Chien-Hung Liu

Bio: Chien-Hung Liu is an academic researcher from National Chung Hsing University. The author has contributed to research in topics: Laser & Diffraction. The author has an hindex of 20, co-authored 82 publications receiving 1266 citations. Previous affiliations of Chien-Hung Liu include National Chung Cheng University & National Formosa University.

Ultraviolet ZnO Nanorod Photosensors

Abstract: This study fabricates and characterizes ultraviolet (UV) photosensors with ZnO nanorods (NRs). The NR arrays were selectively grown in the gap between interdigitated (IDT) electrodes of devices using hydrothermal solution processes and a lithography-based technique. Compared with a conventional ZnO photosensor without NRs, the proposed UV NR photosensors have much higher photoresponse in the UV region. Additionally, the photoconductive gain of an NR photosensor increased as UV illumination time increased; it varied at 34.45−5.32 × 102 under illumination by 18.28 mW/cm2 optical power. Consequently, the substantial photoconductive gain can be attributed to high surface-to-volume ratio of ZnO NRs. The high density of hole-trap states on NR surfaces lead to a persistent photoconductivity (PPC) state, promoting the transport of carriers through devices.

Buckling characterization of vertical ZnO nanowires using nanoindentation

Abstract: Nanomechanical characterization of vertical well-aligned single-crystal ZnO nanowires on ZnO:Ga/glass templates was performed by nanoindentation technique. The buckling loads were found to be 1465 and 215μN for the ZnO nanowires of 100 and 30nm diameters, respectively. Furthermore, the buckling energies for the ZnO nanowires of 100 and 30nm diameters were 3.62×10−10 and 3.69×10−11J, respectively. Based on the Euler buckling model, Young’s modulus of the individual ZnO nanowire has been derived from two possible modes in this work.

Development of a laser-based high-precision six-degrees-of-freedom motion errors measuring system for linear stage

Abstract: This article presents a useful measuring system for the simultaneous measurement of six-degrees-of-freedom motion errors of a moving stage. The system integrates a miniature fiber coupled laser interferometer with specially designed optical paths and quadrant detectors, capable of measuring six-degrees-of-freedom motion errors. Using this model, the proposed measuring method provides rapid performance, simplicity of setup, and preprocess verification of a linear stage. The experimental setups and measuring procedures, and a systematic calculated method for the error verification are presented in the paper. The system’s resolution of measuring straightness error component is about 25nm. The resolution of measuring the pitch and yaw angular error component is about 0.06arcs. With the comparison between the HP calibration system and the proposed system in the measuring range of 120mm, the system accuracy of measuring straightness error and angular error is within the range ±0.6μm and ±0.3arcs.

Design and control of a long-traveling nano-positioning stage

Abstract: In this paper, a Dual-Axis Long-Traveling Nano-Positioning Stage (DALTNPS) is presented. In order to extend the traveling and increase the accuracy, the two sorts of stages, a traditional ball-screw stage and a three-degrees-of-freedom (3-DOF) piezo-stage, were composed. The traditional ball-screw stage which is composed of two guide-ways and a ball-screw at each axis is a long-travel stage, and the 3-DOF piezo-stage, which is composed of three piezoelectric actuators and four translation–rotation mechanisms, is a high precision stage. In addition, a 3-DOF measuring system and a PID controller are composed of a 3-DOF closed-loop controller and applied to implement the DALTNPS. The measuring system which is composed of two laser interferometers and two plane mirrors is a 3-DOF optical measuring system. Thus, the position at the x and y axes and the rotation around the z axis can be obtained and they are the responses of DALTNPS. Finally, the experiment results evidence that the DALTNPS is characterized by long-travel, high linear accuracy, high rotation accuracy, high contouring accuracy and high motion speed.

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

Abstract: Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

25th Anniversary Article: Semiconductor Nanowires – Synthesis, Characterization, and Applications

Abstract: Semiconductor nanowires (NWs) have been studied extensively for over two decades for their novel electronic, photonic, thermal, electrochemical and mechanical properties. This comprehensive review article summarizes major advances in the synthesis, characterization, and application of these materials in the past decade. Developments in the understanding of the fundamental principles of "bottom-up" growth mechanisms are presented, with an emphasis on rational control of the morphology, stoichiometry, and crystal structure of the materials. This is followed by a discussion of the application of nanowires in i) electronic, ii) sensor, iii) photonic, iv) thermoelectric, v) photovoltaic, vi) photoelectrochemical, vii) battery, viii) mechanical, and ix) biological applications. Throughout the discussion, a detailed explanation of the unique properties associated with the one-dimensional nanowire geometry will be presented, and the benefits of these properties for the various applications will be highlighted. The review concludes with a brief perspective on future research directions, and remaining barriers which must be overcome for the successful commercial application of these technologies.

ZnO-Based Ultraviolet Photodetectors

Abstract: Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one of the most promising candidates for UV photodetectors. Additionally, doping in ZnO with Mg elements can adjust the bandgap largely and make it feasible to prepare UV photodetectors with different cut-off wavelengths. ZnO-based photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes and p–n junction photodetectors have been developed. In this work, it mainly focuses on the ZnO and ZnMgO films photodetectors. We analyze the performance of ZnO-based photodetectors, discussing recent achievements, and comparing the characteristics of the various photodetector structures developed to date.

Modeling and Control of Piezo-Actuated Nanopositioning Stages: A Survey

Abstract: Piezo-actuated stages have become more and more promising in nanopositioning applications due to the excellent advantages of the fast response time, large mechanical force, and extremely fine resolution. Modeling and control are critical to achieve objectives for high-precision motion. However, piezo-actuated stages themselves suffer from the inherent drawbacks produced by the inherent creep and hysteresis nonlinearities and vibration caused by the lightly damped resonant dynamics, which make modeling and control of such systems challenging. To address these challenges, various techniques have been reported in the literature. This paper surveys and discusses the progresses of different modeling and control approaches for piezo-actuated nanopositioning stages and highlights new opportunities for the extended studies.