Sung Moon

Fabrication of vanadium oxide thin film with high-temperature coefficient of resistance using V2O5/V/V2O5 multi-layers for uncooled microbolometers

Vanadium oxide thin film is a promising material for uncooled microbolometers due to its high temperature coefficient of resistance (TCR) at room temperature. It is, however, very difficult to deposit vanadium oxide thin films having a high temperature coefficient of resistance and low resistance because of the process limits in microbolometer fabrication. We present a novel fabrication method for vanadium oxide thin films having good electrical properties. Through the formation of a sandwich structure of V2O5 (100 A)/V (∼80 A)/V2O5 (500 A) by a conventional sputter method and post-annealing at 300 °C in oxygen, a mixed phase of VOx is formed. The results show that the mixed phase formed by this process has a high TCR of more than −2%/°C and low resistivity of <0.1 Ω cm at room temperature.

Enhanced characteristics of an uncooled microbolometer using vanadium–tungsten oxide as a thermometric material

To produce a highly sensitive uncooled microbolometer, the development of a high-performance thermometric material is essential. In this work, amorphous vanadium–tungsten oxide was developed as a thermometric material at a low temperature of 300°C, and the microbolometer, coupled with the material, was designed and fabricated using surface micromachining technology. The vanadium–tungsten oxide showed good properties for application to the microbolometer, such as a high-temperature coefficient of resistance of over −4.0%∕K and good compatibility with the surface micromachining and integrated circuit fabrication process due to its low fabrication temperature. As a result, the uncooled microbolometer could be fabricated with high detectivity over 1.0×109cmHz1∕2∕W at a bias current of 7.5μA and a chopper frequency of 10–20Hz.

Enhanced infrared detection characteristics of VOx films prepared using alternating V2O5 and V layers

Multilayer VOx films are reported to improve the infrared (IR) detecting characteristics for application as an IR active layer in a microbolometer. Multilayer VOx films formed from the V2O5/V/V2O5 thin film structure showed some advantages in electrical property control and more effective formation of typically unstable vanadium oxide phases. These phases are difficult to achieve by single-layer VOx film fabrication with conventional reactive sputtering. Multilayer VOx films were fabricated by low temperature oxygen annealing at 300 °C after the alternating deposition of stable V and V2O5 layer using rf sputtering. The electrical measurement and microstructural analysis of annealed films were performed to evaluate the advantage of multilayer VOx film fabrication. Owing to the well-controlled mixed phase formation, including V2O3, VO2, and V2O5 in the annealed V2O5/V/V2O5 multilayer film, the temperature coefficient of resistance value and resistivity of the new multilayer VOx film could be increased up to...

Fabrication and Mechanical Characterization of Micro Electro Mechanical System Based Vertical Probe Tips for Micro Pad Measurements

As a result of new developments in semiconductor technology, the number of pads per unit area is increasing and pad arrays are becoming irregular. Therefore, there is an increased need for a versatile probe card to address these issues. We developed a vertical micro electro mechanical system (MEMS) probe tip that is usable in a small pad (approximately 100 µm) and a two-dimensional pad array. The main process used to produce the tip was wafer bonding, silicon etching by deep reactive ion etcher (RIE) and electro-plating. The material of the electro-plated probe tip was an Ni–Co alloy. To optimize the design of the vertical probe tip, we designed various models and measured them in a micro compression and tensile tester. The structural analyses of the probe tip were accomplished using finite element method (FEM) and compared with actual measurement values. In this study, we demonstrated the potential of the vertical probe tip applied to a small area with the over drive (O.D.) of 10–40 µm and the contact force of 1–8gf.

Quantum discord protection from amplitude damping decoherence

Entanglement is known to be an essential resource for many quantum information processes. However, it is now known that some quantum features may be acheived with quantum discord, a generalized measure of quantum correlation. In this paper, we study how quantum discord, or more specifically, the measures of entropic discord and geometric discord are affected by the influence of amplitude damping decoherence. We also show that a protocol deploying weak measurement and quantum measurement reversal can effectively protect quantum discord from amplitude damping decoherence, enabling to distribute quantum correlation between two remote parties in a noisy environment.

Fabrication and characteristics of MEMS vertical type probe tip for micro sized pads measurement

In this research we proposed, designed, fabricated, and measured a novel micro electro mechanical system (MEMS) based vertical probe tips which differs from conventional cantilever probe tips. The main idea of the vertical probe design was how to distribute the total forces vertically concentrated on the probe tip in measuring semiconductor devices. To solve the problem, we designed the vertical probe tip with meander structure which could provide enough displacements so that the vertical probe tips could distribute the forces acting on the tips. The structural analyses of the probe tip were accomplished using finite element method (FEM) and compared with actual measurement values. The primary fabrication processes were surface micromachining, wafer bonding technology, and electroplating. The material of the electro-plated probe tip was an Ni-Co alloy. In this study, we demonstrated the potential of the vertical probe tip that could apply to a small area with the over drive (O.D.) of 10~40 mum and the contact force of 1~8 gf. The measured contact resistance was less than 2 Omega and little noise was observed.

Low-noise single-photon detector for the 1.5-μm wavelength region

A simple argument is given that a traversable Cauchy horizon inside a black hole is incompatible with unitary black hole evolution. The argument assumes the validity of black hole complementarity and applies to a generic black hole carrying angular momentum and/or charge. In the second part of the paper we review recent work on the semiclassical geometry of two-dimensional charged black holes.

Direct quantum process tomography via measuring sequential weak values of incompatible observables.

The weak value concept has enabled fundamental studies of quantum measurement and, recently, found potential applications in quantum and classical metrology. However, most weak value experiments reported to date do not require quantum mechanical descriptions, as they only exploit the classical wave nature of the physical systems. In this work, we demonstrate measurement of the sequential weak value of two incompatible observables by making use of two-photon quantum interference so that the results can only be explained quantum physically. We then demonstrate that the sequential weak value measurement can be used to perform direct quantum process tomography of a qubit channel. Our work not only demonstrates the quantum nature of weak values but also presents potential new applications of weak values in analyzing quantum channels and operations.Weak measurements constitute a powerful tool for metrology, tomography and even foundations, but in most cases could be explained classically. Here, the authors characterise a quantum channel using sequential weak value measurements of two incompatible observables utilising two-photon quantum interference.

Generation of a non-zero discord bipartite state with classical second-order interference

We report an investigation on quantum discord in classical second-order interference. In particular, we theoretically show that a bipartite state with D = 0.311 of discord can be generated via classical second-order interference. We also experimentally verify the theory by obtaining D = 0.197 ± 0.060 of non-zero discord state. Together with the fact that the nonclassicalities originated from physical constraints and information theoretic perspectives are not equivalent, this result provides an insight to understand the nature of quantum discord.

Countermeasure against blinding attacks on low-noise detectors with a background-noise-cancellation scheme

We developed a countermeasure against blinding attacks on low-noise detectors with a background noise cancellation scheme in quantum key distribution (QKD) systems. Background noise cancellation includes self-differencing and balanced avalanche photon diode (APD) schemes and is considered a promising solution for low-noise APDs, which are critical components in high-performance QKD systems. However, its vulnerability to blinding attacks has been recently reported. In this work, we propose a new countermeasure that prevents this potential security loophole from being used in detector blinding attacks. An experimental QKD setup is implemented and various tests are conducted to verify the feasibility and performance of the proposed method. The obtained measurement results show that the proposed scheme successfully detects occurring blinding-attack-based hacking attempts.