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16 Dec 1996

Volume 69, Issue 25, pp. 3773-3946

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Intensity profile in a distributed feedback fiber laser characterized by a green fluorescence scanning technique

W. H. Loh, B. N. Samson, and J. P. de Sandro

Appl. Phys. Lett. 69, 3773 (1996); http://dx.doi.org/10.1063/1.116994 (3 pages) | Cited 4 times

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We report on an experimental technique for investigating the intensity profile in distributed feedback fiber lasers. By scanning along the laser length and monitoring the side green fluorescence, the intensity distribution in the laser can be inferred. With this approach, we experimentally verify the sharply peaked intensity distribution predicted for λ/4 phase‐shifted distributed feedback lasers. © 1996 American Institute of Physics.
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42.55.Wd Fiber lasers
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Dj Gratings

Enhanced emission from Eu2+ ions in sol‐gel derived Al2O3–SiO2 glasses

Masayuki Nogami and Yoshihiro Abe

Appl. Phys. Lett. 69, 3776 (1996); http://dx.doi.org/10.1063/1.116995 (3 pages) | Cited 30 times

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Eu2+ ions were incorporated in SiO2 and Al2O3–SiO2 glasses using a sol‐gel process of Si(OC2H5)4, Al(OC4H9sec)3, and EuCl3 6H2O. Glasses incorporated with the Eu2+ ions showed the emission with peak at ∼22000 cm−1 due to 4f 6 5d→4f 7(8S7/2) transition of the Eu2+ ions. 1Al2O3⋅99SiO2 (mol %) glass had an intense emission, 250 times larger than that of 100SiO2 glass. The covalency of the Eu–O bonds is decreased by the Al3+ ions. We concluded that this weak covalency causes the offset of the excited 4f 6 5d level to be small, resulting in an increase in the probability of the radiative relaxation from the 4f 6 5d to 4f 7(8S7/2) level. © 1996 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
42.70.Ce Glasses, quartz

Oxide‐free blue photoluminescence from photochemically etched porous silicon

Hiroyuki Mizuno, Hideki Koyama, and Nobuyoshi Koshida

Appl. Phys. Lett. 69, 3779 (1996); http://dx.doi.org/10.1063/1.116996 (3 pages) | Cited 65 times

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It has been shown that the blue photoluminescence (PL) of porous silicon (PS) can be obtained simply from postanodization illumination by white light without any oxidation processes. The PS samples were formed on 5–6 Ω cm p‐type (100) Si wafers. The anodization was carried out in an ethanoic HF solution at a current density of 50 mA/cm2 for 5 min in the dark. After the anodization, the samples were illuminated under the open‐circuit condition by a 500 W tungsten lamp for several minutes. The PL measurements of prepared PS samples were carried out in vacuum. With increasing the postanodization illumination time, the PL band exhibited a continuous shift from red to blue. During this blue shift, fourier transform infrared spectra did not show any signs of the growth of the surface oxide. In addition, the emission energy dependence of the PL decay time for each PL band behaved in accordance with a universal curve. These results strongly suggest that there is an oxide‐free mechanism in the PL emission from PS throughout the visible range. © 1996 American Institute of Physics.
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78.55.Mb Porous materials
81.65.Cf Surface cleaning, etching, patterning

Heterodyne interferometer with two‐wave mixing in photorefractive crystals for ultrasound detection on rough surfaces

Bruno F. Pouet, R. K. Ing, Sridhar Krishnaswamy, and D. Royer

Appl. Phys. Lett. 69, 3782 (1996); http://dx.doi.org/10.1063/1.116997 (3 pages) | Cited 13 times

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Heterodyne interferometers using two‐wave mixing in photorefractive cubic crystals for ultrasound detection on rough surfaces are demonstrated. The speckled scattered beam from a rough surface sample interferes with a planar coherent pump beam inside a photorefractive crystal. A third frequency‐shifted beam is used to read the grating. The diffracted readout beam and the transmitted signal beam are wavefront matched, resulting in an optimal heterodyne interference signal. The signal to noise ratio for the two commonly used crystallographic configurations with cubic crystals, G∥〈110〉∥ and G∥〈001〉, where G is the grating wave vector, are investigated. Very good sensitivity is demonstrated for the detection of small amplitude ultrasonic surface displacements. © 1996 American Institute of Physics.
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07.60.Ly Interferometers
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
68.35.Gy Mechanical properties; surface strains

Z‐propagating waveguide lasers in rare‐earth‐doped Ti:LiNbO3

J. Amin, J. A. Aust, and N. A. Sanford

Appl. Phys. Lett. 69, 3785 (1996); http://dx.doi.org/10.1063/1.116998 (3 pages) | Cited 55 times

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A means of reproducibly fabricating stable cw lasers in rare‐earth‐doped Ti:LiNbO3 has been demonstrated through judicious choice of waveguide orientation. Z‐propagating waveguides have been fabricated in Nd‐ and Er‐diffused Ti:LiNbO3 and room‐temperature laser operation with greatly reduced photorefractive instability has been obtained. The reduced photorefractive damage susceptibility in this waveguide configuration has led to the realization of a 980 nm pumped laser in Er:Ti:LiNbO3, with a threshold of 10.5 mW of absorbed pump power and a slope efficiency of 8.5%. © 1996 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.82.Et Waveguides, couplers, and arrays

Mach–Zehnder interferometer measurement of the Pockels effect in a poled polymer film with a coplanar electrode structure

H. R. Cho, M. J. Shin, S. H. Han, and J. W. Wu

Appl. Phys. Lett. 69, 3788 (1996); http://dx.doi.org/10.1063/1.116999 (3 pages) | Cited 5 times

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Mach–Zehnder interferometry was used to measure the Pockels effect in a poled electro‐optic polymer thin film with a coplanar electrode structure. The beam at the sample arm of the Mach–Zehnder interferometer passed through a polymer thin film which had been spin‐coated on top of a clear gap between two electrodes patterned on an optical substrate. This unique optical geometry enabled the Pockels coefficients of the poled electro‐optic polymer film in the directions of the ordinary and the extraordinary optic axes to be determined independently. As an example, the tensor ratio r33/r13 for a stilbene‐dye‐doped polyimide guest/host polymer film was determined experimentally; the ratio turned out to be 4.6, which was higher than the value of 3 predicted by the thermodynamic model. © 1996 American Institute of Physics.
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42.70.Jk Polymers and organics
78.20.Jq Electro-optical effects
78.66.Qn Polymers; organic compounds
07.60.Ly Interferometers

Time evolution of structural changes and second‐order optical nonlinearity of hemicyanine doped silica film

Lei Xu, Liying Liu, Jing Yu, Wencheng Wang, and Fuming Li

Appl. Phys. Lett. 69, 3791 (1996); http://dx.doi.org/10.1063/1.117000 (3 pages) | Cited 3 times

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Hemicyanine‐doped silica film was fabricated by sol–gel technique. Time evolution of structural changes in hemicyanine and their influence on the second‐order optical nonlinearity were investigated through UV‐visible absorption and second‐harmonic generation (SHG) measurements. We found that the conversion of protonated hemicyanine to monomeric and aggregated hemicyanine occurred within 4 h after film deposition. During this period of time the SHG signal continued to rise and finally reached the maximum. The growth of optical nonlinearity was mainly due to deprotonation of hemicyanine molecules. Blueshift of the absorption peaks for both aggregate and monomer were found during the drying of the film. © 1996 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Sq Composite materials
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Efficient green light‐emitting diodes from a phenylated derivative of poly(p‐phenylene–vinylene)

F. Cacialli, R. H. Friend, N. Haylett, R. Daik, W. J. Feast, D. A. dos Santos, and J. L. Brédas

Appl. Phys. Lett. 69, 3794 (1996); http://dx.doi.org/10.1063/1.117001 (3 pages) | Cited 31 times

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We have used polyvinylcarbazole, PVK, in combination with poly(p‐phenylene vinylene), PPV and a green‐emitting, soluble derivative, poly(4,4′‐diphenylene diphenylvinylene) or briefly PDPV, to fabricate triple‐layer light‐emitting diodes PPV/PVK/PDPV/metal, with indium tin oxide as the anode. We report luminances in excess of 1300 cd/m2 with Al cathodes, turn‐on voltages of ∼8 V in structures 300 nm thick, and internal efficiencies in the range 0.4%–0.8% for Al and Ca cathodes; at least ten times higher than for single‐layer PDPV devices. Quantum efficiencies for Ca or Al electrodes are only a factor 1.5 different. The improvements over single‐layer PDPV devices are considered to be due to better hole injection by PPV and to the formation of a hole barrier at the PPV/PVK interface, which forces a better balance of the electron and hole currents. © 1996 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence

Defect structures in metallic photonic crystals

E. Özbay, B. Temelkuran, M. Sigalas, G. Tuttle, C. M. Soukoulis, and K. M. Ho

Appl. Phys. Lett. 69, 3797 (1996); http://dx.doi.org/10.1063/1.117002 (3 pages) | Cited 56 times

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We have investigated metallic photonic crystals built around a layer‐by‐layer geometry. Two different crystal structures (face‐centered‐tetragonal and tetragonal) were built and their properties were compared. We obtained rejection rates of 7–8 dB per layer from both metallic crystals. Defect modes created by removing rods resulted in high peak transmission (80%), and high quality factors (1740). Our measurements were in good agreement with theoretical simulations. © 1996 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.50.-p Quantum optics

Output performance of a dye‐doped sol‐gel silica laser in the near UV

Chao Ye, King‐Shun Lam, Kin‐Pong Chik, Dennis Lo, and Kin‐Hung Wong

Appl. Phys. Lett. 69, 3800 (1996); http://dx.doi.org/10.1063/1.117109 (3 pages) | Cited 9 times

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Visibly transparent near‐UV dye (Exalite 377E)‐doped silica in the form of parallelepiped were prepared by the low‐temperature sol‐gel process. The laser output performance of dye‐doped sol‐gel silica samples pumped by a short pulse (1 ns) N2 laser at 337 nm was reported. With a grating as the wavelength selection element, the laser was tuned from 367 to 387 nm with a laser linewidth of 2 nm. Using a resonator cavity consisting of two flat mirrors, the sol‐gel laser showed a slope efficiency of 34.7% and a pump energy threshold of 20 μJ. The variation of sol‐gel laser energy output as a function of the number of pulses under repetitive N2 laser excitation was investigated. The laser output energy decreased initially with the number of shots. The output energy recovered to its original intensity after a ten minute interruption in pumping. In this way, the dye‐doped samples showed no signs of long term degradation after being irradiated at 337 nm for tens of thousand shots. © 1996 American Institute of Physics.
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42.55.Mv Dye lasers
42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Ce Glasses, quartz
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Large photoinduced ferroelectric coercive field increase and photodefined domain pattern in lithium‐tantalate crystal

Shiuh Chao and Chien‐Chung Hung

Appl. Phys. Lett. 69, 3803 (1996); http://dx.doi.org/10.1063/1.117110 (3 pages) | Cited 4 times

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We found that the ferroelectric coercive field of LiTaO3, both in forward and reverse directions, can be increased in large amount by high power multiline argon laser illumination. This phenomenon is especially profound when the coercive field measurement is performed closer in time to the previous domain inversion operation. We also demonstrated that the domain in lithium‐tantalate crystal can be patterned in accordance with the argon laser light distribution on the crystal plate surface. © 1996 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.70.Mp Nonlinear optical crystals

Single molecule fluorescence in inhomogeneous environments

Lukas Novotny

Appl. Phys. Lett. 69, 3806 (1996); http://dx.doi.org/10.1063/1.117111 (3 pages) | Cited 57 times

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A single molecule in an inhomogeneous environment is studied theoretically using phenomenological theory. The molecule is located on a planar glass substrate and a finite sized, three dimensional object is scanned over the molecule at different heights. Lifetime and quantum yield are calculated as a function of the lateral position of the object. The analysis is based on a new field expansion method using Green’s functions of a layered reference system as basis functions. It is found that, near the edges of the object, the molecular lifetime is highly sensitive to the orientation of the transition dipole. © 1996 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
07.79.Fc Near-field scanning optical microscopes
33.50.-j Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion)
03.50.De Classical electromagnetism, Maxwell equations

High resolution fluorescence imaging with cantilevered near‐field fiber optic probes

Chad E. Talley, Gregory A. Cooksey, and Robert C. Dunn

Appl. Phys. Lett. 69, 3809 (1996); http://dx.doi.org/10.1063/1.117112 (3 pages) | Cited 34 times

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High resolution near‐field fluorescence and topology images of intact neurons are reported using a cantilevered near‐field fiber optic probe. A bend is introduced into a normal geometry near‐field tip, allowing the probe to be used in a tapping‐mode arrangement, similar to tapping‐mode atomic force microscopy. Features with a full width at half‐maximum of 140 nm are observed in the near‐field fluorescence image, demonstrating the subdiffraction limit spatial resolution possible with the cantilevered near‐field probe design. Characteristics of the cantilevered tips include resonances between 30 and 60 kHz, Q factors greater than 100, and measured spring constants of 300 to 400 N/m. © 1996 American Institute of Physics.
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87.64.Dz Scanning tunneling and atomic force microscopy
07.79.-v Scanning probe microscopes and components

Fourth‐harmonic generation of picosecond glass laser pulses with cesium lithium borate crystals

Lalit B. Sharma, H. Daido, Y. Kato, S. Nakai, T. Zhang, Y. Mori, and T. Sasaki

Appl. Phys. Lett. 69, 3812 (1996); http://dx.doi.org/10.1063/1.117113 (3 pages) | Cited 5 times

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We report the fourth‐harmonic generation of 1.5 ps, 1.053 μm glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW/cm2 using newly developed crystal, cesium lithium borate (CsLiB6O10). Type‐I doubler and type‐I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24% and 53% have been achieved for frequency quadrupling and doubling of the fundamental glass laser pulses, respectively. © 1996 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Mp Nonlinear optical crystals
42.55.Rz Doped-insulator lasers and other solid state lasers
42.79.Nv Optical frequency converters

Improving the plasma immersion ion implantation impact energy inside a cylindrical bore by using an auxiliary electrode

Xuchu Zeng, Baoyin Tang, and Paul K. Chu

Appl. Phys. Lett. 69, 3815 (1996); http://dx.doi.org/10.1063/1.117114 (3 pages) | Cited 24 times

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We propose a method to improve the impact energy of ions implanted into the interior sidewalls of cylindrical specimens during plasma immersion ion implantation. Our idea is based on a zero potential conductive auxiliary electrode positioned at the axis of the implanted cylindrical bore. We calculate the structure of the ion‐matrix sheath in an infinitely long cylindrical bore with an auxiliary electrode and analyze the dependence of the radius of the auxiliary electrode on the electric field in the bore. Our results show that the auxiliary electrode improves significantly the distributions of the potential and the electric field inside the cylindrical bore. In addition, because the auxiliary electrode improves the potential drop from axis to sidewalls of the bore and introduces an electric field component which does not vary when the ions are implanted into the sidewalls, the impact energy can be improved in a cylindrical bore during plasma immersion ion implantation. © 1996 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.40.Hf Plasma-material interactions; boundary layer effects
61.80.Jh Ion radiation effects

Stochastic electron heating in bounded radio‐frequency plasmas

I. D. Kaganovich, V. I. Kolobov, and L. D. Tsendin

Appl. Phys. Lett. 69, 3818 (1996); http://dx.doi.org/10.1063/1.117115 (3 pages) | Cited 2 times

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The mechanisms of electron heating in low‐pressure bounded rf plasmas are analyzed. These processes are determined by the combined effect of electron interaction with the rf electric field, reflections from the walls and collisions. It is shown that when the discharge gap is small with respect to the electron mean‐free path the finite size of the plasmas is crucial for the stochastic heating. A classification of heating regimes is performed and expressions for the power deposition are derived. In many cases, even though in a semi‐infinite plasma heating exists, in a bounded plasma the electron motion is regular and there is no collisionless heating. © 1996 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
52.20.-j Elementary processes in plasmas

Kinetics of processes in the Ti–Si1−xGex systems

W. Freiman, A. Eyal, Yu. L. Khait, R. Beserman, and K. Dettmer

Appl. Phys. Lett. 69, 3821 (1996); http://dx.doi.org/10.1063/1.117116 (3 pages) | Cited 12 times

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The kinetics of processes related to the formation of C49 and C54 Ti(Si1−yGey)2 germanosilicide phases in the two relaxed and strained Ti/Si1−xGex systems (x1=0.35 and x2=0.20) in the temperature range 600–800 °C are considered. These processes have been studied through Auger electron spectroscopy, secondary ion mass spectroscopy, x‐ray diffraction, and Raman scattering spectroscopy supported by ion beam etching techniques. Si/Ge ‘‘intergrain’’ alloy has been found between the grains of the C49 or/and C54 phases, with a Ge‐rich part Si1−zGez of z=2x–3x in the upper region. At higher temperatures, the Ge concentration in the Ge‐rich alloy decreases and its volume increases. The temperature required for obtaining similar changes are higher when x2<x1. A kinetic electron‐related model is proposed to explain the observed phenomena. © 1996 American Institute of Physics.
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68.55.Nq Composition and phase identification
68.60.Dv Thermal stability; thermal effects
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Characterization of 3C–SiC crystals grown by thermal decomposition of methyltrichlorosilane

A. J. Steckl, J. Devrajan, S. Tlali, H. E. Jackson, C. Tran, S. N. Gorin, and L. M. Ivanova

Appl. Phys. Lett. 69, 3824 (1996); http://dx.doi.org/10.1063/1.117117 (3 pages) | Cited 11 times

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Single crystal 3C–SiC platelets, formed by thermal decomposition of methyltrichlorosilane at 1650–1750 °C, have been characterized in terms of structure and morphology. The platelets are ∼3–5 mm in length and 1–1.5 mm in thickness. The (111) C face of the crystal, which has an effective zero growth rate, presents a large, mirrorlike surface in the as‐grown 3C crystals. Atomic force microscopy indicates that these as‐grown surfaces are extraordinarily flat and uniform, with a mean surface roughness of 1–2 Å. This value is comparable with the roughness of state‐of‐art polished Si wafers. X‐ray rocking curves of the 〈111〉 peak were obtained with a linewidth of 12.3 arcsec. This is the smallest value reported to date for any polytype of SiC. Raman spectroscopy at 300 K reveals a very sharp TO–phonon peak at 797.8 cm−1, with a linewidth of 2.1 cm−1. © 1996 American Institute of Physics.
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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
61.05.C- X-ray diffraction and scattering
81.10.Bk Growth from vapor
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Brillouin spectroscopy on dried sonogels

M. García‐Hernández, R. J. Jiménez‐Riobóo, C. Prieto, J. J. Fuentes‐Gallego, E. Blanco, and M. Ramírez‐del‐Solar

Appl. Phys. Lett. 69, 3827 (1996); http://dx.doi.org/10.1063/1.117118 (3 pages) | Cited 4 times

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The elastic properties of organically modified silicates prepared by ultrasonics aided polycondensation of Tetraethoxysilane and Polidimethylsiloxane is studied by means of high resolution Brillouin spectroscopy. Our results evidence the microseparation of the organic and inorganic phases for the systems with high content of polymer. We propose a mechanical model that qualitatively explains the observed variation of the elastic constant c11 vs molar fraction of dimethylsiloxane in these vitreous materials and develop a structural model that accounts for the observed dynamical behavior. © 1996 American Institute of Physics.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.05.Pj Glass-based composites, vitroceramics
62.20.D- Elasticity
82.70.Gg Gels and sols

Measuring Ge segregation by real‐time stress monitoring during Si1−xGex molecular beam epitaxy

J. A. Floro and E. Chason

Appl. Phys. Lett. 69, 3830 (1996); http://dx.doi.org/10.1063/1.117119 (3 pages) | Cited 27 times

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Real‐time stress measurements during Si1−xGex/Si molecular beam epitaxy are used to dynamically monitor Ge surface segregation. Segregation during alloy growth produces a change in the surface stress that offsets the coherency stress in the pseudomorphic film. We outline a method for analyzing the stress evolution kinetics to determine the alloy composition profile resulting from segregation. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.60.Bs Mechanical and acoustical properties
68.55.Nq Composition and phase identification
81.30.Mh Solid-phase precipitation

Quantitative orientational analysis of a polymeric material (Kevlar® fibers) with x‐ray microspectroscopy

A. P. Smith and H. Ade

Appl. Phys. Lett. 69, 3833 (1996); http://dx.doi.org/10.1063/1.117120 (3 pages) | Cited 17 times

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It has previously been shown that x‐ray linear dichroism microscopy can be utilized to image and determine orientation in a polymeric material at high spatial resolution. We have now expanded on this technique and extracted quantitative information about the orientation of specific functional groups in a polymeric system from submicron areas. This is accomplished by acquiring and analyzing spectral data sets rather than just images at specific energies. It has allowed us to compare the relative lateral orientation of various grades of Kevlar® fibers. © 1996 American Institute of Physics.
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61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
61.41.+e Polymers, elastomers, and plastics
07.85.Nc X-ray and γ-ray spectrometers

Electron paramagnetic resonance characterization of diamond films fabricated with different methane concentrations

D. J. Keeble and B. Ramakrishnan

Appl. Phys. Lett. 69, 3836 (1996); http://dx.doi.org/10.1063/1.117121 (3 pages)

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Electron paramagnetic resonance (EPR) studies were performed on thin diamond films fabricated by hot‐filament chemical vapor deposition using methane concentrations varying from 0.25% to 5%. The bulk spin concentration and the peak to peak linewidth for the characteristic g=2.0027(2) EPR spectrum were found to increase for samples grown with increased methane concentration. The results show the spectrum contains component/s due to paramagnetic defects related to nondiamond carbon phases within the films. © 1996 American Institute of Physics.
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61.72.J- Point defects and defect clusters
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
76.30.-v Electron paramagnetic resonance and relaxation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Structural and ferroelectric properties of the c‐axis oriented SrBi2Ta2O9 thin films deposited by the radio‐frequency magnetron sputtering

T. K. Song, J.‐K. Lee, and H. J. Jung

Appl. Phys. Lett. 69, 3839 (1996); http://dx.doi.org/10.1063/1.117122 (3 pages) | Cited 52 times

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Radio‐frequency magnetron sputtering was used to deposit SrBi2Ta2O9 ferroelectric thin films on Pt(111)/Ti/SiO2/Si(001) substrates. Thin films were deposited at room temperature with argon pressures of 0.5–100 mTorr and with sputtering power of 2.5 W/cm2. The crystal orientations of thin films were strongly affected by the argon pressures, the c‐axis oriented SrBi2Ta2O9 thin film was obtained with argon pressure of 30 mTorr. The crystal structures of the c‐axis oriented SrBi2Ta2O9 thin film were investigated by x‐ray diffraction methods: θ‐2θ scan, rocking curve, and ϕ scans. The well aligned microstructure was observed with the average grain size of about 2000 Å in an atomic force microscopic image. Ferroelectric properties were observed for the c‐axis oriented thin film: Pr∗−PrΛ and Ec were 9.7 μC/cm2 and 50 kV/cm, respectively, with excitation voltage of 3 V. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
77.80.Fm Switching phenomena
81.15.Cd Deposition by sputtering

The relationship between the spatially resolved field emission characteristics and the raman spectra of a nanocrystalline diamond cold cathode

A. A. Talin, L. S. Pan, K. F. McCarty, T. E. Felter, H. J. Doerr, and R. F. Bunshah

Appl. Phys. Lett. 69, 3842 (1996); http://dx.doi.org/10.1063/1.117123 (3 pages) | Cited 108 times

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Spatially resolved electron field emission measurements from a nanocrystalline diamond film grown by plasma‐enhanced chemical transport deposition have been obtained using a scanning probe apparatus with micrometer resolution. Macroscopic regions with a high emission site density, and turn‐on fields below 3 V/μm, comprised approximately 1/2 of the total sample area. The emitting and the nonemitting regions of the specimen are differentiated distinctly by Raman spectra and subtly by morphologies. Both areas are largely sp3‐bonded, but only the nonemitting regions exhibit a sharp line at 1332 cm−1, a well‐known signature of diamond in larger crystallites. © 1996 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
78.30.Am Elemental semiconductors and insulators
85.45.Db Field emitters and arrays, cold electron emitters
81.07.-b Nanoscale materials and structures: fabrication and characterization

Helium ion‐induced stoichiometry modification in hydrogenated silicon oxide films

C. Godet, R. Etemadi, and C. Clerc

Appl. Phys. Lett. 69, 3845 (1996); http://dx.doi.org/10.1063/1.117124 (3 pages) | Cited 6 times

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The stoichiometry of amorphous hydrogenated silicon oxide films, grown in a dual‐plasma system, has been investigated using elastic recoil detection (ERD), Rutherford backscattering, and infrared transmission. During ERD measurement of H profiles, using a 4He2+ beam of 3.0 MeV, ion‐induced depletion of hydrogen atoms was observed, homogeneous over the 1 μm film thickness. Si‐rich films (with H essentially bonded as Si–H) and nearly stoichiometric films (with H only bonded in Si–OH configurations) have been compared. The depletion is more pronounced in nearly stoichiometric oxides, whereas the apparent cross sections (≊1–2 nm2) are similar for both types of films. These observations are discussed in terms of an electron excitation process, with a subsequent chemical reconstruction via electron‐hole recombination. © 1996 American Institute of Physics.
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61.66.Bi Elemental solids
61.66.Dk Alloys
61.80.Jh Ion radiation effects
61.43.Dq Amorphous semiconductors, metals, and alloys
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