(Color online) Schematic of in situ silicidation from low conductivity CoSi to highly conductive CoSi2 during CNT growth.
Typical CNT forest growth results with the CVD conditions from Table II (SEM micrographs at a tilt of ∼60 °). In particular, (a) shows atmospheric pressure CVD at 650 °C. (b) shows low pressure CVD at ∼0.1 mbar with 30 min pretreatment and 30 min growth at ∼650 °C (Ref. 41).
(Color online) (a) Process-step resolved structural evolution of silicide supports during near-atmospheric pressure CVD as measured by in situ XRD. CoSi in the as loaded samples is transformed into CoSi2 during the CNT CVD. * designates reflections which may be related to a minor Co-oxide/silicate contribution. (b) Ex-situ XRD scan of a sample after low pressure CVD conditions. (Diffraction patterns are plotted for 1.541 Å x-ray wavelength.)
(from left to right) In situ XPS spectra of the Si2p, Co 2p3/2 and Fe 2p3/2 regions showing the evolution of the surface (Fe, Co; Ekin(e−) = 150 eV) and near surface (Si; Ekin(e−) = 1000 eV) chemistry under low pressure CVD.
(Color online) I-V characteristics of atmospheric pressure CVD samples: (a) Macroscopic probe station measurements of CVD processed samples from as loaded (black) and only pretreated (red) to fully CVDed (blue) state. Note that as no Fe was on the samples the measurements do not include a contribution from CNTs. (b) Post-CVD probe station measurements comparing conduction through the silicide only (black) to conduction through the silicide and the CNT forest (red). (c) Post-CVD IV-AFM measurements through silicide and CNT forest [with only microscopic top contact area compared to (b)].
Surface energies of solid metals, metallic compounds and oxides, in J/m2, from Ref. 26.
Summary of CVD conditions. Low pressure and near-atmospheric pressure CVD were conducted in custom-built reaction chambers with heating stages (cold wall). Atmospheric pressure CVD was done in a custom-built quartz tube furnace (hot wall).
Article metrics loading...
Full text loading...