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16 Jul 2007

Volume 91, Issue 3, Articles (03xxxx)

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Appl. Phys. Lett. 91, 033106 (2007); http://dx.doi.org/10.1063/1.2757609 (3 pages)

S. Ingole, P. Aella, Sean J. Hearne, and S. T. Picraux
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Surface-depletion controlled gas sensing of ZnO nanorods grown at room temperature

C. C. Li, Z. F. Du, L. M. Li, H. C. Yu, Q. Wan, and T. H. Wang

Appl. Phys. Lett. 91, 032101 (2007); http://dx.doi.org/10.1063/1.2752541 (3 pages) | Cited 56 times

Online Publication Date: 16 July 2007

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The authors report on surface-depletion controlled gas sensing ZnO nanorods. These nanorods were synthesized through a simple wet chemical route at room temperature. The diameter of nanorods is about 15 nm, which is close to two times of the Debye length of ZnO. In contrast to the previous report, the sensing is surface-depletion controlled rather than contact controlled and the sensitivity is up to 29.7 against 100 ppm ethanol. Such high sensitivity is due to an almost complete depletion of the rods in air, which is confirmed from photoluminescence spectrum and x-ray photoelectron spectroscopy. The gas sensing mechanism controlled by surface depletion provides another approach to realize high-performance gas sensors.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
78.55.Et II-VI semiconductors
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Demonstration of a quantum cellular automata cell in a GaAs/AlGaAs heterostructure

F. Perez-Martinez, I. Farrer, D. Anderson, G. A. C. Jones, D. A. Ritchie, S. J. Chorley, and C. G. Smith

Appl. Phys. Lett. 91, 032102 (2007); http://dx.doi.org/10.1063/1.2759257 (3 pages) | Cited 6 times

Online Publication Date: 17 July 2007

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The authors report on the experimental demonstration of a GaAs/AlGaAs-based quantum cellular automata cell fabricated using electron beam lithographically defined gates. These surface metallic gates form a pair of double quantum dots, as well as a pair of quantum point contacts (QPCs) that act as noninvasive voltage probes. Measurements at cryogenic temperatures show that an electron transfer in the input dots induces the relocation of a single electron in the output dots. Using the QPCs they were also able to determine the operating limits of the cell.
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85.35.Ds Quantum interference devices

Population inversion by resonant tunneling in quantum wells

Giacomo Scalari, Romain Terazzi, Marcella Giovannini, Nicolas Hoyler, and Jérôme Faist

Appl. Phys. Lett. 91, 032103 (2007); http://dx.doi.org/10.1063/1.2759271 (3 pages) | Cited 17 times

Online Publication Date: 18 July 2007

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A terahertz quantum cascade laser based on a single quantum well active region is reported. It displays laser action at 3.74 THz with low threshold current densities around 30 A/cm2. Analysis of the optical and electrical characteristics and their comparison with a transport model based on a density matrix approach clearly demonstrate the role of resonant tunneling for both injection and extraction of the electrons from the upper and lower states of the laser transition.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

SiGe double barrier resonant tunneling diodes on bulk SiGe substrates with high peak-to-valley current ratio

S. Tsujino, N. Usami, A. Weber, G. Mussler, V. Shushunova, D. Grützmacher, Y. Azuma, and K. Nakajima

Appl. Phys. Lett. 91, 032104 (2007); http://dx.doi.org/10.1063/1.2756363 (3 pages) | Cited 3 times

Online Publication Date: 19 July 2007

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The authors present high-quality p-type SiGe double barrier resonant tunneling diodes obtained from bulk SiGe substrates grown by the multicomponent zone-melting method and by the layer deposition with molecular beam epitaxy. Devices exhibit a high peak-to-valley current ratio up to 8.8 at 4.2 K and a negative differential resistance up to 340 K. The result demonstrates that bulk SiGe substrates have a clear potential impact for fabricating high-performance SiGe heterostructure devices based on quantum transport.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
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