ABSTRACT
Focused electron-beam-induced deposition (EBID) using bulk liquid precursors is a novel approach to nanofabrication that has shown improvements in purity compared to EBID with gas-phase precursors. Here we report the first EBID of gold using bulk liquid precursors. We study the differences in gold deposited from three different aqueous solutions containing chloroauric acid (HAuCl(4)), sodium tetrachloroaurate (NaAuCl(4)), and the disulfitoaurate complex ([Au(SO(3))(2)](3-)). We also examine the dependence of threshold dose upon precursor concentration and demonstrate high-resolution patterning with a pitch as small as 50 nm. Finally, we show that the purity of gold deposited using these liquid precursors is significantly improved in comparison with deposits from metal-organic gaseous precursors.
ABSTRACT
While electron-beam-induced deposition (EBID) from various gaseous precursors has been known and studied for decades, EBID from bulk liquid precursors is very much in its infancy and the following is only the second report on this technique. Here we present liquid-precursor (LP-)EBID of platinum (Pt) nanostructures from a dilute aqueous solution of chloroplatinic acid (H(2)PtCl(6)). We investigate how the lateral size of Pt nanoparticles (NPs) varies with charge dose, and how already deposited Pt NPs are affected by the subsequent deposition of their neighbors (proximity effect). We also demonstrate LP-EBID of dense arrays of small Pt dots (60 nm pitch, 30 nm diameter) and thin Pt lines (60 nm pitch, 25 nm width), which compare favorably with the typical resolution of resist-based electron-beam lithography.
ABSTRACT
Urban and non-urban rural ozone (O3) concentrations are high in Bulgaria and often exceed the European AOT40 ecosystem as well as the AOT60 human health standards. This paper presents preliminary estimates to establish background, non-urban O3 concentrations for the southern region of Bulgaria. Ozone concentrations from three distinctly different sites are presented: a mountain site influenced by mountain-valley wind flow; a coastal site influenced by sea-breeze wind flow; and a 1700-m mountain peak site without 'local' wind flow characteristics. The latter offers the best estimate of 46-50 ppb for a background O3 level. The highest non-urban hourly value, 118 ppb, was measured at the mountain-valley site.
