Zinc oxide (ZnO) is an attractive material for microscale and nanoscale devices. Its desirable semiconductor, piezoelectric and optical properties make it useful in applications ranging from microphones to missile warning systems to biometric sensors. This work introduces a demonstration of blending statistics and chemical etching of thin films to identify the dominant factors and interaction between factors, and develop statistically enhanced models on etch rate and selectivity of c-axis-oriented nanocrystalline ZnO thin films.
View Article and Find Full Text PDFVO-based MEMS tunable optical shutters are demonstrated. The design consists of a VO-based cantilever attached to a VO-based optical window with integrated resistive heaters for individual mechanical actuation of the cantilever structure, tuning of the optical properties of the window, or both. Optical transmittance measurements as a function of current for both heaters demonstrates that the developed devices can be used as analog optical shutters, where the intensity of a light beam can be tuned to any value within the range of VO phase transition.
View Article and Find Full Text PDFHeterogeneous integration strategies are increasingly being employed to achieve more compact and capable electronics systems for multiple applications including space, electric vehicles, and wearable and medical devices. To enable new integration strategies, the growth and transfer of thin electronic films and devices, including III-nitrides, metal oxides, and 2D materials, using 2D boron nitride (BN)-on-sapphire templates are demonstrated. The van der Waals (vdW) BN layer, in this case, acts as a preferred mechanical release layer for precise separation at the substrate-film interface and leaves a smooth surface suitable for vdW bonding.
View Article and Find Full Text PDFHere, we investigate the use of few-layer metal organic chemical vapor deposition (MOCVD) grown BN as a two-dimensional buffer layer for plasma enhanced atomic layer deposition (PE-ALD) of AlO on graphene for top gated field effect transistors (FETs). The reactive nature of PE-ALD enables deposition of thin (2 nm) dielectrics directly on graphene and other two-dimensional materials without the need for a seed or functionalization layer; however, this also leads to significant oxidation of the graphene layer as observed by Raman. In FETs, we find this oxidation destroys conductivity in the graphene channel.
View Article and Find Full Text PDFThe conductivity σ, quantum-based magnetoconductivity Δσ = σ(B) - σ(0), and Hall coefficient R (= µ/σ) of degenerate, homoepitaxial, (010) Si-doped β-GaO, have been measured over a temperature range T = 9-320 K and magnetic field range B = 0-10 kG. With ten atoms in the unit cell, the normal-mode phonon structure of β-GaO is very complex, with optical-phonon energies ranging from kT ~ 20-100 meV. For heavily doped samples, the phonon spectrum is further modified by doping disorder.
View Article and Find Full Text PDFPlasmon based field effect transistors (FETs) can be used to convert energy induced by incident optical radiation to electrical energy. Plasmonic FETs can efficiently detect incident light and amplify it by coupling to resonant plasmonic modes thus improving selectivity and signal to noise ratio. The spectral responses can be tailored both through optimization of nanostructure geometry as well as constitutive materials.
View Article and Find Full Text PDFA ceramic/graphene metamaterial (GCM) with microstructure-derived superelasticity and structural robustness is achieved by designing hierarchical honeycomb microstructures, which are composited with two brittle constituents (graphene and ceramic) assembled in multi-nanolayer cellular walls. Attributed to the designed microstructure, well-interconnected scaffolds, chemically bonded interface, and coupled strengthening effect between the graphene framework and the nanolayers of the Al O ceramic (NAC), the GCM demonstrates a sequence of multifunctional properties simultaneously that have not been reported for ceramics and ceramics-matrix-composite structures, such as flyweight density, 80% reversible compressibility, high fatigue resistance, high electrical conductivity, and excellent thermal-insulation/flame-retardant performance simultaneously. The 3D well-ordered graphene aerogel templates are strongly coupled with the NAC by the chemically bonded interface, exhibiting mutual strengthening, compatible deformability, and a linearly dependent relationship between the density and Young's modulus.
View Article and Find Full Text PDFZinc oxide field effect transistors (ZnO-FET), covalently functionalized with single stranded DNA aptamers, provide a highly selective platform for label-free small molecule sensing. The nanostructured surface morphology of ZnO provides high sensitivity and room temperature deposition allows for a wide array of substrate types. Herein we demonstrate the selective detection of riboflavin down to the pM level in aqueous solution using the negative electrical current response of the ZnO-FET by covalently attaching a riboflavin binding aptamer to the surface.
View Article and Find Full Text PDFIEEE Trans Ultrason Ferroelectr Freq Control
July 2010
Ba(0.6)Sr(0.4)TiO(3) (BST) thin-films with large dielectric tunability as high as 4:1 were obtained using a large-area pulsed laser deposition process, with low loss-tangents below 0.
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