Ing-Shouh Hwang
Academia Sinica
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Publication
Featured researches published by Ing-Shouh Hwang.
Japanese Journal of Applied Physics | 2006
Hong Shi Kuo; Ing-Shouh Hwang; Tsu Yi Fu; Yu Chun Lin; Che Cheng Chang; Tien T. Tsong
We have developed a simple, reliable and reproducible method for preparing single-atom tips. With electrochemical techniques, a very small amount of a noble metal is plated on the surface of a clean W tip. Upon annealing the tip at an appropriate temperature in vacuum, a three-sided {211} pyramid with a single-atom sharpness is formed spontaneously at the tip apex by adsorbate-induced faceting. This tip is both thermally and chemically stable, and can be regenerated several ten times when accidentally damaged. We use a field ion microscope to examine the atomic structure of the tip apex layer by layer and characterize the corresponding electron emission in the field emission mode. Some properties of Ne+ ions emitted from a single-atom tip are also measured, indicating a high brightness and a small extension angle. Many desirable features make the single-atom tips very promising for future particle beam applications in nanoscience and nanotechnology.
Nanotechnology | 2009
Che-Cheng Chang; Hong-Shi Kuo; Ing-Shouh Hwang; Tien T. Tsong
In quantum mechanics, a wavefunction contains two factors: the amplitude and the phase. Only when the probing beam is fully phase coherent, can complete information be retrieved from a particle beam based experiment. Here we use the electron beam field emitted from a noble-metal covered W(111) single-atom tip to image single-walled carbon nanotubes (SWNTs) in an electron point projection microscope (PPM). The interference fringes of an SWNT bundle exhibit a very high contrast and the fringe pattern extends throughout the entire beam width. This indicates good phase correlation at all points transverse to the propagation direction. Application of these sources can significantly improve the performance and expand the capabilities of current electron beam based techniques. New instrumentation based on the full spatial coherence may allow determination of the three-dimensional atomic structures of nonperiodic nanostructures and make many advanced experiments possible.
Langmuir | 2012
Yi-Hsien Lu; Chih-Wen Yang; Ing-Shouh Hwang
It was numerically predicted that dissolved gas particles could enrich and adsorb at hydrophobic-liquid interfaces. Here we observe nucleation and growth of bright patches of ∼0.45 nm high on the graphite surface in pure water with frequency-modulation atomic force microscopy when the dissolved gas concentration is below the saturation level. The bright patches, suspected to be caused by adsorption of nitrogen molecules at the graphite-water interface, are composed of domains of a rowlike structure with the row separation of 4.2 ± 0.3 nm. The observation of this ordered adlayer might underline the gas segregation at various water interfaces.
Applied Physics Letters | 2008
Hong Shi Kuo; Ing-Shouh Hwang; Tsu Yi Fu; Yi Hsien Lu; Chun Yueh Lin; Tien T. Tsong
We show that a thermally stable Ir∕W⟨111⟩ single-atom tip is a very good point ion source for rare gases (He, Ar) and reactive gases (H2, O2). The ion beams are emitted from the topmost atom with a very small opening angle (<1°) and, most importantly, they exhibit high brightness. In addition, the ion currents are very stable. These good properties together with the long lifetime of the tip and the reliable tip preparation method make this tip especially suitable for applications in gas field ion source focused ion beam systems.
Applied Physics Letters | 2007
En-Te Hwu; Shao-Kang Hung; Chih-Wen Yang; Ing-Shouh Hwang; Kuang-Yuh Huang
An astigmatic detection system is constructed with a modified digital-versatile-disk optical head. This system, with a detecting spot of ∼1μm, can simultaneously measure the vertical displacements and two-dimensional angular tilts of micromachined elements. It can detect thermal vibrations of microfabricated cantilevers with noise levels of 1.3pmHz−1∕2 for the linear displacement and of 3.2nradHz−1∕2 for angular displacements over a frequency range from 1to800kHz. The detecting frequency can even reach beyond 100MHz if high-speed electronic devices are adopted. Further optimization of the system will broaden its applications in diverse technological fields.
Japanese Journal of Applied Physics | 2006
En-Te Hwu; Kuang-Yuh Huang; Shao-Kang Hung; Ing-Shouh Hwang
We use the optical pickup head of a commercial compact disk (CD)/digital versatile disk (DVD) read only memory (ROM) drive to detect the vertical displacement of micro fabricated cantilever in atomic force microscopy (AFM). Both the contact and AC modes of AFM are demonstrated. The single atomic steps of graphite can be resolved, indicating that atomic resolution in the vertical displacement detection can be achieved with this new setup. The low cost, compact size, and the light weight of CD/DVD optical pickups may offer new advantages in future AFM designs.
Journal of Physics: Condensed Matter | 2013
Chih-Wen Yang; Yi-Hsien Lu; Ing-Shouh Hwang
We have imaged nanobubbles on highly ordered pyrolytic graphite (HOPG) surfaces in pure water with different atomic force microscopy (AFM) modes, including the frequency-modulation, the tapping, and the PeakForce techniques. We have compared the performance of these modes in obtaining the surface profiles of nanobubbles. The frequency-modulation mode yields a larger height value than the other two modes and can provide more accurate measurement of the surface profiles of nanobubbles. Imaging with PeakForce mode shows that a nanobubble appears smaller and shorter with increasing peak force and disappears above a certain peak force, but the size returns to the original value when the peak force is reduced. This indicates that imaging with high peak forces does not cause gas removal from the nanobubbles. Based on the presented findings and previous AFM observations, the existing models for nanobubbles are reviewed and discussed. The model of gas aggregate inside nanobubbles provides a better explanation for the puzzles of the high stability and the contact angle of surface nanobubbles.
Lab on a Chip | 2011
Filippo Bosco; En-Te Hwu; Ching-Hsiu Chen; Stephan Sylvest Keller; Michael Bache; Mogens Havsteen Jakobsen; Ing-Shouh Hwang; Anja Boisen
Sensors are crucial in many daily operations including security, environmental control, human diagnostics and patient monitoring. Screening and online monitoring require reliable and high-throughput sensing. We report on the demonstration of a high-throughput label-free sensor platform utilizing cantilever based sensors. These sensors have often been acclaimed to facilitate highly parallelized operation. Unfortunately, so far no concept has been presented which offers large datasets as well as easy liquid sample handling. We use optics and mechanics from a DVD player to handle liquid samples and to read-out cantilever deflection and resonant frequency. Also, surface roughness is measured. When combined with cantilever deflection the roughness is discovered to hold valuable additional information on specific and unspecific binding events. In a few minutes, 30 liquid samples can be analyzed in parallel, each by 24 cantilever-based sensors. The approach was used to detect the binding of streptavidin and antibodies.
Review of Scientific Instruments | 2012
Wei-Tse Chang; Ing-Shouh Hwang; Mu-Tung Chang; Chung-Yueh Lin; Wei-Hao Hsu; Jin-Long Hou
We demonstrate a new and simple process to fabricate tungsten tips with good control of the tip profile. In this process, we use a commercial function generator without any electronic cutoff circuit or complex mechanical setup. The tip length can be varied from 160 μm to 10 mm, corresponding to an aspect ratio of 1.6-100. The radius of curvature of the tip apex can be controlled to a size <10 nm. Surface roughness and the taper angle can be controlled independently. Through control of the etching parameters, the tip length, the radius of curvature, surface roughness, and the taper angle can be controlled to suit different requirements of various applications. The possible etching mechanisms are also discussed.
Scientific Reports | 2015
Yi-Hsien Lu; Chih-Wen Yang; Chung-Kai Fang; Hsien-Chen Ko; Ing-Shouh Hwang
The thermodynamic properties of gases have been understood primarily through phase diagrams of bulk gases. However, observations of gases confined in a nanometer space have posed a challenge to the principles of classical thermodynamics. Here, we investigated interfacial structures comprising either O2 or N2 between water and a hydrophobic solid surface by using advanced atomic force microscopy techniques. Ordered epitaxial layers and cap-shaped nanostructures were observed. In addition, pancake-shaped disordered layers that had grown on top of the epitaxial base layers were observed in oxygen-supersaturated water. We propose that hydrophobic solid surfaces provide low-chemical-potential sites at which gas molecules dissolved in water can be adsorbed. The structures are further stabilized by interfacial water. Here we show that gas molecules can agglomerate into a condensed form when confined in a sufficiently small space under ambient conditions. The crystalline solid surface may even induce a solid-gas state when the gas-substrate interaction is significantly stronger than the gas-gas interaction. The ordering and thermodynamic properties of the confined gases are determined primarily according to interfacial interactions.