Browsing by Author "Lo, Hung-Chun"

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Electron field emission from well-aligned GaP nanotips
(2010-11-01)
Lo, Hung-Chun
;
Tsai, Jeff T. H.
;
leu, Jih-Perng
;
Chen, Chia-Fu
;
材料科學與工程學系
Field emission of electrons from single crystal gallium phosphide (GaP) nanotips has been investigated. GaP nanotip arrays were fabricated using silane-methane-argon-hydrogen based plasma using the self-masking dry etching technique in an electron-cyclotron-resonance microwave plasma enhanced chemical vapor deposition system. These nanotips have an average of 2 and 80 nm in apex and bottom diameters, respectively. They are 900 nm in height, which makes them the perfect electron emission source for their high aspect ratio topography. A nanosized silicon carbide (SiC) cap on each GaP nanotip in the array has been found. The SiC core has a heterointerface with GaP crystal that was observed using a high resolution transmission electron microscope. Field emission analysis shows low turn-on fields of 8.5-9 V/mu m. Cold electron emissions in Fowler-Nordheim type current-voltage were observed from such GaP nanotip arrays. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3506089]
High-density one-dimensional well-aligned germanium quantum dots on a nanoridge array
(2008-08-25)
Chen, Yan-Ru
;
Kuan, Chieh-Hsiung
;
Suen, Yuen-Wuu
;
Peng, Yu-Hwa
;
Chen, Peng-Shiu
The selective growth of high-density one-dimensional well-aligned Ge quantum dots (QDs) on the top of nanoridges patterned on Si substrate is reported. The period of ridge array is 150 nm, the width of each ridge is 80 nm, and the depth of the trench is 20 nm. The areal density of QDs is about 5.4 x 10(9) cm(-2). Simulations of the chemical potential show that a proper distribution of the surface curvature may give rise to a suitable chemical potential minimum helping positioning the QDs. These ridges can also be used to control the shape and the uniformity of QDs. (C) 2008 American Institute of Physics.
Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures
(2007-12-01)
Huang, Yi-Fan
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Chattopadhyay, Surojit
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Jen, Yi-Jun
;
Peng, Cheng-Yu
;
Liu, Tze-An
Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.
Label free sub-picomole level DNA detection with Ag nanoparticle decorated Au nanotip arrays as surface enhanced Raman spectroscopy platform
(2011-01-15)
Lo, Hung-Chun
;
Hsiung, Hsin-I
;
Chattopadhyay, Surojit
;
Han, Hsieh-Cheng
;
Chen, Chia-Fu
Label free optical sensing of adenine and thymine oligonucleotides has been achieved at the sub-picomole level using self assembled silver nanoparticles (AgNPs) decorated gold nanotip (AuNT) arrays. The platform consisting of the AuNTs not only aids in efficient bio-immobilization, but also packs AgNPs in a three dimensional high surface area workspace, assisting in surface enhanced Raman scattering (SERS). The use of sub-10 nm AgNPs with optimum inter-particle distance ensures amplification of the chemically specific Raman signals of the adsorbed adenine, thymine, cytosine and guanine molecules in SERS experiments. High temporal stability of the Raman signals ensured reliable and repeatable DNA detection even after three weeks of ambient desk-top conservation. This facile architecture, being three dimensional and non-lithographic, differs from conventional SERS platforms. (C) 2010 Elsevier B.V. All rights reserved.