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Comparison of V 2 O 5 Microbolometer Optical Performance Using NiCr and Ti Thin-Films

The optical performance characteristics of vanadium-oxide microbolometer with on-top nichrome (NiCr) thin-film metal absorber layer are evaluated using numerical simulations. A thin-film NiCr metal is sputter deposited and its optical parameters are experimentally characterized over the long-wave infrared (LWIR) range 8-

A SLOT ANTENNA-COUPLED MICROBOLOMETER FOR DETECTION AT 94 GHz

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Fabrication and design of vanadium oxide microbolometer

m. The optical performance of microbolometer with NiCr has been compared with titanium (Ti) and without any metal thin-film. The comparison indicates that the optical absorption response of NiCr device is nearly flat and has a broadband enhancement over the LWIR range. In addition, it shows large insensitivity to variations in air-gap and metal thin-film thickness, which permits for a large fabrication tolerance. In addition, the optimized air-gap devices show that the NiCr-based device has the smallest air-gap thickness, which can lead to short leg-length and mechanically robust device.

Fabrication and Characterization of a W-Band Cylindrical Dielectric Resonator Antenna-Coupled Niobium Microbolometer

In this paper, we report on the design, fabrication and characterization of a slot antenna on a quarter wavelength silicon (Si) substrate coupled to an uncooled titanium (Ti) microbolometer for detection at 94GHz. The detector was fabricated using conventional photolithographic and microfabrication techniques. The detector exhibited a voltage responsivity (Rv) of 0.779V/W, a noise equivalent power (NEP) of 10.2nW/ p Hz, and a time constant (?) of 3.88sec.

B8. CPW fed hybrid planar monopole/dielectric resonator antenna for W-band applications

Vanadium oxide (VxOy) multilayer sandwich structures previously studied by our group were found to yield a sensitive thermometer thin film material suitable for microbolometer applications. In this work, we aim to estimate the performance of a proposed air-bridge microbolometer configuration based on VxOy multilayer sandwich structure thermometer thin films. For this purpose, a microbolometer was fabricated on silicon (Si) substrate covered with a silicon nitride (Si3N4) insulating layer using VxOy thermometer thin film material. The fabricated microbolometer was patterned using electron-beam lithography and liftoff techniques and it was characterized in terms of its voltage repsonsivity (Rv), signal to noise ratio (SNR), noise equivalent power (NEP) and detectivity D*. A model was then developed by the aid of numerical optical/thermal simulations and experimentally measured parameters to estimate the performance of the microbolometer when fabricated in an air-bridge configuration. The estimated D* was fo...

Effect of the optical power and active layer thickness on the photocurrent in metal-semiconductor-metal detectors

We report on the fabrication and characterization of a novel antenna-coupled detector configuration for detection at 94 GHz, a coplanar waveguide- (CPW-) fed, slot-excited twin dielectric resonator antenna- (DRA-) coupled niobium (Nb) microbolometer. The antenna is based on two low permittivity cylindrical dielectric resonators (CDRs) excited by rectangular slots placed below the CDRs. The antenna resonant currents are fed to an Nb microbolometer by the means of a CPW feed. The ceramic DRA structure is manufactured using a novel fabrication process that enables patterning an SU-8–Alumina (Al2O3) nanopowder composite using conventional photolithography. The detector measured a voltage responsivity of 0.181 V/W at a modulation frequency of 150 Hz. The detector measured a time constant of 1.94 μs. The antenna radiation pattern of the developed detector configuration was measured and shows a good agreement with the simulation.

Estimation of band-gap offsets of heterojunctions using J-V-T characteristics

This paper presents a coplanar waveguide (CPW) fed hybrid monopole/dielectric resonator antenna for W-band imaging system applications. The proposed antenna consists of a CPW-fed printed monopole and cylindrical dielectric resonator. In this hybrid configuration, the printed monopole is used as an effective radiator as well as to excite the dielectric resonator. The obtained simulation results show that the 10 dB return-loss impedance bandwidth of the proposed antenna can reach up to 16% with the center frequency at 101.85 GHz (93.7 GHz-110 GHz). Also, the proposed antenna shows nearly omni directional radiation characteristics with maximum achieved realized gain of about 2.67 dBi at 94 GHz. The prototype fabrication procedure is outlined.

Numerical simulation of the I-V characteristics of heterojunctions including thermionic emission mechanism

The dependence of the photocurrent, in a planar metal-semiconductor-metal photodetectors (MSM), on active layer thickness and incident optical power is investigated using a two-dimensional drift-diffusion model. The model numerically solves the basic semiconductor equations using appropriate boundary conditions at the Schottky contacts. The calculated results show good agreement with experimental results reported in the literature. The current-voltage characteristics show an offset voltage of about 0.2V that depends on the incident optical power. The results also show that the photocurrent increases with active layer thickness but saturates beyond few microns.

Temperature coefficient of resistance and thermal conductivity of Vanadium oxide ‘Big Mac’ sandwich structure

This article presents investigation of use of the current-voltage-temperature characteristics (J-V-T) of an isotype GaAs-AlGaAs (n-N) structure to estimate its conduction band offset (/spl Delta/E/sub c/). The J-V-T characteristics of the heterojunction are calculated using numerical simulation with different assumed values for /spl Delta/E/sub c/. The activation energy (E/sub A/) is then extracted and compared to the assumed value of the offset /spl Delta/E/sub c/. The activation energy is found to be in a direct linear relation with the band offset with a constant that depends on the doping level and applied bias. Using this process, we show that an n-n/sup +/-N GaAs-GaAs-AlGaAs structure has many advantages in the estimation of the offset over the simple structure.

Fabrication and characterisation of high sensitivity copper-copper oxide-copper (Cu-CuO-Cu) metal-insulator-metal tunnel junctions

The effects of temperature, Al mole fraction, and doping on the I-V characteristics of abrupt GaAs/AlGaAs heterojunctions are studied by numerically solving the basic semiconductor equations. Numerical models based on drift-diffusion with and without inclusion of thermionic emission current at the heterointerface are used and their results are compared. The simulation shows that neglecting the thermionic emission will overestimate the current, especially, at lower temperatures, at higher mole fraction, or for n-N structures. Under high injection, as temperature increases, current becomes limited mainly by the series resistance. The asymmetry of doping level its found to affect significantly the transport process at lower temperatures only.