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20 Feb 2012

Volume 100, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 082401 (2012); http://dx.doi.org/10.1063/1.3684972 (4 pages)

Elizabeth Rapoport and Geoffrey S. D. Beach
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Low leakage current in metal-insulator-metal capacitors of structural Al2O3/TiO2/Al2O3 dielectrics

Jong-Chang Woo, Yoon-Soo Chun, Young-Hee Joo, and Chang-Il Kim

Appl. Phys. Lett. 100, 081101 (2012); http://dx.doi.org/10.1063/1.3687702 (3 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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Metal–insulator–metal (MIM) capacitors with Al2O3/TiO2/Al2O3 (ATA) dielectrics were fabricated and investigated. At 0 V and frequencies of 100 kHz and 1 MHz, the MIM capacitors with ATA (3/20/3 nm) and ATA (6/20/6 nm) thin films had low leakage current densities of approximately 5.2 × 10−13 and 1.5 × 10−13 A/cm2, respectively, and high capacitance densities of ∼19.48 and ∼20.13 fF/μm2, respectively. The frequency dispersion effect for these MIM capacitors was very small. The electrical transport mechanism, which is the device conduction mechanism, was determined for the varying structures of MIM capacitors.
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73.40.Rw Metal-insulator-metal structures

Stabilized hot electron bolometer heterodyne receiver at 2.5 THz

D. J. Hayton, J. R. Gao, J. W. Kooi, Y. Ren, W. Zhang, and G. de Lange

Appl. Phys. Lett. 100, 081102 (2012); http://dx.doi.org/10.1063/1.3688032 (4 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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We report on a method to stabilize a hot electron bolometer (HEB) mixer at 2.5 THz. The technique utilizes feedback control of the local oscillator (LO) laser power by means of a swing-arm actuator placed in the optical beam path. We demonstrate that this technique yields a factor of 50 improvement in the spectroscopic Allan variance time which is shown to be over 30 s in a 12 MHz noise fluctuation bandwidth. Furthermore, broadband signal direct detection effects may be minimized by this technique. The technique is versatile and can be applied to practically any local oscillator at any frequency.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

85 °C error-free operation at 38 Gb/s of oxide-confined 980-nm vertical-cavity surface-emitting lasers

P. Moser, P. Wolf, A. Mutig, G. Larisch, W. Unrau, W. Hofmann, and D. Bimberg

Appl. Phys. Lett. 100, 081103 (2012); http://dx.doi.org/10.1063/1.3688040 (3 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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Extremely temperature stable oxide-confined high-speed 980-nm vertical-cavity surface-emitting lasers (VCSELs) for optical interconnects are presented. Error-free performance at 38 Gb/s and 40 Gb/s is demonstrated at temperatures as high as 85 °C and 75 °C, respectively. No adjustment of driving conditions was found to be necessary from room temperature up to 85 °C. In addition, energy-efficient 35 Gb/s operation at a very low pump current of only 4 mA is demonstrated with a low dissipated heat-to-bit rate ratio of 233 mW/Tbps. These are by far the highest bit rates reported for VCSELs at such temperatures.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Highly modified spontaneous emissions in YVO4:Eu3+ inverse opal and refractive index sensing application

Yongsheng Zhu, Wen Xu, Hanzhuang Zhang, Wei Wang, Liu Tong, Sai Xu, Zhipeng Sun, and Hongwei Song

Appl. Phys. Lett. 100, 081104 (2012); http://dx.doi.org/10.1063/1.3688167 (4 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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Here, we present strong modification of photonic crystals on the spontaneous emissions of Eu3+ ions in YVO4:Eu3+ inverse opal. It is interesting that due to the effect of local field, the 5D0-7FJ radiative lifetimes of Eu3+ ions in the PCs are all prolonged ∼2.5 times in contrast to the grinded reference (REF) in air, consistent with the empty cavity model. The photonic stop band and the radiative lifetime are both highly sensitive to the refractive index of the infiltrated solutions, in accordance with the real cavity model.
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42.70.Qs Photonic bandgap materials
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Improved dielectric functions in metallic films obtained via template stripping

Jong Hyuk Park, Prashant Nagpal, Sang-Hyun Oh, and David J. Norris

Appl. Phys. Lett. 100, 081105 (2012); http://dx.doi.org/10.1063/1.3687910 (4 pages) | Cited 3 times

Online Publication Date: 22 February 2012

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We compare the dielectric functions of silver interfaces obtained via thermal evaporation with those obtained with template stripping. Ellipsometry measurements show that the smoother template-stripped surfaces exhibit effective dielectric functions with a more negative real component and a smaller imaginary component, implying higher conductivity and less energy loss, respectively. These results agree with the relation between dielectric function and surface roughness derived from combining the effective-medium model and the Drude-Lorentz model. The improvement in the effective dielectric properties shows that metallic films prepared via template stripping can be favorable for applications in electronics, nanophotonics, and plasmonics.
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77.22.Ch Permittivity (dielectric function)
78.66.Bz Metals and metallic alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Temperature dependent efficiency droop in GaInN light-emitting diodes with different current densities

David S. Meyaard, Qifeng Shan, Jaehee Cho, E. Fred Schubert, Sang-Heon Han, Min-Ho Kim, Cheolsoo Sone, Seung Jae Oh, and Jong Kyu Kim

Appl. Phys. Lett. 100, 081106 (2012); http://dx.doi.org/10.1063/1.3688041 (3 pages) | Cited 2 times

Online Publication Date: 22 February 2012

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The effect of chip area on the temperature-dependent light-output power (LOP) in GaInN-based light-emitting diodes (LEDs) is investigated. The larger the chip size, the faster the reduction in LOP with increasing temperature becomes, indicating that increasing the size of LED chips, a technology trend for reducing the efficiency droop at high currents, is detrimental for high temperature-tolerant LEDs. In addition, it is found that regardless of chip size, the temperature-dependent LOP is identical for the LEDs operating at the same current density.
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85.60.Jb Light-emitting devices

Multimodal strong coupling of photonic crystal cavities of dissimilar size

Mehmet A. Dündar, Joost A. M. Voorbraak, Richard Nötzel, Andrea Fiore, and Rob W. van der Heijden

Appl. Phys. Lett. 100, 081107 (2012); http://dx.doi.org/10.1063/1.3688301 (4 pages) | Cited 2 times

Online Publication Date: 22 February 2012

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A photonic crystal three missing holes nanocavity, having only a few modes, is coupled to a 60 missing holes long multimode cavity, both fabricated in the same InGaAsP membrane. The coupling was studied in detail by the photothermal tuning of the small cavity over about three free spectral ranges of the large cavity. Strong coupling effects, involving at least three large cavity modes simultaneously, were observed from level anticrossing data. The observations are excellently reproduced by a model of coupled Fabry Perot resonators.
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42.70.Qs Photonic bandgap materials
42.86.+b Optical workshop techniques

Whispering gallery mode selection in optical bottle microresonators

Ming Ding, Ganapathy Senthil Murugan, Gilberto Brambilla, and Michalis N. Zervas

Appl. Phys. Lett. 100, 081108 (2012); http://dx.doi.org/10.1063/1.3688601 (3 pages) | Cited 2 times

Online Publication Date: 23 February 2012

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We demonstrated a method to excite selected whispering gallery modes in optical bottle microresonators (BMR) by inscribing microgroove scars on their surface by focused ion beam milling. Substantial spectral clean-up is obtained in appropriately scarred BMRs, providing the potential for high performance sensors and other optical devices.
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42.79.-e Optical elements, devices, and systems
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Nonvanishing turn-on delay in quantum dot lasers

G. S. Sokolovskii, V. V. Dudelev, E. D. Kolykhalova, A. G. Deryagin, M. V. Maximov, A. M. Nadtochiy, V. I. Kuchinskii, S. S. Mikhrin, D. A. Livshits, E. A. Viktorov, and T. Erneux

Appl. Phys. Lett. 100, 081109 (2012); http://dx.doi.org/10.1063/1.3688604 (3 pages)

Online Publication Date: 23 February 2012

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A turn-on of a quantum dot semiconductor laser is analyzed in detail both theoretically and experimentally. We show that quantum dot lasers have a nonlinear damping rate which strongly affects laser turn-on dynamics due to the non-instantaneous capture of carriers to a dot. It results in nonvanishing turn-on delay even at very high pumping in good agreement with experiment.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.65.-k Nonlinear optics

AlGaN-based ultraviolet light-emitting diodes using fluorine-doped indium tin oxide electrodes

Dong Ju Chae, Dong Yoon Kim, Tae Geun Kim, Yun Mo Sung, and Moon Doeck Kim

Appl. Phys. Lett. 100, 081110 (2012); http://dx.doi.org/10.1063/1.3689765 (3 pages) | Cited 2 times

Online Publication Date: 23 February 2012

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In this paper, improved electrical and optical properties of aluminum gallium nitride (AlGaN)-based ultraviolet light-emitting diodes using fluorine-doped indium tin oxide (F-ITO) electrodes are reported. F-doping was found to increase the work function as well as the energy bandgap of the ITO and, thereby, reduce the Shottky barrier height in contact with p-(Al)GaN. As a result, the optical transmittance increased from 79.7% to 86.9% at 380 nm, while the specific contact resistance decreased from 1.04 × 10−3 Ω·cm2 to 9.12 × 10−4 Ω·cm2 after F-doping, which led to an increase in the output power from 2.41 mW to 5.99 mW.
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85.60.Jb Light-emitting devices
85.30.Kk Junction diodes

Tuning the nonlinear response of coupled split-ring resonators

Kirsty E. Hannam, David A. Powell, Ilya V. Shadrivov, and Yuri S. Kivshar

Appl. Phys. Lett. 100, 081111 (2012); http://dx.doi.org/10.1063/1.3689775 (3 pages)

Online Publication Date: 23 February 2012

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We introduce the concept of controlling the nonlinear response of the metamaterial by altering its internal structure. We experimentally demonstrate tuning of the nonlinear response of two coupled split-ring resonators by changing their mutual position. This effect is achieved through modification of the structure of the coupled resonant modes and their interaction with the incident field. By offsetting the resonators we control the maximum currents through the nonlinear elements, which affect the nonlinear response of the system.
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84.40.Az Waveguides, transmission lines, striplines

Controlling extraordinary transmission characteristics of metal hole arrays with spoof surface plasmons

Fumiaki Miyamaru, Mototsugu Kamijyo, Naoki Hanaoka, and Mitsuo W. Takeda

Appl. Phys. Lett. 100, 081112 (2012); http://dx.doi.org/10.1063/1.3689784 (4 pages) | Cited 2 times

Online Publication Date: 23 February 2012

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We experimentally controlled the spectral characteristics of the extraordinary transmissions observed in metal hole arrays by analogy with spoof surface plasmon-polaritons (spoof SPPs). We constructed doubly periodic metal hole arrays. The larger and smaller periodic holes are for inducing extraordinary transmissions and modifying the spoof SPPs’ characteristics, respectively. Introducing the smaller holes that surround the larger hole arrays can modify the dispersion curve of the surface waves excited on a structured metal surface analogous to the spoof SPP model, and consequently, the extraordinary transmission peak will show a redshift.
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78.66.Bz Metals and metallic alloys
78.68.+m Optical properties of surfaces
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Fm Birefringence
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Impact of structural transitions on electron transport at LaAlO3/SrTiO3 heterointerfaces

Frank Schoofs, Mehmet Egilmez, Thomas Fix, Judith L. MacManus-Driscoll, and Mark G. Blamire

Appl. Phys. Lett. 100, 081601 (2012); http://dx.doi.org/10.1063/1.3687706 (4 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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We have studied conductive LaAlO3/SrTiO3 heterostructures deposited at different oxygen pressures. Photoluminescence spectra confirm the presence of a significant amount of oxygen vacancies in samples deposited at low oxygen pressures. Power law fitting of resistance versus temperature measurements reveals fundamental characteristics of the conduction mechanism at the interface. A distinct non-Fermi-liquid behavior is observed for samples grown in higher oxygen pressure, which give two-dimensionally confined conducting interfaces, whereas characteristic electron-electron scattering is observed for samples grown in lower oxygen pressures, as seen in bulk doped SrTiO3 (i.e., oxygen deficient SrTiO3). Transitions between different conduction modes occur throughout the studied temperature range (10–270 K) as a result of structural transformations in the near-surface region of the SrTiO3.
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
61.72.jd Vacancies
64.70.K- Solid-solid transitions
78.55.-m Photoluminescence, properties and materials

Chiral recognition of zinc phthalocyanine on Cu(100) surface

Feng Chen, Xiu Chen, Lacheng Liu, Xin Song, Shuyi Liu, Juan Liu, Hongping Ouyang, Yingxiang Cai, Xiaoqing Liu, Haibing Pan, Junfa Zhu, and Li Wang

Appl. Phys. Lett. 100, 081602 (2012); http://dx.doi.org/10.1063/1.3685713 (4 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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The windmill-like chiral nature of individual ZnPc molecules adsorbed on Cu(100) surface at room temperature has been revealed by scanning tunneling microscopy (STM) and the origin of such chirality is attributed to asymmetrical charge transfer between the molecules and the copper surface. Such chiral enantiomers do recognize each other in molecular level and spontaneously form second-level chiral supramolecular structures with the same chirality during thermally driven movements. The interactions between the ZnPc molecules during such chiral recognition process have been discussed based on the analysis of the sub-molecule-resolution STM images.
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68.43.Mn Adsorption kinetics
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions

Magnetic and electronic properties of the interface between half metallic Fe3O4 and semiconducting ZnO

S. Brück, M. Paul, H. Tian, A. Müller, D. Kufer, C. Praetorius, K. Fauth, P. Audehm, E. Goering, J. Verbeeck, G. Van Tendeloo, M. Sing, and R. Claessen

Appl. Phys. Lett. 100, 081603 (2012); http://dx.doi.org/10.1063/1.3687731 (4 pages) | Cited 3 times

Online Publication Date: 22 February 2012

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We have investigated the magnetic depth profile of an epitaxial Fe3O4 thin film grown directly on a semiconducting ZnO substrate by soft x-ray resonant magnetic reflectometry (XRMR) and electron energy loss spectroscopy (EELS). Consistent chemical profiles at the interface between ZnO and Fe3O4 are found from both methods. Valence selective EELS and XRMR reveal independently that the first monolayer of Fe at the interface between ZnO and Fe3O4 contains only Fe3+ ions. Besides this narrow 2.5 Å interface layer, Fe3O4 shows magnetic bulk properties throughout the whole film making highly efficient spin injection in this system feasible.
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81.05.Bx Metals, semimetals, and alloys
81.05.Dz II-VI semiconductors
79.20.Uv Electron energy loss spectroscopy
75.76.+j Spin transport effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Ak Magnetic properties of monolayers and thin films

Droplet jumping by electrowetting and its application to the three-dimensional digital microfluidics

Seung Jun Lee, Sanghyun Lee, and Kwan Hyoung Kang

Appl. Phys. Lett. 100, 081604 (2012); http://dx.doi.org/10.1063/1.3688487 (3 pages) | Cited 1 time

Online Publication Date: 23 February 2012

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We introduce droplet jumping by electrowetting (DJE), which stretches droplets to store energy for jumping by electrowetting. The capillarity-driven droplet jumping is effective to overcome the energy barrier, where the threshold for jumping is less than 100 V. We studied the detailed jumping mechanisms with regard to the jumping height and the energy conversion and demonstrated the transport of sessile droplets to upper surfaces under diverse electrode configurations. While the droplet jumping on the superhydrophobic surface is the primary focus of our research, DJE is also found to be possible on conventional Teflon surfaces, envisioning the three-dimensional droplet-based digital microfluidics.
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68.08.Bc Wetting
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Near-resonant two-photon absorption in luminescent CdTe quantum dots

Jayakrishna Khatei, C. S. Suchand Sandeep, Reji Philip, and K. S. R. Koteswara Rao

Appl. Phys. Lett. 100, 081901 (2012); http://dx.doi.org/10.1063/1.3687695 (3 pages)

Online Publication Date: 21 February 2012

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We report the nonlinear optical absorption studies in two differently sized water-soluble cadmium telluride quantum dot (QD) samples, exhibiting first excitonic absorption peaks at 493 nm and 551 nm, respectively. An optical limiting behavior is observed for near-resonant excitation at 532 nm using nanosecond laser pulses, originating from the effective two-photon absorption (TPA) mechanism. The effective TPA coefficient (βeff) is measured to be in the range of 10−12 m/W. This is one order of magnitude higher than the TPA coefficient (β) reported for off-resonant excitation. At this excitation wavelength, the smaller QD shows a relatively weaker photoluminescence and stronger nonlinear absorption.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors

Stimulated emission in AlGaN/AlGaN quantum wells with different Al content

J. Mickevičius, J. Jurkevičius, K. Kazlauskas, A. Žukauskas, G. Tamulaitis, M. S. Shur, M. Shatalov, J. Yang, and R. Gaska

Appl. Phys. Lett. 100, 081902 (2012); http://dx.doi.org/10.1063/1.3688051 (4 pages) | Cited 4 times

Online Publication Date: 21 February 2012

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Stimulated emission (SE) is studied in AlGaN/AlGaN multiple quantum wells (MQWs) with different Al content grown on sapphire substrate. The spectra of spontaneous and stimulated emission and their transformations with increasing temperature as well as stimulated emission thresholds were measured in the temperature range from 8 to 300 K. Phonon-assisted band broadening in low-Al-content MQWs and double-scaled potential profile in high-Al-content MQWs were observed in the samples and linked with carrier localization conditions. The temperature dependence of the stimulated emission threshold was similar in the samples where the stimulated transitions occur between extended states and in the samples where the transitions occur in localized states. The stimulated emission threshold depends predominantly on the density of nonradiative recombination centers.
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78.45.+h Stimulated emission
78.67.De Quantum wells

Micro-fabricated channel with ultra-thin yet ultra-strong windows enables electron microscopy under 4-bar pressure

Tuncay Alan, Tadahiro Yokosawa, João Gaspar, Gregory Pandraud, Oliver Paul, Fredrik Creemer, Pasqualina M. Sarro, and Henny W. Zandbergen

Appl. Phys. Lett. 100, 081903 (2012); http://dx.doi.org/10.1063/1.3688490 (4 pages) | Cited 1 time

Online Publication Date: 23 February 2012

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Transmission electron microscopy (TEM) of (de-)hydrogenation reactions is crucial to characterize efficiency of hydrogen storage materials. The nanoreactor, a micromachined channel with 15-nm-thick windows, effectively confines the gas flow to an electron-transparent chamber during TEM of reactions. Realistic experiments require very high pressures to be sustained by the device. Nanomechanical bulge tests and simulations show that due to a very strong size effect, ultra-thin device components can reliably withstand tensile stresses as high as 19.5 GPa enabling high pressure operation. We use the device to characterize Pd particles under a 4-bar H2 pressure within the ultra-high-vacuum of the TEM.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

Non-resonant femtosecond laser control of the molecular dynamics in liquid chloroform

V. G. Nikiforov, A. G. Shmelev, G. M. Safiullin, and V. S. Lobkov

Appl. Phys. Lett. 100, 081904 (2012); http://dx.doi.org/10.1063/1.3689776 (4 pages) | Cited 1 time

Online Publication Date: 23 February 2012

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The optical control of the molecular motions in chloroform CHCl3 at room temperature through the non-resonant excitation was enhanced by means of the double-pulse pump-probe technique. When the separation time of the pump pulses and their relative intensity were varied, the amplification or the cancellation of the coherent vibrations of the molecules was achieved. The molecular responses were detected by the time-resolved optically heterodyne-detected optical-Kerr-effect technique.
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78.47.D- Time resolved spectroscopy (>1 psec)
61.20.Ja Computer simulation of liquid structure
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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Impact of the misfit dislocations on two-dimensional electron gas mobility in semi-polar AlGaN/GaN heterostructures

Guipeng Liu, Ju Wu, Guijuan Zhao, Shuman Liu, Wei Mao, Yue Hao, Changbo Liu, Shaoyan Yang, Xianglin Liu, Qinsheng Zhu, and Zhanguo Wang

Appl. Phys. Lett. 100, 082101 (2012); http://dx.doi.org/10.1063/1.3688047 (4 pages) | Cited 3 times

Online Publication Date: 21 February 2012

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The mobility of two-dimensional electron gas as influenced by the charged misfit dislocations located at the interface of the semi-polar AlGaN/GaN heterostructure is quantitatively analyzed. The results indicate that the strength of the scattering due to the misfit dislocations in the semi-polar AlGaN/GaN heterointerface is comparable to the well-known scattering associated with the threading dislocations in the well-known polar c-plane AlGaN/GaN heterostructures.
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81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Plasmonic detector/spectrometer of subterahertz radiation based on two-dimensional electron system with embedded defect

V. M. Muravev and I. V. Kukushkin

Appl. Phys. Lett. 100, 082102 (2012); http://dx.doi.org/10.1063/1.3688049 (3 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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We demonstrate that the introduction of a defect in the form of an electron density step into a two-dimensional electron system (2DES) locally rectifies the alternating potential of plasma waves. The rectification mechanism is active at temperatures up to room temperature. We observe photovoltage oscillations in a back-gated 2DES with a density defect, when tuning the density under incident subterahertz radiation. The oscillations originate from the interference of 2D plasma waves excited by subterahertz radiation. The period of oscillations depends on the radiation wavelength. These phenomena can be exploited further to produce detectors/spectrometers for millimeter waves.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Assessment of deep level defects in m-plane GaN grown by metalorganic chemical vapor deposition

T. A. Henry, A. Armstrong, K. M. Kelchner, S. Nakamura, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 100, 082103 (2012); http://dx.doi.org/10.1063/1.3687700 (4 pages) | Cited 1 time

Online Publication Date: 22 February 2012

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We report on deep level defect incorporation in n-type m-plane (10math0) GaN grown by metalorganic chemical vapor deposition (MOCVD) on bulk m-plane GaN substrates. Deep levels were observed at 2.85 eV and 3.31 eV relative to the conduction band minimum. While the energetic distribution of defect states for m-plane GaN was similar to the previous reports of n-type c-plane GaN grown by MOCVD, the deep level densities of the m-plane GaN were significantly lower. The comparatively low defect density in homoepitaxially grown m-plane GaN is attributed to reduced point defect incorporation. In addition to the absence of polarization fields, the low deep level density achieved by homoepitaxial growth on high quality bulk GaN substrates makes m-plane GaN highly attractive for opto-electronic devices.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors

Optical observation of single-carrier charging in type-II quantum ring ensembles

R. J. Young, E. P. Smakman, A. M. Sanchez, P. Hodgson, P. M. Koenraad, and M. Hayne

Appl. Phys. Lett. 100, 082104 (2012); http://dx.doi.org/10.1063/1.3688037 (4 pages) | Cited 4 times

Online Publication Date: 22 February 2012

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A high-purity GaSb/GaAs quantum ring system is introduced that provides both strong hole-confinement in the GaSb ring and electron confinement in its GaAs core. The latter is responsible for a reduced inhomogeous linewidth measured in photoluminescence, in comparison to the previous measurements made on nanostructures with differing morphology in this material system. This allows the resolution of multiple peaks in the photoluminescence due to discrete charging with holes, revealing the mechanism responsible for the excitation-power-induced blueshift.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Cr III-V semiconductors

Characterization of silicon dioxide films on 4H-SiC Si (0001) face by cathodoluminescence spectroscopy and x-ray photoelectron spectroscopy

M. Yoshikawa, S. Ogawa, K. Inoue, H. Seki, Y. Tanahashi, H. Sako, Y. Nanen, M. Kato, and T. Kimoto

Appl. Phys. Lett. 100, 082105 (2012); http://dx.doi.org/10.1063/1.3688173 (4 pages) | Cited 1 time

Online Publication Date: 22 February 2012

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We measured cathodoluminescence (CL) spectra of SiO2 films grown on 4H-SiC wafers and found that for an acceleration voltage of 5 kV, CL peaks at 460 and 490 nm, assigned to oxygen vacancy centers (OVCs), become weak by post-oxidation annealing in N2O ambient at 1300 °C whereas the CL peak around 580 nm, related to Si-N bonding structures, becomes intense. Furthermore, the peak assigned to N-Si3 configurations in x-ray photoelectron spectroscopy (XPS) spectra was observed in the SiO2/SiC interface in only samples annealed in N2O ambient. These results suggest that the interface trap densities decrease and the channel mobility in n-type MOS capacitors increases by the termination of dangling bonds by the N atom in the SiO2/SiC interface. CL spectroscopy and XPS provide us with extensive information on OVCs and dangling bonds in the SiO2/SiC interface on the 4H-SiC substrate.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Nk Insulators
81.40.Gh Other heat and thermomechanical treatments
61.72.jd Vacancies
79.60.Bm Clean metal, semiconductor, and insulator surfaces
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