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24 Jan 2011

Volume 98, Issue 4, Articles (04xxxx)

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Appl. Phys. Lett. 98, 043101 (2011); http://dx.doi.org/10.1063/1.3536475 (3 pages)

Zhichao Ruan and Shanhui Fan
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A field-induced ferrielectric liquid crystal phase

S. Jaradat, P. D. Brimicombe, M. A. Osipov, R. Pindak, and H. F. Gleeson

Appl. Phys. Lett. 98, 043501 (2011); http://dx.doi.org/10.1063/1.3545847 (3 pages) | Cited 2 times

Online Publication Date: 24 January 2011

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Understanding the structures and stability conditions of emerging liquid crystal (LC) phases brings us a step closer to the crucial understanding of delicate self-assembling nanoscale systems and the consequential impact on their macroscopic properties. We report experimental evidence and a theoretical model for a ferrielectric LC phase which has a three-layer repeat structure and is field-induced but exhibits a symmetry and electro-optical properties that are distinct from those of the known ferrielectric (SmC�∗FI1) phase. This discovery has implications for the ways in which LC phases are identified, and offers the potential for better control of ferroelectric LC devices.
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61.30.-v Liquid crystals
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
78.20.Jq Electro-optical effects
64.70.mj Experimental studies of liquid crystal transitions
64.70.mf Theory and modeling of specific liquid crystal transitions, including computer simulation

Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors

M. Spijkman, E. C. P. Smits, J. F. M. Cillessen, F. Biscarini, P. W. M. Blom, and D. M. de Leeuw

Appl. Phys. Lett. 98, 043502 (2011); http://dx.doi.org/10.1063/1.3546169 (3 pages) | Cited 6 times

Online Publication Date: 24 January 2011

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The sensitivity of conventional ion-sensitive field-effect transistors (ISFETs) is limited to 59 mV/pH, which is the maximum detectable change in electrochemical potential according to the Nernst equation. Here we demonstrate a transducer based on a ZnO dual-gate field-effect transistor that breaches this boundary. To enhance the response to the pH of the electrolyte, a self-assembled monolayer has been used as a top gate dielectric. The sensitivity scales linearly with the ratio between the top and bottom gate capacitances. The sensitivity of our ZnO ISFET of 22 mV/pH is enhanced by more than two orders of magnitude up to 2.25 V/pH.
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85.30.Tv Field effect devices
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
72.20.Pa Thermoelectric and thermomagnetic effects

InP-based heterojunction bipolar transistors with InGaAs/GaAs strained-layer-superlattice

R. Driad, R. Aidam, Q. Yang, M. Maier, H. Güllich, M. Schlechtweg, and O. Ambacher

Appl. Phys. Lett. 98, 043503 (2011); http://dx.doi.org/10.1063/1.3549199 (3 pages) | Cited 2 times

Online Publication Date: 26 January 2011

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In this paper, we report the design, fabrication, and characterization of an InP/InGaAs heterojunction bipolar transistor (HBT) employing a lattice-mismatched In0.53Ga0.47As/GaAs strained-layer-superlattice (SLS) base structure. The performance of the SLS-base device is also compared with that of an In0.53Ga0.47As uniform-base structure. The digitally graded-base devices exhibit a slightly lower gain at low bias voltage and a higher current gain at high currents. While the offset voltage remains comparable in the two structures, the graded-base InP/InGaAs HBTs, with built-in fields of ∼ 66 kV/cm, have typically a maximum dc current gain of 18% larger than that of transistors with uniform base.
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85.30.Pq Bipolar transistors

YBa2Cu3O7−δ quasioptical detectors for fast time-domain analysis of terahertz synchrotron radiation

P. Probst, A. Scheuring, M. Hofherr, D. Rall, S. Wünsch, K. Il’in, M. Siegel, A. Semenov, A. Pohl, H.-W. Hübers, V. Judin, A.-S. Müller, A. Hoehl, R. Müller, and G. Ulm

Appl. Phys. Lett. 98, 043504 (2011); http://dx.doi.org/10.1063/1.3546173 (3 pages) | Cited 4 times

Online Publication Date: 27 January 2011

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Thin YBa2Cu3O7−δ (YBCO) film detectors embedded into a log-spiral planar antenna were implemented for the detection and analysis of ultrashort terahertz pulses emitted by electron bunches in a synchrotron storage ring. In the direct detection mode terahertz radiation pulses from single electron bunches were resolved. A response time of 45 ps was determined as the full width at half maximum of the voltage transient at the output of the detection system. The sensitivity of the YBCO detector to pulsed terahertz radiation was 70 mV/pJ along with a sensitivity of 30 V/W for continuous radiation at 0.8 THz and a very broad dynamic range of over 30 dB. We found experimental evidences of a nonbolometric nature of the detection mechanism.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
74.78.-w Superconducting films and low-dimensional structures
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
84.40.-x Radiowave and microwave (including millimeter wave) technology

Photoresponse in photoconductor devices fabricated from HgTe-HgCdTe superlattices

S. D. Hatch, C. A. Musca, C. R. Becker, J. M. Dell, and L. Faraone

Appl. Phys. Lett. 98, 043505 (2011); http://dx.doi.org/10.1063/1.3540655 (3 pages)

Online Publication Date: 27 January 2011

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Results of photoresponse measurements performed on long-wave infrared photoconductors fabricated from HgTe-HgCdTe superlattices grown by molecular beam epitaxy are presented. Absolute spectral photoresponse measurements as a function of temperature and applied electric field have be undertaken, with the peak photoresponse of 3.3×103 V/W measured at 100 K. Sweepout effects were observed for fields greater than 20 V/cm and quantum efficiencies approaching 80% for 5 μm thick devices have been predicted from absorption measurements of grown material.
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78.56.-a Photoconduction and photovoltaic effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.40.+w Photoconduction and photovoltaic effects
78.30.Hv Other nonmetallic inorganics
73.21.Cd Superlattices

Impact of SF6 plasma treatment on performance of TaN–HfO2–InP metal-oxide-semiconductor field-effect transistor

Yanzhen Wang, Yen-Ting Chen, Han Zhao, Fei Xue, Fei Zhou, and Jack C. Lee

Appl. Phys. Lett. 98, 043506 (2011); http://dx.doi.org/10.1063/1.3549197 (3 pages) | Cited 5 times

Online Publication Date: 28 January 2011

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In this work, the experimental impact of SF6 plasma treatment on the performance of InP metal-oxide-semiconductor field-effect transistors is presented. S and F are incorporated into atomic layer deposited HfO2 via postgate SF6 plasma treatment. The decreased subthreshold swing, gate leakage (Ig), and increased effective channel mobility (μeff) indicate that better interface and bulk oxide quality have been achieved with SF6 plasma treatment due to the formation of stronger Hf–F bonds. Drive current (Id), transconductance (Gm), and effective channel mobility (μeff) are improved by 22.3%, 35%, and 35%, respectively, compared with those of control devices.
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85.30.Tv Field effect devices
52.77.-j Plasma applications
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