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14 Jul 2003

Volume 83, Issue 2, pp. 207-403

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Appl. Phys. Lett. 83, 225 (2003); http://dx.doi.org/10.1063/1.1591241 (3 pages)

A. Borowiec, D. M. Bruce, Daniel T. Cassidy, and H. K. Haugen
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Reflective thermal lensing and optical measurement of thermal diffusivity in liquids

Daniel Comeau, Alain Haché, and Noureddine Melikechi

Appl. Phys. Lett. 83, 246 (2003); http://dx.doi.org/10.1063/1.1589199 (3 pages) | Cited 11 times

Online Publication Date: 8 July 2003

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Using a pump-probe laser technique, we analyze the relaxation dynamics of a thermal lens generated at the surface of metal films deposited on a glass substrate. When the film is in contact with a liquid and the film is periodically heated with an optical source, the dynamics of the thermal lens is found to be closely related to the thermal properties of its environment. As a result, reflective thermal lensing can be used to measure the thermal diffusivity of a variety of liquids placed in contact with the film to an accuracy better than 2%. Experimental results point to applications to the study of transient effects in fluids and immiscible liquids, and detection of trace of contaminants in solvents. © 2003 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
66.25.+g Thermal conduction in nonmetallic liquids
07.60.-j Optical instruments and equipment

Nanosecond time-resolved Raman spectroscopy on phase transition of polytetrafluoroethylene under laser-driven shock compression

H. Nagao, A. Matsuda, K. G. Nakamura, and K. Kondo

Appl. Phys. Lett. 83, 249 (2003); http://dx.doi.org/10.1063/1.1590742 (2 pages) | Cited 13 times

Online Publication Date: 8 July 2003

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Nanosecond time-resolved Raman spectroscopy is performed on polytetrafluoroethylene (PTFE) under laser shock compression at approximately 1 GPa. Blueshifts (8 cm−1) of a C–C stretching and redshifts (−8 cm−1) of a CF2 twisting in Raman spectrum due to a high-pressure phase (phase III) are observed. High-pressure phase transition to phase III of PTFE is suggested to occur within 10 ns. © 2003 American Institute of Physics.
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78.30.Jw Organic compounds, polymers
78.47.-p Spectroscopy of solid state dynamics
64.70.K- Solid-solid transitions
62.50.-p High-pressure effects in solids and liquids
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Pv Polymers, organic compounds

Effects of film polarities on InN growth by molecular-beam epitaxy

K. Xu and A. Yoshikawa

Appl. Phys. Lett. 83, 251 (2003); http://dx.doi.org/10.1063/1.1592309 (3 pages) | Cited 95 times

Online Publication Date: 8 July 2003

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Effects of the film polarity on InN growth were investigated in molecular-beam epitaxy (MBE). It was found that N-polarity InN could be grown at higher temperatures than In-polarity one. For the In-polarity films, which were grown on Ga-polar GaN template, the highest growth temperature was limited below 500 °C, and the surface morphology and crystal quality tended to be poor mainly because of the tolerated low growth temperature. While for the N-polarity InN films, which were grown on MBE-grown N-polar GaN, the growth temperature could be as high as 600 °C. The step-flow-like growth morphology was achieved for the InN films grown with N polarity at 580 °C. The resulting full widths of half maximum of x-ray rocking curve around InN (002) and (102) reflections were about 200–250 and 950–1100 arc sec, respectively. The photoluminescence of the InN films peaked at 0.697 eV. The recording Hall mobility of InN film grown in N polarity is 1400 cm2/V s with a background carrier concentration of 1.56×1018 cm−3 at room temperature. For both-polarity films, we found N-rich condition was necessary for the stable InN growth. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Optical properties of annealed CdTe self-assembled quantum dots

S. Mackowski, L. M. Smith, H. E. Jackson, W. Heiss, J. Kossut, and G. Karczewski

Appl. Phys. Lett. 83, 254 (2003); http://dx.doi.org/10.1063/1.1591239 (3 pages) | Cited 19 times

Online Publication Date: 8 July 2003

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We report on the influence of postgrowth thermal annealing on the optical properties of CdTe/ZnTe self-assembled quantum dots (SAQDs). Ultrasharp emission lines in the micro-photoluminescence spectra demonstrate the continued presence of quantum dots (QDs) after annealing. Upon annealing, the emission from CdTe QDs shifts toward higher energies with a narrowing of the photoluminescence line of QDs ensemble. In addition, the decay time of the excitonic recombination decreases from 300 ps to 200 ps. These results indicate that interdiffusion of Zn and Cd into and out of the QDs leads to an increase of the average dot size and simultaneously a decrease in the confining potentials of the QD. The absence of a wetting layer makes the II–VI CdTe SAQDs much more sensitive to the thermal treatment than the III–V InAs-based dots. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
61.72.Cc Kinetics of defect formation and annealing
73.21.La Quantum dots
78.55.Et II-VI semiconductors
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Shape memory effect in nanoindentation of nickel–titanium thin films

G. A. Shaw, D. S. Stone, A. D. Johnson, A. B. Ellis, and W. C. Crone

Appl. Phys. Lett. 83, 257 (2003); http://dx.doi.org/10.1063/1.1591235 (3 pages) | Cited 18 times

Online Publication Date: 8 July 2003

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In this study, a series of nanoindentations was made on NiTi shape memory alloy thin films at millinewton loads with a Berkovich indenter. Mapping of the indentation topography using atomic force microscopy reveals direct evidence that the thermally induced martensitic transformation of these films allows for partial indent recovery on the nanoscale. Indeed, recovery is nearly complete at indentation depths of less than 100 nm. A hemispherical cavity model is presented to predict an upper limit to shape memory recovery of sharp indentations. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.Qp Friction, tribology, and hardness
62.20.F- Deformation and plasticity
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
81.40.Lm Deformation, plasticity, and creep
68.37.Ps Atomic force microscopy (AFM)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Three-beam interference method for measuring very thin films

I. Leizerson and S. G. Lipson

Appl. Phys. Lett. 83, 260 (2003); http://dx.doi.org/10.1063/1.1591234 (3 pages) | Cited 5 times

Online Publication Date: 8 July 2003

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We present an experimental method which allows the real time measurement of the thickness of a thin film on a transparent substrate in an imaging mode. Imaging ellipsometry cannot be used for such problems because of reflections from the backsurface of the substrate. Its application to the measurement of water films down to 30 Å on mica is described. The sensitivity is found to be comparable to that of imaging ellipsometry. We investigate the relationship between thickness resolution and spatial resolution and give an optional modification of the method which can be applied to opaque substrates. © 2003 American Institute of Physics.
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68.15.+e Liquid thin films
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Resonant optical nonlinearities from intersubband transitions in GaN/AlN quantum wells

R. Rapaport, Gang Chen, O. Mitrofanov, C. Gmachl, H. M. Ng, and S. N. G. Chu

Appl. Phys. Lett. 83, 263 (2003); http://dx.doi.org/10.1063/1.1591247 (3 pages) | Cited 19 times

Online Publication Date: 8 July 2003

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We measured the resonant nonlinear optical response of the intersubband transitions in GaN/AlGaN multiple quantum well structures. The measured value for the nonlinear susceptibility is found to be much smaller than previous theoretical predictions. This is attributed to a large electron dephasing due to material imperfections. We show that at higher incident intensities, absorption saturation is possible, and measure the saturation intensity for various wavelengths around the transition resonance. We also discuss the prospects of using such structures as building blocks for all-optical nonlinear switches, in light of our experimental findings. © 2003 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
78.67.De Quantum wells
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption

Long-lasting photoluminescence in freestanding GaN templates

M. A. Reshchikov, M. Zafar Iqbal, H. Morkoç, S. S. Park, and K. Y. Lee

Appl. Phys. Lett. 83, 266 (2003); http://dx.doi.org/10.1063/1.1589194 (3 pages) | Cited 6 times

Online Publication Date: 8 July 2003

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We studied time-resolved photoluminescence (PL) over a temporal range 10−6–103 s in high-purity freestanding GaN templates. Red, yellow, green, blue, and shallow donor–acceptor emission bands can be resolved in the PL spectrum. Observation of luminescence long after the excitation is switched off is a striking feature of our study. The persistent PL observed for all above bands, except for the green band, is primarily attributed to the donor–acceptor-pair-type recombination. An unusually slow, nonexponential decay of radiative transitions from the conduction band to the shallow acceptor was also observed, pointing to some additional mechanism for the persistent PL. Possible role of the surface states in this effect is discussed. © 2003 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics

Correlation between the ordered structure and the valence-band splitting in highly strained CdxZn1−xTe epilayers

T. W. Kim, K. D. Kwack, J. G. Park, H. S. Lee, J. Y. Lee, M. S. Jang, and H. L. Park

Appl. Phys. Lett. 83, 269 (2003); http://dx.doi.org/10.1063/1.1592622 (3 pages) | Cited 3 times

Online Publication Date: 8 July 2003

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Selected-area electron diffraction pattern (SADP) results showed two sets of {1/2 1/2 1/2} superstructure reflections with symmetrical intensities along the [110] axis, and the corresponding high-resolution transmission electron microscopy images indicated a doublet periodicity in the contrast of the {111} lattice planes. Photoluminescence spectra from highly strained CdxZn1−xTe/GaAs heterostructures showed that the valence-band splitting into the heavy hole and the light hole bands occurred as the Cd mole fraction was increased. The valence-band splitting is strongly correlated to the CuPtB-type ordered structure in highly strained heterostructures. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
68.55.-a Thin film structure and morphology

Strong photoluminescence and cathodoluminescence due to f–f transitions in Eu3+ doped Al2O3 powders prepared by direct combustion synthesis and thin films deposited by laser ablation

Nikifor Rakov, Francisco E. Ramos, Gustavo Hirata, and Mufei Xiao

Appl. Phys. Lett. 83, 272 (2003); http://dx.doi.org/10.1063/1.1592636 (3 pages) | Cited 35 times

Online Publication Date: 8 July 2003

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In this letter, we report on fabrication and luminescent properties of phosphor powders and thin films of Eu3+ doped alumina Al2O3. The powders were fabricated by combustion synthesis process at a low temperature, 280 °C and showed strong photoluminescent and cathodoluminescent emissions. Powders of Eu3+ doped Al2O3 of concentration 1.0 mol % were deposited on quartz-glass substrates to form thin films by means of laser ablation. Under ultraviolet excitation and electron beam excitation, these samples containing microcrystalline structures showed strong luminescence due to f–f transitions, and the dominant transition was the hypersensitive 5D0→7F2 red emission of Eu3+. © 2003 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Nk Insulators
81.05.Cy Elemental semiconductors
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.15.Fg Pulsed laser ablation deposition

Stacking-fault-induced intermediate structure in bismuth titanate

Y. Yoneda, J. Mizuki, R. Katayama, K. Yagi, H. Terauchi, S. Hamazaki, and M. Takashige

Appl. Phys. Lett. 83, 275 (2003); http://dx.doi.org/10.1063/1.1592000 (3 pages) | Cited 9 times

Online Publication Date: 8 July 2003

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We observed an intermediate structure during the recrystallization process from the amorphous state of Bi4Ti3O12 prepared by rapid quenching. The intermediate structure which appears during the recrystallization process consists of two phases; one is pyrochlore Bi2Ti2O7 phase and the other is a stacking-fault-induced structure under the excessive Bi condition. The microstructure of the stacking-fault-induced structure was investigated by synchrotron x-ray diffraction. In the case of a large number of Bi2O2, some are inserted between the pseudoperovskite layers of Bi4Ti3O12, and a nonstoichiometric Bi2WO6-like structure is stabilized. © 2003 American Institute of Physics.
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61.66.Fn Inorganic compounds
61.72.Nn Stacking faults and other planar or extended defects
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)

Optical properties and electronic structure of rock-salt ZnO under pressure

A. Segura, J. A. Sans, F. J. Manjón, A. Muñoz, and M. J. Herrera-Cabrera

Appl. Phys. Lett. 83, 278 (2003); http://dx.doi.org/10.1063/1.1591995 (3 pages) | Cited 49 times

Online Publication Date: 8 July 2003

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This letter reports on the pressure dependence of the optical absorption edge of ZnO in the rock-salt phase, up to 20 GPa. Both vapor-phase monocrystals and pulsed-laser-deposition thin films on mica have been investigated. Rock-salt ZnO is shown to be an indirect semiconductor with a band gap of 2.45±0.15 eV, whose pressure coefficient is very small. At higher photon energies, a direct transition is observed (4.6 eV at 10 GPa), with a positive pressure coefficient (around 40±3 meV/GPa between 5 and 19 GPa). These results are interpreted on the basis of first-principles electronic band structure calculations. © 2003 American Institute of Physics.
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78.40.Fy Semiconductors
78.66.Hf II-VI semiconductors
81.15.Fg Pulsed laser ablation deposition
71.20.Nr Semiconductor compounds
62.50.-p High-pressure effects in solids and liquids
71.15.-m Methods of electronic structure calculations

Measurements and calculations of the sound attenuation by a phononic band gap structure suitable for an insulating partition application

C. Goffaux, F. Maseri, J. O. Vasseur, B. Djafari-Rouhani, and Ph. Lambin

Appl. Phys. Lett. 83, 281 (2003); http://dx.doi.org/10.1063/1.1592016 (3 pages) | Cited 17 times

Online Publication Date: 8 July 2003

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We report a strong attenuation of sound waves in a phononic band gap crystal of steel rods arranged in air. We investigate the attenuation level reached in the gaps for finite thickness samples. We show that a bypassing of sound waves by the sides of the sample are responsible for the observed saturation of the attenuation level in the gaps. Beyond this effect, we demonstrate the improvement of the acoustic insulation performance brought about by the periodicity of the crystal in comparison with the so-called mass law. © 2003 American Institute of Physics.
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62.65.+k Acoustical properties of solids
43.20.Hq Velocity and attenuation of acoustic waves
42.70.Qs Photonic bandgap materials
43.50.Ki Active noise control

Effect of crystal nature on upconversion luminescence in Er3+:ZrO2 nanocrystals

Amitava Patra, Christopher S. Friend, Rakesh Kapoor, and Paras N. Prasad

Appl. Phys. Lett. 83, 284 (2003); http://dx.doi.org/10.1063/1.1592891 (3 pages) | Cited 85 times

Online Publication Date: 8 July 2003

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The effects of crystal size and crystal phase on the upconverted emission of Er3+ in ZrO2 oxide nanocrystals are reported. Green (550 nm) and red (670 nm) upconversion emission were observed at room temperature from the 4S3/2 and 4F9/2 levels of Er3+:ZrO2 nanocrystals. It is found that at 850 mW of cw excitation power, the total luminescence was 11960 Cd/m2 for 1000 °C heated sample. We observed that the overall upconversion luminescence intensity depends on crystal structure and particle size. We have also confirmed that upconversion process in all these samples results from a two-photon excited-state absorption process. © 2003 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
73.22.-f Electronic structure of nanoscale materials and related systems
61.66.Fn Inorganic compounds
71.55.Ht Other nonmetals

Electrical activity of nitrogen acceptors in ZnO films grown by metalorganic vapor phase epitaxy

J. F. Rommeluère, L. Svob, F. Jomard, J. Mimila-Arroyo, A. Lusson, V. Sallet, and Y. Marfaing

Appl. Phys. Lett. 83, 287 (2003); http://dx.doi.org/10.1063/1.1592621 (3 pages) | Cited 77 times

Online Publication Date: 8 July 2003

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The electrical activity of nitrogen as an acceptor in ZnO has been investigated in two ways. First, nitrogen was introduced by means of diallylamine during metalorganic vapor phase epitaxy (MOVPE) yielding incorporation of nitrogen in the range 1016–1021 cm−3. This led to significant compensation of the natural donors with a minimum electron concentration of 5×1014 cm−3. Second, diffusion of nitrogen was carried out on undoped MOVPE layers under high pressure conditions stemming from the decomposition of NH4NO3. Conversion to p-type conductivity was observed in a systematic way with measured hole concentrations up to 6.5×1017 cm−3. © 2003 American Institute of Physics.
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73.61.Ga II-VI semiconductors
66.30.J- Diffusion of impurities
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