Showing papers by "Simon Brown published in 2004"

Templated-assembly of conducting antimony cluster wires

Abstract: Wires with meso- and nanoscale widths have been fabricated using a novel assembly technique based on the deposition of Sb clusters on templated surfaces. The template elements are V-grooves etched into the surface of a Si wafer. It is demonstrated that the clusters bounce or slide to the apex of the V-grooves, without significant fragmentation, and that this motion is the underlying mechanism behind the formation of the wires. The flow rate of inert gas into the cluster growth chamber controls the average velocity of the clusters and the morphology and width of the wires. Sb cluster-assembled wires with lengths over 150 µ ma nd widths down to 100 nm have been assembled from ∼40 nm diameter Sb clusters. Electrical contacts to the wire sh av eb een achieved via lithographic alignment of NiCr/Au contacts to the V-grooves prior to deposition.

Templated cluster assembled wires

Abstract: Methods of preparing electrically conducting wire-like structures for use in for example electronic devices, and the devices formed by such methods are described. One example of such a method of preparing said structures relies on the assembly of conducting particles using surface templates to assist in the formation of a wire-like structure. Said structures may be prepared on the nanoscale, but also up to the micronscale.

Etch masks based on template-assembled nanoclusters

Abstract: Nanoscale or mesoscale structures are fabricated on the surface of a substrate (e.g. silicon) by the aggregation of atomic clusters (e.g. antimony or bismuth) into V-grooves. These structures, preferably in the form of nanowires, are used as etching masks for the subsequent etching of the substrate. In an embodiment the V-grooves are metallised (e.g. with titanium or gold) prior to the deposition of the clusters. In this case the use of the nanostructures (e.g. antimony or bismuth) as an etching mask results in the formation of nanostructures of the underlying metal (e.g. titanium or gold). In this way the dimensions of the nanowires are transferred into the underlying metal film and the method allows fabrication of nanowires from materials (e.g. titanium or gold) that cannot be deposited as clusters.

Formation of electrically conducting mesoscale wires through self-assembly of atomic clusters

Abstract: Bi and Sb clusters deposited from an inert gas aggregation source have been used to form cluster-assembled wires on unpassivated, and SiO/sub 2/ passivated, V-grooved Si substrates. V-grooves (4-7 /spl mu/m in width, 6 /spl mu/m-1 mm in length) were prepared using optical lithography and anisotropic etching in KOH solution. The effectiveness of the surface templating technique was demonstrated by scanning electron microscope analysis carried out after deposition. When Sb clusters were deposited onto SiO/sub 2/ passivated substrates, the surface coverage was seen to vary from 100% at the apexes of the V-grooves used to promote growth of the wire. Sb wires produced with this technique currently have minimum widths of /spl sim/400 nm and lengths of /spl sim/1 mm. Electrical contacts can be positioned within the V-grooves prior to cluster deposition, thus enabling the initial onset of conduction and subsequent I(V) characteristic of a wire to be monitored in vacuum.

Assembly of Bismuth Clusters into Nanowires Using Etched V-Grooves as Templates

Abstract: The cluster assembly method reported here employs V-grooves as templates for nanowire fabrication. This technique allows the formation of contacted electrically conducting nanowires using simple optical lithography and without painstaking manipulation of the clusters. In–vacuum, temperature dependent I(V) measurements were performed on Bi wires with widths ∼1 μm and lengths 50 μm. The temperature dependent resistance of the Bi wires is explained by the variation in the carrier concentration in Bi with temperature.

Electron Diffraction from Atomic Cluster Beams

Abstract: Electron diffraction is a direct method which can be used to probe insitu the structure of unsupported nanoparticles in molecular beams. The technique is important because it permits a determination of structure, free of the perturbing effects of a substrate, matrix or chemical contamination.

Photoconductivity spectra from n-doped GaN: evidence for two distinct types of donors

Abstract: Low temperature photoconductivity (PC) and photoluminescence (PL) measurements from Si-doped GaN samples reveal evidence for two distinct types of donor. The PC spectra contain two strong features, one of which is very unusual because it is observed at lower energy than the sole feature in PL. The dominant feature in the PC of unetched samples, at 3.484 eV, is associated with deliberately incorporated Si donors. The second feature, 14 meV to lower energy, is associated with a native defect. The density of this defect can be increased by etching with an argon plasma.

Masques de gravure bases sur des nanoagregats assembles en gabarit etch masks based on template-assembled nanoclusters

Abstract: L'invention concerne des structures d'echelle nanometrique ou de moyenne echelle fabriquees sur la surface d'un substrat (silicium, par exemple) par rassemblement d'agregats atomiques (antimonie ou bismuth, par exemple) dans des rainures en V. Ces structures, qui se presentent de preference sous la forme de nanocâbles, sont utilisees comme masques de gravure pour la gravure ulterieure du substrat. Dans un mode de realisation, les rainures en V sont metallisees (avec du titane ou de l'or, par exemple) avant depot des agregats. Dans ce cas, l'utilisation de nanostructures (antimonie ou bismuth, par exemple) comme masque de gravure donne lieu a la formation de nanostructures du metal sous-jacent (titane ou or, par exemple). Ainsi, les dimensions des nanocâbles sont transferees dans le film metallique sous-jacent, et le procede permet de fabriquer des nanocâbles a partir de materiaux, tels que le titane ou l'or, qui ne peuvent etre deposes comme agregats.