[show abstract][hide abstract] ABSTRACT: By using complementary-metal-oxide-semiconductor processes, a silicon based bi-stable nanoelectromechanical non-volatile memory is fabricated and characterized. The main feature of this device is an 80 nm wide and 3 μm high silicon nanofin (SiNF) of a high aspect ratio (1:35). The switching mechanism is realized by electrostatic actuation between two lateral electrodes, i.e., terminals. Bi-stable hysteresis behavior is demonstrated when the SiNF maintains its contact to one of the two terminals by leveraging on van der Waals force even after voltage bias is turned off. The compelling results indicate that this design is promising for realization of high density non-volatile memory application due to its nano-scale footprint and zero on-hold power consumption.
[show abstract][hide abstract] ABSTRACT: We present a silicon nanofin (Si-NF) that can be actuated bidirectionally by electrostatic force between two contact surfaces. The switch is able to maintain its contact leveraging on van der Waals force, which holds the Si-NF to either terminal without an on-hold bias, thus exhibiting bistable hysteresis behavior. The measured pull-in voltage (VPI) and reset voltage (VRESET) are 10 and -12 V, respectively, confirming that the switch can be reset by the opposite electrode. Since the switch toggles between two stable states, it can be an ideal device for nonvolatile memory (NVM) applications.
[show abstract][hide abstract] ABSTRACT: A novel electromagnetic energy harvester (EH) with multiple vibration modes has been developed and characterized using three-dimensional (3D) excitation at different frequencies. The device consists of a movable circular-mass patterned with three sets of double-layer aluminum (Al) coils, a circular-ring system incorporating a magnet and a supporting beam. The 3D dynamic behavior and performance analysis of the device shows that the first vibration mode of 1285 Hz is an out-of-plane motion, while the second and third modes of 1470 and 1550 Hz, respectively, are in-plane at angles of 60° (240°) and 150° (330°) to the horizontal (x-) axis. For an excitation acceleration of 1 g, the maximum power density achieved are 0.444, 0.242 and 0.125 µW cm−3 at vibration modes of I, II and III, respectively. The experimental results are in good agreement with the simulation and indicate a good potential in the development of a 3D EH device.
Journal of Micromechanics and Microengineering 11/2012; 22(12):125020. · 1.79 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aluminium-coated micromirrors driven by electrothermal and electromagnetic actuations have been demonstrated for 3-D variable optical attenuation applications. Three types of attenuation schemes based on electrothermal, electromagnetic and hybrid, i.e. combination of electrothermal and electromagnetic, actuations have been developed. In addition, two different designs have been fabricated and characterized to investigate the effects of the variations made to both the actuators on the optical attenuation performances of the micromirror. Our unique design of using both ET and EM actuators simultaneously to achieve attenuation is the first demonstration of such hybrid driven CMOS compatible MEMS VOA device.
[show abstract][hide abstract] ABSTRACT: Phononic crystal (PnC) resonators of Bloch-mode resonance made by replacing periodically arranged two or three rows of air holes with one row of air holes on a two-dimensional (2-D) silicon slab with air holes of square lattice have been investigated. Piezoelectric aluminum nitride (AlN) film is employed as the interdigital transducers to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS compatible. We also fabricate a PnC structure which has a stopband of 140 MHz <; f <; 195 MHz which agrees well with the simulation results. From our experimental results, we found that the two kinds of microfabricated PnC resonators have different optimization conditions in terms of resonant frequency and Q factor, as well as insertion loss, despite their similar design approach. As compared to PnC resonators of hexagonal lattice, the proposed Bloch-mode PnC resonators of square lattice demonstrated higher resonant frequency, higher Q factor, and a smaller device area. The promising acoustic characteristics may be further optimized for applications such as microfluidics, biomedical devices, and radio-frequency communications in the gigahertz range.
Journal of Microelectromechanical Systems 01/2012; 21(4):801-810. · 2.13 Impact Factor
[show abstract][hide abstract] ABSTRACT: A 2-D silicon phononic crystal (PnC) slab of a square array of cylindrical air holes in a 10-μm-thick freestanding silicon plate with line defects is characterized as a cavity-mode PnC resonator. A piezoelectric aluminum nitride (AlN) film is employed as the interdigital transducers to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS compatible. Both the band structure of the PnC and the transmission spectrum of the proposed PnC resonator are analyzed and optimized using finite-element method. The measured quality factor ( Q factor) of the microfabricated PnC resonator is over 1000 at its resonant frequency of 152.46 MHz. The proposed PnC resonator shows promising acoustic resonance characteristics for radio-frequency communications and sensing applications.
IEEE Electron Device Letters 07/2011; · 2.79 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper shows the design, fabrication and characterization of a novel design micromechanical resonators with Bloch-mode resonance by creating defects on a two- dimensional (2-D) silicon phononic crystal (PnC) slab made by etching a square array of cylindrical air holes in a 10μm thick free-standing silicon plate. Piezoelectric aluminum nitride (AlN) film is deployed as the inter-digital transducers (IDT) to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS-compatible. We also fabricate a PnC structure which has a stopband of 140MHz < f
[show abstract][hide abstract] ABSTRACT: A membrane pressure sensor with embedded piezoresistive silicon nanowires (NW) has been demonstrated to have an ultrasensitive piezoresistive response of (ΔR/R)/ΔP of 13 Pa−1. This was achieved through the effective tuning of the transverse electric field across the NW. The fabrication of the sensor is fully based on CMOS compatible technique. P-type 〈110〉 oriented NWs with a square cross-section of 100 nm were fabricated on silicon-on-insulator (SOI) wafers, acting as the sensing elements. The NWs’ exceptional properties and minute size will enable further shrinking of footprint of pressure sensors and other NEMS sensors with increased sensitivity, opening a way to new applications like implantable medical devices.