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29 Dec 2003

Volume 83, Issue 26, pp. 5347-5569

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Appl. Phys. Lett. 83, 5527 (2003); http://dx.doi.org/10.1063/1.1637143 (3 pages)

Chad R. Barry, Nyein Z. Lwin, Wei Zheng, and Heiko O. Jacobs
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Polarized organic electroluminescence: Ordering from the top

Nicolas Godbert, Paul L. Burn, Sandra Gilmour, Jonathan P. J. Markham, and Ifor D. W. Samuel

Appl. Phys. Lett. 83, 5347 (2003); http://dx.doi.org/10.1063/1.1632025 (3 pages) | Cited 10 times

Online Publication Date: 22 December 2003

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We demonstrate a method for achieving polarized organic electroluminescence for liquid crystalline conjugated polymers that allows the polymer to be deposited directly onto the anode. The technique utilizes a top-down alignment approach whereby the predeposited polymer was aligned from above using a rubbed polyimide master and a smectic liquid crystal transfer layer. The liquid crystal/polyimide master bilayer was sandwiched with the liquid crystalline polymer that had been deposited onto the electrode. The sandwiched layers were then heated to achieve alignment before the removal of the polyimide master and liquid crystal transfer layer. Using this method, poly[2,7-{9,9-di(2-ethylhexyl)}fluorene] (PF2-6) was aligned to give an anisotropic polymer film. Light emitted from single layer light-emitting diodes containing the aligned PF2-6 had integrated dichroic ratios of up to 9.7. At 100 cd/m2, the single layer devices had external quantum and power efficiencies of 0.08% and 0.05 lm/W, respectively. Bilayer devices containing an electron transport layer between the PF2-6 and the cathode gave emitted light with good dichroic ratios and with the external quantum and power efficiencies at 100 cd/m2 being increased to 2.2% and 1.1 lm/W. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices

Nonlinear optical spectroscopy in one-dimensional photonic crystals

Garrett J. Schneider and George H. Watson

Appl. Phys. Lett. 83, 5350 (2003); http://dx.doi.org/10.1063/1.1636249 (3 pages) | Cited 15 times

Online Publication Date: 22 December 2003

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We have conducted a spectroscopic investigation of the enhancement of nonlinear optical effects around a defect in a one-dimensional photonic crystal. Degenerate four-wave mixing studies were performed on a dielectric stack that contained a polymer thin-film defect layer doped with a nonlinear organic dye. This sample exhibited a large nonlinear response at a resonant defect frequency. Nonlinear spectroscopy was performed around the defect resonance and at frequencies well away from resonance. We have shown that the four-wave mixing signal exhibits extremely high-quality resonance, consistent with the expected cubic dependence on the calculated intensity within the defect layer. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Phototunable lasing in dye-doped cholesteric liquid crystals

Andro Chanishvili, Guram Chilaya, Gia Petriashvili, Riccardo Barberi, Roberto Bartolino, Gabriella Cipparrone, Alfredo Mazzulla, and Luis Oriol

Appl. Phys. Lett. 83, 5353 (2003); http://dx.doi.org/10.1063/1.1636818 (3 pages) | Cited 57 times

Online Publication Date: 22 December 2003

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In this letter, we report the results of phototunable lasing in dye-doped cholesteric liquid crystals (DD–CLC). Photoexcitation of DD–CLC films gives rise to laser emission in the violet-UV range. Control of the structure of the chiral dopant driven by UV phototransformation is exploited in order to obtain a permanent variation of the cholesteric pitch. Laser emission wavelength tuning, by means of photoinduced shifting of the selective reflection band of the cholesteric liquid crystals is established. A tuning interval of about 35 nm, in the wavelength range of 385–415 nm, is observed. © 2003 American Institute of Physics.
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42.55.Mv Dye lasers
42.70.Df Liquid crystals
42.60.Fc Modulation, tuning, and mode locking

Tunable repetition-rate multiplication of a 10 GHz pulse train using linear and nonlinear fiber propagation

C. J. S. de Matos and J. R. Taylor

Appl. Phys. Lett. 83, 5356 (2003); http://dx.doi.org/10.1063/1.1636824 (3 pages) | Cited 9 times

Online Publication Date: 22 December 2003

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The temporal Talbot effect and soliton propagation in an optical fiber were exploited to yield a series of pulse train sources with tunable repetition rate simply through variation of the pulse train power in sections of the fiber. In a dual-repetition-rate configuration, 10 and 20 GHz or 10 and 30 GHz repetition rates could be achieved depending on the fiber length used, with pulse durations lower than 21 ps. In a triple-repetition-rate configuration, 10, 20, and 30 GHz repetition rates were obtained, with pulse durations lower than 15 ps. © 2003 American Institute of Physics.
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42.81.Dp Propagation, scattering, and losses; solitons
42.65.Tg Optical solitons; nonlinear guided waves

Combinatorial fabrication and studies of bright white organic light-emitting devices based on emission from rubrene-doped 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl

G. Li and J. Shinar

Appl. Phys. Lett. 83, 5359 (2003); http://dx.doi.org/10.1063/1.1635658 (3 pages) | Cited 82 times

Online Publication Date: 22 December 2003

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Very bright and efficient white multilayer organic light-emitting devices based on orange-emitting 2–10-nm-thick layers of 0.25 and 0.5 wt % rubrene-doped 4,4′-bis(2,2′-diphenylvinyl)-1,1′biphenyl are described. The color coordinates of all but one of the devices are well within the white region at 6–12 V, corresponding to a dynamic white brightness range of 30 dB. Their highest brightness Lmax was over 74 000 Cd/m2; in all devices Lmax exceeded 50 000 Cd/m2. The maximum efficiencies were 11.0 Cd/A, 6.0 lm/W, and 4.6% at 5.8 V, 0.6 mA/cm2, and 68 Cd/m2 in the 0.25 wt %, 2-nm-thick doped layer device. The color variation is attributed to either emission from different zones in devices with a thin doped layer, or saturation of emission sites due to relatively light doping. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
73.61.Ph Polymers; organic compounds
78.60.Fi Electroluminescence

Calculated and measured transmittance of a tunable metallic photonic crystal filter for terahertz frequencies

Timothy D. Drysdale, Richard J. Blaikie, and David R. S. Cumming

Appl. Phys. Lett. 83, 5362 (2003); http://dx.doi.org/10.1063/1.1636822 (3 pages) | Cited 24 times

Online Publication Date: 22 December 2003

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A tunable metallic photonic crystal filter with a mechanical tuning mechanism is demonstrated. The performance is predicted with rigorous full-vector electromagnetic simulations (finite-difference time domain). A prototype has been built and characterized in the W band (70–110 GHz) using a vector network analyzer configured for free-space measurement of S parameters. The measured filter’s passband has a quality factor of 11, a tuning range of 3.5 GHz, and insertion loss of only 1.1–1.7 dB. Device fabrication is straightforward, yielding an inexpensive, robust and compact tunable filter. © 2003 American Institute of Physics.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
84.30.Vn Filters
02.70.Bf Finite-difference methods
42.70.Qs Photonic bandgap materials

Single-lobe, surface-normal beam surface emission from second-order distributed feedback lasers with half-wave grating phase shift

G. Witjaksono, S. Li, J. J. Lee, D. Botez, and W. K. Chan

Appl. Phys. Lett. 83, 5365 (2003); http://dx.doi.org/10.1063/1.1636248 (3 pages) | Cited 8 times

Online Publication Date: 22 December 2003

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Half-wave phase shifts were fabricated in the center of second-order GaAs gratings, for use in surface-emitting, horizontal-cavity, semiconductor diode lasers (λ=0.98 μm). Incorporating such gratings in diode lasers with distributed-feedback (DFB) active regions and distributed Bragg reflectors (DBRs) is found to provide surface-normal, single-lobe beam emission, as predicted by theory. InGaAs/AlGaAs/InGaP, two-quantum-well structures are employed. A 500-μm-long GaAs/Au second-order grating with half-wave phase shift represents the DFB region, which provides feedback and unidirectional light outcoupling. GaAs/SiO2/Au, 500-μm-long, second-order gratings are the DBR regions, on either side of the DFB region, which provide both frequency-selective feedback as well as unidirectional outcoupling. Lateral-mode control is achieved via a 2.5-μm-wide ridge waveguide. Surface emission is obtained through a 80-μm-wide window stripe in the metallization on the substrate n-side. Single-frequency lasing in an orthonormally emitted, single-lobe, diffraction-limited beam is obtained to 3× threshold under pulsed-drive conditions (200 ns wide pulses, 1 kHz repetition rate). © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Dj Gratings

Two lasing thresholds in semiconductor lasers with a quantum-confined active region

Levon V. Asryan and Serge Luryi

Appl. Phys. Lett. 83, 5368 (2003); http://dx.doi.org/10.1063/1.1636245 (3 pages) | Cited 7 times

Online Publication Date: 22 December 2003

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We show that the free-carrier-density dependence of internal optical loss gives rise, in general, to the existence of a second lasing threshold above the conventional threshold. Above the second threshold, the light-current characteristic is two-valued up to a maximum current at which the lasing is quenched. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

Nonradiative relaxation times in diagonal transition Si/SiGe quantum cascade structures

I. Bormann, K. Brunner, S. Hackenbuchner, G. Abstreiter, S. Schmult, and W. Wegscheider

Appl. Phys. Lett. 83, 5371 (2003); http://dx.doi.org/10.1063/1.1631381 (3 pages) | Cited 15 times

Online Publication Date: 22 December 2003

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Here, we explore experimentally and theoretically the possibility to prolong the upper hole state nonradiative lifetime of Si/SiGe quantum cascade (QC) structures by using a spatially indirect diagonal transition between two SiGe quantum well ground states. With the recent observation of well resolved midinfrared electroluminescence from heavy hole intersubband transitions in Si/SiGe valence-band QC structures, a Si-based QC laser seems no longer to be out of reach. A long carrier lifetime and maybe population inversion, however, appear to be impossible for structure designs with a vertical intersubband transition studied so far. This is due to the nonresonant behavior of deformation potential scattering dominant in unipolar SiGe. We report on calculations of the band structure using a six-band k⋅p model and of hole deformation potential scattering that predict significantly increased nonradiative lifetimes for large barrier thickness, reaching about 20 ps for 35 Å Si barrier layer width. Electroluminesence measurements of a series of QC structures with varied barrier width reveal comparable efficiencies and the deduced lifetimes confirm our model calculations. © 2003 American Institute of Physics.
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78.60.Fi Electroluminescence
78.67.De Quantum wells
73.21.Fg Quantum wells

Midinfrared “W” diode lasers with improved electrical characteristics

M. Kim, W. W. Bewley, J. R. Lindle, C. S. Kim, I. Vurgaftman, J. R. Meyer, J. G. Kim, and R. U. Martinelli

Appl. Phys. Lett. 83, 5374 (2003); http://dx.doi.org/10.1063/1.1637450 (3 pages) | Cited 16 times

Online Publication Date: 22 December 2003

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Midinfrared “W” quantum-well diode lasers with reduced turn-on voltages are reported. Devices with coated facets operated in continuous-wave mode up to 195 K, where the emission wavelength was 3.56 μm. At 78 K, the threshold current density was 67 A/cm2, the maximum output power was 198 mW, and the slope efficiency was 106 mW/A. © 2003 American Institute of Physics.
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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.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Strong coupling in high-finesse organic semiconductor microcavities

L. G. Connolly, D. G. Lidzey, R. Butté, A. M. Adawi, D. M. Whittaker, M. S. Skolnick, and R. Airey

Appl. Phys. Lett. 83, 5377 (2003); http://dx.doi.org/10.1063/1.1637146 (3 pages) | Cited 22 times

Online Publication Date: 22 December 2003

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We report the fabrication of high-finesse strongly coupled microcavities composed of a polystyrene film doped with the dye tetraphenyl–porphyrin zinc positioned between two high reflectivity dielectric mirrors. The bottom mirror was deposited by plasma enhanced chemical vapor deposition, and was composed of 11 λ/4 thick (silicon oxide/silicon nitride) pairs. The organic layer was deposited on to this by spin coating. Finally, the top mirror was deposited by thermal evaporation and consisted of 12 λ/4 thick (tellurium oxide/lithium fluoride) pairs. Such cavities are characterized by Q factors of between 440 and 620. Strong coupling was evidenced via white light reflectivity measurements. Due to the high cavity Q factor, a Rabi splitting of 135 meV at resonance was very clearly resolved. © 2003 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Bh Lenses, prisms and mirrors
78.66.Qn Polymers; organic compounds
42.79.Wc Optical coatings
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Temperature dependence of the wavelength and threshold of fiber-taper-coupled L-band Er3+-doped tellurite glass microsphere laser

Xiang Peng, Feng Song, Makoto Kuwata-Gonokami, Shibin Jiang, and N. Peyghambarian

Appl. Phys. Lett. 83, 5380 (2003); http://dx.doi.org/10.1063/1.1637454 (3 pages) | Cited 7 times

Online Publication Date: 22 December 2003

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We report on the temperature dependence of L-band laser emission of fiber-taper-coupled Er3+-doped tellurite glass microsphere. The microsphere laser emission threshold increased and the emitted laser wavelength shifted with temperature. The experimental results are explained with a quasi-four-level model, showing that a significant reduction of laser threshold can be achieved at lower temperatures and higher Q values of this microsphere laser. © 2003 American Institute of Physics.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Broad-stripe midinfrared photonic-crystal distributed-feedback lasers with laser-ablation confinement

W. W. Bewley, C. S. Kim, M. Kim, C. L. Canedy, J. R. Lindle, I. Vurgaftman, J. R. Meyer, R. E. Muller, P. M. Echternach, and R. Kaspi

Appl. Phys. Lett. 83, 5383 (2003); http://dx.doi.org/10.1063/1.1637153 (3 pages) | Cited 6 times

Online Publication Date: 22 December 2003

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We investigate broad-stripe photonic-crystal distributed-feedback lasers emitting at λ = 4.4 μm. The beam quality improves dramatically when a laser ablation technique is used to eliminate parasitic Fabry–Pérot-like modes, by inducing loss in the regions adjoining the pump stripe. Even though the peak of the gain spectrum never fully aligns with the grating resonance, for pulsed pumping the output beam is essentially diffraction limited up to a stripe width of 150 μm, and remains no worse than six times the diffraction limit for stripes as broad as 400 μm. © 2003 American Institute of Physics.
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42.55.Tv Photonic crystal lasers and coherent effects
42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.70.Qs Photonic bandgap materials
42.60.By Design of specific laser systems

Omnidirectional gap and defect mode of one-dimensional photonic crystals containing negative-index materials

Haitao Jiang, Hong Chen, Hongqiang Li, Yewen Zhang, and Shiyao Zhu

Appl. Phys. Lett. 83, 5386 (2003); http://dx.doi.org/10.1063/1.1637452 (3 pages) | Cited 157 times

Online Publication Date: 22 December 2003

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We show theoretically that a one-dimensional photonic crystal containing a negative-index material has an omnidirectional gap, owing to the mechanism of zero (volume) averaged refractive index. In contrast to the Bragg gap, the edge of such a zero-math gap is insensitive to incident angle and polarization. When an impurity is introduced, a defect mode appears inside the zero-math gap with a very weak dependence on incident angle and invariant with scaling. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.-e Optical properties of bulk materials and thin films

Optical phase conjugation and efficient wave front correction of weak light beams by dye-doped liquid crystals

L. Lucchetti, M. Di Fabrizio, M. Gentili, and F. Simoni

Appl. Phys. Lett. 83, 5389 (2003); http://dx.doi.org/10.1063/1.1637453 (3 pages) | Cited 8 times

Online Publication Date: 22 December 2003

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We report the observation of optical phase conjugation by thin nematic liquid crystal films by using submilliwatt incident power without any external applied field. The light-induced average birefringence evaluated by solving the wave equations for the four interacting waves, is in agreement with that typical of the colossal optical nonlinearity recently observed in the same materials. The high conjugated reflectivity values, obtained with the analyzed samples, allows correction of severely aberrated wave fronts of very weak light beams. © 2003 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.66.Qn Polymers; organic compounds
42.70.Df Liquid crystals
78.20.Fm Birefringence
78.20.-e Optical properties of bulk materials and thin films
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Capacity-coupled multidischarge for atmospheric plasma production

Hiroshi Mase, Tamiya Fujiwara, and Noriyoshi Sato

Appl. Phys. Lett. 83, 5392 (2003); http://dx.doi.org/10.1063/1.1636825 (3 pages) | Cited 7 times

Online Publication Date: 22 December 2003

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We propose a method of plasma production by capacity-coupled multidischarge (CCMD) at atmospheric pressure. The discharge gaps in the CCMD consist of a common electrode and a number of compact electrodes (CCE) which are directly coupled with small capacitors for quenching the discharge. A simple CCE structure is provided by a cylindrical capacitor, the inner conductor of which is used as a gap electrode. A short pulse discharge is observed to appear homogeneously at each CCE. A charge transfer for the single-pulsed discharge is 10–100 times as large as that of the conventional dielectric barrier discharge. A high efficiency of ozone production has been confirmed in the CCMD using O2 gas. A device configuration of the CCMD is quite flexible with respect to its geometrical shape and size. The CCMD could be used to produce plasmas for various kinds of industrial applications at atmospheric pressure. © 2003 American Institute of Physics.
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52.50.Dg Plasma sources
52.80.-s Electric discharges

Excitation temperatures in the ionizing plasma of high-pressure mercury discharges

Dimitrios Karabourniotis

Appl. Phys. Lett. 83, 5395 (2003); http://dx.doi.org/10.1063/1.1636819 (3 pages) | Cited 10 times

Online Publication Date: 22 December 2003

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The excitation temperatures of mercury as well as the electron and gas temperature in two high-pressure pure-Hg discharges operated on ac have been determined by measuring the ground- and excited-state densities. The excitation temperature depends on the excited-state energy, is significantly lower than the electron temperature, and higher than the gas temperature. The differences in the temperatures are higher at the maximum current phase and for the lower pressure discharge. Comparison with the Saha densities shows that the plasma at the maximum current is in ionizing phase, whereas it is close to local thermodynamic equilibrium at the voltage zero crossing. © 2003 American Institute of Physics.
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52.25.-b Plasma properties
52.80.Pi High-frequency and RF discharges
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Thermal diffusivity and thermoelectric figure of merit of Al1−xInxN prepared by reactive radio-frequency sputtering

Shigeo Yamaguchi, Ryohei Izaki, Ken-ichi Yamagiwa, Kyoichiro Taki, Yasuo Iwamura, and Atsushi Yamamoto

Appl. Phys. Lett. 83, 5398 (2003); http://dx.doi.org/10.1063/1.1637156 (3 pages) | Cited 18 times

Online Publication Date: 22 December 2003

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We studied the thermal properties of AlN, InN, and Al1−xInxN films, prepared by reactive sputtering, as a function of the temperature. The results indicated minimum thermal diffusivities of 3.14×10−6 m2/s for AlN, 7.65×10−7 m2/s for InN, 7.53×10−7 m2/s for Al0.57In0.43N, and 7.03×10−7 m2/s for Al0.28In0.72N. We estimated the dimensionless thermoelectric figure of merit to be 0.1 for Al0.28In0.72N at 873 K. © 2003 American Institute of Physics.
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73.50.Lw Thermoelectric effects
66.30.Xj Thermal diffusivity
72.20.Pa Thermoelectric and thermomagnetic effects
73.61.Ey III-V semiconductors
72.80.Ey III-V and II-VI semiconductors

Heating and structural disordering effects of the nonlinear viscous flow in a Zr55Al10Ni5Cu30 bulk metallic glass

Hidemi Kato, Akihisa Inoue, and H. S. Chen

Appl. Phys. Lett. 83, 5401 (2003); http://dx.doi.org/10.1063/1.1637441 (3 pages) | Cited 12 times

Online Publication Date: 22 December 2003

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The heat evolution of stress-induced structural disorder, ΔHs(ε), of a Zr55Al10Ni5Cu30 bulk metallic glass (BMG) during compressive constant ram-velocity deformation at the glass transition region (Tg = 680 K) was deduced from in situ measurements of temperature change of the deforming sample. At the transition from the linear to nonlinear viscoelasticity, the behavior of viscosity change with strain, η(ε), is qualitatively consistent with the enthalpy evolution of the structural disordering, ΔHs(ε), but not with the temperature change, ΔT(ε). It is concluded that the initial softening deformation is due to the stress-induced structural disordering. The change in the nonlinearity, −log math  ≡ −log η /ηN, is found to be proportional to the ΔHs and the slope of ΔHs(−log math) can be estimated to 400 J/mol, where ηN is the Newtonian viscosity. On the other hand, the temperature raise, ΔT(ε), is pronouncedly delayed as compared with the η (ε) and ΔHs(ε) at the transition, but is determined by a product of stress and plastic strain-rate, σ⋅mathp, and is nearly proportional to it at the steady state. The slope of ΔT(σ⋅mathp) can be estimated to 5.2×10−2 K mol/W. © 2003 American Institute of Physics.
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61.43.Fs Glasses
83.60.Df Nonlinear viscoelasticity
81.40.Lm Deformation, plasticity, and creep
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
66.20.-d Viscosity of liquids; diffusive momentum transport
81.05.Kf Glasses (including metallic glasses)
83.60.Fg Shear rate dependent viscosity
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Roughening kinetics of thin films in the presence of both stress and Ehrlich–Schwobel barrier

Z.-J. Liu and Y. G. Shen

Appl. Phys. Lett. 83, 5404 (2003); http://dx.doi.org/10.1063/1.1637448 (3 pages) | Cited 5 times

Online Publication Date: 22 December 2003

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The growth of thin films under the interplay of shot noise, Ehrlich–Schwobel barrier (ESB), stress, and surface diffusion has been studied within a linear continuum model. It is shown that the roughening kinetics of such a system is sensitive to the growth temperature. At low temperatures, the surface growth is dominated by the ESB, while the stress controls the morphology instability at high temperatures. In the intermediate temperature regime, both the ESB effect and the stress instability become weak, thus the surface roughening is primarily driven by noise. An analysis of the film growth in this relatively stable regime reveals that at the early stages of growth the surface roughness shows an exponential dependence on the growth time, with a time-dependent growth exponent β being larger than the value of 0.25 generated by the competition between pure noise and surface diffusion. At the late stages of growth, however, the scaling law is broken and the growth becomes unstable due to the enhanced stress and ESB effects induced by growth time. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation
81.15.Aa Theory and models of film growth
68.60.Bs Mechanical and acoustical properties
68.35.Gy Mechanical properties; surface strains

Clusters formation in ultralow-energy high-dose boron-implanted silicon

F. Cristiano, X. Hebras, N. Cherkashin, A. Claverie, W. Lerch, and S. Paul

Appl. Phys. Lett. 83, 5407 (2003); http://dx.doi.org/10.1063/1.1637440 (3 pages) | Cited 27 times

Online Publication Date: 22 December 2003

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The formation and evolution of small cluster defects in 500 eV, 1×1015 cm−2 boron-implanted silicon is investigated. These clusters are identified by high-resolution transmission electron microscopy (TEM) as small dislocation loops lying on {100} planes with an interstitial character. Weak-beam dark-field TEM analysis shows that, during annealing at 650 °C, they evolve following an Ostwald ripening mechanism. Spike anneals at high temperatures make them dissolve but an immobile boron peak is still detected in the secondary ion mass spectroscopy profiles. Upon oxidation, the average size of the clusters increases, while boron electrical deactivation occurs. These results strongly indicate that the observed clusters contain both boron interstitials and silicon self-interstitials atoms. © 2003 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Solid-like dynamics in ultrathin films of polymeric liquids

Gaurav Singh, Ravi F. Saraf, and Yves Martin

Appl. Phys. Lett. 83, 5410 (2003); http://dx.doi.org/10.1063/1.1637145 (3 pages) | Cited 1 time

Online Publication Date: 22 December 2003

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In this letter, we demonstrate that, at mesoscales, nonferroelectric liquid films of poly(dimethyl siloxane) exhibit significant electrostriction not present in the corresponding bulk state. Remarkably, the observed electrostrictive effect has a response time <20 μs in contrast to >5 ms recorded in conventional bulk (ferroelectric) polymers. The emergence of this fast electrostrictive strain in thin films is explained in terms of the amalgamation of two contrasting dynamic features—the influence of a highly mobile, viscous layer (at the air/film interface) on the less-mobile, but fast responding, solid-like layer at the film/substrate interface. The effect is observed for thickness below 200 nm. © 2003 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
68.15.+e Liquid thin films
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.55.-g Dielectric thin films

InGaAs/InP double heterostructures on InP/Si templates fabricated by wafer bonding and hydrogen-induced exfoliation

A. Fontcuberta i Morral, J. M. Zahler, Harry A. Atwater, S. P. Ahrenkiel, and M. W. Wanlass

Appl. Phys. Lett. 83, 5413 (2003); http://dx.doi.org/10.1063/1.1637429 (3 pages) | Cited 26 times

Online Publication Date: 22 December 2003

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Hydrogen-induced exfoliation combined with wafer bonding has been used to transfer ∼ 600-nm-thick films of (100) InP to Si substrates. Cross-section transmission electron microscopy (TEM) shows a transferred crystalline InP layer with no observable defects in the region near the bonded interface and an intimately bonded interface. InP and Si are covalently bonded as inferred by the fact that InP/Si pairs survived both TEM preparation and thermal cycles up to 620 °C necessary for metalorganic chemical vapor deposition growth. The InP transferred layers were used as epitaxial templates for the growth of InP/In0.53Ga0.47As/InP double heterostructures. Photoluminescence measurements of the In0.53Ga0.47As layer show that it is optically active and under tensile strain, due to differences in the thermal expansion between InP and Si. These are promising results in terms of a future integration of Si electronics with optical devices based on InP-lattice-matched materials. © 2003 American Institute of Physics.
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68.35.Ct Interface structure and roughness
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.47.Fg Semiconductor surfaces
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.37.Lp Transmission electron microscopy (TEM)
68.55.A- Nucleation and growth

Enhanced thermoelectric properties of NaxCoO2 whisker crystals

G. Peleckis, T. Motohashi, M. Karppinen, and H. Yamauchi

Appl. Phys. Lett. 83, 5416 (2003); http://dx.doi.org/10.1063/1.1634371 (3 pages) | Cited 11 times

Online Publication Date: 22 December 2003

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Single-crystalline whiskers of thermoelectric cobalt oxide, NaxCoO2, have been grown by an unconventional method from potassium-containing compositions, and their transport properties, and chemical compositions were determined. The growth mechanism was analyzed and interpreted by means of thermogravimetric analysis. At 300 K, electrical resistivity ρ, and thermoelectric power S of the whisker are 102 μΩ cm and 83 μV/K, respectively. The power-factor, S2/ρ, thus is enhanced up to ∼ 68 μW/K2 cm. © 2003 American Institute of Physics.
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72.20.Pa Thermoelectric and thermomagnetic effects
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Electron-beam-induced strain within InGaN quantum wells: False indium “cluster” detection in the transmission electron microscope

T. M. Smeeton, M. J. Kappers, J. S. Barnard, M. E. Vickers, and C. J. Humphreys

Appl. Phys. Lett. 83, 5419 (2003); http://dx.doi.org/10.1063/1.1636534 (3 pages) | Cited 90 times

Online Publication Date: 22 December 2003

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InGaN quantum wells have been found to be extremely sensitive to exposure to the electron beam in the transmission electron microscope (TEM). High-resolution TEM images acquired immediately after first irradiating a region of quantum well indicates no gross fluctuations of indium content in the InGaN alloy. During only a brief period of irradiation, inhomogeneous strain is introduced in the material due to electron beam damage. This strain is very similar to that expected from genuine nanometer-scale indium composition fluctuations which suggests there is the possibility of falsely detecting indium-rich “clusters” in a homogeneous quantum well. © 2003 American Institute of Physics.
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68.65.Fg Quantum wells
81.07.St Quantum wells
68.37.Lp Transmission electron microscopy (TEM)
61.46.-w Structure of nanoscale materials
81.05.Ea III-V semiconductors
61.80.Fe Electron and positron radiation effects
61.66.Bi Elemental solids
61.66.Dk Alloys
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