| 1. |
- Gjerde, Kjetil, et al.
(författare)
-
On the suitability of carbon nanotube forests as non-stick surfaces for nanomanipulation
- 2008
-
Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 4:3, s. 392-399
-
Tidskriftsartikel (refereegranskat)abstract
- A carbon nanotube forest provides a unique non-stick surface for nanomanipulation, as the nanostructuring of the surface allows micro- and nanoscale objects to be easily removed after first being deposited via a liquid dispersion. A common problem for smooth surfaces is the strong initial stiction caused by adhesion forces after deposition onto the surface. In this work, carbon nanotube forests fabricated by plasma-enhanced chemical vapour deposition are compared to structures with a similar morphology, silicon nanograss, defined by anisotropic reactive ion-etching. While manipulation experiments with latex microbeads on structured as well as smooth surfaces ( gold, silicon, silicon dioxide, Teflon, diamond-like carbon) showed a very low initial stiction for both carbon nanotube forests and silicon nanograss, a homogeneous distribution of particles was significantly easier to achieve on the carbon nanotube forests. Contact-angle measurements during gradual evaporation revealed that the silicon nanograss was superhydrophic with no contact-line pinning, while carbon nanotube forests in contrast showed strong contact-line pinning, as confirmed by environmental scanning electron microscopy of microdroplets. As a consequence, latex microbeads dispersed on the surface from an aqueous solution distributed evenly on carbon nanotube forests, but formed large agglomerates after evaporation on silicon nanograss. Lateral manipulation of latex microbeads with a microcantilever was found to be easier on carbon nanotube forests and silicon nanograss compared to smooth diamond-like carbon, due to a substantially lower initial stiction force on surfaces with nanoscale roughness. Nanomanipulation of bismuth nanowires, carbon nanotubes and organic nanofibres was demonstrated on carbon nanotube forests using a sharp tungsten tip. We find that the reason for the remarkable suitability of carbon nanotube forests as a non-stick surface for nanomanipulation is indeed the strong contact-line pinning in combination with the nanostructured surface, which allows homogeneous dispersion and easy manipulation of individual particles.
|
|
| 2. |
- Kallesoe, Christian, et al.
(författare)
-
Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching
- 2010
-
Ingår i: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 28:1, s. 21-26
-
Tidskriftsartikel (refereegranskat)abstract
- Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections simultaneously on multiple nanowires. They investigate the potential of combining nanostencil deposition of catalyst, epitaxial III-V heterostructure nanowire growth, and selective etching, as a road toward wafer scale integration and engineering of nanowires with existing silicon technology. Nanostencil lithography is used for deposition of catalyst particles on trench sidewalls and the lateral growth of III-V nanowires is achieved from such catalysts. The selectivity of a bromine-based etch on gallium arsenide segments in gallium phosphide nanowires is examined, using a hydrochloride etch to remove the III-V native oxides. Depending on the etching conditions, a variety of gap topologies and tiplike structures are observed, offering postgrowth engineering of material composition and morphology.
|
|
| 3. |
- Kallesoe, Christian, et al.
(författare)
-
Selective etching of III-V nanowires for molecular junctions
- 2008
-
Ingår i: Microelectronic Engineering. - : Elsevier BV. - 1873-5568 .- 0167-9317. ; 85:5-6, s. 1179-1181
-
Tidskriftsartikel (refereegranskat)abstract
- Selective etching of heterostructure III-V nanowires can be used to form tips and narrow gaps simultaneously on multiple nanowires on a single wafer. In this study we tested bromine based etching of gallium arsenide segments in gallium phosphide nanowires. Depending on the etchant and etching conditions, a variety of gap topologies and tip-like structures were observed. The method is compatible with wafer-scale integration of molecular electronics within existing silicon technology, offering control of materials composition, morphology and electronic band gap of the electrodes that can be made so small they might be used as contact electrodes for individual molecules. (C) 2008 Elsevier B.V. All rights reserved.
|
|
| 4. |
- Molhave, Kristian, et al.
(författare)
-
Epitaxial Integration of Nanowires in Microsystems by Local Micrometer-Scale Vapor-Phase Epitaxy
- 2008
-
Ingår i: Small. - : Wiley. - 1613-6829 .- 1613-6810. ; 4:10, s. 1741-1746
-
Tidskriftsartikel (refereegranskat)abstract
- Free-standing epitaxially grown nanowires provide a controlled growth system and an optimal interface to the underlying substrate for advanced optical, electrical, and mechanical nanowire device connections. Nanowires can be grown by vapor-phase epitaxy (VPE) methods such as chemical vapor deposition (CVD) or metal organic VPE (MOVPE). However, VPE of semiconducting nanowires is not compatible with several microfabrication processes due to the high synthesis temperatures and issues such as cross-contamination interfering with the intended microsystem or the VPE process. By selectively heating a small microfabricated heater, growth of nanowires can be achieved locally without heating the entire microsystem, thereby reducing the compatibility problems. The first demonstration of epitaxial growth of silicon nanowires by this method is presented and shows that the microsystem can be used for rapid optimization of VPE conditions. The important issue of the cross-contamination of other parts of the microsystem caused by the local growth of nanowires is also investigated by growth of GaN near previously grown silicon nanowires. The design of the cantilever heaters makes it possible to study the grown nanowires with a transmission electron microscope without sample preparation.
|
|
