Spiral Deposition with Alternating Indium Composition in Growing an InGaN Nanoneedle with the Vapor-Liquid-Solid Growth Mode
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The spiral deposition of InGaN with a quasiperiodical distribution of indium content along the growth direction for forming InGaN nanoneedles (NNs) with the vapor‐liquid‐solid (VLS) growth mode is demonstrated. The VLS growth is implemented by using Au nanoparticles (NPs) as the catalyst in metalorganic chemical vapor deposition. The Au NPs on a GaN template are generated through pulsed laser irradiation. The observation of spiral deposition is based on the analyses of the scanning results in the high angle annular dark field and energy dispersive X‐ray measurements of transmission electron microscopy. In the measurements, the composition variations along and perpendicular to the growth direction (the c ‐axis) are illustrated. The alternating indium content along the growth direction is attributed to a quasiperiodically pulsed behavior of indium supersaturation process in the melted Au NP at the top of an InGaN NN. The spiral deposition of InGaN is due to the formation of an NN at the location of an Au NP with a screw‐type dislocation beneath in the GaN template, at which the growth of a quasi‐one‐dimensional structure can be easily initiated.Keywords:
Nanoneedle
Deposition
Abstract We developed an optical‐driven nanoneedle that is operated in aqueous solution by two focused laser beams. A nanoneedle tool consists of 2 μm‐sized structures for optical trapping and a nanoneedle having 200 nm width and 20 μm length. Nanoneedle tools are fabricated with single ultraviolet (UV) lithography of SU‐8 photoresist with highly scalable manner. We evaluated the conditions of the lithography processes: rinse, hard bake and post exposure bake (PEB) that determine the shape of the nanoneedles and recovery rate. We demonstrated the trapping of a nanoneedle tool to verify the manipulation of the position and the orientation. Nanoneedle tools have an advantage in the use of closed microchanells, which can lead to the applications including delivery and extraction of substances inside single cells and pinpoint molecular processing of biomolecules. In this paper, we report on the fabrication process of the nanoneedle tools and the demonstration of the manipulation.
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Alternate employment of etching gas (SF/sub 6/) and deposition gas (C/sub 4/F/sub 8/) on an unpolished SiO/sub 2/ surface in an inductive coupling plasma system generates a perfluorocarbon nanoneedle array at low pressure and at ambient temperature. The nanoneedle averages 300 nm in diameter and the nanoneedle surface has a large water contact angle of 171/spl deg/. The superhydrophobicity of the perfluorocarbon nanoneedle surface may be used in many industrial and biological processes.
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We developed an optical-driven nanoneedle that is operated in aqueous solution by 2 focused laser beams. A nanoneedle tool consists of 2 micrometer-sized structures for optical trapping and a nanoneedle having 200 nm width and 20 μm length. Nanoneedle tools are fabricated with single UV lithography of SU-8 photoresist with highly scalable manner. We evaluated the conditions of the lithography processes: rinse, hardbake and PEB that determine the shape of the nanoneedles and recovery rate. We demonstrated the trapping of a nanoneedle tool to verify the manipulation of the position and the orientation. Nanoneedle tools have an advantage in the use of closed microchanells, which can lead to the applications including delivery and extraction of substances inside single cells and pinpoint molecular processing of biomolecules. In this paper, we report on the fabrication process of the nanoneedle tools and the demonstration of the manipulation.
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Micrometer
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We have developed a tool for directly inserting proteins into living cells by using atomic force microscopy (AFM) and an ultrathin needle, termed a nanoneedle. The surface of the nanoneedle was modified with His-tagged proteins using nickel chelating nitrilotriaceticacid (NTA). The fluorescent proteins, DsRed2-His6 and EGFP-His6, could be attached to and detached from the surface of the nanoneedle. These results suggest that the Ni-NTA modified nanoneedle can successfully be used for specific delivery of proteins. The nanoneedle modified with DsRed2-His6 was able to penetrate the surface of a living HeLa cell, as confirmed by laser scanning fluorescence microscopy and monitoring an exerting force on the nanoneedle using AFM. Force curves using the nanoneedle indicated that the needle was able to penetrate at displacement speeds of 0.10–10 µm/s. These results suggest that this technique can be used to directly insert proteins into living cells and is applicable for modulation or regulation of single cell activity.
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Large-area and crack-free films of CuO nanoneedle arrays were synthesized by heating ZnO coated copper foils at a temperature of 400 °C. Scanning electron microscopy shows that the cracking and exfoliation of CuO nanoneedle films are effectively eliminated by predeposition of ZnO layers by a solution route before the heating processes. In addition, the diameters, lengths, and area densities of CuO nanoneedles are tunable by varying the thickness of the ZnO layers. High-resolution transmission electron microscopy demonstrates that the CuO nanoneedles are single-crystalline structures growing along the <31̅0> direction. X-ray diffraction and energy dispersive X-ray spectra reveal that the predeposited ZnO prevents quick oxidation of the copper substrate and prohibits the formation of Cu2O. Field-emission measurements show enhanced emission of the crack-free CuO nanoneedle film with a low turn-on field of 0.85 V/μm. The enhanced emission is attributed to the improved morphologies of CuO nanoneedles, as well as elimination of cracks of nanoneedle films. The work provides an efficient route to synthesize well-controlled CuO nanoneedle arrays for nanodevice applications.
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We develop a new nano-peeling technique to realize high-density Ag nanoneedle forest arrays for sensitively detecting target molecules in the NIR region. The excellent SERS performance is ascribed to abundant hotspots from both gaps and tips formed in the unique Ag nanoneedle forest structure.
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