Fabrication of Diamond Nanowires for Quantum Information Processing Applications

We present a design and a top-down fabrication method for realizing diamond nanowires in both bulk single crystal and polycrystalline diamond. Numerical modeling was used to study coupling between a Nitrogen Vacancy (NV) color center and optical modes of a nanowire, and to find an optimal range of nanowire diameters that allows for large collection efficiency of emitted photons. Inductively coupled plasma (ICP) reactive ion etching (RIE) with oxygen is used to fabricate the nanowires. Drop-casted nanoparticles (including $\mathrm{Au}$, $\mathrm{SiO_{2}}$ and $\mathrm{Al_2O_3}$) as well as electron beam lithography defined spin-on glass and evaporated $\mathrm{Au}$ have been used as an etch mask. We found $\mathrm{Al_2O_3}$ nanoparticles to be the most etch resistant. At the same time FOx e-beam resist (spin-on glass) proved to be a suitable etch mask for fabrication of ordered arrays of diamond nanowires. We were able to obtain nanowires with near vertical sidewalls in both polycrystalline and single crystal diamond. The heights and diameters of the polycrystalline nanowires presented in this paper are \unit[\approx1]{\mu m} and \unit[120-340]{nm}, respectively, having a \unit[200]{nm/min} etch rate. In the case of single crystal diamond (types Ib and IIa) nanowires the height and diameter for different diamonds and masks shown in this paper were \unit[1-2.4]{\mu m} and \unit[120-490]{nm} with etch rates between \unit[190-240]{nm/min}.Comment: 11 pages, 26 figures, submitted to Diamond and related Materials; http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWV-4Y7MM1M-1&_user=10&_coverDate=01%2F25%2F2010&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6dc58b30f4773a710c667306fc541cc

Controlling for transactions bias in regional house price indices

Transactions bias arises when properties that trade are not a random sample of the total housing stock. Price indices are susceptible because they are typically based on transactions data. Existing approaches to this problem rely on Heckman-type correction methods, where a probit regression is used to capture the differences between properties that sell and those that do not sell in a given period. However, this approach can only be applied where there is reliable data on the whole housing stock. In many countries—the UK included—no such data exist and there is little prospect of correcting for transactions bias in any of the regularly updated mainstream house price indices. Thispaper suggests a possible alternative approach, using information at postcode sector level and Fractional Probit Regression to correct for transactions bias in hedonic price indices based on one and a half million house sales from 1996 to 2004, distributed across 1200 postcode sectors in the South East of England