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15 Jul 2002

Volume 81, Issue 3, pp. 391-566

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Development and application of a laterally driven electromagnetic microactuator

Jong Soo Ko, Myung Lae Lee, Dae-Sik Lee, Chang Auck Choi, and Youn Tae Kim

Appl. Phys. Lett. 81, 547 (2002); http://dx.doi.org/10.1063/1.1494462 (3 pages) | Cited 14 times

Online Publication Date: 2 July 2002

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A laterally driven electromagnetic microactuator (LaDEM) is introduced, and a micro-optical switch is designed and fabricated as an application. LaDEM offers parallel movement of the microactuator to the silicon substrate surface (in-plane mode). Polysilicon-on-insulator wafers and a reactive ion etching process were used to fabricate high-aspect-ratio vertical microstructures, which allowed the equipping of vertical micromirrors. A fabricated single leaf spring had a width of 1.2 μm, thickness of 16 μm, and length of 920 μm. The resistance of the fabricated leaf spring for the optical switch was 5 Ω. The deflection of the leaf spring started to profoundly increase at about 400 mA, and it showed snap-through phenomenon over that current value. Owing to the snap-through phenomenon, a large deflection of 60 μm was detected at 566 mA. © 2002 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Adjustable responsivity for thermal infrared detectors

Woo-Bin Song and Joseph J. Talghader

Appl. Phys. Lett. 81, 550 (2002); http://dx.doi.org/10.1063/1.1493223 (3 pages) | Cited 5 times

Online Publication Date: 2 July 2002

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With the recent interest in adaptive IR imaging, focal plane arrays are desired that can operate linearly over an enormous dynamic range. Unfortunately, large signals can cause thermal detectors to operate at temperatures significantly above their ambient resulting in intensity dependent performance or even device damage. In this letter, the responsivity of microbolometer devices is controlled using the detector and substrate as a simple electrostatic actuator. Microbolometers are demonstrated to switch between states that are over a factor of 50 apart in responsivity. The limits of the switching are theoretically separated by four to five orders of magnitude. In addition, intermediate values of responsivity can be obtained by designing devices in which the support beams snap down at lower voltage than the detector plate. Combining this idea with the pressure dependence of the thermal contact conductance, continuous thermal conductance tuning over a factor of 3 is demonstrated. © 2002 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Pw Imaging detectors and sensors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Miniature vapor-cell atomic-frequency references

J. Kitching, S. Knappe, and L. Hollberg

Appl. Phys. Lett. 81, 553 (2002); http://dx.doi.org/10.1063/1.1494115 (3 pages) | Cited 55 times

Online Publication Date: 2 July 2002

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We propose a sub-millimeter-scale vapor-cell atomic-frequency reference based on a micromachined vapor cell, all-optical excitation, and advanced diode-laser technology. We analyze theoretically the performance of such a device as a function of cell size. Initial measurements on small-scale vapor cells support the theoretical treatment. © 2002 American Institute of Physics.
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06.20.F- Units and standards
07.10.Cm Micromechanical devices and systems
81.16.-c Methods of micro- and nanofabrication and processing
06.30.Ft Time and frequency
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.20.Wk Machining, milling
06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)

Photovoltaic hybrid device with broad tunable spectral response achieved by organic/inorganic thin-film heteropairing

R. Schroeder and B. Ullrich

Appl. Phys. Lett. 81, 556 (2002); http://dx.doi.org/10.1063/1.1494117 (3 pages) | Cited 9 times

Online Publication Date: 2 July 2002

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By means of laser deposition, spin casting and vacuum evaporation, optoelectronic hybrid devices were manufactured based upon the thin-film heteropairing of a perylene-derived molecule [di-isoquinoline perylene derivative (DQP)] and CdS. The photovoltaic characteristics of the devices are presented and discussed. We demonstrate that by exploitation of relatively high carrier mobilities in the CdS layer and the high photonic yield and deposition ease of the DQP film, efficient and technologically appealing optoelectronic devices are feasible. In addition, bias dependence of the spectral sensitivity demonstrates the versatility of the introduced device concept in light of photonic sensor applications. © 2002 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
42.70.Qs Photonic bandgap materials
72.20.Fr Low-field transport and mobility; piezoresistance

Enhanced figure of merit in thermal to electrical energy conversion using diode structures

P. L. Hagelstein and Y. Kucherov

Appl. Phys. Lett. 81, 559 (2002); http://dx.doi.org/10.1063/1.1493224 (3 pages) | Cited 7 times

Online Publication Date: 2 July 2002

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A characterization of the electrical and thermal properties of thermoelectric diode structures indicates that the figure of merit for thermal to electrical energy conversion is significantly enhanced in our devices over thermoelectric values. Enhancements are due to current injection and blockage of the ohmic return current within the devices. The resulting device takes advantage of both thermoelectric and thermionic effects, and can be considered to be a hybrid. Experiments indicate an enhancement as high as a factor of 8 in the effective figure of merit. The best results are consistent with a conversion efficiency on the order of 35% of the Carnot limit. Enhancements have been observed in InSb and in HgCdTe, and we believe that the approach applies generally to all thermoelectric semiconductors. © 2002 American Institute of Physics.
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85.80.Fi Thermoelectric devices
84.60.Rb Thermoelectric, electrogasdynamic and other direct energy conversion
84.60.Ny Thermionic conversion
85.30.Kk Junction diodes
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