A5091740257- Semiconductor Quantum Structures and Devices
- Terahertz technology and applications
- Superconducting and THz Device Technology
- Metamaterials and Metasurfaces Applications
- Nanowire Synthesis and Applications
- Semiconductor materials and devices
- Photonic and Optical Devices
- Semiconductor materials and interfaces
- Advanced Antenna and Metasurface Technologies
- Antenna Design and Analysis
- Photonic Crystals and Applications
- Spectroscopy and Laser Applications
- Quantum Dots Synthesis And Properties
- Plasmonic and Surface Plasmon Research
- Advanced Semiconductor Detectors and Materials
- Adhesion, Friction, and Surface Interactions
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Memory and Neural Computing
- Transition Metal Oxide Nanomaterials
- Infection Control and Ventilation
- Semiconductor Lasers and Optical Devices
- Millimeter-Wave Propagation and Modeling
- Optical Coatings and Gratings
- COVID-19 and healthcare impacts
- Nanofabrication and Lithography Techniques
Agency for Science, Technology and Research
2010-2024
Institute of Materials Research and Engineering
2010-2024
Institute of Microelectronics
2011
Nanyang Technological University
2005-2009
A switchable magnetic metamaterial is demonstrated via reshaping micromachined molecules. It experimentally verified that the effective permeability can be switched from negative to positive near resonant frequency. The micromachining technology offers a powerful platform for metamaterials and provides more degrees of freedom design, easy fabrication, large tunability.
We experimentally demonstrated a polarization dependent state to independent change in terahertz (THz) metamaterials. This is accomplished by reconfiguring the lattice structure of metamaterials from 2-fold 4-fold rotational symmetry using micromachined actuators. In experiment, it measures resonance frequency shift 25.8% and 12.1% for TE TM polarized incidence, respectively. Furthermore, single-band dual-band switching also demonstrated. Compared with previous reported tunable...
Ga-doped ZnO (GZO) transparent nanostructured thin films were fabricated via the magnetron sputtering process, and effect of Ga doping level in GaxZn1–xO on their thermoelectric performance was investigated. Nanostructured composite Ga0.085Zn0.915O could achieve a power factor up to 1428 μW/mK2 at 850 K, which is one highest among reported thin-film GZO other metal oxides-based thermoelectrics. A corresponding generator module using as n-type legs attain maximum output 230 nW ΔT = 138 K with...
We experimentally demonstrate a micromachined switchable metamaterial with dual mode resonance which is induced at THz regime under oblique incidence. Here, we explore, both theoretically and experimentally, the dynamic switching by reshaping elements using actuators. The allows robust control over transmission reflection of 0.76 1.16 THz. Such promises wide applications in optical switches, tunable filters, detectors.
We report highly efficient continuous-wave terahertz (THz) photoconductive antenna based photomixer employing nano-gap electrodes in the active region. The tip-to-tip electrode structure provides strong THz field enhancement and acts as a nano-antenna to radiate wave generated region of photomixer. In addition, it good impedance matching planar exhibits lower RC time constant, allowing more radiation especially at higher part spectrum. As result, output intensity with new is two orders...
In this article, we demonstrate the influence of substrate temperature during migration-enhanced epitaxy (MEE) process GaAs on a vicinal surface Ge (100), 6° offcut towards (111) plane. It was found that is not sufficient condition for suppressing formation antiphase domains at GaAs∕Ge interface. Rather, it has to be complemented by low MEE process. grown 250°C, lowest among all samples, exhibits smoothest and best structural optical qualities, as characterized atomic force microscopy,...
We report a method for selective silver coating of SU-8 structures on Si substrates by treating the sample with radio frequency plasma prior to electroless plating. Silver films high conductivity 9 × 10−8Ω.m and low surface roughness nm have been obtained. When combined two-photon lithography, this process can be utilized three-dimensional metamaterials applications. Unlike previous work coating, our coat directly photoresist that is widely used lithography does not require any resin modification.
This paper reports a switchable metamaterial working at terahertz (THz) regime, which is realized by using MEMS fabrications. The resonance induced 2.60-THz incidence switched reconfiguring the element, analyzed coupled oscillators model. switching of has potential applications, such as optical switching, tunable filtering, THz sensing, etc.
High gain AlGaAs∕GaAs heterojunction bipolar transistors grown on SiGe∕Si substrate have been fabricated. Measured peak dc current of ∼100 is obtained for a device with emitter area ∼1.6×103μm2, base concentration 1×1019cm−3. The dominant component discussed and determined. breakdown characteristic studied compared that the GaAs substrate. Our experimental results demonstrate could provide robust method monolithic integration high speed GaAs-based electronic devices silicon-based circuitry.
We studied the electroluminescence and structural characteristics of five-layer stacked self-assembled InAs/In0.1Ga0.9As quantum dot (QD) structures grown on graded Si1−xGex/Si substrate. The QD was found to take a lens shaped structure with aspect ratio 0.23±0.05. Room-temperature at 1.29 μm observed from structures. external efficiency as function injected current investigated dominant carrier recombination processes were identified analysis current-optical power relationship.
Layered nickel hydroxide thin films with mesoporous structure were prepared on ITO substrates by a facile chemical bath deposition method. The electrochemical properties of the hydroxide/oxyhydroxide investigated in both potassium and lithium perchlorate propylene carbonate electrolytes. We show that high reversible charge cycling capability material is enabled redox reaction involving hydroxyl ions, especially oxidative cycle. Li ion requires available or adsorption sites can be provided...
The origin and evolution of surface microstructures in the GaAs layer grown on Ge/Si1−xGex/Si substrate were studied. characteristic are formed pairs. By correlating results from atomic force microscopy cross-sectional transmission electron characterization, these paired identified as {1 1 1} stacking faults that propagate at 54° with respect to surface. originate single-stepped GaAs/Ge heterointerface, a consequence situ annealing Ge microstructure density becomes lower mean lateral size...
We have investigated the effects of InAs monolayer coverage on structural and optical characteristics stacked quantum dot (QD) layers graded Si1−xGex∕Si substrate. No preferential QDs nucleation was observed along cross-hatched lines Employing alternate-beam molecular beam epitaxy, with areal density as high 7×1010cm−2 achieved. Temperature dependence properties is discussed. The show room-temperature photoluminescence at 1.3μm full width half-maximum 65nm. results are significant for...
In this paper, heteroepitaxial growth of GaAs on nominal (100) Ge/Si substrate was investigated. The root-mean square surface roughness the sample where first few monolayers were nucleated by migration enhanced epitaxy (MEE) is four times smaller compared to without such a process, indicating better planarity. From (004) x-ray diffraction rocking curve measurement, full width at half maximum layer MEE 40% lower that crystal quality. Furthermore, it found experienced early relaxation. As...
Branchlike nano-electrode structures were found to improve the THz emission intensity of a photomixer by approximately one order magnitude higher than that with row nano-electrodes separated same 100 nm gap. The enhancement is attributed more efficient collection generated carriers, which in turn due intense electric field under branchlike nano-electrodes' structures. This coupled an increased number effective areas where strong tip-to-tip enhancements observed. optical-to-THz conversion...
The coronavirus disease 2019 (COVID-19) pandemic had caused a severe depletion of the worldwide supply N95 respirators. development methods to effectively decontaminate respirators while maintaining their integrity is crucial for respirator regeneration and reuse. In this study, we systematically evaluated five decontamination using vaporized hydrogen peroxide (VHP) or ultraviolet (254 nm wavelength, UVC) radiation. Through testing bioburden, filtration, fluid resistance, fit (shape)...
Terahertz wire-grid polarizer with 500 nm grating period on high resistivity silicon (100) is fabricated using nanoimprinting lithography (NIL). Preliminary results show a good polarization characteristic ranging from 0.5 to 5 THz. The method throughput and low cost.
What is believed to be the first InGaP/GaAs heterojunction bipolar transistor grown on SiGe/Si substrate reported. The collector-emitter offset voltage and knee of device are ∼150 mV <1 V, respectively. maximum gain is∼25 at collector current of∼100 mA. base ideality factor ∼1.01 ∼1.4, These results show good potential for integrating Si using compositionally graded SiGe buffer layer approach.
Self-assembled InAs quantum dots (QDs) on graded Si1−xGex/Si substrate were observed to adopt a truncated pyramidal shape when capped with GaAs. Our results suggest that atomic migration from the QD apex GaAs cap layer contributes formation of symmetrical V-shaped defects near top edges QDs. By employing an In0.1Ga0.9As cap, material and strain around QDs reduced, hence suppressing occurrence defects. Furthermore, photoluminescence thermal quenching rate is significantly slower compared cap....
This paper reports a micromachined metamaterial which is tunable between anisotropic and isotropic state. The tuning rescales the lattice constant instead of changing element structure. It realizes resonance independent change transmission tunes transmitted phase polarized THz wave. decreases from 15% to 0 for circularly wave up tens degrees linearly can be potentially applied as switch, attenuator waveplate.