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19 Nov 2012

Volume 101, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 213101 (2012); http://dx.doi.org/10.1063/1.4767230 (3 pages)

Yu Zhang, Yang Gao, Lianqing Liu, Ning Xi, Yuechao Wang, Laipeng Ma, Zaili Dong, and Uchechukwu C. Wejinya
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1.55 μm direct bandgap electroluminescence from strained n-Ge quantum wells grown on Si substrates

K. Gallacher, P. Velha, D. J. Paul, S. Cecchi, J. Frigerio, D. Chrastina, and G. Isella

Appl. Phys. Lett. 101, 211101 (2012); http://dx.doi.org/10.1063/1.4767138 (4 pages) | Cited 2 times

Online Publication Date: 19 November 2012

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Electroluminescence from strained n-Ge quantum well light emitting diodes grown on a silicon substrate are demonstrated at room temperature. Electroluminescence characterisation demonstrates two peaks around 1.55 μm and 1.8 μm, which correspond to recombination between the direct and indirect transitions, respectively. The emission wavelength can be tuned by around 4% through changing the current density through the device. The devices have potential applications in the fields of optical interconnects, gas sensing, and healthcare.
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85.60.Jb Light-emitting devices

Demonstration of an excited-state Faraday anomalous dispersion optical filter at 1529 nm by use of an electrodeless discharge rubidium vapor lamp

Qinqing Sun, Yelong Hong, Wei Zhuang, Zhiwen Liu, and Jingbiao Chen

Appl. Phys. Lett. 101, 211102 (2012); http://dx.doi.org/10.1063/1.4767140 (4 pages)

Online Publication Date: 19 November 2012

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An excited-state Faraday anomalous dispersion optical filter (ESFADOF) operating on the rubidium 5P3/2-4D5/2 transition (1529.4 nm in vacuum) is demonstrated, which utilizes an electrodeless discharge lamp rather than a laser-pumped Rb vapor cell as in a traditional ESFADOF system. When the lamp operates in the red mode with 3.5 W radio-frequency driving power, a twin-peak line-shaped transmission spectrum is obtained, which has a maximum transmittance of 21.9% (without taking into account the system loss and fluorescence background). ESFADOF by exploiting the 5P3/2-4D3/2 transition (1529.3 nm in vacuum) is also explored. A single-peak transmission spectrum with a maximum transmittance of about 3% is achieved. The electrodeless discharge lamp based ESFADOF holds promise for realizing a compact, low-cost, and good long-term frequency-stabilized laser system for optical communication applications.
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42.79.Ci Filters, zone plates, and polarizers

Heterojunction photodiode fabricated from hydrogen treated ZnO nanowires grown on p-silicon substrate

Dali Shao, Mingpeng Yu, Jie Lian, and Shayla Sawyer

Appl. Phys. Lett. 101, 211103 (2012); http://dx.doi.org/10.1063/1.4767679 (4 pages) | Cited 1 time

Online Publication Date: 21 November 2012

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A heterojunction photodiode was fabricated from ZnO nanowires (NWs) grown on a p-type Si (100) substrate using a hydrothermal method. Post growth hydrogen treatment was used to improve the conductivity of the ZnO NWs. The heterojunction photodiode showed diode characteristics with low reverse saturation current (5.58 × 10−7 A), relatively fast transient response, and high responsivity (22 A/W at 363 nm). Experiments show that the photoresponsivity of the photodiode is dependent on the polarity of the voltages. The photoresponsivity of the device was discussed in terms of the band diagrams of the heterojunction and the carrier diffusion process.
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85.60.Dw Photodiodes; phototransistors; photoresistors

Achromatic polarization splitting effect of metallic gratings with sub-50 nm wide slits

Guoguo Kang, Yue Fang, Ismo Vartiainen, Qiaofeng Tan, and Yongtian Wang

Appl. Phys. Lett. 101, 211104 (2012); http://dx.doi.org/10.1063/1.4767909 (4 pages) | Cited 1 time

Online Publication Date: 21 November 2012

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We report on a broadband polarization splitting phenomenon in an aluminum grating with its period much smaller than the wavelength of incident light. Under oblique incidence, grating is highly transparent for one polarization, but it is opaque and reflects the orthogonal polarization. By using the Fourier modal method and planar waveguide theory, we show that, comparing with the traditional metallic wire grid polarizers, the improved confinement of TM0 mode within the sub-50 nm wide grating slits is responsible for this polarization splitting effect.
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42.79.Dj Gratings
42.81.Gs Birefringence, polarization

Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal

Kota Okazaki, Tetsuya Shimogaki, Koshi Fusazaki, Mitsuhiro Higashihata, Daisuke Nakamura, Naoto Koshizaki, and Tatsuo Okada

Appl. Phys. Lett. 101, 211105 (2012); http://dx.doi.org/10.1063/1.4768696 (5 pages) | Cited 1 time

Online Publication Date: 21 November 2012

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We report ultraviolet (UV) whispering-gallery-mode (WGM) lasing in a zinc oxide (ZnO) micro/nanosphere crystal fabricated by simply ablating a ZnO sintered target, which was much more productive method without any time-consuming crystal-growth process. The lasing spectral mode spacing was controlled by changing the diameters, and single-mode lasing was realized from a ZnO nanosphere. Experimental results were in good agreement with predictions from WGM theories. Since the ZnO sphere can operate as an active WGM refractometric sensor for small molecules in UV region, high sensitivity enhanced by high quality factor, refractive index, and wavelength dispersion can be expected.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Sa Microcavity and microdisk lasers
42.60.By Design of specific laser systems

Ultra-short pulse generation by a topological insulator based saturable absorber

Chujun Zhao, Han Zhang, Xiang Qi, Yu Chen, Zhiteng Wang, Shuangchun Wen, and Dingyuan Tang

Appl. Phys. Lett. 101, 211106 (2012); http://dx.doi.org/10.1063/1.4767919 (4 pages) | Cited 2 times

Online Publication Date: 21 November 2012

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Under strong laser radiation, a Dirac material, the topological insulator (TI) Bi2Te3, exhibits an optical transmittance increase as a result of saturable absorption. Based on an open-aperture Z-scan measurement at 1550 nm, we clearly show that the TI, Bi2Te3 under our investigation, is indeed a very-high-modulation-depth (up to 95%) saturable absorber. Furthermore, a TI based saturable absorber device was fabricated and used as a passive mode locker for ultrafast pulse formation at the telecommunication band. This contribution unambiguously shows that apart from its fantastic electronic property, a TI (Bi2Te3) may also possess attractive optoelectronic property for ultrafast photonics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption

Ultrabroadband terahertz conductivity of Si nanocrystal films

D. G. Cooke, A. Meldrum, and P. Uhd Jepsen

Appl. Phys. Lett. 101, 211107 (2012); http://dx.doi.org/10.1063/1.4767145 (4 pages)

Online Publication Date: 21 November 2012

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The terahertz conductivity of silicon nanoparticles embedded in glass with varying density is studied with ultra-broadband terahertz spectroscopy on picosecond time scales following fs optical excitation. The transition from relatively isolated charge carriers to densities which allow inter-particle transport is clearly observed. For the times immediately following carrier injection, we observe Drude-like long range transport that is rapidly replaced with a localized response on picosecond time scales. The localized response can be very well described by a phenomenological Drude-Smith model, verifying the applicability of this simple model to the conductivity of nanoparticle ensembles over the entire THz spectral window.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.70.Gq Microwave and radio-frequency interactions
78.47.J- Ultrafast spectroscopy (<1 psec)

Post-fabrication control of evanescent tunnelling in photonic crystal molecules

N. Caselli, F. Intonti, C. Bianchi, F. Riboli, S. Vignolini, L. Balet, L. H. Li, M. Francardi, A. Gerardino, A. Fiore, and M. Gurioli

Appl. Phys. Lett. 101, 211108 (2012); http://dx.doi.org/10.1063/1.4767216 (5 pages)

Online Publication Date: 21 November 2012

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The post-fabrication control of evanescent tunnelling in photonic crystal molecules is demonstrated through the combination of selective infiltration and oxidation. By laser non thermal oxidation, we reduce the photonic coupling by more than 30% while by means of water micro-infiltration, we increase it by 28%. Fine-tuning of the photonic coupling is achieved by low-power laser oxidation and forced evaporation, opening the route to post-fabrication control of array of coupled cavities.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.70.Qs Photonic bandgap materials

Photomixing in topological insulator HgTe/CdTe quantum wells in terahertz regime

Qinjun Chen, Yee Sin Ang, R. A. Lewis, Xiaolin Wang, and Chao Zhang

Appl. Phys. Lett. 101, 211109 (2012); http://dx.doi.org/10.1063/1.4768781 (3 pages)

Online Publication Date: 21 November 2012

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We reveal that topological insulators (TI) HgTe/CdTe quantum well have a strong nonlinear optical property in the three-photon mixing. While the gapless surface state in TI can exhibit strong nonlinear effect due to the linear energy dispersion, the nonparabolic energy dispersion of the bulk state is responsible for the photo mixing effect reported here. To produce response at terahertz frequency regime from femtosecond electrical fields, the mixing efficiency is around 10−4 comparable to that of nonlinear semiconductor crystals. The optimal temperature for this nonlinear effect is around 100 K. The results suggest a potential application of TI in terahertz photonics.
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78.67.De Quantum wells
78.66.Hf II-VI semiconductors

Broadband photon-counting Raman spectroscopy in short optical waveguides

M. J. Collins, A. C. Judge, A. S. Clark, S. Shahnia, E. C. Mägi, M. J. Steel, C. Xiong, and B. J. Eggleton

Appl. Phys. Lett. 101, 211110 (2012); http://dx.doi.org/10.1063/1.4767220 (4 pages)

Online Publication Date: 21 November 2012

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We present a method of directly measuring the spontaneous Raman scattering in optical waveguides in an alignment-free setup. Using a pulsed laser, liquid-crystal-on-silicon spatial light modulator and single-photon detector, we create a broadband photon-counting Raman spectrometer. The temperature and polarization dependence are characterized in an As2S3 amorphous glass fiber for a Stokes detuning range of 1 to 9 THz from the pump frequency. We fit our experimental data with a theoretical model and extract the Raman-gain spectrum and compare to free-space measurements of bulk As2S3. The sensitivity of the method in principle allows direct characterization of chip-scale nanophotonic devices.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.79.Hp Optical processors, correlators, and modulators
42.79.Kr Display devices, liquid-crystal devices
42.81.Gs Birefringence, polarization
42.81.Wg Other fiber-optical devices
85.60.Gz Photodetectors (including infrared and CCD detectors)

Selectively grown photonic crystal structures for high efficiency InGaN emitting diodes using nanospherical-lens lithography

Tongbo Wei, Kui Wu, Ding Lan, Qingfeng Yan, Yu Chen, Chengxiao Du, Junxi Wang, Yiping Zeng, and Jinmin Li

Appl. Phys. Lett. 101, 211111 (2012); http://dx.doi.org/10.1063/1.4767334 (5 pages)

Online Publication Date: 21 November 2012

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We report a low-cost and high-throughput process for the fabrication of two-dimensional SiO2 photonic crystal (PhC) by nanospherical-lens photolithography method to improve the light extraction of GaN-based light-emitting diodes (LEDs). The PhC structures were realized by the selective area growth of p-GaN using SiO2 nanodisks, which were patterned utilizing a self-assembled nanosphere as an optical lens. Without prejudice to the electrical properties of LEDs, the light output power (at 350 mA) of LEDs with the SiO2 and corresponding air-hole PhC was enhanced by 71.3% and 49.3%, respectively, compared to that without PhC. The LEDs with selectively grown PhC structures were found to exhibit partial compression strain release and reduced emission divergence. The finite-difference time-domain simulation was also performed to further reveal the emission characteristics of PhC LEDs.
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81.16.Nd Micro- and nanolithography
81.16.Dn Self-assembly
61.46.-w Structure of nanoscale materials
85.60.Jb Light-emitting devices
02.60.-x Numerical approximation and analysis

Optical pulse compression on a silicon chip—Effect of group velocity dispersion and free carriers

D. T. H. Tan

Appl. Phys. Lett. 101, 211112 (2012); http://dx.doi.org/10.1063/1.4767371 (4 pages)

Online Publication Date: 21 November 2012

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The effect of group velocity dispersion and free carrier lifetime on pulse quality and nonlinear phase acquisition is studied in a two-stage pulse compressor on a silicon chip. Appropriately, designing the dispersion in the nonlinear medium enables compressed pulses with more than 90% of the pulse energy confined in the main lobe to be generated. Free carrier lifetime is observed to impact nonlinear phase acquisition in the single pulse regime. The pulse compression factor decreases monotonically as the pulse repetition rate increases. Conditions for efficient compression at high repetition rates in the absence of free carrier quenching techniques are discussed.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.60.-q Optoelectronic devices
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Nonlinear response of quantum cascade structures

David O. Winge, Martin Lindskog, and Andreas Wacker

Appl. Phys. Lett. 101, 211113 (2012); http://dx.doi.org/10.1063/1.4767373 (4 pages)

Online Publication Date: 21 November 2012

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The gain spectrum of a terahertz quantum cascade laser is analyzed by a nonequilibrium Green's functions approach. Higher harmonics of the response function were retrievable, providing a way to approach nonlinear phenomena in quantum cascade lasers theoretically. Gain is simulated under operation conditions and results are presented both for linear response and strong laser fields. An iterative way of reconstructing the field strength inside the laser cavity at lasing conditions is described using a measured value of the level of the losses of the studied system. Comparison with recent experimental data from time-domain-spectroscopy indicates that the experimental situation is beyond linear response.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
02.30.-f Function theory, analysis

Čerenkov nonlinear diffraction in random nonlinear photonic crystal of strontium tetraborate

A. M. Vyunishev, A. S. Aleksandrovsky, A. I. Zaitsev, and V. V. Slabko

Appl. Phys. Lett. 101, 211114 (2012); http://dx.doi.org/10.1063/1.4767385 (5 pages)

Online Publication Date: 21 November 2012

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Čerenkov-type second harmonic generation of femtosecond pulses in random one-dimensional nonlinear photonic crystal of strontium tetraborate is investigated experimentally and theoretically. Sidebands in angular-spectral dependence of generated second harmonic were detected and found to be in perfect agreement with calculations. Spectral maximum of generated radiation experiences deviation from Čerenkov relation due to influence of nonlinear photonic crystal structure. Pulse duration and local spectrum of Čerenkov second harmonic are measured and found to be in fair agreement with each other.
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42.70.Qs Photonic bandgap materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Observation of quantum Talbot effect from a domain-engineered nonlinear photonic crystal

H. Jin, P. Xu, J. S. Zhao, H. Y. Leng, M. L. Zhong, and S. N. Zhu

Appl. Phys. Lett. 101, 211115 (2012); http://dx.doi.org/10.1063/1.4766728 (4 pages) | Cited 1 time

Online Publication Date: 21 November 2012

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The quantum Talbot effect is observed from a domain-engineered nonlinear photonic crystal dispensing with a real grating. We deduce and experimentally verify the quantum self-imaging formula which is related to the crystal's structure parameter and working wavelengths. A two-photon Talbot carpet is captured to characterize the Fresnel diffraction dynamics of entangled photons wherein the quantum fractional Talbot effect is specified. The compact and stable quantum Talbot effect can be considered as the contactless diagnosis of domain's homogeneity and developed for new types of entangled photon source and quantum technologies such as quantum lithography with improved performance.
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42.70.Qs Photonic bandgap materials
42.79.Dj Gratings
03.65.Ud Entanglement and quantum nonlocality (e.g. EPR paradox, Bell's inequalities, GHZ states, etc.)
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift
42.65.-k Nonlinear optics
42.70.Mp Nonlinear optical crystals

ZnO-nanorod-array/p-GaN high-performance ultra-violet light emitting devices prepared by simple solution synthesis

Shrawan Kumar Jha, Chunyan Luan, Chap Hang To, Oleksandr Kutsay, Jaroslav Kováč, Jr., Juan Antonio Zapien, Igor Bello, and Shuit-Tong Lee

Appl. Phys. Lett. 101, 211116 (2012); http://dx.doi.org/10.1063/1.4764061 (4 pages) | Cited 1 time

Online Publication Date: 21 November 2012

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Pure ultra-violet (UV) (378 nm) electroluminescence (EL) from zinc oxide (ZnO)-nanorod-array/p-gallium nitride (GaN) light emitting devices (LEDs) is demonstrated at low bias-voltages (∼4.3 V). Devices were prepared merely by solution-synthesis, without any involvement of sophisticated material growth techniques or preparation methods. Three different luminescence characterization techniques, i.e., photo-luminescence, cathodo-luminescence, and EL, provided insight into the nature of the UV emission mechanism in solution-synthesized LEDs. Bias dependent EL behaviour revealed blue-shift of EL peaks and increased peak sharpness, with increasing the operating voltage. Accelerated bias stress tests showed very stable and repeatable electrical and EL performance of the solution-synthesized nanorod LEDs.
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85.60.Jb Light-emitting devices
78.67.Qa Nanorods
78.55.Cr III-V semiconductors
78.55.Et II-VI semiconductors
78.60.Fi Electroluminescence
78.60.Hk Cathodoluminescence, ionoluminescence
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High performance InGaAs/GaAsSb terahertz quantum cascade lasers operating up to 142 K

C. Deutsch, M. Krall, M. Brandstetter, H. Detz, A. M. Andrews, P. Klang, W. Schrenk, G. Strasser, and K. Unterrainer

Appl. Phys. Lett. 101, 211117 (2012); http://dx.doi.org/10.1063/1.4766915 (4 pages) | Cited 2 times

Online Publication Date: 21 November 2012

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We report on the demonstration of a maximum operating temperature of 142 K for InGaAs-based terahertz quantum cascade lasers. This result is achieved by using the alternative material combination In0.53Ga0.47As/GaAs0.51Sb0.49, lattice-matched to InP, which exhibits fabrication advantages over standard In0.53Ga0.47As/In0.52Al0.48As due to more suitable material parameters. An active region, based on a three-well phonon depletion design, with improved injection and extraction tunneling coupling, was designed. The devices exhibit threshold current densities of 0.75 kA/cm2 and provide peak optical powers up to 9 mW. A broad spectral emission range between 3.3 and 4 THz is measured.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Impact of grating spacing and electric field on real time updatable holographic recording in nanoscale ZnSe film assisted liquid crystal cells

Hua Zhao, Chao Lian, Feng Huang, Tingyu Xue, Xiudong Sun, Yingyin K. Zou, and Jingwen Zhang

Appl. Phys. Lett. 101, 211118 (2012); http://dx.doi.org/10.1063/1.4767444 (4 pages)

Online Publication Date: 20 November 2012

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Real time updatable holographic recording was demonstrated in C60 doped 4,4′-n-pentylcyanobiphenyl liquid crystal cells made of indium tin oxide glass plates covered with nanoscale ZnSe thin films, without aligning layers required. Possible governing mechanism behind the associated findings was proposed and supported experiments were presented, based on the excellent charge carrier generation/migration in the ZnSe and liquid crystal layers and near the ZnSe/liquid crystal interfaces.
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42.40.Ht Hologram recording and readout methods
42.79.Kr Display devices, liquid-crystal devices
42.40.Eq Holographic optical elements; holographic gratings

Electrically driven single photon source based on a site-controlled quantum dot with self-aligned current injection

W. Unrau, D. Quandt, J.-H. Schulze, T. Heindel, T. D. Germann, O. Hitzemann, A. Strittmatter, S. Reitzenstein, U. W. Pohl, and D. Bimberg

Appl. Phys. Lett. 101, 211119 (2012); http://dx.doi.org/10.1063/1.4767525 (4 pages) | Cited 1 time

Online Publication Date: 20 November 2012

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Electrical operation of single photon emitting devices employing site-controlled quantum dot (QD) growth is demonstrated. An oxide aperture acting as a buried stressor structure is forcing site-controlled QD growth, leading to both QD self-alignment with respect to the current path in vertical injection pin-diodes and narrow, jitter-free emission lines. Emissions from a neutral exciton, a neutral bi-exciton, and a charged exciton are unambiguously identified. Polarization-dependent measurements yield an exciton fine-structure splitting of (84 ± 2) μeV at photon energies of 1.28–1.29 eV. Single-photon emission is proven by Hanbury Brown and Twiss experiments yielding an anti-bunching value of g(2)(0) = 0.05 under direct current injection.
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42.50.Dv Quantum state engineering and measurements
85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)
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Role of ethylene on surface oxidation of TiO2(110)

Y. Murata, V. Petrova, I. Petrov, C. V. Ciobanu, and S. Kodambaka

Appl. Phys. Lett. 101, 211601 (2012); http://dx.doi.org/10.1063/1.4767954 (5 pages)

Online Publication Date: 21 November 2012

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Using in situ high-temperature (700-1000 K) scanning tunneling microscopy (STM), we studied the influence of ethylene on the surface dynamics of oxygen-deficient, rutile-structured TiO2(110). STM images were acquired during annealing the sample as a function of time, oxygen and ethylene pressures, and temperature. With increasing oxygen pressure and/or decreasing temperature, TiO2(110) surface mass increased, consistent with previous results. Interestingly, annealing the sample in ethylene with traces of oxygen also results in the growth of TiO2 at higher rates than those observed during annealing in pure oxygen. Our results indicate that ethylene promotes oxidation of TiO2(110).
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81.65.Mq Oxidation
68.35.Ja Surface and interface dynamics and vibrations
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.40.Gh Other heat and thermomechanical treatments

“Boiling” in the water evaporating meniscus induced by Marangoni flow

Xiang Liu, Dan Guo, Guoxin Xie, Shuhai Liu, and Jianbin Luo

Appl. Phys. Lett. 101, 211602 (2012); http://dx.doi.org/10.1063/1.4767991 (4 pages)

Online Publication Date: 21 November 2012

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A counterintuitive phenomenon, “boiling,” was directly observed near the contact line of the pure water meniscus formed in a ball and disk configuration, when the ball temperature was far lower than the saturation temperature of water. The number of the emerging bubbles due to “boiling” increased with ball temperature rising; each bubble would expanse initially and then collapse. When two surfaces were heated to the same temperature, “boiling” disappeared. It was proposed that the temperature gradient between the two surfaces initiated Marangoni flow, which hindered flow toward the film, resulting in the negative pressure and cavitation in the liquid film.
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47.27.te Turbulent convective heat transfer
47.55.dp Cavitation and boiling
47.55.dd Bubble dynamics
68.03.Cd Surface tension and related phenomena

Densification of functional plasma polymers by momentum transfer during film growth

Dirk Hegemann, Enrico Körner, Noémi Blanchard, Martin Drabik, and Sébastien Guimond

Appl. Phys. Lett. 101, 211603 (2012); http://dx.doi.org/10.1063/1.4767999 (4 pages) | Cited 1 time

Online Publication Date: 21 November 2012

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Functional plasma polymers were deposited from pure ethylene discharges and with the addition of carbon dioxide or ammonia. The incorporation of oxygen and nitrogen-containing functional groups depends on the fragmentation in the gas phase as well as on the densification during film growth. While a minimum energy per deposited carbon atom is required for cross-linking, the densification and accompanying reduction of functional group incorporation was found to scale linearly with momentum transfer through ion bombardment during film growth.
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68.55.A- Nucleation and growth
52.77.Dq Plasma-based ion implantation and deposition
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

In situ atomic layer deposition half cycle study of Al2O3 growth on AlGaN

Barry Brennan, Xiaoye Qin, Hong Dong, Jiyoung Kim, and Robert M. Wallace

Appl. Phys. Lett. 101, 211604 (2012); http://dx.doi.org/10.1063/1.4767520 (4 pages)

Online Publication Date: 21 November 2012

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The atomic layer deposition (ALD) of Al2O3 on the native oxide and hydrofluoric acid treated Al0.25Ga0.75 N surface was studied using in situ X-ray photoelectron spectroscopy (XPS), after each individual “half cycle” of the ALD process. Initially, Al2O3, Ga2O3, and N-O states were detected on both surfaces at differing concentrations. During the course of the deposition process, the N-O bonds are seen to decrease to within XPS detection limits, as well as a small decrease in the Ga2O3 concentration. The Al2O3 growth rate initially is seen to be very low, indication of low reactivity between the trimethyl-aluminum molecule and the AlGaN surface.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.20.At Surface states, band structure, electron density of states
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Effects of oxygen on electron beam induced deposition of SiO2 using physisorbed and chemisorbed tetraethoxysilane

James Bishop, Milos Toth, Matthew Phillips, and Charlene Lobo

Appl. Phys. Lett. 101, 211605 (2012); http://dx.doi.org/10.1063/1.4767521 (3 pages)

Online Publication Date: 21 November 2012

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Electron beam induced deposition (EBID) is limited by low throughput and purity of as-grown material. Co-injection of O2 with the growth precursor is known to increase both the purity and deposition rate of materials such as SiO2 at room temperature. Here, we show that O2 inhibits rather than enhances EBID from tetraethoxysilane (TEOS) precursor at elevated temperatures. This behavior is attributed to surface site competition between chemisorbates at elevated temperature, and TEOS decomposition by atomic oxygen produced through electron dissociation of physisorbed O2 at room temperature.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
68.43.Mn Adsorption kinetics

Electronic properties at the oxide interface with silicon and germanium through x-ray induced oxide charging

M. Perego, A. Molle, and G. Seguini

Appl. Phys. Lett. 101, 211606 (2012); http://dx.doi.org/10.1063/1.4766925 (5 pages)

Online Publication Date: 21 November 2012

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A dependence of the binding energy of the Hf 4f and O 1s photoemission lines on the thickness of the HfO2 film is identified in HfO2/Si heterojunctions and associated with differential charging phenomena. No shifts of Hf 4f and O 1s binding energies are observed in HfO2/Ge heterojunctions, irrespective of the HfO2 film thickness. The time evolution of Hf 4f and Ge 3d signals correlates with a large number of electrically active traps, which are close to the Ge valence bands and determine a negative charge builds-up at the interface, causing the commonly observed p-type surface inversion in n-Ge.
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71.20.Mq Elemental semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.55.-a Thin film structure and morphology
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