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5 Sep 2005

Volume 87, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 101107 (2005); http://dx.doi.org/10.1063/1.2039987 (3 pages)

A. David, C. Meier, R. Sharma, F. S. Diana, S. P. DenBaars, E. Hu, S. Nakamura, C. Weisbuch, and H. Benisty
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Miniaturized injection-locked laser using microelectromechanical systems technology

A. Q. Liu, X. M. Zhang, H. Cai, D. Y. Tang, and C. Lu

Appl. Phys. Lett. 87, 101101 (2005); http://dx.doi.org/10.1063/1.2035321 (3 pages) | Cited 4 times

Online Publication Date: 29 August 2005

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This letter reports a miniaturized injection-locked laser (ILL) using the microelectromechanical systems (MEMS) technology. The device is formed by the integration of a MEMS grated-tuned laser and a Fabry–Perot multimode laser within dimensions of 3 mm×2 mm×0.6 mm. A movable prism serves for both active alignment and optical isolation. Single injection and multiple injections to the slave laser are both tested, it has achieved a side mode suppression ratio of 55 dB, a range of fully locked state of 0.16 nm and a rate of all optical switching at 100 MHz. Some observed phenomena such as the wave mixing and detuning hysteresis are explained qualitatively. The miniaturization may help pave the way for the ILLs to the emerging applications such as all optical networks, coherent communications and portable atomic clocks.
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42.60.Fc Modulation, tuning, and mode locking
42.82.-m Integrated optics
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Evanescent light scattering with magnetic colloids

V. Blickle, D. Babič, and C. Bechinger

Appl. Phys. Lett. 87, 101102 (2005); http://dx.doi.org/10.1063/1.2035888 (3 pages) | Cited 11 times

Online Publication Date: 29 August 2005

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We measure magnetic interactions between paramagnetic colloidal beads and an external magnetic field by using total internal reflection microscopy (TIRM). Our results demonstrate that TIRM can be applied to absorptive paramagnetic probe particles and thus extends the range of interaction types which can be addressed with this method. With our setup, we can detect magnetic forces on single superparamagnetic particle ranging from about 10 to 600 fN.
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07.60.Pb Conventional optical microscopes
82.70.Dd Colloids
75.50.Tt Fine-particle systems; nanocrystalline materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
75.30.Cr Saturation moments and magnetic susceptibilities
75.20.-g Diamagnetism, paramagnetism, and superparamagnetism

Defocused imaging of quantum-dot angular distribution of radiation

Digambara Patra, Ingo Gregor, Jörg Enderlein, and Markus Sauer

Appl. Phys. Lett. 87, 101103 (2005); http://dx.doi.org/10.1063/1.2037194 (3 pages) | Cited 13 times

Online Publication Date: 29 August 2005

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We have applied defocused imaging of single fluorescent quantum dots to study the angular distribution of their emission. It is found that quantum dots exhibit an angular distribution best described by a superposition of emission of three perpendicular dipoles. A theory of the defocused images of such emitters is presented and compared with the measurements. Furthermore, it is shown that standard fluorescence anisotropy measurements are not able to uncover such complex emission behavior.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors

Clarinet laser: Semiconductor laser design for high-brightness applications

Luis Borruel, Ignacio Esquivias, Pablo Moreno, Michel Krakowski, Sophie Charlotte Auzanneau, Michel Calligaro, Olivier Parillaud, Michel Lecomte, Slawomir Sujecki, Jim Wykes, and Eric C. Larkins

Appl. Phys. Lett. 87, 101104 (2005); http://dx.doi.org/10.1063/1.2037854 (3 pages) | Cited 3 times

Online Publication Date: 29 August 2005

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High-power and high-brightness continuous-wave (cw) operation has been achieved with an optimized design of fully index-guided tapered laser emitting at 975 nm. The device achieves simultaneously negligible astigmatism and stable low divergence in the lateral axis at high-power operation. By using a quasi-three-dimensional simulation model, the different mechanisms modifying the slow axis beam divergence at high power have been carefully balanced in the clarinet design, easing the use of collective optics in laser bars. The devices consist of a relatively long ridge-waveguide filtering section coupled to a relatively short tapered section with an aperture angle of 2°. InGaAs/InGaAsP lasers were fabricated with this design, demonstrating an output power of 1 W cw, a maximum wall-plug efficiency of 50%, negligible astigmatism, a slow-axis far-field divergence (measured at 1/e2) of 5° at 1 W and beam quality parameter M2<3.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Annealing effects on the loss and birefringence of silicon oxynitride rectangular optical waveguides

Ailing Zhang, Kam Tai Chan, M. S. Demokan, Victor W. C. Chan, Philip C. H. Chan, and Andy H. P. Chan

Appl. Phys. Lett. 87, 101105 (2005); http://dx.doi.org/10.1063/1.2037856 (3 pages) | Cited 3 times

Online Publication Date: 29 August 2005

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Silicon oxynitride rectangular optical waveguides have been fabricated by plasma-enhanced chemical vapor deposition and dry etching. The propagation loss and polarization dependent loss in as-grown samples show a substantial reduction after the samples have been annealed. Birefringence measurements before and after annealing on waveguides of different widths suggest that the waveguide modal birefringence is strongly affected by both waveguide geometry and stress in the material. Hence, the modal birefringence can be minimized by designing the appropriate waveguide geometry to compensate for any stress effects.
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78.20.Fm Birefringence
81.40.Gh Other heat and thermomechanical treatments
42.82.Et Waveguides, couplers, and arrays

Enhanced second- and third-harmonic generation and induced photoluminescence in a two-dimensional GaN photonic crystal

Dominique Coquillat, Gabriele Vecchi, Carlo Comaschi, Andrea Marco Malvezzi, Jérémi Torres, and Marine Le Vassor d’Yerville

Appl. Phys. Lett. 87, 101106 (2005); http://dx.doi.org/10.1063/1.2037849 (3 pages) | Cited 12 times

Online Publication Date: 29 August 2005

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We observed visible second-harmonic and ultraviolet third-harmonic fields generated in reflection from the surface of a two-dimensional triangular GaN/sapphire photonic crystal. When the pump radiation resonates with a photonic mode, enhancement factors as high as 250 and 3500 occurred for the second- and third-harmonic signals, respectively, as compared to the unpatterned GaN slab. The very large increase of third-harmonic field, with a photon energy exceeding that of the electronic band gap, was used as an efficient mechanism to induce GaN photoluminescence.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
42.70.Qs Photonic bandgap materials

Photonic bands in two-dimensionally patterned multimode GaN waveguides for light extraction

A. David, C. Meier, R. Sharma, F. S. Diana, S. P. DenBaars, E. Hu, S. Nakamura, C. Weisbuch, and H. Benisty

Appl. Phys. Lett. 87, 101107 (2005); http://dx.doi.org/10.1063/1.2039987 (3 pages) | Cited 66 times

Online Publication Date: 30 August 2005

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We observe experimentally by photoluminescence the band structure and specific emission properties of an in-plane, light-diffracting photonic crystal formed onto a multimode gallium nitride waveguide. Clear-cut two-dimensional photonic crystal effects are reported. Comparison with modeling results in identification of the band structure, provides insight into the light diffraction mechanism and points out design issues for enhancement of the extraction efficiency.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
78.55.Cr III-V semiconductors

Hindering effect of the core-cladding interface on the progression of the second-order nonlinearity layer in thermally poled optical fibers

Honglin An and Simon Fleming

Appl. Phys. Lett. 87, 101108 (2005); http://dx.doi.org/10.1063/1.2040007 (3 pages) | Cited 13 times

Online Publication Date: 30 August 2005

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The spatial distribution of the second-order nonlinearity layer induced in thermally poled Ge-doped optical fibers has been investigated with second-harmonic microscopy. It was found that the core-cladding interface acts as an insurmountable barrier to the nonlinear layer at lower poling voltages. At higher poling voltages (>2.5 kV), the nonlinear layer can partially overcome this barrier and reach the fiber core, in which it is isolated from the rest of the nonlinear layer in the cladding.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.81.Wg Other fiber-optical devices

Scanning near field infrared radiometry for thermal imaging of infrared emitters with subwavelength resolution

Sharon Sade, Lev Nagli, and Abraham Katzir

Appl. Phys. Lett. 87, 101109 (2005); http://dx.doi.org/10.1063/1.2040008 (3 pages) | Cited 6 times

Online Publication Date: 30 August 2005

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We have developed a scanning near field microscopy system based on tapered silver halide fibers which had tips of diameters smaller than a wavelength. The system was calibrated for temperature measurement and then determined the dependence of the minimum resolvable temperature difference and that of the spatial resolution on the tip diameter. This system was used for measurement of the temperature distribution of miniature infrared (IR) emitters. As an example we used a tapered fiber of tip diameter 5 μm to carry out infrared emission measurements on a miniature IR emitter of dimensions 30 μm×30 μm in the spectral range 8.5–13.5 μm. These measurements made it possible to obtain the thermal image of the element with a subwavelength resolution. Such a system would be useful for measuring the temperature distribution on a scene simulator projector or on an integrated circuit.
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07.79.Fc Near-field scanning optical microscopes
07.60.Dq Photometers, radiometers, and colorimeters
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.20.-n Thermal instruments and apparatus
42.81.Wg Other fiber-optical devices

Tuning of transmission peaks in two-dimensional semiconductor-based photonic crystals with line defects of cylinders

J. Manzanares-Martinez, F. Ramos-Mendieta, and P. Halevi

Appl. Phys. Lett. 87, 101110 (2005); http://dx.doi.org/10.1063/1.2042633 (3 pages) | Cited 2 times

Online Publication Date: 30 August 2005

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We have studied transmission of light through two-dimensional photonic crystals of finite width, with the radii of the cylinders in the middle row altered in comparison to the host cylinders. Either the cylinder or the host material (for cylindrical holes) is a semiconductor, modeled by a realistic dielectric constant that takes into account free electrons, free holes, and lattice vibrations, as well as the dissipation related to each of these contributions. We considered both an intrinsic, narrow-gap semiconductor (InSb) and an extrinsic elemental semiconductor (Si). Our simulations of the transmission peak due to the line defects demonstrate that it can be substantially tuned by varying the temperature (for InSb) or the density of injected charge (for Si). The downside is absorption, which rapidly increases with temperature and impurity density. An optimized structure is suggested for experimental purposes.
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42.70.Qs Photonic bandgap materials
78.20.-e Optical properties of bulk materials and thin films

Superresolution and corrections to the diffusion approximation in optical tomography

George Y. Panasyuk, Vadim A. Markel, and John C. Schotland

Appl. Phys. Lett. 87, 101111 (2005); http://dx.doi.org/10.1063/1.2040010 (3 pages) | Cited 4 times

Online Publication Date: 1 September 2005

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We demonstrate that the spatial resolution of images in optical tomography is not limited to the fundamental length scale of one transport mean free path. This result is facilitated by the introduction of novel corrections to the standard integral equations of scattering theory within the diffusion approximation to the radiative transport equation.
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87.63.L- Visual imaging
87.57.C- Image quality
42.30.Wb Image reconstruction; tomography
87.10.-e General theory and mathematical aspects

Negative refraction of left-handed behavior in porous alumina with infiltrated silver at an optical wavelength

Xianyu Ao and Sailing He

Appl. Phys. Lett. 87, 101112 (2005); http://dx.doi.org/10.1063/1.2042548 (3 pages) | Cited 14 times

Online Publication Date: 2 September 2005

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Porous alumina with infiltrated silver is suggested to achieve a negative refraction of left-handed behavior at an optical wavelength. Numerical simulations of subwavelength focusing by a slab lens are performed for both H and E polarizations. Beam refraction by a wedge is also simulated to verify the left-handed behavior.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

All-optical spin-dependent polarization switching in Bragg-spaced quantum well structures

W. J. Johnston, M. Yildirim, J. P. Prineas, Arthur L. Smirl, H. M. Gibbs, and G. Khitrova

Appl. Phys. Lett. 87, 101113 (2005); http://dx.doi.org/10.1063/1.2042550 (3 pages) | Cited 19 times

Online Publication Date: 2 September 2005

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All-optical polarization switching is demonstrated in a resonant photonic band-gap structure consisting of Bragg-spaced quantum wells (BSQWs). The switch takes advantage of the large spin-dependent optical nonlinearities and the ultrafast recovery present in BSQWs to produce large throughputs (greater than 40%), high contrast ratios (greater than 40 dB), and large optical bandwidths ( ∼ 0.6 THz), where both switching time and sample recovery time are control-pulse-width limited.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.70.Qs Photonic bandgap materials
78.67.De Quantum wells
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Temperature dependence of terahertz optical transitions from boron and phosphorus dopant impurities in silicon

S. A. Lynch, P. Townsend, G. Matmon, D. J. Paul, M. Bain, H. S. Gamble, J. Zhang, Z. Ikonic, R. W. Kelsall, and P. Harrison

Appl. Phys. Lett. 87, 101114 (2005); http://dx.doi.org/10.1063/1.2042544 (3 pages) | Cited 12 times

Online Publication Date: 2 September 2005

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There has been considerable interest in using impurity dopants in silicon, such as boron and phosphorus, since it was demonstrated that such materials can show emission in the THz region of the electromagnetic spectrum. The measured temperature dependence of these transitions in this letter shows that the most optimistic maximum operating temperature of such an impurity-based laser is 90 K. In a real device with current flowing and associated Joule heating, the actual operating range is likely to be much narrower and it is therefore unlikely that such a device would have a maximum operating temperature above 40 K.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
78.70.Gq Microwave and radio-frequency interactions
61.72.uf Ge and Si
78.60.Fi Electroluminescence
42.70.Hj Laser materials
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Free-volume evolution and its temperature dependence during rolling of Cu60Zr20Ti20 bulk metallic glass

Q. P. Cao, J. F. Li, Y. H. Zhou, A. Horsewell, and J. Z. Jiang

Appl. Phys. Lett. 87, 101901 (2005); http://dx.doi.org/10.1063/1.2037858 (3 pages) | Cited 14 times

Online Publication Date: 29 August 2005

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The free-volume evolution during rolling Cu60Zr20Ti20 bulk metallic glass at room and cryogenic temperatures has been investigated by differential scanning calorimetry. When the specimen is rolled at cryogenic temperature, the free-volume content increases as the rolling proceeds first, and then saturates accompanied by the occurrence of phase separation as the thickness reduction exceeds 89%. If the rolling is performed at room temperature, although the free-volume content also rises in the earlier stage, it tends to decrease rather than saturate when the thickness reduction exceeds 87%, accompanied by partial crystallization. Phase separation does not change the annihilation rate of free volume, while the appearance of crystal/amorphous boundaries can enhance the annihilation.
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81.05.Kf Glasses (including metallic glasses)
61.43.Fs Glasses
64.70.K- Solid-solid transitions
64.75.-g Phase equilibria
81.40.Gh Other heat and thermomechanical treatments

Compact strain-sensitive flexible photonic crystals for sensors

Otto L. J. Pursiainen, Jeremy J. Baumberg, Kevin Ryan, Josef Bauer, Holger Winkler, Benjamin Viel, and Tilmann Ruhl

Appl. Phys. Lett. 87, 101902 (2005); http://dx.doi.org/10.1063/1.2032590 (3 pages) | Cited 22 times

Online Publication Date: 30 August 2005

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A promising fabrication route to produce absorbing flexible photonic crystals is presented, which exploits self-assembly during the shear processing of multi-shelled polymer spheres. When absorbing material is incorporated in the interstitial space surrounding high-refractive-index spheres, a dramatic enhancement in the transmission edge on the short-wavelength side of the band gap is observed. This effect originates from the shifting optical field spatial distribution as the incident wavelength is tuned around the band gap, and results in a contrast up to 100 times better than similar but nonabsorbing photonic crystals. An order-of-magnitude improvement in strain sensitivity is shown, suggesting the use of these thin films in photonic sensors.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.70.Qs Photonic bandgap materials
81.16.Dn Self-assembly

Optical properties of Zn1−xCoxO thin films grown on Al2O3 (0001) substrates

K. Samanta, P. Bhattacharya, and R. S. Katiyar

Appl. Phys. Lett. 87, 101903 (2005); http://dx.doi.org/10.1063/1.2039995 (3 pages) | Cited 21 times

Online Publication Date: 30 August 2005

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Thin films of Zn1−xCoxO (x = 1–15%) were grown on an Al2O3 (0001) substrate by pulsed laser deposition and characterized by investigating their photoluminescence (PL) and other optical properties. The films were highly (0001) oriented without any impurity phases as observed in x-ray diffraction. The optical transmittance spectra showed that the band edge of Zn1−xCoxO was decreased with increase of Co concentration along with a subbandgap absorption in the range of 1.8 to 2.2 eV. The near band-edge PL spectrum of ZnO thin films at 77 K showed a strong peak of donor bound exciton at 3.307 eV along with the free excitons. However, the PL spectra for free excitons of the Zn1−xCoxO films at 77 K did not show any significant redshift due to Co incorporation.
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75.50.Pp Magnetic semiconductors
78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Investigation of Ostwald ripening in nitrogen doped Czochralski silicon

G. Kissinger, A. Huber, K. Nakai, O. Lysytskij, T. Müller, H. Richter, and W. von Ammon

Appl. Phys. Lett. 87, 101904 (2005); http://dx.doi.org/10.1063/1.2041835 (3 pages) | Cited 5 times

Online Publication Date: 30 August 2005

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Infrared laser scattering tomography was used to investigate Ostwald ripening in nitrogen-doped Czochralski silicon. Contrary to previous assumptions about oxide precipitation in nitrogen-doped silicon, the results clearly demonstrate that Ostwald ripening takes place during annealing of N-doped silicon wafers at 1000 °C and 1100 °C. The higher the nitrogen doping and the higher the temperature the faster the oxide precipitates grow and the faster they split into two fractions. One fraction is growing at the expense of the other.
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61.72.Cc Kinetics of defect formation and annealing
81.10.Fq Growth from melts; zone melting and refining
81.30.Mh Solid-phase precipitation
61.72.uf Ge and Si

Tuning the hole injection barrier height at organic/metal interfaces with (sub-) monolayers of electron acceptor molecules

Norbert Koch, Steffen Duhm, Jürgen P. Rabe, Stephan Rentenberger, Robert L. Johnson, Jürgen Klankermayer, and Frank Schreiber

Appl. Phys. Lett. 87, 101905 (2005); http://dx.doi.org/10.1063/1.2041838 (3 pages) | Cited 17 times

Online Publication Date: 30 August 2005

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We demonstrate that the insertion of an electron acceptor molecular (sub-) monolayer at organic/metal interfaces enables systematic tuning of the hole injection barrier height (Δh). Ultraviolet photoemission spectroscopy results show that Δh for α-sexithiophene thin films deposited on Ag(111) can be reduced from 1.3 to 1.0 eV by introducing a chemisorbed monolayer of 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) on the metal surface. Fine-tuning of Δh within the interval of 0.3 eV is achieved by using TCAQ coverages in the submonolayer range.
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68.43.Mn Adsorption kinetics
79.60.Dp Adsorbed layers and thin films
78.66.Qn Polymers; organic compounds
79.60.Fr Polymers; organic compounds
78.40.Me Organic compounds and polymers

Growth of highly resistive BiMnO3 films

W. Eerenstein, F. D. Morrison, J. F. Scott, and N. D. Mathur

Appl. Phys. Lett. 87, 101906 (2005); http://dx.doi.org/10.1063/1.2039988 (3 pages) | Cited 36 times

Online Publication Date: 31 August 2005

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BiMnO3 (010) films (100 nm) were grown epitaxially on SrTiO3 (001) and 0.2 at. % Nb-doped SrTiO3 (001) substrates using pulsed laser deposition. The microstructure, electrical, and magnetic properties, and indeed the formation of the correct phase, were found to be very sensitive to growth parameters. This optimization has resulted in highly resistive BiMnO3 films and thus enabled room-temperature dielectric measurements: We obtained a resistivity of 5×107 Ω cm, and an effective (i.e. thickness dependent) dielectric constant of 1400. These findings pave the way for magnetoelectric measurements and further optimization.
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77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
77.22.Ch Permittivity (dielectric function)
75.80.+q Magnetomechanical effects, magnetostriction

Transient quantum yield evolution of organic light-emitting devices submitted to low-level excitation: A photon counting investigation

Abdellatif Gherabi, Normand Beaudoin, and Serge Gauvin

Appl. Phys. Lett. 87, 101907 (2005); http://dx.doi.org/10.1063/1.2041817 (3 pages) | Cited 2 times

Online Publication Date: 1 September 2005

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The continuously growing interest in organic light-emitting devices (OLEDs) requires exhaustive experimental investigations to validate the theoretical models. Here, we propose a solution to the problem of the measurement of quantum yield when devices are probed with low-level signals that minimize perturbations. Our approach is based on the wave form recovery methodology. Under pulsed excitation, our results reveal a considerable increase of the quantum yield throughout the excitation pulse. This enhancement persists for 10 ms. The procedure has the capability to reveal features of the transient behaviors and aging that are blurred when OLEDs are operated with normal driving electric field and current density. This approach may provide a complementary way to a thorough investigation of the electronic processes and aging mechanisms of OLEDs.
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85.60.Jb Light-emitting devices

Growth of single crystal ZnO nanorods on GaN using an aqueous solution method

H. Q. Le, S. J. Chua, Y. W. Koh, K. P. Loh, Z. Chen, C. V. Thompson, and E. A. Fitzgerald

Appl. Phys. Lett. 87, 101908 (2005); http://dx.doi.org/10.1063/1.2041833 (3 pages) | Cited 30 times

Online Publication Date: 1 September 2005

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Uniformly distributed ZnO nanorods with diameter 80–120 nm and 2 μm long have been grown at low temperatures on gallium nitride (GaN) by using the inexpensive aqueous solution method. The formation of the ZnO nanorods and the growth parameters are controlled by reactant concentration, temperature and pH. No catalyst is required. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) studies show that the ZnO nanorods are single crystals and they grow along the c axis of the crystal plane. The room temperature photoluminescence (PL) measurements have shown ultraviolet peaks at 388 nm with high intensity, which are comparable to those found in high quality ZnO films. The mechanism of the nanorod growth in the aqueous solution is also proposed.
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78.30.Fs III-V and II-VI semiconductors
81.05.Dz II-VI semiconductors
81.07.−b
81.10.Dn Growth from solutions

Crystal structure of the high-temperature paraelectric phase in barium titanate BaTi2O5

Masatomo Yashima, Rong Tu, Takashi Goto, and Hisanori Yamane

Appl. Phys. Lett. 87, 101909 (2005); http://dx.doi.org/10.1063/1.2042636 (3 pages) | Cited 13 times

Online Publication Date: 1 September 2005

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Crystal structure of a ferroelectric barium titanate BaTi2O5 was investigated by the Rietveld analysis of neutron powder diffraction data measured at 706 °C. The crystal structure of BaTi2O5 at 706 °C was refined assuming the centrosymmetric monoclinic A2/m space group. The crystal structures of the high-temperature A2/m and low-temperature A2 phases are similar. The displacement of atoms along the b axis is accompanied by the paraelectric A2/m to ferroelectric A2 phase transformation. The A2/m‐A2 transition is not reconstructive but displacive.
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61.66.Fn Inorganic compounds
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
64.70.K- Solid-solid transitions
77.80.B- Phase transitions and Curie point

Studies of the annihilation mechanism of threading dislocation in AlN films grown on vicinal sapphire (0001) substrates using transmission electron microscopy

X. Q. Shen, H. Okumura, and H. Matsuhata

Appl. Phys. Lett. 87, 101910 (2005); http://dx.doi.org/10.1063/1.2042533 (3 pages) | Cited 9 times

Online Publication Date: 2 September 2005

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Annihilation phenomena of threading dislocations (TDs) in AlN films grown on vicinal sapphire (0001) substrates are investigated by transmission electron microscopy. It is found that the dislocation density is greatly reduced when the AlN is grown on a 2°-cut vicinal sapphire substrate. Two different types of the annihilation mechanisms of TDs were observed: (i) The coalescence of two TDs with opposite Burger’s vectors b to form a dislocation loop with one b, and (ii) the formation of one TD from the combination of two TDs with different Burger’s vectors, such as [math2math0]+[2mathmath0]→[11math0]. These interactions between TDs are caused by the formation of inclined TDs (ITDs), where ITDs are locked and dragged by the macrosteps on the surface during the growth.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)

Surface morphology of annealed titanium /silicon bilayer in the presence of oxygen

S. Ilango, G. Raghavan, M. Kamruddin, Santanu Bera, and A. K. Tyagi

Appl. Phys. Lett. 87, 101911 (2005); http://dx.doi.org/10.1063/1.2042537 (3 pages) | Cited 3 times

Online Publication Date: 2 September 2005

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The evolution of surface morphology and chemical composition of vacuum-annealed titanium films deposited on Si(111) substrate with native oxide is investigated. We show that changes in topography and chemical composition of the surface are related to the simultaneous transport of Si and oxygen. The elucidation of this process is done through a combined use of atomic force microscopy, scanning spreading resistance imaging, x-ray photoelectron spectroscopy, and secondary ion mass spectrometry depth profiling. Coalescence of TiO2 columnar grains formed on the silicide surface results in the coarsening of the surface. Variations in root-mean-square roughness of the surface oxide in the presence of the silicide is compared with that of pure titanium oxide for similar heat-treatment conditions.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
79.60.Dp Adsorbed layers and thin films
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.40.Gh Other heat and thermomechanical treatments
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