9,341 research outputs found
Superconducting nano-mechanical diamond resonators
In this work we present the fabrication and characterization of
superconducting nano-mechanical resonators made from nanocrystalline boron
doped diamond (BDD). The oscillators can be driven and read out in their
superconducting state and show quality factors as high as 40,000 at a resonance
frequency of around 10 MHz. Mechanical damping is studied for magnetic fields
up to 3 T where the resonators still show superconducting properties. Due to
their simple fabrication procedure, the devices can easily be coupled to other
superconducting circuits and their performance is comparable with
state-of-the-art technology.Comment: 5 pages 6 figures, Accepted for publication in Carbo
Chemical mechanical polishing of thin film diamond
The demonstration that Nanocrystalline Diamond (NCD) can retain the superior
Young's modulus (1,100 GPa) of single crystal diamond twinned with its ability
to be grown at low temperatures (<450 {\deg}C) has driven a revival into the
growth and applications of NCD thin films. However, owing to the competitive
growth of crystals the resulting film has a roughness that evolves with film
thickness, preventing NCD films from reaching their full potential in devices
where a smooth film is required. To reduce this roughness, films have been
polished using Chemical Mechanical Polishing (CMP). A Logitech Tribo CMP tool
equipped with a polyurethane/polyester polishing cloth and an alkaline
colloidal silica polishing fluid has been used to polish NCD films. The
resulting films have been characterised with Atomic Force Microscopy, Scanning
Electron Microscopy and X-ray Photoelectron Spectroscopy. Root mean square
roughness values have been reduced from 18.3 nm to 1.7 nm over 25 {\mu}m,
with roughness values as low as 0.42 nm over ~ 0.25 {\mu}m. A polishing
mechanism of wet oxidation of the surface, attachment of silica particles and
subsequent shearing away of carbon has also been proposed.Comment: 6 pages, 6 figure
Superconducting Diamond on Silicon Nitride for Device Applications
Chemical vapour deposition (CVD) grown nanocrystalline diamond is an
attractive material for the fabrication of devices. For some device
architectures, optimisation of its growth on silicon nitride is essential.
Here, the effects of three pre-growth surface treatments, often employed as
cleaning methods of silicon nitride, were investigated. Such treatments provide
control over the surface charge of the substrate through modification of the
surface functionality, allowing for the optimisation of electrostatic diamond
seeding densities. Zeta potential measurements and X-ray photoelectron
spectroscopy (XPS) were used to analyse the silicon nitride surface following
each treatment. Exposing silicon nitride to an oxygen plasma offered optimal
surface conditions for the electrostatic self-assembly of a hydrogen-terminated
diamond nanoparticle monolayer. The subsequent growth of boron-doped
nanocrystalline diamond thin films on modified silicon nitride substrates under
CVD conditions produced coalesced films for oxygen plasma and solvent
treatments, whilst pin-holing of the diamond film was observed following RCA-1
treatment. The sharpest superconducting transition was observed for diamond
grown on oxygen plasma treated silicon nitride, demonstrating it to be of the
least structural disorder. Modifications to the substrate surface optimise the
seeding and growth processes for the fabrication of diamond on silicon nitride
devices
Observation of conduction electron spin resonance in boron doped diamond
We observe the electron spin resonance of conduction electrons in boron doped
(6400 ppm) superconducting diamond (Tc =3.8 K). We clearly identify the
benchmarks of conduction electron spin resonance (CESR): the nearly temperature
independent ESR signal intensity and its magnitude which is in good agreement
with that expected from the density of states through the Pauli
spin-susceptibility. The temperature dependent CESR linewidth weakly increases
with increasing temperature which can be understood in the framework of the
Elliott-Yafet theory of spin-relaxation. An anomalous and yet unexplained
relation is observed between the g-factor, CESR linewidth, and the resistivity
using the empirical Elliott-Yafet relation.Comment: 10 pages, 11 figures, submitted to Phys. Rev.
Chemical nucleation of diamond films
With the large differences in surface energy between film and substrate in combination with the low sticking coefficient of hydrocarbon radicals, nanocrystalline diamond growth on foreign substrates typically results in poor nucleation densities. A seeding technique is therefore required to realize pinhole-free and thin coalesced films. In this work, a chemical nucleation method for growth of diamond on nondiamond substrates based on 2,2-divinyladamantane is shown. After treating with the carbon-containing DVA, the chemically treated wafers were exposed to low-power-density plasma, known as the incubation phase, to facilitate the formation of diamond nucleation sites followed by a high-power-density growth regime to produce coalesced films. The resulting films demonstrate high crystallinity, whereas the Raman spectra suggest high-quality diamond with low sp² content
Digital Platform Work in Australia: Preliminary findings from a national survey
Digital platforms such as Airtasker, Uber or Freelancer can connect workers with individuals or businesses looking to obtain services of various kinds on demand. There has been much debate about ‘gig work’ of this kind, but little data on its prevalence in Australia. This report presents preliminary findings from a national survey that was commissioned by the Victorian Government to address that gap
CO2 laser micromachining of nanocrystalline diamond films grown on doped silicon substrates
We demonstrate that nanocrystalline diamond films grown on highly doped silicon substrates can be patterned using a CO2 laser operating at a wavelength of 10.6 μm, where both low doped silicon and diamond exhibit negligible optical absorption. The patterning is initiated by free carrier absorption in the silicon substrate and further enhanced by the thermal runaway effect, which results in surface heating in the silicon substrate and subsequent thermal ablation of the diamond film in an oxygen rich atmosphere. Using this approach, micron-scale grating and dot patterns are patterned in thin film diamond. The localized heating is simulated and analyzed using concurrent optical and thermal finite element modelling. The laser patterning method described here offers a cost effective and rapid solution for micro-structuring diamond films
Climatic versus biotic constraints on carbon and water fluxes in seasonally drought-affected ponderosa pine ecosystems
We investigated the relative importance of climatic versus biotic controls on gross primary production (GPP) and water vapor fluxes in seasonally drought-affected ponderosa pine forests. The study was conducted in young (YS), mature (MS), and old stands (OS) over 4 years at the AmeriFlux Metolius sites. Model simulations showed that interannual variation of GPP did not follow the same trends as precipitation, and effects of climatic variation were smallest at the OS (50%), and intermediate at the YS (<20%). In the young, developing stand, interannual variation in leaf area has larger effects on fluxes than climate, although leaf area is a function of climate in that climate can interact with age-related shifts in carbon allocation and affect whole-tree hydraulic conductance. Older forests, with well-established root systems, appear to be better buffered from effects of seasonal drought and interannual climatic variation. Interannual variation of net ecosystem exchange (NEE) was also lowest at the OS, where NEE is controlled more by interannual variation of ecosystem respiration, 70% of which is from soil, than by the variation of GPP, whereas variation in GPP is the primary reason for interannual changes in NEE at the YS and MS. Across spatially heterogeneous landscapes with high frequency of younger stands resulting from natural and anthropogenic disturbances, interannual climatic variation and change in leaf area are likely to result in large interannual variation in GPP and NEE
- …