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22 Oct 2012

Volume 101, Issue 17, Articles (17xxxx)

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Appl. Phys. Lett. 101, 171101 (2012); http://dx.doi.org/10.1063/1.4758996 (4 pages)

Wolfram H. P. Pernice and Harish Bhaskaran
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Photonic non-volatile memories using phase change materials

Wolfram H. P. Pernice and Harish Bhaskaran

Appl. Phys. Lett. 101, 171101 (2012); http://dx.doi.org/10.1063/1.4758996 (4 pages) | Cited 1 time

Online Publication Date: 22 October 2012

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We propose an all-photonic, non-volatile memory, and processing element based on phase-change thin-films deposited onto nanophotonic waveguides. Using photonic microring resonators partially covered with Ge2Sb2Te5 (GST) multi-level memory operation in integrated photonic circuits can be achieved. GST provides a dramatic change in refractive index upon transition from the amorphous to crystalline state, which is exploited to reversibly control both the extinction ratio and resonance wavelength of the microcavity with an additional gating port in analogy to optical transistors. Our analysis shows excellent sensitivity to the degree of crystallization inside the GST, thus providing the basis for non-von Neumann neuromorphic computing.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.60.-q Optoelectronic devices
84.30.Sk Pulse and digital circuits
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

Effect of diamond like carbon layer on heat dissipation and optoelectronic performance of vertical-type InGaN light emitting diodes

Ray-Hua Horng, Wei-Cheng Kao, Sin-Liang Ou, and Dong-Sing Wuu

Appl. Phys. Lett. 101, 171102 (2012); http://dx.doi.org/10.1063/1.4764007 (4 pages)

Online Publication Date: 23 October 2012

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This study reports the transfer of InGaN light-emitting diodes (LEDs) embedded with and without a diamond like carbon (DLC) layer to Si substrates. It also investigates the heat dissipation and output power performance after the addition of the DLC layer. The LED device with a DLC layer had a lower thermal resistance (13.2 K/W) and surface temperature (55.51-65.34 °C at 700 mA) than that without a DLC layer. This likely resulted from the fast heat dissipation of the DLC layer in both vertical and horizontal directions. The LED device with a DLC layer achieved a 20.8% improvement in output power.
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85.60.Jb Light-emitting devices

Spin Hall effect of light reflected from a magnetic thin film

Jinli Ren, Yan Li, Yida Lin, Yi Qin, Rui Wu, Jinbo Yang, Yun-Feng Xiao, Hong Yang, and Qihuang Gong

Appl. Phys. Lett. 101, 171103 (2012); http://dx.doi.org/10.1063/1.4764008 (4 pages) | Cited 1 time

Online Publication Date: 23 October 2012

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The displacements for |P> polarization (electric field parallel to the plane-of-incidence) and |S> polarization (electric field perpendicular to the plane-of-incidence) induced by the spin Hall effect of light reflected from a magnetic cobalt thin film have been investigated. The significant differences from those of an air-glass interface are attributed to the special complex permittivity and refractive index of the cobalt film. The real part of the complex refractive index has more influence on displacements for |P> polarization than for |S> polarization. There also exists a particular incident angle corresponding to the zero displacement for |P> polarization. It shifts from 52° to 76° when the real part rises from 1.0 to 4.0. For both |P> and |S> polarizations, the maximal displacements rapidly rise with the decrease of the imaginary part. Our simulations further demonstrate that polarization-insensitive spin separations can be realized by choosing the medium with an optimal permeability.
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72.25.-b Spin polarized transport
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
75.70.Ak Magnetic properties of monolayers and thin films
72.20.My Galvanomagnetic and other magnetotransport effects
78.66.Bz Metals and metallic alloys

Polarization-stable vertical-cavity surface-emitting lasers with inverted grating relief for use in microscale atomic clocks

A. Al-Samaneh, M. Bou Sanayeh, M. J. Miah, W. Schwarz, D. Wahl, A. Kern, and R. Michalzik

Appl. Phys. Lett. 101, 171104 (2012); http://dx.doi.org/10.1063/1.4764010 (4 pages) | Cited 1 time

Online Publication Date: 23 October 2012

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Vertical-cavity surface-emitting lasers (VCSELs) with single-mode, single-polarization emission at a wavelength of 894.6 nm have become attractive light sources for miniaturized Cs-based atomic clocks. So far, VCSELs used for these applications are single-mode because of small active diameters which has the drawbacks of increased ohmic resistance and reduced lifetime. By employing surface grating reliefs, enhanced fundamental-mode emission as well as polarization-stable laser oscillation are achieved. VCSELs with 5 μm active diameter show side-mode suppression ratios of 20 dB even at currents close to thermal roll-over with orthogonal polarization suppression ratios better than 20 dB at elevated ambient temperatures up to 100 °C.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Dj Gratings

Impact of growth temperature on InAs/GaInSb strained layer superlattices for very long wavelength infrared detection

H. J. Haugan, G. J. Brown, S. Elhamri, W. C. Mitchel, K. Mahalingam, M. Kim, G. T. Noe, N. E. Ogden, and J. Kono

Appl. Phys. Lett. 101, 171105 (2012); http://dx.doi.org/10.1063/1.4764015 (4 pages)

Online Publication Date: 23 October 2012

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We explore the optimum growth space for a 47.0 Å InAs/21.5 Å Ga0.75In0.25Sb superlattices (SLs) designed for the maximum Auger suppression for a very long wavelength infrared gap. Our growth process produces a consistent gap of 50 ± 5 meV. However, SL quality is sensitive to the growth temperature (Tg). For the SLs grown at 390−470 °C, a photoresponse signal gradually increases as Tg increases from 400 to 440 °C. Outside this temperature window, the SL quality deteriorates very rapidly. All SLs were n-type with mobility of ∼10 000 V/cm2 and 300 K recombination lifetime of ∼70 ns for an optimized SL.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
73.61.Ey III-V semiconductors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Dn Low-field transport and mobility; piezoresistance

Narrow-band optical transmission of metallic nanoslit arrays

Zhijun Sun, Ying Yang, and Xiaoliu Zuo

Appl. Phys. Lett. 101, 171106 (2012); http://dx.doi.org/10.1063/1.4764113 (4 pages)

Online Publication Date: 23 October 2012

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Metallic nanoslit arrays usually demonstrate wide transmission bands for transverse-magnetic-polarized incidence light. Here, we show that by introducing multi-dielectric layers underneath the metallic structure layer on the substrate, a narrow peak is formed, whose bandwidth can be down to a few nanometers. Three types of resonance modes in the region under the metal layer are identified responsible for the formation of the peak, i.e., a two-dimensional cavity resonance mode, which supports optical transmission, and two in-plane hybrid surface plasmon resonance modes locating on both sides of the peak that suppresses the transmission. Such structures can be applied in advanced photonic devices.
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81.05.Bx Metals, semimetals, and alloys
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
73.22.Lp Collective excitations
73.21.Ac Multilayers
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Detection of ultrafast laser ablation using quantum cascade laser-based sensing

F. P. Mezzapesa, V. Spagnolo, A. Ancona, and G. Scamarcio

Appl. Phys. Lett. 101, 171107 (2012); http://dx.doi.org/10.1063/1.4764115 (4 pages) | Cited 1 time

Online Publication Date: 23 October 2012

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The impact of quantum cascade lasers (QCLs) intrinsically high sensitivity to external optical feedback intended for sensing applications such as in-line ablation rate measurements is experimentally demonstrated. We developed a QCL-based sensor to assess the voltage modulation at the laser terminals induced by fast displacement of the ablation front during the process. This work shows that the detection range of our diagnostic system is only limited by the emission wavelength of the QCL probe source and the capability to measure ablation rates as high as 160 nm/pulse was reported. This sensing technique can be employed with the whole class of quantum cascade lasers, whose emission spans from mid-IR to THz spectral region, thus enabling the extension of its applications to ultra-fast laser ablation processes.
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42.55.Px Semiconductor lasers; laser diodes
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.60.By Design of specific laser systems

Three-photon near-infrared quantum cutting in Tm3+-doped transparent oxyfluoride glass ceramics

D. C. Yu, J. P. Zhang, Q. J. Chen, W. J. Zhang, Z. M. Yang, and Q. Y. Zhang

Appl. Phys. Lett. 101, 171108 (2012); http://dx.doi.org/10.1063/1.4764005 (4 pages)

Online Publication Date: 24 October 2012

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Efficient three-step sequential three-photon near-infrared (NIR) quantum cutting in Tm3+-doped transparent oxyfluoride glass ceramics has been demonstrated, where an absorbed blue photon could be cut into three NIR photons at 1190, 1460, and 1800 nm with quantum yield greater than unity. On the basis of static and dynamic photoemission, monitored excitation, and time-resolved fluorescence spectra, we investigate in detail the underlying optoelectronic mechanism. Further development of an efficient triply-cutting material might open up a path towards ultra-efficient photonic devices, which enables more photons emitted than absorbed in the excitation process.
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81.05.Pj Glass-based composites, vitroceramics
78.55.Hx Other solid inorganic materials
78.60.-b Other luminescence and radiative recombination

Current dependence of electro-optical parameters in green and blue (AlIn)GaN laser diodes

T. Hager, G. Brüderl, T. Lermer, S. Tautz, A. Gomez-Iglesias, J. Müller, A. Avramescu, C. Eichler, S. Gerhard, and U. Strauss

Appl. Phys. Lett. 101, 171109 (2012); http://dx.doi.org/10.1063/1.4764067 (4 pages)

Online Publication Date: 24 October 2012

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We present a detailed study of laser characteristics of blue and green R&D laser diodes grown on free standing GaN substrates with c-plane orientation under forward current condition. The slope efficiency of the blue emitting device exhibits a constant value over the entire operation range. In contrast to that, the green laser shows a decrease in slope efficiency with increasing current. A reduction of slope efficiency can be caused either by increasing internal losses or decreasing injection efficiency. A series of different mirror coatings is used to correlate the decreasing slope efficiency with a slight decrease of the injection efficiency as a function of current density. Furthermore, the reduction of the injection efficiency does not depend on the junction temperature. We could also verify that the internal losses are not temperature sensitive for blue and green laser diodes.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Bh Lenses, prisms and mirrors

Single photon adiabatic wavelength conversion

Stefan Preble, Liang Cao, Ali Elshaari, Abdelsalam Aboketaf, and Donald Adams

Appl. Phys. Lett. 101, 171110 (2012); http://dx.doi.org/10.1063/1.4764068 (5 pages) | Cited 1 time

Online Publication Date: 24 October 2012

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Adiabatic wavelength conversion is experimentally demonstrated at a single photon power-level using an integrated silicon ring resonator. This approach allows conversion of a photon to arbitrary wavelengths with no energy or phase matching constraints. The conversion is inherently low-noise and efficient with greater than 10% conversion efficiencies for wavelength changes up to 0.5 nm, more than twenty times the resonators line-width. The observed wavelength change and efficiency agrees well with theory and bright coherent light demonstrations. These results will enable integrated quantum optical wavelength conversion for application ranging from wavelength-multiplexed quantum networks to frequency bin entanglement.
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42.65.Lm Parametric down conversion and production of entangled photons
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.50.Ex Optical implementations of quantum information processing and transfer
42.82.-m Integrated optics

A quantum dot rolled-up microtube directional coupler

Sishir Bhowmick, Junseok Heo, and Pallab Bhattacharya

Appl. Phys. Lett. 101, 171111 (2012); http://dx.doi.org/10.1063/1.4764530 (4 pages) | Cited 1 time

Online Publication Date: 25 October 2012

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A rolled-up microtube directional coupler made of twin microtubes is demonstrated. The microtube is made of a InGaAs/GaAs strained bilayer and InAs self-organized quantum dots are inserted in the GaAs layer. The input and coupled microtubes have length and outer diameter of ∼50 and 6 μm, respectively. The coupling characteristics have been analyzed by the three-dimensional finite difference time domain method. The coupling characteristics have also been measured with isopropyl alcohol, instead of air, as the surrounding media to demonstrate the potential of the device as a sensor.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays

Dielectric strength, optical absorption, and deep ultraviolet detectors of hexagonal boron nitride epilayers

J. Li, S. Majety, R. Dahal, W. P. Zhao, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 101, 171112 (2012); http://dx.doi.org/10.1063/1.4764533 (4 pages) | Cited 2 times

Online Publication Date: 25 October 2012

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Hexagonal boron nitride (hBN) epilayers have been synthesized by metal organic chemical vapor deposition and their dielectric strength, optical absorption, and potential as a deep ultraviolet (DUV) detector material have been studied. Based on the graphene optical absorption concept, the estimated band-edge absorption coefficient of hBN is about 7 × 105/cm, which is more than 3 times higher than the value for wurtzite AlN (∼2 × 105 /cm). The dielectric strength of hBN epilayers exceeds that of AlN and is greater than 4.4 MV/cm based on the measured result for an hBN epilayer released from the host sapphire substrate. The hBN epilayer based DUV detectors exhibit a sharp cut-off wavelength around 230 nm, which coincides with the band-edge photoluminescence emission peak and virtually no responses in the long wavelengths. Based on the present study, we have identified several advantageous features of hBN DUV photodetectors: (1) low long wavelength response or high DUV to visible rejection ratio; (2) requiring very thin active layers due to high optical absorption; (3) high dielectric strength and chemical inertness and resistance to oxidation and therefore suitable for applications in extreme conditions; (4) high prospects of achieving flexible devices; and (5) possible integration with graphene optoelectronics due to their similar structures and lattice constants.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.60.Gz Photodetectors (including infrared and CCD detectors)
77.22.Jp Dielectric breakdown and space-charge effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Cr III-V semiconductors

Amplified spontaneous emission of Rhodamine 6G embedded in pure deoxyribonucleic acid

Ileana Rau, Adam Szukalski, Lech Sznitko, Andrzej Miniewicz, Stanislaw Bartkiewicz, Francois Kajzar, Bouchta Sahraoui, and Jaroslaw Mysliwiec

Appl. Phys. Lett. 101, 171113 (2012); http://dx.doi.org/10.1063/1.4764535 (3 pages)

Online Publication Date: 25 October 2012

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Deoxyribonucleic acid (DNA) is commonly viewed as a genetic information carrier. However, now it is recognized as a nanomaterial, rather than as a biological material, in the research field of nanotechnology. Here, we show that using pure DNA, doped with rhodamine 6G, we are able to observe amplified spontaneous emission (ASE) phenomenon. Moderate ASE threshold, photodegradation, and reasonable gain coefficient observed in this natural host gives some perspectives for practical applications of this system in biophotonics. Obtained results open the way and will be leading to construction of truly bio-lasers using nature made luminophores, such as anthocyanins.
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87.85.Rs Nanotechnologies-applications
42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
87.14.gk DNA
87.85.Qr Nanotechnologies-design

Light propagation in an optically active plate with topological charge

Yicheng Wang, Huaijin Zhang, Haohai Yu, Zhengping Wang, and Jiyang Wang

Appl. Phys. Lett. 101, 171114 (2012); http://dx.doi.org/10.1063/1.4764546 (3 pages)

Online Publication Date: 25 October 2012

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We propose the optical zero-spin-to-orbital angular momentum and linear-to-vector polarization conversion realization by an optically active plate with a topological charge. By the geometric phase, the zero spin will also contribute to the orbital optical angular momentum and induce the optical spin-to-orbital angular momentum conversion. Moreover, the proposed angular momentum converter can convert the polarization from linear to radial or azimuthal with high efficiency. We believe that the proposed efficient converter will find potential applications in the study of quantum information conversion, generation and interaction of vector fields, phase and polarization singularities, etc.
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42.25.Ja Polarization
42.50.-p Quantum optics
03.67.-a Quantum information
42.25.Bs Wave propagation, transmission and absorption

Nanocrystalline diamond photonics platform with high quality factor photonic crystal cavities

X. Checoury, D. Néel, P. Boucaud, C. Gesset, H. Girard, S. Saada, and P. Bergonzo

Appl. Phys. Lett. 101, 171115 (2012); http://dx.doi.org/10.1063/1.4764548 (4 pages) | Cited 1 time

Online Publication Date: 25 October 2012

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We demonstrate a diamond photonics platform with integrated suspended waveguide-cavity structures and two dimensional photonic crystal (PhC) cavities. PhC cavities with quality factors exceeding 2800 have been fabricated using a top-down approach from thin nanocrystalline diamond films. The developed technological process allows one to access these cavities in a fully planar geometry, including light injection and collection from the outside using lensed-fibers. This diamond platform opens the road to large scale fabrication of photonics devices including optical sensor chips.
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42.70.Qs Photonic bandgap materials
42.81.Bm Fabrication, cladding, and splicing
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays

Direct observation of guided-mode interference in polymer-loaded plasmonic waveguide

Q. Q. Cheng, T. Li, R. Y. Guo, L. Li, S. M. Wang, and S. N. Zhu

Appl. Phys. Lett. 101, 171116 (2012); http://dx.doi.org/10.1063/1.4764116 (4 pages)

Online Publication Date: 25 October 2012

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We report a direct observation of guided-mode interference in polymer-loaded plasmonic waveguides by the technique of leakage radiation microscopy (LRM). Spatial beating patterns of the interferences were clearly characterized with respect to different structural parameters, and the interference properties were analyzed in detail. Besides, the capability of LRM for characterizing the multiple modes was also discussed extensively. Our finding not only offers an efficient technique in analyzing the guided modes and their interference, but also provides a definite guideline in evaluating the validity of LRM and deepens further studies on the dielectric-loaded hybrid waveguide system.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.68.+m Optical properties of surfaces
73.22.Lp Collective excitations

Importance of interface roughness induced intersubband scattering in mid-infrared quantum cascade lasers

YenTing Chiu, Yamac Dikmelik, Peter Q. Liu, Nyan L. Aung, Jacob B. Khurgin, and Claire F. Gmachl

Appl. Phys. Lett. 101, 171117 (2012); http://dx.doi.org/10.1063/1.4764516 (4 pages) | Cited 2 times

Online Publication Date: 26 October 2012

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The electron transit time of many different quantum cascade lasers has been measured and compared to the calculated upper laser level lifetimes with and without taking into account interface roughness induced intersubband scattering. A significantly better correlation is found between the experimental results and the calculation when including the contribution from the interface roughness (corr. coeff.: 0.79 vs. 0.43 with and without the consideration of interface roughness, respectively). This suggests that in addition to longitudinal optical phonons, interface roughness is also crucial in determining the intersubband lifetimes in mid-infrared quantum cascade laser and should routinely be included in design.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Single-waveguide dual-wavelength interband cascade lasers

Lu Li, Lihua Zhao, Yuchao Jiang, Rui Q. Yang, Joel C. Keay, Tetsuya D. Mishima, Michael B. Santos, and Matthew B. Johnson

Appl. Phys. Lett. 101, 171118 (2012); http://dx.doi.org/10.1063/1.4764910 (4 pages)

Online Publication Date: 26 October 2012

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Dual-wavelength interband cascade (IC) lasers with two different cascade regions in a single waveguide have been demonstrated in pulsed conditions to simultaneously lase based on spatially overlapping fundamental vertical modes near 5 and 6 μm. The fabricated broad-area devices operate at temperatures up to 155 K and 235 K in cw and pulsed modes, respectively. The temperature dependence of the device performance characteristics has been investigated. The threshold current of the dual wavelength IC lasers at the shorter wavelength showed different characteristics from that at the longer wavelength.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
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Electronic states and curved surface effect of silicon quantum dots

Wei-Qi Huang, Zhong-Mei Huang, Han-Qiong Cheng, Xin-Jian Miao, Qin Shu, Shi-Rong Liu, and Chao-Jian Qin

Appl. Phys. Lett. 101, 171601 (2012); http://dx.doi.org/10.1063/1.4761945 (4 pages)

Online Publication Date: 22 October 2012

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The calculation results show that the bonding energy and electronic states of silicon quantum dots (Si QDs) are different on various curved surfaces (CS), for example, a Si-O-Si bridge bond on curved surface provides the localized levels in band gap and its bonding energy is shallower than that on facet. Curved surface breaks symmetrical shape of silicon quantum dots on which some bonds can produce localized electronic states in band gap. The red-shifting of photoluminescence spectra on smaller silicon quantum dots can be explained by CS effect. In CS effect, surface curvature is determined by the shape of Si QDs or silicon nanostructures, which is independent of their sizes. The CS effect has the interesting fundamental physical properties in nanophysics as that of quantum confinement effect.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Ap Elemental semiconductors
73.20.At Surface states, band structure, electron density of states
78.67.Hc Quantum dots
81.07.Ta Quantum dots

Optimal hydrogenated amorphous silicon/silicon nitride bilayer passivation of n-type crystalline silicon using response surface methodology

Dmitri S. Stepanov and Nazir P. Kherani

Appl. Phys. Lett. 101, 171602 (2012); http://dx.doi.org/10.1063/1.4764011 (4 pages)

Online Publication Date: 23 October 2012

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This study reports the highest quality surface passivation achieved with hydrogenated amorphous silicon and amorphous silicon nitride (SiNx) bilayer stack deposited using plasma enhanced chemical vapour deposition on 1–2 Ωcm n-type crystalline silicon. The SiNx deposition conditions were investigated using response surface methodology (RSM). Optimized deposition parameters obtained from the RSM study yielded a low surface recombination velocity (SRV) of 3.5 cm/s. Interface defect and charge densities, inferred using the interface dangling bond recombination model, revealed a strong influence of charge on the SRV reduction. The model predicts a lower SRV of 1.5 cm/s for the bilayer passivation scheme.
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81.65.Rv Passivation
02.60.-x Numerical approximation and analysis
71.55.-i Impurity and defect levels
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Growth mechanisms of in situ TiC in laser melted Ti–Si–C ternary system

Dongdong Gu, Donghua Dai, Guoquan Zhang, and Hongqiao Wang

Appl. Phys. Lett. 101, 171603 (2012); http://dx.doi.org/10.1063/1.4764055 (5 pages) | Cited 1 time

Online Publication Date: 24 October 2012

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Laser rapid melting and recrystallization of in situ crystals is an interesting issue in research fields of applied physics and materials science. This letter investigated the growth mechanisms of in situ dendritic TiC from laser melted Ti–Si–C ternary system. The growth of TiC dendritic trunks was kinetically dependent on laser scan speed and was influenced negligibly by laser power. A higher scan speed produced the elongated dendritic trunks. The development of TiC dendritic arms was temperature-dependent. An increase in laser energy density by increasing laser power or decreasing scan speed enhanced the growth of primary and even secondary dendritic arms.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
42.62.-b Laser applications
64.70.dj Melting of specific substances

Damage at hydrogenated amorphous/crystalline silicon interfaces by indium tin oxide overlayer sputtering

Bénédicte Demaurex, Stefaan De Wolf, Antoine Descoeudres, Zachary Charles Holman, and Christophe Ballif

Appl. Phys. Lett. 101, 171604 (2012); http://dx.doi.org/10.1063/1.4764529 (4 pages) | Cited 2 times

Online Publication Date: 25 October 2012

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Damage of the hydrogenated amorphous/crystalline silicon interface passivation during transparent conductive oxide sputtering is reported. This occurs in the fabrication process of silicon heterojunction solar cells. We observe that this damage is at least partially caused by luminescence of the sputter plasma. Following low-temperature annealing, the electronic interface properties are recovered. However, the silicon-hydrogen configuration of the amorphous silicon film is permanently changed, as observed from infra-red absorbance spectra. In silicon heterojunction solar cells, although the as-deposited film's microstructure cannot be restored after sputtering, no significant losses are observed in their open-circuit voltage.
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88.40.jj Silicon solar cells

Temperature and pressure dependent Mott potentials and their influence on self-limiting oxide film growth

Na Cai, Guangwen Zhou, Kathrin Müller, and David E. Starr

Appl. Phys. Lett. 101, 171605 (2012); http://dx.doi.org/10.1063/1.4764552 (4 pages)

Online Publication Date: 25 October 2012

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Classic Cabrera-Mott theory stipulates that the limited oxide-film growth results from electron tunneling from the metal through the oxide film to adsorbed oxygen. This leads to an electric field across the oxide film that assists ion migration for low-temperature oxide-film growth. Here, we show that the field-driven oxide-film growth can be manipulated via the temperature and pressure of oxidation. The magnitude of the self-generated electric field depends on the oxygen surface coverage that exhibits a Langmuir isotherm behavior with changes in temperature and oxygen pressure. These observations demonstrate the ability to tune an interfacial reaction via self-adaptation to its environment.
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68.55.A- Nucleation and growth
66.30.Qa Electromigration
68.43.Mn Adsorption kinetics
73.40.Gk Tunneling
81.65.Mq Oxidation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
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Effect of length scale on mechanical properties of Al-Cu eutectic alloy

C. S. Tiwary, D. Roy Mahapatra, and K. Chattopadhyay

Appl. Phys. Lett. 101, 171901 (2012); http://dx.doi.org/10.1063/1.4761944 (4 pages)

Online Publication Date: 22 October 2012

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This paper attempts a quantitative understanding of the effect of length scale on two phase eutectic structure. We first develop a model that considers both the elastic and plastic properties of the interface. Using Al-Al2Cu lamellar eutectic as model system, the parameters of the model were experimentally determined using indentation technique. The model is further validated using the results of bulk compression testing of the eutectics having different length scales.
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81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Elasticity of diamond at high pressures and temperatures

Maribel Núñez Valdez, Koichiro Umemoto, and Renata M. Wentzcovitch

Appl. Phys. Lett. 101, 171902 (2012); http://dx.doi.org/10.1063/1.4754548 (4 pages)

Online Publication Date: 23 October 2012

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Show Abstract
We combine density functional theory within the local density approximation, the quasiharmonic approximation, and vibrational density of states to calculate single crystal elastic constants, and bulk and shear moduli of diamond at simultaneous high pressures and temperatures in the ranges of 0–500 GPa and 0–4800 K. Comparison with experimental values at ambient pressure and high temperature shows an excellent agreement with our first-principles results validating our method. We show that the anisotropy factor of diamond increases to 40% at high pressures and becomes temperature independent.
Show PACS
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
62.20.dq Other elastic constants
62.50.-p High-pressure effects in solids and liquids
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
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