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25 Aug 1997

Volume 71, Issue 8, pp. 993-1132

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Defect formation in GeO2–SiO2 glass by poling with ArF laser excitation

M. Takahashi, T. Fujiwara, T. Kawachi, and A. J. Ikushima

Appl. Phys. Lett. 71, 993 (1997); http://dx.doi.org/10.1063/1.119749 (3 pages) | Cited 15 times

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We have investigated formation of Ge-related defects in a GeO2–SiO2 glass fiber preformed by poling with ArF laser excitation. Electric field dependence of the induced-defect concentrations was measured by means of the optical absorption. Several color centers such as the germanium electron-trapped centers and the Ge E′ center were induced. Concentrations of the induced germanium electron-trapped centers and Ge E′ center increase with increasing the electric field. Conversion efficiency from the germanium electron-trapped centers to the Ge E′ center was found to be independent of the electric field. The present result strongly suggests that the poling with ArF laser excitation is effective in the present GeO2–SiO2 glass for the formation of germanium electron-trapped centers. © 1997 American Institute of Physics.
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61.82.Ms Insulators
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.40.Pg Disordered solids
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Jv Disordered structures; amorphous and glassy solids

Formation and laser-induced-fluorescence study of SiO+ ions produced by laser ablation of Si in oxygen gas

Yukari Matsuo, Takashi Nakajima, Tohru Kobayashi, and Michio Takami

Appl. Phys. Lett. 71, 996 (1997); http://dx.doi.org/10.1063/1.119750 (3 pages) | Cited 15 times

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We have studied laser-induced-fluorescence (LIF) spectra of SiO+ produced by laser ablation of a Si wafer in oxygen ambient gas. Emission from neutral and ionic species of Si atoms and SiO molecules is also studied in the laser-induced plasma plume. The optimum oxygen pressure for the formation of molecular ions is found to be ∼120 mTorr. The rotational temperature of SiO+ ions shows rapid thermalization toward room temperature within 20 μs. © 1997 American Institute of Physics.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
81.05.Cy Elemental semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
81.65.-b Surface treatments

Solid-state tunable cavity lasing in a poly(para-phenylene vinylene) derivative alternating block co-polymer

N. Deepak Kumar, Jayant D. Bhawalkar, Paras N. Prasad, Frank E. Karasz, and B. Hu

Appl. Phys. Lett. 71, 999 (1997); http://dx.doi.org/10.1063/1.119751 (3 pages) | Cited 34 times

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There is a great deal of interest in developing π-conjugated polymeric semiconductor based diode lasers which can yield lasing under electrical excitation. Towards this goal, tunable cavity lasing was achieved in a poly(para-phenylene vinylene) derivative alternating block copolymer, BMPPV, dispersed in an active solid matrix of poly(9-vinylcarbazole), with which this block co-polymer also exhibits strong electroluminescence. The laser operated in the blue region of the spectrum over the range 480 to 510 nm, with an optical efficiency approaching 10%. Linewidth narrowing and a narrowing of the temporal profile are reported. Operating lifetime of the solid-state laser was in excess of 5000 pulses at the same pumping position on the sample. Lasing properties of the same block copolymer in the solution phase were also investigated and the results compared with the solid state laser performance. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds
42.60.By Design of specific laser systems
73.61.Ph Polymers; organic compounds

Using strained (AlxGa1−x)yIn1−yAszP1−z system materials to improve the performance of 850 nm surface- and edge-emitting lasers

T. E. Sale, C. Amamo, Y. Ohiso, and T. Kurokawa

Appl. Phys. Lett. 71, 1002 (1997); http://dx.doi.org/10.1063/1.119708 (3 pages) | Cited 7 times

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We compute the optical gain of various quantum wells for use in 850 nm lasers. In particular, we investigate compressively strained wells of AlGaInAs, InGaAs, or InGaAsP without any assumptions of the material quality. Reductions of up to 43% in the radiative current and 24% in the sheet carrier density can be expected, compared with GaAs/AlGaAs wells. For the case of vertical-cavity surface-emitting lasers and distributed feedback lasers, compressive strain is particularly attractive in reducing the temperature sensitivity and fabrication tolerances for low threshold and efficient operation. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors

Deposition-induced photoluminescence quenching of tris-(8-hydroxyquinoline) aluminum

V.-E. Choong, Y. Park, N. Shivaparan, C. W. Tang, and Y. Gao

Appl. Phys. Lett. 71, 1005 (1997); http://dx.doi.org/10.1063/1.119709 (3 pages) | Cited 31 times

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Ca, Ag, and Ge atoms quench the photoluminescence (PL) of an organic thin film, tris-(8-hydroxyquinoline) aluminum (Alq3), a model organic material for organic light emitting diodes. The observed PL quenching behavior was similar for all three elements, independent of their metallic nature. Due to strong interactions at the Ca/Alq3 interface, the quenching was much less effective at submonolayer coverages. We have also observed that proper oxidation of Ca at the Ca/Alq3 interface can significantly recover the quenched luminescence of Alq3. © 1997 American Institute of Physics.
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78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Bx Metals, semimetals, and alloys

Guided mode resonance filters using polymer films

P. Rochon, A. Natansohn, C. L. Callender, and L. Robitaille

Appl. Phys. Lett. 71, 1008 (1997); http://dx.doi.org/10.1063/1.119710 (3 pages) | Cited 38 times

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Guided-mode resonance optical filters are made from thin-film structures which consist of azopolymer films deposited on top of slab waveguides. Surface relief gratings can be optically induced on the azopolymer films. The transmission and reflection spectra as a function of the angle of incidence of the probe beam exhibit very sharp resonance features which correspond to coupling into the waveguide modes. Coupling into the overlying azopolymer film is also observed. © 1997 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Dj Gratings
42.70.Jk Polymers and organics

Contradirectional two-wave mixing in Rh-doped BaTiO3 crystal

Xiaodong Mu, Xinguang Xu, Zongshu Shao, Minhua Jiang, Haosu Luo, and Weizhuo Zhong

Appl. Phys. Lett. 71, 1011 (1997); http://dx.doi.org/10.1063/1.119711 (3 pages) | Cited 3 times

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Contradirectional two-wave mixing (CTWM) in Rh-doped BaTiO3 crystal is investigated. The experimental results show that the energy transfer of CTWM has some distinctive characteristics different from forward two-wave mixing. Theoretical analysis of CTWM is presented in good agreement with the experimental observations. Both the experimental and theoretical studies show that the energy transfer direction of CTWM depends not only on the orientation of the crystal c axis and the sign of the light-induced carriers, but also on the electro-optic coefficients. © 1997 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.20.Jq Electro-optical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Effect of the miniband width on the characteristics of a surface-normal reflective optical modulator at 1.3 μm using the Wannier–Stark effect

Osamu Tadanaga, Toshiaki Kagawa, and Yutaka Matsuoka

Appl. Phys. Lett. 71, 1014 (1997); http://dx.doi.org/10.1063/1.119712 (3 pages)

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A surface-normal reflective optical modulator for 1.3 μm wavelength was investigated using the Wannier–Stark effect of an InP/InGaAsP superlattice. Electroabsorption properties of two devices with different miniband widths were compared. A larger extinction ratio was obtained from the modulator with the larger miniband width. The extinction ratio of 3.3 dB was achieved at 28 V. © 1997 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.20.Jq Electro-optical effects
78.66.Fd III-V semiconductors

Demonstration of waveguide couplers fabricated using microtransfer molding

Xiao-Mei Zhao, Stephen P. Smith, Samuel J. Waldman, George M. Whitesides, and Mara Prentiss

Appl. Phys. Lett. 71, 1017 (1997); http://dx.doi.org/10.1063/1.119713 (3 pages) | Cited 23 times

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Arrays of single-mode optical waveguides, couplers, and interferometers were fabricated from a UV curable prepolymer using microtransfer molding. The coupling between the waveguides was reproducible and consistent across the array and was controlled after fabrication by additional UV exposure. © 1997 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.65.Wi Nonlinear waveguides

Efficient wavelength shifting over the erbium amplifier bandwidth via cascaded second order processes in lithium niobate waveguides

Katia Gallo, Gaetano Assanto, and George I. Stegeman

Appl. Phys. Lett. 71, 1020 (1997); http://dx.doi.org/10.1063/1.119714 (3 pages) | Cited 49 times

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We investigate two schemes for wavelength conversion based on the cascading of two successive second order processes in a quasi-phase-matched lithium niobate channel waveguide. Efficient conversion over the full erbium amplifier bandwidth is possible with a single multi-hundred milliwatt pump laser operating around 1.55 μm. © 1997 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.65.Wi Nonlinear waveguides
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.79.Gn Optical waveguides and couplers
42.65.An Optical susceptibility, hyperpolarizability
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.70.Mp Nonlinear optical crystals

Room temperature 1.54 μm light emission of erbium doped Si Schottky diodes prepared by molecular beam epitaxy

Chun-Xia Du, Wei-Xin Ni, Kenneth B. Joelsson, and Göran V. Hansson

Appl. Phys. Lett. 71, 1023 (1997); http://dx.doi.org/10.1063/1.119715 (3 pages) | Cited 18 times

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Schottky-type light emitting devices have been fabricated on Er-oxide doped Si layers grown by molecular beam epitaxy, in order to study the light emission process of Er-doped Si structures. By applying a reverse bias on the Schottky junction, Er ions incorporated within the depletion layer can be electrically excited via a hot electron impact process. Rather intense electroluminescence (EL) at a wavelength of 1.54 μm has been observed at room temperature. The optoelectronic properties of the devices have been characterized by both input-power dependent and temperature dependent EL measurements. An activation energy value of ∼ 160 meV responsible for luminescence thermal quenching has been obtained. © 1997 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.30.Kk Junction diodes
61.72.uf Ge and Si

Wavelength control in II–VI laser diodes with first order distributed Bragg reflectors

D. Eisert, G. Bacher, M. Legge, A. Forchel, J. Nürnberger, K. Schüll, W. Faschinger, and G. Landwehr

Appl. Phys. Lett. 71, 1026 (1997); http://dx.doi.org/10.1063/1.119716 (3 pages) | Cited 3 times

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Longitudinal single mode emission from ZnSe-based laser diodes with first order distributed Bragg reflectors has been achieved. The emission energy could be varied in the green spectral range over more than 80 meV by changing the grating period from 97.7 to 102.2 nm. The variation of the lasing threshold current in this range is explained as a consequence of the optical gain spectrum of the structure. Wavelength fine tuning with a rate of Δλ/ΔT = 2.9×10−2 nm/K was realized by temperature variation. © 1997 American Institute of Physics.
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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
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.05.Dz II-VI semiconductors
42.60.By Design of specific laser systems

Nonlinear optical properties of armchair nanotube

Rui-Hua Xie and Jie Jiang

Appl. Phys. Lett. 71, 1029 (1997); http://dx.doi.org/10.1063/1.119717 (3 pages) | Cited 35 times

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The magnitude of the third-order nonlinear polarizability γ of armchair nanotube is theoretically studied. The calculated results for the C70 tube are consistent with those measured by Neher et al. [Opt. Lett. 17, 1491 (1992)]. The static and dynamical magnitudes of γ can be greatly enhanced by increasing the carbon number. When the carbon number is big enough, the major dynamical response peaks with large γ magnitudes are located at the optical frequency ω near the energy gap Eg (i.e., 3ω ∼ 3Eg), and the highest peak magnitude is much larger than that of C70, which is important in practical use. © 1997 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.An Optical susceptibility, hyperpolarizability
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Tr Fullerenes and related materials

Second-harmonic generation in germanosilicate glass poled with ArF laser irradiation

Takumi Fujiwara, Masahide Takahashi, and Akira J. Ikushima

Appl. Phys. Lett. 71, 1032 (1997); http://dx.doi.org/10.1063/1.119718 (3 pages) | Cited 55 times

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We report on a remarkably large second-harmonic generation (SHG) in a germanosilicate glass (15.7 GeO2–84.3 SiO2 in mol %), which was induced by poling while the sample was irradiated with the ArF laser at the wavelength of 193 nm. The SHG coefficient, d, thus induced was measured at various poling electric-field strengths using the Maker-fringe technique. The value of d increases with increasing poling field and then saturates around 1.5×105 V/cm. The largest d coefficient value obtained in this work, which is 3.4±0.3 pm/V, seems to exceed d22 of LiNbO3. Furthermore, polarization dependence of the induced SHG shows an anisotropy of the refractive index. © 1997 American Institute of Physics.
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42.70.Ce Glasses, quartz
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
77.22.Ej Polarization and depolarization
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Effects of the auxiliary electrode radius during plasma immersion ion implantation of a small cylindrical bore

X. C. Zeng, T. K. Kwok, A. G. Liu, P. K. Chu, B. Y. Tang, and T. E. Sheridan

Appl. Phys. Lett. 71, 1035 (1997); http://dx.doi.org/10.1063/1.119719 (3 pages) | Cited 22 times

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The temporal evolution of the plasma sheath in a small cylindrical bore in the presence of an auxiliary electrode is determined for different electrode radii. The ion density, velocity, flux, dose, ion energy distribution, and average impact energy are calculated by solving Poisson’s Equation and the equations of ion motion and continuity using finite difference methods. The particle-in-cell method is also used to confirm the validity of the data. Our results indicate that more ions will attain high impact energy when the auxiliary electrode radius is increased, but the dose will decrease. Our results suggest that the normalized auxiliary electrode radius should range from 0.10 to 0.30 in order to maximize the dose and produce a larger number of ions with higher impact energy. © 1997 American Institute of Physics.
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61.72.up Other materials
61.80.Jh Ion radiation effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
02.70.Bf Finite-difference methods
52.40.Hf Plasma-material interactions; boundary layer effects
52.75.-d Plasma devices

Selective thermal decomposition of ultrathin silicon oxide layers induced by electron-stimulated oxygen desorption

Heiji Watanabe, Shinobu Fujita, Shigemitsu Maruno, Ken Fujita, and Masakazu Ichikawa

Appl. Phys. Lett. 71, 1038 (1997); http://dx.doi.org/10.1063/1.119720 (3 pages) | Cited 10 times

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The mechanism of electron-beam-induced selective thermal decomposition of ultrathin oxide layers on Si surfaces was studied by scanning reflection electron microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy. We found that the change in the oxide layer composition caused by electron-stimulated oxygen desorption accounted for the selective thermal decomposition, where nanometer-scale voids were densely generated at a low heating temperature (720 °C). This implies that oxygen desorption from the oxide layers promotes the formation of a volatile oxide (SiO), and generates void nucleation sites. © 1997 American Institute of Physics.
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79.20.La Photon- and electron-stimulated desorption
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
79.20.Fv Electron impact: Auger emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.65.Mq Oxidation

Thin films of layered-structure (1−x)SrBi2Ta2O9−xBi3Ti(Ta1−yNby)O9 solid solution for ferroelectric random access memory devices

S. B. Desu, P. C. Joshi, X. Zhang, and S. O. Ryu

Appl. Phys. Lett. 71, 1041 (1997); http://dx.doi.org/10.1063/1.119721 (3 pages) | Cited 41 times

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We report on the thin films of solid–solution material (1−x)SrBi2Ta2O9−xBi3Ti(Ta1−yNby)O9 fabricated by a modified metalorganic solution deposition technique for ferroelectric random access memory devices. Using the modified technique, it was possible to obtain the pyrochlore free crystalline thin films at an annealing temperature as low as 600 °C. The solid–solution of layered perovskite materials helped us to significantly improve the ferroelectric properties, higher Pr and higher Tc, compared to SrBi2Ta2O9; a leading candidate material for memory applications. For example, the films with 0.7 SrBi2Ta2O9–0.3Bi3TiTaO9 composition and annealed in the temperature range 650–750 °C exhibited 2Pr and Ec values in the range 12.4–27.8 μC/cm2 and 68–80 kV/cm, respectively. The leakage current density was lower than 10−8 A/cm2 at an applied electric field of 200 kV/cm. The films exhibited good fatigue characteristics under bipolar stressing. © 1997 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.55.-g Dielectric thin films
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
81.40.Gh Other heat and thermomechanical treatments
77.80.B- Phase transitions and Curie point
77.80.Fm Switching phenomena
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization

Observation and control of surface morphology of AlP grown by atomic layer epitaxy

Masashi Ishii, Sohachi Iwai, Tatzuo Ueki, and Yoshinobu Aoyagi

Appl. Phys. Lett. 71, 1044 (1997); http://dx.doi.org/10.1063/1.119722 (3 pages) | Cited 6 times

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The surface of the epitaxial layer of AlP grown by atomic layer epitaxy (ALE) was observed by atomic force microscopy. It was discovered that the atomic scale surface flatness was not always retained during ALE growth even though the self-limiting growth of 1 monolayer per 1 alternative source gas supply was maintained. A reaction process model that focused on the methyl adsorbate lifetime on the Al surface was proposed to explain the experimental results. Based on this model, AlP surface morphology was improved by gas feeding control, and a flat surface with atomic steps was obtained even after 250 cycles of the ALE sequence. © 1997 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Ea III-V semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Epitaxial SrRuO3 thin films on (001) SrTiO3

C. L. Chen, Y. Cao, Z. J. Huang, Q. D. Jiang, Z. Zhang, Y. Y. Sun, W. N. Kang, L. M. Dezaneti, W. K. Chu, and C. W. Chu

Appl. Phys. Lett. 71, 1047 (1997); http://dx.doi.org/10.1063/1.119723 (3 pages) | Cited 42 times

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Highly conductive metallic oxide thin films of SrRuO3 with single crystalline quality have been grown on (001) SrTiO3 by using pulsed laser deposition. The films have a [00l] orientation with an in-plane relationship of [110]SrRuO3 // [100]SrTiO3. They have excellent metallic behavior with room temperature resistivity of ∼ 310 μΩ cm and a residual resistance ratio of about 7 at 4.2 K, the largest reported to date. A clear ferromagnetic transition at ∼ 147 K was detected by resistivity and magnetic measurements. However, the transition becomes blurred as the density-of-point defects increases in the films following a 400 keV proton irradiation with an accumulative dose up to ∼ 6.0×1016 ions/cm2. © 1997 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
73.61.Ng Insulators
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films

Surface tensions and anchoring transitions of nematic liquid crystals on gradually oxidized substrates

Pascal Hubert and Yves Galerne

Appl. Phys. Lett. 71, 1050 (1997); http://dx.doi.org/10.1063/1.119724 (3 pages) | Cited 1 time

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Intermediate anchorings of nematic liquid crystals onto substrates are now intensively studied essentially because of their potential display applications. Here, we use the active oxygen gas arising from a plasma reactor to realize progressive chemical modifications of glass substrates covered with silane. In this manner, the dispersive and nondispersive surface tensions of the substrate are gradually modified involving a continuous change in the differential wetting properties of the substrate with both parts of the liquid crystal molecules, and in the anchoring energy. Intermediate anchorings with tilted angles are thus obtained in the vicinity of an anchoring transition from the pseudohomeotropic to the planar alignment, where symmetry is broken. © 1997 American Institute of Physics.
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61.30.-v Liquid crystals
64.70.M- Transitions in liquid crystals
68.03.Cd Surface tension and related phenomena
68.08.Bc Wetting

Microstructure studies of Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloy by electron diffraction intensity analysis

Wei-Hua Wang, Qing Wei, S. Friedrich, M. P. Macht, N. Wanderka, and H. Wollenberger

Appl. Phys. Lett. 71, 1053 (1997); http://dx.doi.org/10.1063/1.119725 (3 pages) | Cited 38 times

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Reduced density function analyses for the bulk amorphous alloy Zr41Ti14Cu12.5Ni10Be22.5 and its decomposition and crystallization have been made by means of electron diffraction intensity measurement with imaging plate. The local atomic structure of the amorphous alloy as well as its development in the course of the decomposition and crystallization is described from the analysis of the atomic distribution function. The origin of the high thermal stability and the large glass forming ability of the alloy as well as the effect of the decomposition on the crystallization is discussed from the viewpoint of the local atomic structure characteristics of the alloy. © 1997 American Institute of Physics.
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61.43.Fs Glasses
64.70.K- Solid-solid transitions
64.75.-g Phase equilibria
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction

Jeff Terry, Matthew R. Linford, Christer Wigren, Renyu Cao, Piero Pianetta, and Christopher E. D. Chidsey

Appl. Phys. Lett. 71, 1056 (1997); http://dx.doi.org/10.1063/1.119726 (3 pages) | Cited 50 times

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The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H–Si bond on the H–Si(111) surface, and (ii) replacement of Cl on the Cl–Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C 1s signal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C–Si bond length of 1.85±0.05 Å. Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. © 1997 American Institute of Physics.
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79.60.Dp Adsorbed layers and thin films
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.08.-p Liquid-solid interfaces

Effect of roughness on the measurement of nanohardness—a computer simulation study

M. S. Bobji, S. K. Biswas, and J. B. Pethica

Appl. Phys. Lett. 71, 1059 (1997); http://dx.doi.org/10.1063/1.119727 (3 pages) | Cited 20 times

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This letter reports a simulation study of depth sensing nanoindentation on a rough surface. The estimated mean hardness and scatter are both influenced by roughness, irrespective of whether there is a genuine variation in mechanical property with deformation volume/depth. The scatter due to roughness always decreases with penetration depth. The roughness dependency of hardness is the product of two terms. The first term is independent of property variation with deformation volume/depth and arises due to the discrete nature of multiple contacts during indentation. The second term is due to property variation with deformation volume/depth, as changing roughness changes the aggregate strength of each contact island. © 1997 American Institute of Physics.
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81.70.Bt Mechanical testing, impact tests, static and dynamic loads
68.35.B- Structure of clean surfaces (and surface reconstruction)
62.20.F- Deformation and plasticity
62.20.Qp Friction, tribology, and hardness

Role of defect distributions and mobility on ferroelectric phase transformations in lead zirconate titanate

Qi Tan, Z. Xu, Jie-Fang Li, and Dwight Viehland

Appl. Phys. Lett. 71, 1062 (1997); http://dx.doi.org/10.1063/1.119728 (3 pages) | Cited 23 times

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Studies of the influence of defect distributions and mobility on ferroelectric phase transformations in lead zirconate titanate have been performed by transmission electron microscopy, high resolution electron microscopy, polarization switching measurements, and dielectric spectroscopy. Investigations focused on La3+ and K1+ modified lead zirconate titanates. Defects which could be randomly quenched-in from temperatures significantly above that of the ferroelectric phase transformation resulted in relaxor ferroelectric behavior characterized by polar nanodomains. However, defects which remained mobile until temperatures significantly below that of the phase transformation resulted in a normal ferroelectric state which was characterized by domain pinning. Mobile impurities/vacancies are revealed to order into chain fragments or clusters which diffuse to domain boundaries resulting in a pinning of the boundaries on cooling. © 1997 American Institute of Physics.
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77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
61.72.J- Point defects and defect clusters
66.30.Lw Diffusion of other defects
61.72.S- Impurities in crystals

Growth and characterization of phosphorous doped {111} homoepitaxial diamond thin films

S. Koizumi, M. Kamo, Y. Sato, H. Ozaki, and T. Inuzuka

Appl. Phys. Lett. 71, 1065 (1997); http://dx.doi.org/10.1063/1.119729 (3 pages) | Cited 234 times

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An n-type semiconducting diamond thin film was obtained by microwave enhanced plasma chemical vapor deposition using phosphine (PH3) as a dopant source. A homoepitaxial diamond thin film with a thickness of about 300 nm was grown on the {111} surface of a type Ib diamond with a variety of dopant concentrations. Over a wide range of dopant concentrations (PH3/CH4: 1000–20 000 ppm), the n-type conduction was confirmed by Hall-effect measurements. The activation energy of carriers was 0.43 eV. The Hall mobility of about 23 cm2/V s has been obtained at around 500 K for the 1000 ppm sample. No significant increase of hydrogen has been observed by secondary-ion-mass-spectroscopy analysis for the phosphorous doped layers. © 1997 American Institute of Physics.
Show PACS
81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
73.61.Cw Elemental semiconductors
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