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14 Sep 2009

Volume 95, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 113101 (2009); http://dx.doi.org/10.1063/1.3197646 (3 pages)

Jesse J. Cole, En-Chiang Lin, Chad R. Barry, and Heiko O. Jacobs
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Extraction of semiconductor microchip differential gain by use of optically pumped semiconductor laser

Matthew Walton, Nathan Terry, Jorg Hader, Jerome Moloney, and Robert Bedford

Appl. Phys. Lett. 95, 111101 (2009); http://dx.doi.org/10.1063/1.3222899 (3 pages) | Cited 3 times

Online Publication Date: 14 September 2009

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The small-signal modulation response of a vertical external cavity surface emitting laser is analyzed to determine its resonance frequency in relation to photon density, allowing nondestructive extraction of characteristic parameters of chips, such as internal loss and differential gain.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Sa Microcavity and microdisk lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Nonpolar m-plane GaN on patterned Si(112) substrates by metalorganic chemical vapor deposition

X. Ni, M. Wu, J. Lee, X. Li, A. A. Baski, Ü. Özgür, and H. Morkoç

Appl. Phys. Lett. 95, 111102 (2009); http://dx.doi.org/10.1063/1.3225157 (3 pages) | Cited 5 times

Online Publication Date: 14 September 2009

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The concept of nonpolar (1math00) m-plane GaN on Si substrates has been demonstrated by initiating growth on the vertical (mathmath1) sidewalls of patterned Si(112) substrates using metalorganic chemical vapor deposition. The Si(112) substrates were wet-etched to expose {111} planes using stripe-patterned SiNx masks oriented along the [math10] direction. Only the vertical Si(mathmath1) sidewalls were allowed to participate in GaN growth by masking other Si{111} planes using SiO2, which led to m-plane GaN films. Growth initiating on the Si(mathmath1) planes normal to the surface was allowed to advance laterally and also vertically toward full coalescence. InGaN double heterostructure active layers grown on these m-GaN templates on Si exhibited two times higher internal quantum efficiencies as compared to their c-plane counterparts at comparable carrier densities. These results demonstrate a promising method to obtain high-quality nonpolar m-GaN films on large area, inexpensive Si substrates.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.ag Semiconductors

Noncollinear interaction of femtosecond filaments with enhanced third harmonic generation in air

Xuan Yang, Jian Wu, Yan Peng, Yuqi Tong, Shuai Yuan, Liangen Ding, Zhizhan Xu, and Heping Zeng

Appl. Phys. Lett. 95, 111103 (2009); http://dx.doi.org/10.1063/1.3227658 (3 pages) | Cited 15 times

Online Publication Date: 14 September 2009

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We demonstrate that the interaction between two intense femtosecond filaments noncollinearly crossed in air results in third harmonic generation of more than two orders enhancement in energy conversion as compared with that from a single filament. The dependences of the third harmonic generation on the noncollinear crossing angles, input intensity ratios, and input pulse polarizations are investigated.
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52.38.Hb Self-focussing, channeling, and filamentation in plasmas
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
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Wavelength dependence of the damage threshold of inorganic materials under extreme-ultraviolet free-electron-laser irradiation

S. P. Hau-Riege, R. A. London, R. M. Bionta, D. Ryutov, R. Soufli, S. Bajt, M. A. McKernan, S. L. Baker, J. Krzywinski, R. Sobierajski, R. Nietubyc, D. Klinger, J. B. Pelka, M. Jurek, L. Juha, et al.

Appl. Phys. Lett. 95, 111104 (2009); http://dx.doi.org/10.1063/1.3216845 (3 pages) | Cited 9 times

Online Publication Date: 14 September 2009

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We exposed bulk SiC and films of SiC and B4C to single 25 fs long free-electron-laser pulses with wavelengths between 13.5 and 32 nm. The materials are candidates for x-ray free-electron laser optics. We found that the threshold for surface-damage of the bulk SiC samples exceeds the fluence required for thermal melting at all wavelengths. The damage threshold of the film sample shows a strong wavelength dependence. For wavelengths of 13.5 and 21.7 nm, the damage threshold is equal to or exceeds the melting threshold, whereas at 32 nm the damage threshold falls below the melting threshold.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
41.60.Cr Free-electron lasers
42.55.Vc X- and γ-ray lasers

Radiation loss of photonic crystal coupled-cavity waveguides

J. Jágerská, H. Zhang, N. Le Thomas, and R. Houdré

Appl. Phys. Lett. 95, 111105 (2009); http://dx.doi.org/10.1063/1.3222905 (3 pages) | Cited 4 times

Online Publication Date: 15 September 2009

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We experimentally investigate the out-of-plane radiation losses of photonic crystal coupled-cavity waveguides. We observe a strong variation in the losses along the dispersion curve and show that such variation is closely linked with the specific far-field radiation pattern of a single cavity constituent. A simple theoretical model based on tight-binding approximation is used to describe this behavior.
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42.79.Gn Optical waveguides and couplers

GaAs/AlAs coupled multilayer cavity structures for terahertz emission devices

Takahiro Kitada, Fumiya Tanaka, Tomoya Takahashi, Ken Morita, and Toshiro Isu

Appl. Phys. Lett. 95, 111106 (2009); http://dx.doi.org/10.1063/1.3226667 (3 pages) | Cited 12 times

Online Publication Date: 15 September 2009

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GaAs/AlAs coupled multilayer cavity structures are proposed as terahertz emission devices. Two cavity modes with an optical frequency difference in the terahertz region can be realized when two cavity layers are coupled by an intermediate distributed Bragg reflector multilayer. Interference between the enhanced light fields of the cavity modes has been demonstrated by the simultaneous injection of two cavity-mode lights using an ultrashort pulse laser. Such coupled multilayer cavity structures are promising for use as compact and room temperature operable terahertz emission devices based on difference frequency generation by the cavity-mode lights.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.66.Fd III-V semiconductors

Tailoring near-field patterns with concentrically corrugated plates

Mohammadreza F. Imani and Anthony Grbic

Appl. Phys. Lett. 95, 111107 (2009); http://dx.doi.org/10.1063/1.3224882 (3 pages) | Cited 3 times

Online Publication Date: 16 September 2009

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We present a device that can form a two-dimensional subwavelength focus along a specified near-field focal plane. The device, referred to as a corrugated near-field plate, consists of a coaxially fed aperture in a concentrically corrugated metallic surface. A procedure for designing such devices is outlined. In addition, simulation results are reported for a design that operates at around 1 GHz and forms a focus with a null-to-null beamwidth of λ/20 at a focal plane λ/15 from its surface. The effect of losses is also studied. Such devices will find use in near-field microscopy and probing systems.
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42.79.Gn Optical waveguides and couplers

Nanosecond-pulse fiber lasers mode-locked with nanotubes

E. J. R. Kelleher, J. C. Travers, Z. Sun, A. G. Rozhin, A. C. Ferrari, S. V. Popov, and J. R. Taylor

Appl. Phys. Lett. 95, 111108 (2009); http://dx.doi.org/10.1063/1.3207828 (3 pages) | Cited 43 times

Online Publication Date: 16 September 2009

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We demonstrate that mode-locking of ytterbium fiber lasers with a carbon nanotube saturable absorber can produce pulses ranging from 20 ps to 2 ns at repetition rates between 21 MHz and 177 kHz, respectively, depending on cavity length. Nonlinear polarization evolution is not responsible for mode-locking. Even in the nanosecond regime, clean single pulses are observed and the pulse train exhibits low jitter. Combined with extremely large chirp, these properties are suited for chirped-pulse amplification systems.
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42.60.Fc Modulation, tuning, and mode locking
61.46.Fg Nanotubes
42.55.Wd Fiber lasers

Erbium-doped GaN optical amplifiers operating at 1.54 μm

R. Dahal, C. Ugolini, J. Y. Lin, H. X. Jiang, and J. M. Zavada

Appl. Phys. Lett. 95, 111109 (2009); http://dx.doi.org/10.1063/1.3224203 (3 pages) | Cited 12 times

Online Publication Date: 16 September 2009

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Strip optical waveguides based on erbium (Er)-doped AlGaN/GaN:Er/AlGaN heterostructures have been fabricated and characterized in the optical communication wavelength window near 1.54 μm. The propagation loss of these waveguide amplifiers have been measured at 1.54 μm and found to be 3.5 cm−1. Moreover, the optical amplification properties of the waveguides were measured using a signal input at 1.54 μm and a broadband GaN light-emitting diode at 365 nm as pump source. A relative signal enhancement of ∼ 8 cm−1 was observed. The implications of such devices in photonic integrated circuits for optical communications are discussed.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
85.60.Jb Light-emitting devices
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.81.Dp Propagation, scattering, and losses; solitons

Polymer hydrophilicity and hydrophobicity induced by femtosecond laser direct irradiation

Z. K. Wang, H. Y. Zheng, C. P. Lim, and Y. C. Lam

Appl. Phys. Lett. 95, 111110 (2009); http://dx.doi.org/10.1063/1.3232212 (3 pages) | Cited 12 times

Online Publication Date: 17 September 2009

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Controlled modification of surface wettability of polymethyl methacrylate (PMMA) was achieved by irradiation of PMMA surface with femtosecond laser pulses at various laser fluences and focus distances. Fluences from 0.40 to 2.1 J/cm2 produced a hydrophobic surface and 2.1 to 52.7 J/cm2 (maximum investigated) produced a hydrophilic surface. Fluences less than 0.31 J/cm2 had no effect on the wettability of the raw PMMA. This change in wettability was caused dominantly by laser induced chemical structure modification and not by a change in surface roughness.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.41.+e Polymers, elastomers, and plastics
68.35.bm Polymers, organics

Transmission of doughnut light through a bull’s eye structure

Lu-Lu Wang, Xi-Feng Ren, Rui Yang, Guang-Can Guo, and Guo-Ping Guo

Appl. Phys. Lett. 95, 111111 (2009); http://dx.doi.org/10.1063/1.3231929 (3 pages) | Cited 2 times

Online Publication Date: 17 September 2009

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We experimentally investigate the extraordinary optical transmission of doughnut light through a bull’s eye structure. Since the intensity is vanished in the center of the beam, almost all the energy reaches the circular corrugations (not on the hole), and excites surface plasmons, which propagate through the hole and reradiate photons. The transmitted energy is about 32 times of the energy input on the hole area. It is also interesting that the transmitted light has a similar spatial shape with the input light even though the diameter of the hole is much smaller than the wavelength of light.
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78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Coupling of InGaN/GaN multiquantum-wells photoluminescence to surface plasmons in platinum nanocluster

Tae Su Oh (오태수), Hyun Jeong (정현), Yong Seok Lee (이용석), Jan Di Kim (김잔디), Tae Hoon Seo (서태훈), Hun Kim (김흔), Ah Hyun Park (박아현), Kang Jea Lee (이강재), and Eun-Kyung Suh (서은경)

Appl. Phys. Lett. 95, 111112 (2009); http://dx.doi.org/10.1063/1.3224176 (3 pages) | Cited 15 times

Online Publication Date: 17 September 2009

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We present the coupling of InGaN/GaN multiquantum-wells (MQWs) photoluminescence (PL) to surface plasmons (SPs) in platinum (Pt) nanoclusters (PNCs). To tune the extinction spectrum of Pt thin film through surface modification such as PNC, the thermal annealing method was employed. From conventional PL and time-resolved PL measurements, enhanced emission and faster luminescence decay time of the PNC-formed InGaN/GaN MQWs was observed with blueshifted emission behavior near the plasmon absorption band of PNC. A Purcell enhancement factor, which was calculated to describe the increase in spontaneous emission rate (Rse), revealed an approximate 2.2 times enhancement of Rse at 425 nm. We believe that these phenomena result from efficient energy transfer in PNC-formed InGaN/GaN MQWs by SPs coupling.
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78.67.De Quantum wells
78.47.jd Time resolved luminescence
73.22.Lp Collective excitations
61.72.Cc Kinetics of defect formation and annealing
78.55.Cr III-V semiconductors
73.21.Fg Quantum wells

High performance, high temperature λ ≈ 3.7 μm InGaAs/AlAs(Sb) quantum cascade lasers

J. P. Commin, D. G. Revin, S. Y. Zhang, A. B. Krysa, and J. W. Cockburn

Appl. Phys. Lett. 95, 111113 (2009); http://dx.doi.org/10.1063/1.3232219 (3 pages) | Cited 11 times

Online Publication Date: 18 September 2009

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We report the development of λ ≈ 3.7 μm strain-compensated InGaAs/AlAs(Sb) quantum cascade lasers operating up to at least 400 K with high peak power and high wall plug efficiency in pulsed regime. We present a detailed comparison of the laser characteristics for devices containing AlAs barriers in the active region with those for devices of identical design but with AlAsSb barriers throughout. The devices with AlAs barriers show significantly superior performance with peak optical power of 2.6 W at 300 K decreasing to 1 W at 400 K, and threshold current densities of 3.3 and 8.2 kA/cm2 at 300 and 400 K, respectively.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
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Experimental measurement of the total energy losses in a low pressure inductively coupled argon plasma

Young-Kwang Lee, Min-Hyong Lee, and Chin-Wook Chung

Appl. Phys. Lett. 95, 111501 (2009); http://dx.doi.org/10.1063/1.3097020 (3 pages) | Cited 2 times

Online Publication Date: 14 September 2009

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Total energy losses per electron-ion pair lost (εT) were measured experimentally in a low pressure inductively coupled argon plasma. A floating probe working at very low bias voltage ( ∼ 1 V) was used to obtain the electron temperatures and plasma densities at the plasma-sheath boundary. εT was found from a power balance equation between the absorbed power and dissipated power by electrons and ions. At 10 mTorr, the measurement shows that the measured εT ( ∼ 100 V) gradually decreased with absorbed power, and this indicates that the ionization efficiency enhances by multistep ionizations. These εT are consistent with the theoretical results.
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52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties
52.40.Kh Plasma sheaths

Role of low-frequency power in dual-frequency capacitive discharges

S. K. Ahn and H. Y. Chang

Appl. Phys. Lett. 95, 111502 (2009); http://dx.doi.org/10.1063/1.3223593 (3 pages) | Cited 9 times

Online Publication Date: 15 September 2009

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Changes in plasma characteristics depending on low-frequency power in dual-frequency capacitive discharges were found from the measurement of electrical characteristics and electron energy probability functions. It is shown that as the low-frequency (2 MHz) power increases for the fixed high-frequency (27.12 MHz) current, the ion bombardment energy, and the ion flux onto the electrode increase simultaneously. It is also shown that the coupling between the low-frequency power and the ion flux originates from change in electron heating mechanisms when varying the low-frequency power. Depending on the discharge pressure, changes in the collisional electron heating in the bulk plasma and participation of the secondary electron emission in the ionization process are observed.
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52.80.Pi High-frequency and RF discharges
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.20.Fs Electron collisions
52.70.Ds Electric and magnetic measurements
52.25.Tx Emission, absorption, and scattering of particles

Nonthermal and screening effects on the inelastic Compton scattering in Lorentzian plasmas

Hwa-Min Kim and Young-Dae Jung

Appl. Phys. Lett. 95, 111503 (2009); http://dx.doi.org/10.1063/1.3229941 (3 pages) | Cited 1 time

Online Publication Date: 15 September 2009

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The nonthermal and screening effects on the inelastic Compton scattering process are investigated in Lorentzian plasmas. The screened atomic wave functions and energies for the hydrogenic ion in Lorentzian plasmas are obtained by the Rayleigh–Ritz variational method. The transition matrix element for the inelastic Compton scattering process in Lorentzian plasmas is also obtained as a function of the spectral index and plasma parameters by the two photon-perturbation Hamiltonian. It is found that the nonthermal character of the Lorentzian plasma suppresses the inelastic Compton scattering cross section. In addition, the nonthermal effects are found to be significant for 2<κ<5, where κ is the spectral index of the Lorentzian plasma.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Tx Emission, absorption, and scattering of particles
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
32.80.Wr Other multiphoton processes

Contaminant gas removal using thin-film Ti electrode microdischarges

Scott A. Wright and Yogesh B. Gianchandani

Appl. Phys. Lett. 95, 111504 (2009); http://dx.doi.org/10.1063/1.3226679 (3 pages) | Cited 2 times

Online Publication Date: 16 September 2009

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We report a method for the selective chemisorption of oxygen and nitrogen in sealed cavities utilizing microdischarges between thin-film Ti electrodes. The method is used to remove contaminating air from both inert and organic gas environments, reducing the nitrogen and oxygen concentrations by factors of 50 and 16, respectively. A microchip-based optical emission spectroscopic sensor is used to monitor the purification. The purification improves the ability of the optical emission sensor to detect carbon by a factor of 8. The method has been tested at temperatures between 23 and 200 °C.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
81.20.Ym Purification
68.43.Mn Adsorption kinetics
52.77.-j Plasma applications
52.80.-s Electric discharges
82.80.Dx Analytical methods involving electronic spectroscopy

Self-organized vertically aligned single-crystal silicon nanostructures with controlled shape and aspect ratio by reactive plasma etching

S. Xu, I. Levchenko, S. Y. Huang, and K. Ostrikov

Appl. Phys. Lett. 95, 111505 (2009); http://dx.doi.org/10.1063/1.3232210 (3 pages) | Cited 36 times

Online Publication Date: 18 September 2009

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The formation of vertically aligned single-crystalline silicon nanostructures via “self-organized” maskless etching in Ar+H2 plasmas is studied. The shape and aspect ratio can be effectively controlled by the reactive plasma composition. In the optimum parameter space, single-crystalline pyramid-like nanostructures are produced; otherwise, nanocones and nanodots are formed. This generic nanostructure formation approach does not involve any external material deposition. It is based on a concurrent sputtering, etching, hydrogen termination, and atom/radical redeposition and can be applied to other nanomaterials.
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81.16.-c Methods of micro- and nanofabrication and processing
81.07.-b Nanoscale materials and structures: fabrication and characterization
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.15.Cd Deposition by sputtering
61.46.-w Structure of nanoscale materials
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Formation of creases on the surfaces of elastomers and gels

Wei Hong, Xuanhe Zhao, and Zhigang Suo

Appl. Phys. Lett. 95, 111901 (2009); http://dx.doi.org/10.1063/1.3211917 (3 pages) | Cited 28 times

Online Publication Date: 14 September 2009

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When a block of an elastomer is bent, the compressed surface may form a crease. The critical strain for creasing measured experimentally is known to disagree with that predicted by linear perturbation analysis. This paper calculates the critical strain by comparing the elastic energy in a creased body and that in a smooth body. This difference in energy is expressed by a scaling relation. Critical conditions for creasing are determined for elastomers subject to general loads and gels swelling under constraint. The theoretical results are compared with existing experimental observations.
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82.70.Gg Gels and sols
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Interband transitions of InAsxSb1−x alloy films

T. J. Kim, J. J. Yoon, S. Y. Hwang, D. E. Aspnes, Y. D. Kim, H. J. Kim, Y. C. Chang, and J. D. Song

Appl. Phys. Lett. 95, 111902 (2009); http://dx.doi.org/10.1063/1.3216056 (3 pages) | Cited 6 times

Online Publication Date: 14 September 2009

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We report pseudodielectric-function spectra from 1.5 to 6.0 eV of InAsxSb1−x ternary alloys obtained by spectroscopic ellipsometry. Energies of the E1, E1+Δ1, E0′, E0′+Δ0′, E2, E2+Δ2, E2′, E2′+Δ2, and E1′ critical points (CPs) were obtained from numerically calculated second derivatives, and identifications established by band-structure calculations using the linear augmented Slater-type orbital method. The E2, E2+Δ2, E2′, and E2′+Δ2 CP structures cross with increasing As-composition. Two saddle-point transitions, Δ5cu-Δ5vu and Δ5cl−Δ5vu, are found for InSb.
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81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
68.55.ag Semiconductors
71.20.Nr Semiconductor compounds
71.15.-m Methods of electronic structure calculations
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Optical and microstructural studies of InGaN/GaN quantum dot ensembles

S. C. Davies, D. J. Mowbray, F. Ranalli, P. J. Parbrook, Q. Wang, T. Wang, B. S. Yea, B. J. Sherliker, M. P. Halsall, R. J. Kashtiban, and U. Bangert

Appl. Phys. Lett. 95, 111903 (2009); http://dx.doi.org/10.1063/1.3226645 (3 pages) | Cited 4 times

Online Publication Date: 14 September 2009

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An optical and structural study of InGaN/GaN quantum dots (QDs) is reported. With increasing InGaN deposition time, the dominant emission changes from wetting layer (WL) to QDs, and a strong redshift of the emission occurs. Emission from localized WL states is observed, with a density and nature very different to that due to the QDs. Structural measurements reveal a disordered WL, consistent with the form of the WL photoluminescence excitation spectra.
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78.67.Hc Quantum dots
81.07.Ta Quantum dots
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
73.21.La Quantum dots

Resonance transmission or absorption in deep gratings explained by magnetic polaritons

L. P. Wang and Z. M. Zhang

Appl. Phys. Lett. 95, 111904 (2009); http://dx.doi.org/10.1063/1.3226661 (3 pages) | Cited 17 times

Online Publication Date: 14 September 2009

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Resonance transmission or absorption has been observed in metallic deep gratings and previously characterized as coupled surface plasmon polaritons or Fabry–Pérot-like resonances. This letter provides a quantitative explanation of this phenomenon by means of localized magnetic polaritons. Rigorous coupled-wave analysis is used to predict the spectral transmittance and absorptance of subwavelength gratings. The resonance condition is compared with that predicted by the LC circuit model. Some geometric effects that cannot be explained by previous models can be well understood in terms of magnetic polaritons. The insight gained from this study may facilitate future design and applications of subwavelength periodic structures.
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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)

Preferential oxidation of stacking faults in epitaxial off-axis (111) 3C-SiC films

A. Severino, M. Camarda, S. Scalese, P. Fiorenza, S. Di Franco, C. Bongiorno, A. La Magna, and F. La Via

Appl. Phys. Lett. 95, 111905 (2009); http://dx.doi.org/10.1063/1.3227886 (3 pages) | Cited 3 times

Online Publication Date: 14 September 2009

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The effect of thermal dry oxidation on an off-axis (111) 3C-SiC film have been studied in order to subsequently realize a metal-oxide-semiconductor structure. A morphological characterization of the SiO2 surface, grown at 1200 °C in an O2 flux, pointed out some defect-related effects as a consequence of the preferential oxidation of stacking faults over the (111) 3C-SiC surface. Scanning electron microscopy and atomic force microscopy confirmed such a hypothesis. Stacking faults are seen as promoters of a local polarity inversion in (111) 3C-SiC, from Si- to C-terminated surface, resulting in a higher oxidation rate as compared to defect-free zones.
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61.72.Nn Stacking faults and other planar or extended defects
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)
81.65.Mq Oxidation
68.55.ag Semiconductors

Thermal stability of epitaxial Fe films on GaN(0001)

Cunxu Gao, Oliver Brandt, Hans-Peter Schönherr, Uwe Jahn, Jens Herfort, and Bernd Jenichen

Appl. Phys. Lett. 95, 111906 (2009); http://dx.doi.org/10.1063/1.3230004 (3 pages) | Cited 7 times

Online Publication Date: 14 September 2009

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Epitaxial Fe films are grown on GaN(0001) by molecular beam epitaxy at 50 °C. Several samples of one Fe/GaN structure are subjected to rapid thermal annealing from 300 to 950 °C. Using a variety of experimental techniques, we examine the impact of this annealing step upon the morphological, structural, and magnetic properties of these samples. The results demonstrate that the material system Fe/GaN is thermally stable up to a temperature of 700 °C.
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68.60.Dv Thermal stability; thermal effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.70.Ak Magnetic properties of monolayers and thin films

Extremely anisotropic, direction-dependent elastic grain interaction: The case of ultrathin films

U. Welzel, A. Kumar, and E. J. Mittemeijer

Appl. Phys. Lett. 95, 111907 (2009); http://dx.doi.org/10.1063/1.3224904 (3 pages) | Cited 8 times

Online Publication Date: 15 September 2009

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The elastic grain interaction in a 50-nm-thick Pd thin film sputter deposited on a single-crystalline Si substrate has been investigated employing x-ray diffraction residual stress analysis. The occurrence of pronouncedly nonlinear sin2 ψ-plots (i.e., plots of the lattice strain for a particular hkl reflection versus the squared sine of the inclination angle of the diffraction vector with respect to the surface normal ψ) in diffraction stress analysis for the 200 and 222 reflections revealed anisotropic grain interaction of severity not observed before near free surfaces. Application of a direction-dependent elastic grain-interaction model showed that the grain interaction perpendicular to the surface is of Reuss character, whereas the in-plane grain interaction is of Voigt character.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
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