Annealing Temperature Dependence of C60 on Silicon Surfaces Bond Evolution and Fragmentation as Detected by NEXAFS

Abstract

We report a near-edge x-ray absorption spectroscopy (NEXAFS) study of the C K-edge of C 60 molecules interacting with Si(100) and Si(111) surfaces. Annealing the C 60/Si systems at 1050 K induces fullerene fragmentation and leads to SiC nucleation. Tuning the probing depth and studying polarization dependence, the NEXAFS results shed light on the evolution of the molecular states after thermal treatment, up to the fullerene fragmentation and SiC formation. The NEXAFS spectra of a single layer of C 60 deposited at 670 K onto both surfaces show a strong C 60-substrate interaction. A polarization dependence of the spectra can be detected; this behaviour is similar to the results obtained on C 60 covalently chemisorbed on Al surfaces. We find, for both substrates, that fullerene fragmentation starts at the C-Si interfaces, involving the C atoms lying close to the Si substrate, implying an increase of the number of C-Si bonds at the fragmentation stage

Magnetic behavioural change of silane exposed graphene nanoflakes

“…The compositional and quantitative analysis of GNFs and GNFs:Si obtained from XPS analysis is tabulated in Table I. In general, the peak observed at $284.6 eV for GNFs can be assigned as the C-C bond (carbon sp 2 -hybridization), which is shifted to the higher energy at $285.4 eV and became broaden for GNFs:Si having Si/(Si þ C) of 0.35, as clearly shown in Figure 2 Pedio et al 19 studied the dependence of the formation of C60 on silicon surfaces on the annealing temperature using C 1s XPS measurements and found that the C-C bond and C-Si bond features are located at 284.2 and 282.6 eV, respectively. We have observed a peak at $283.3 eV, which is in between the peaks 284.2 and 282.6 eV (films having Si/(Si þ C) ¼ 0.35) as shown in Figure 2(d) and is assigned as C-Si peak.…”

“…We have observed a peak at $283.3 eV, which is in between the peaks 284.2 and 282.6 eV (films having Si/(Si þ C) ¼ 0.35) as shown in Figure 2(d) and is assigned as C-Si peak. 19,20 The peak observed at $283.9 eV and 284.5 eV in Figures 2(c) and 2(d), respectively, is assigned as C¼C sp 2 , whereas the peak 285.0 eV and 285.6 eV in Figures 2(c) and 2(d), respectively, is defined as "defect peaks" 16 or Si-C-O bonding peaks. 21 The peak observed in Figure 2(c) at 286.8 eV is the C-O bonds.…”

“…16 Figure 3 shows the Si 2p and 2s XPS spectra, where the main peaks are at$100 eV and at $150 eV, respectively. However, these peaks are observed in 15,19,20 In case of Si 2s XPS, the peaks observed within the range $151.1-153.0 eV are Si-Si peaks, whereas other peaks above 153.0 eV are assigned as Si-O. 22 It is very clear from these results that the changes of microstructural and bonding properties are of significance when Si is functionalized with GNFs that effect the change in electron field emission.…”

Change of Structural Behaviors of Organo-Silane Exposed Graphene Nanoflakes

“…The peak observed at ∼284.4 eV for GNFs can be assigned as the C-C bond, which is shifted to the higher energy at ∼285.2 eV and became broader for GNFs:Si. Pedio et al 21 studied the dependence of the formation of C 60 on silicon surfaces on the annealing temperature using C 1s XPS measurements and found that the C-C bond and C-Si bond features are located at 284.2 and 282.6 eV, respectively. In the present case, the spectral features are different and do not have the signature of SiC segregations in C 1s core-level XPS spectra, which further confirms enhanced sp 3 bonding (i.e., diamond and/ or diamond-like carbon) rather than sp 2 bonding (like graphite and/or CNTs) and/or C-Si bonding.…”

Electronic, Electrical, and Magnetic Behavioral Change of SiO2-NP-Decorated MWCNTs

“…The C 1s peak of oxidized Si-NPs decorated MWCNTs shifts towards a lower energy, significantly indicating the formation of sp 3 -rich material. The deconvoluted C 1s XPS peaks of MWCNTs/SiO 2 -NP (Si-NPs = 5.75 atom %) nanocomposites are observed at ∼281.8 and ∼282.4 eV which are strong indicators of the C–Si bonds, 37 and confirm the formation of MWCNTs/SiO 2 -NP nanocomposites.…”