Catalyst-Free Growth of Networked Nanographite on Si and SiO2 Substrates by Photoemission-Assisted Plasma-Enhanced Chemical Vapor Deposition

Abstract

We have developed a photoemission-assisted plasma-enhanced chemical vapor deposition (CVD) process, where DC discharge plasma is assisted by photoelectrons emitted from the substrate under ultraviolet (UV) light irradiation. Under Ar gas atmosphere and in vacuum, plasma current was measured as a function of sample bias voltage to clarify the mechanism, by which photoemission-assisted plasma is generated. Owing to the advantages of the photoemission-assisted plasma-enhanced CVD, where the plasma is generated close to the substrate and in a controllable volume, we have succeeded in growing shiny black films of networked nanographite, without any catalyst, on Si(001) and SiO2(350 nm)/Si(001) substrates at a deposition rate of ∼2 µm/min despite of low electric power consumption of plasma, ∼4 W. Cross-sectional transmission electron microscopy (TEM) and diffraction (TED) observations revealed that samples grown at ∼700 • C with Ar-diluted CH4 were composed of multilayer graphene particles (diameter of ∼10 nm) that were closely connected to each other and shared some graphene sheets between them, although their crystallographic configurations were randomly oriented. In bulk-sensitive C 1s photoelectron spectra using synchrotron radiation at 7933 eV, a chemically-shifted component of sp 2-bonded carbon atom was dominant and the π-π * transition loss peak was clearly observed for the samples grown on both substrates, indicating that the multilayer graphene particles substantially contain high-quality graphene sheets in agreement with evaluations by microscopic Raman spectroscopy. We named the layered carbon structure "carbon mille-feuille." [

Nanographite sheets derived from polyaniline nanocoating of cellulose nanofibers

“…The valence and conduction bands of graphite is overlapping, but the energy band gaps can be opened by reducing the number of sp 2 -hybridized carbon layers [3], giving unique structural properties [4,5] as well as distinguished functions such as electricity [6] and thermal conductivity [7]. Researches on graphitic nanomaterials are being developed at an astonishing pace [8], and various approaches such as mechanical peeling-off of graphite [9], chemical exfoliation using graphite and its derivatives [10], chemical vapor deposition [11], segregation growth on metal substrates [12], epitaxial growth by vacuum graphitization [13], thermal reduction of graphene oxide [14] and direct bottomup synthesis from organic precursors [15] were reported.…”

Controlled oxygen-doped diamond-like carbon film synthesized by photoemission-assisted plasma

“…The excited photoelectrons pass through the doped layer in the opposite direction by an electric field and are finally emitted from the surface of the doped layer. The doped layer plays a transparent window [21].…”

“…Graphene devices have attracted a lot of electronics/ photonics engineers and physicists enthusiastically for the last decade [17][18][19][20]. The authors succeeded to form a DLC film on a graphene sheet directly as a top-gate dielectric in the photoemission-assisted Townsend (PAT) discharge plasma [21]. The DLC-top-gated graphenechannel FET (DLC-GFET) exhibited ambipolar behavior which is specific to graphene [15].…”

Formation of Diamond-Like Carbon Films by Photoemission-Assisted Plasma-Enhanced Chemical Vapor Deposition

“…23) The DLC gate dielectric film was prepared using our original photoemission-assisted plasma-enhanced chemical vapor deposition (PA-PECVD), which differs from conventional PECVD systems. 30,31) Thus, DLC deposition by PA-PECVD should realize various types of new DLC films. One of which may be a suitable gate dielectric for graphene.…”