Ternary Logic Transistors Using Multi-Stacked 2D Electron Gas Channels in Ultrathin Oxide Heterostructures.

2D electron gas field-effect transistors (2DEG-FETs), employing 2DEG formed at an interface of ultrathin (≈6 nm) AlO/ZnO heterostructure as the active channel, exhibit outstanding drive current (≈215 µA), subthreshold swing (≈132 mV dec), and field effect mobility (≈49.6 cm V s) with a high on/off current ratio of ≈10. It is demonstrated that the AlO upper layer in AlO/ZnO heterostructure acts as the source/drain resistance component during transistor operations, and the applied potential to the 2DEG channel is successfully modulated by AlO thickness variations so that the threshold voltage (V) is effectively tuned.

Black Si Photocathode with a Conformal and Amorphous MoS Catalytic Layer Grown Using Atomic Layer Deposition for Photoelectrochemical Hydrogen Evolution.

We demonstrated how the photoelectrochemical (PEC) performance was enhanced by conformal deposition of an amorphous molybdenum sulfide (a-MoS) thin film on a nanostructured surface of black Si using atomic layer deposition (ALD). The a-MoS is found to predominantly consist of an octahedral structure (S-deficient metallic phase) that exhibits high electrocatalytic activity for the hydrogen evolution reaction with a Tafel slope of 41 mV/dec in an acid electrolyte. The a-MoS has a smaller work function (4.

A emitter for passive heat release from enclosures.

Passive radiative cooling functions by reflecting the solar spectrum and emitting infrared waves in broadband or selectively. However, cooling enclosed spaces that trap heat by greenhouse effect remains a challenge. We present a emitter (ET) consisting of an Ag-polydimethylsiloxane layer on micropatterned quartz substrate.

Highly Uniform Resistive Switching Performances Using Two-Dimensional Electron Gas at a Thin-Film Heterostructure for Conductive Bridge Random Access Memory.

This research demonstrates, for the first time, the development of highly uniform resistive switching devices with self-compliance current for conductive bridge random access memory using two-dimensional electron gas (2DEG) at the interface of an AlO/TiO thin-film heterostructure via atomic layer deposition (ALD). The cell is composed of Cu/Ti/AlO/TiO, where Cu/Ti and AlO overlayers are used as the active/buffer metals and solid electrolyte, respectively, and the 2DEG at the interface of AlO/TiO heterostructure, grown by the ALD process, is adopted as a bottom electrode. The Cu/Ti/AlO/TiO device shows reliable resistive switching characteristics with excellent uniformity under a repetitive voltage sweep (direct current sweep).

Silicon Photonic MEMS Phase-Shifter.

We present a design for an analog phase shifter based on Silicon Photonic MEMS technology. The operation principle is based on a two-step parallel plate electrostatic actuation mechanism to bring a vertically movable suspended tapered waveguide in a first step into proximity of the bus waveguide and to tune the phase of the propagating coupled mode in a second step by actuation of the suspended waveguide to tune the vertical gap. In the coupled state, the effective index of the optical supermode and the total accumulated phase delay can be varied by changing the vertical separation between the adiabatically tapered suspended and the fixed bus waveguides.

Multicast silicon photonic MEMS switches with gap-adjustable directional couplers.

We report on 4x20 silicon photonic MEMS switch that is capable of multicasting. The switch is built on passive optical crossbar network with gap-adjustable directional couplers. The switch has high on-off extinction ratio (59 dB), low insertion loss (< 4.

Field-Effect Device Using Quasi-Two-Dimensional Electron Gas in Mass-Producible Atomic-Layer-Deposited AlO/TiO Ultrathin (<10 nm) Film Heterostructures.

We report the field-effect transistors using quasi-two-dimensional electron gas generated at an ultrathin (∼10 nm) AlO/TiO heterostructure interface grown via atomic layer deposition (ALD) on a SiO/Si substrate without using a single crystal substrate. The 2DEG at the AlO/TiO interface originates from oxygen vacancies generated at the surface of the TiO bottom layer during ALD of the AlO overlayer. High-density electrons (∼10 cm) are confined within a ∼2.

Germanium wrap-around photodetectors on Silicon photonics.

We present a novel waveguide coupling scheme where a germanium diode grown via rapid melt growth is wrapped around a silicon waveguide. A 4 fF PIN photodiode is demonstrated with 0.95 A/W responsivity at 1550 nm, 6 nA dark current, and nearly 9 GHz bandwidth.

Mass-producible and efficient optical antennas with CMOS-fabricated nanometer-scale gap.

Optical antennas have been widely used for sensitive photodetection, efficient light emission, high resolution imaging, and biochemical sensing because of their ability to capture and focus light energy beyond the diffraction limit. However, widespread application of optical antennas has been limited due to lack of appropriate methods for uniform and large area fabrication of antennas as well as difficulty in achieving an efficient design with small mode volume (gap spacing < 10nm). Here, we present a novel optical antenna design, arch-dipole antenna, with optimal radiation efficiency and small mode volume, 5 nm gap spacing, fabricated by CMOS-compatible deep-UV spacer lithography.

Fast, high-throughput creation of size-tunable micro/nanoparticle clusters via evaporative self-assembly in picoliter-scale droplets of particle suspension.

We report a fast, high-throughput method to create size-tunable micro/nanoparticle clusters via evaporative assembly in picoliter-scale droplets of particle suspension. Mediated by gravity force and surface tension force of a contacting surface, picoliter-scale droplets of the suspension are generated from a nanofabricated printing head. Rapid evaporative self-assembly of the particles on a hydrophobic surface leads to fast clustering of micro/nanoparticles and forms particle clusters of tunable sizes and controlled spacing.

Development of standard digital images for pneumoconiosis.

We developed the standard digital images (SDIs) to be used in the classification and recognition of pneumoconiosis. From July 3, 2006 through August 31, 2007, 531 retired male workers exposed to inorganic dust were examined by digital (DR) and analog radiography (AR) on the same day, after being approved by our institutional review board and obtaining informed consent from all participants. All images were twice classified according to the International Labour Office (ILO) 2000 guidelines with reference to ILO standard analog radiographs (SARs) by four chest radiologists.

Microenvironmental geometry guides platelet adhesion and spreading: a quantitative analysis at the single cell level.

To activate clot formation and maintain hemostasis, platelets adhere and spread onto sites of vascular injury. Although this process is well-characterized biochemically, how the physical and spatial cues in the microenvironment affect platelet adhesion and spreading remain unclear. In this study, we applied deep UV photolithography and protein micro/nanostamping to quantitatively investigate and characterize the spatial guidance of platelet spreading at the single cell level and with nanoscale resolution.

Roll-to-roll anodization and etching of aluminum foils for high-throughput surface nanotexturing.

A high-throughput process for nanotexturing of hard and soft surfaces based on the roll-to-roll anodization and etching of low-cost aluminum foils is presented. The process enables the precise control of surface topography, feature size, and shape over large areas thereby presenting a highly versatile platform for fabricating substrates with user-defined, functional performance. Specifically, the optical and surface wetting properties of the foil substrates were systematically characterized and tuned through the modulation of the surface texture.

Radiation engineering of optical antennas for maximum field enhancement.

Optical antennas have generated much interest in recent years due to their ability to focus optical energy beyond the diffraction limit, benefiting a broad range of applications such as sensitive photodetection, magnetic storage, and surface-enhanced Raman spectroscopy. To achieve the maximum field enhancement for an optical antenna, parameters such as the antenna dimensions, loading conditions, and coupling efficiency have been previously studied. Here, we present a framework, based on coupled-mode theory, to achieve maximum field enhancement in optical antennas through optimization of optical antennas' radiation characteristics.

Enhanced Raman scattering from nanoparticle-decorated nanocone substrates: a practical approach to harness in-plane excitation.

We investigate surface-enhanced Raman scattering (SERS) from gold-coated silicon-germanium nanocone substrates that are decorated with 30-nm spherical gold nanoparticles (AuNPs). Finite-element simulations suggest that individual nanocones generate stronger electromagnetic enhancement with axial polarization (i.e.