO sheets are partially reduced soon after the deposition onto hydrogen-terminated Si via C–O–Si bonds . Similarly, it is supposed that a fraction of epoxides (C–O–C) in GO were reduced by the contact with the bare Ge surface.…”