Microfabrication of diamond films by localized electron beam chemical vapour deposition

Abstract

We have investigated the microfabrication of diamond films on silicon substrates using the localized electron beam (EB) chemical vapour deposition (CVD) method with a hydrogen (H 2) and methane (CH 4) mixed gas source. Micro-Raman spectra at 1, 3 and 5% CH 4 concentrations for the accelerating voltage of 10 kV have indicated the presence of a diamond (sp 3 bonding) peak at 1333 cm −1 , a graphite (sp 2 bonding) peak at 1580 cm −1 and a diamond peak, and an amorphous carbon peak at 1360 cm −1 and graphite peak, respectively; those at 7 and 10% concentrations have indicated broad amorphous carbon peaks around 1500 and 1300 cm −1. We have found that the films consist of a mixture of sp 3 and sp 2 bonded structures. The film quality (sp 3) content decreases with increasing CH 4 concentration. Consequently, the localized EB CVD diamond films have been fabricated under the following deposition conditions: an accelerating voltage of 10 kV and a CH 4 concentration of 1%. The EB was scanned in areas of 2 × 10 µm 2 rectangle and 1 × 1 µm 2 square on a silicon substrate. The two-dimensional cross-sectional profiles (X-Z axis) of the resulting micro-rectangular diamond patterns were very similar to those of the resulting micro-square diamond patterns. The deposited thickness of the resulting micro-rectangular and square diamond patterns increased linearly with increasing EB irradiation time up to a limit of 10 h. The deposition rate was approximately 0.1 µm h −1 in both cases. The full width at half maximum (FWHM) of the cross-sectional profiles, having the triangular form of the resulting micro-rectangular and square diamond patterns, first increased with increasing EB irradiation time and reached a maximum width at an EB irradiation time of 4 and 6 h, respectively and then decreased gradually with a further increase of the EB irradiation time. The deposited thickness and FWHM of the resulting micro-rectangular and square diamond patterns for a 10 h EB irradiation time were 1.1, 0.98 µm and 3.6, 3.3 µm, respectively.

A one-pot-one-reactant synthesis of platinum compounds at the nanoscale

“…The formation of small metallic nanoparticles rather than a continuous metal nanowire is determined by the limited number of metal atoms available in the nanotube, the stabilising effect of the nanotube and the release of gaseous ligand fragments upon heating, as was reported previously for W, Re and Os nanoparticles formed using similar conditions. 26 The energy of the Pt LIII edge in Pt@SWNT is increased significantly relative to bulk metallic platinum. Figure 1: Schematic illustration depicting how inorganic materials can be formed using nanotubes as templates; a) the encapsulation of a selected metal precursor for the desired metallic element followed by thermal decomposition to form metal nanoparticles@SWNT; b) the addition of the second element by adding a second precursor followed by chemical reaction to form the inorganic material; c) the formation of inorganic materials using a one-step filling process in which both precursors, metallic and non-metallic, are added at the same time followed by chemical reaction; d) the transformation of one encapsulated inorganic material to another by treatment with a suitable reagent inside the nanotube.…”

Gas-assisted focused electron beam and ion beam processing and fabrication

“…Heating a silicon substrate to 800°C under electron irradiation in the presence of 1% of methane in hydrogen results in local deposition of diamond. 271 Methyl-isobutylketone with isopropanol in a ratio 1:3 was applied to do FEBID of C. 259 In this context styrene as a precursor was used by Ochiai 272 and a deposition yield of 0.001 C atoms per electron was obtained. This was lower than deposits from other metalorganic precursors and explained by the authors with the low sticking coefficient of styrene on the substrate surface.…”

“…The deposit materials range from amorphous carbon to graphite; under special gas composition conditions and irradiated parameters, diamond or at least diamond like carbon ͑as a mixture of sp 2 and sp 3 hybrized Carbon͒ was also claimed. 271…”

Characterization of focused electron beam induced carbon deposits from organic precursors

“…The study of C deposition as a single element could help to understand more complex chemical systems, while allowing for a large number of available cheap precursors. A few volatile organic compounds were tested and reported as carbon ''precursors'': styrene [21], methane [22,23], and resist developer solvents [24]. The same precursors can be used for focused ion beam induced deposition, for which screening series have been performed [25].…”