Nanobuckling and x-ray photoelectron spectra of carbyne-rich tetrahedral carbon films deposited by femtosecond laser ablation at cryogenic temperatures

Abstract

The growth, surface morphology, and electronic binding states of diamondlike films deposited by femtosecond laser ablation on Si wafers at 77 K have been studied in order to elucidate the mechanical properties of this material. Nanoscale buckling has been observed and is found to have a morphology that exhibits a strong dependence on film thickness. Nanobuckling takes the form of quasiperiodic discrete pointlike excursions extending over widths of 50–100 nm. This morphology converts to a regular structure of grooves/ripples with a modulation period of 30–50 nm as the film thickness increases to 300–600 nm. We find that microhardness is not changed in regions where nanobuckling is present. Analysis of Raman and x-ray photoelectron spectra (XPS) demonstrate that nanobuckling can be attributed to the relaxation of internal stress and to the formation of strong C-Si covalent bonds at the C-Si interface. XPS spectra show that the C 1s peak is broadened compared to that found in spectra of films deposited using nanosecond laser ablation. This is found to be consistent with a composition that includes sp, sp2, and sp3-bonded carbon. The unique composition of these films suggests that these materials may find application in electromechanical devices.

Electronic states of trans-polyacetylene, poly(p-phenylene vinylene) and sp-hybridised carbon species in amorphous hydrogenated carbon probed by resonant Raman scattering

“…Figure 8 shows the broad core-level XPS C 1s spectra of a-C:H; in order to deduct the information about the relative abundance of carbon hybridised fractions in the examined materials, the spectra were decomposition onto three main constituent 20 peaks corresponding to sp, sp 2 and sp 3 hybridised states. An sp peak was fitted at an assigned BE of 283.5 eV in confirmation with previous reports [26,35,36], while sp 2 and sp 3 constituents were fitted restricted to their respective energy separation gap, ΔBE, eV, defined as the difference between the binding energies of sp 3 and sp 2 constituents: ΔBE = BE sp3 − BE sp2 and with 0.85≤ ΔBE ≤ 0.9 eV [37, 55] the following binding energy positions were obtained for sp 2 at ~284.4 eV and sp 3 at ~285.3 eV. Due to ex situ XPS measurements and the exposure of samples to air two secondary peaks were added into the fitting of the main C 1s spectra: a single C-O peak at ~286.8 eV and a carbonyl C=O peak at ~288.5 eV.…”

Synthesis of Nanocrystalline Hexagonal Diamond Films in Organic Solvents by Femtosecond Laser Irradiation

“…4 shows the XPS spectra of hexagonal diamond catalyzed by Fe in hexane in the C1s region. The fraction of different carbon binding components can be estimated by deconvolution [10,17]. Deconvolution of the C1s core-level peak into sp 2 -bonded carbon (at 284.6 eV) and sp 3 -bonded carbon (at 285.2 eV) shows that 85.4% of the carbon is sp 3 -bonded.…”

Variations on a theme – the evolution of hydrocarbon solids

“…In their HRTEM images they are able to discern aromatic clusters containing 3-8 rings (with diameters 0.4-0.7 nm). As Ferrari & Robertson (2004), Hu et al (2007a) and Hu et al (2007b) point out, sp 2 chain and cage-like clusters and sp 1 (cumulenic) chains may be rather common structures in some a-C:H materials. Petrie et al (2003) have theoretically studied an interesting suite of structures that they call locally aromatic polycyclic hydrocarbons (LAPHs), which lie in the compositional range C 19 H 22 to C 36 H 32 .…”