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21 Jul 1997

Volume 71, Issue 3, pp. 297-421

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Excitation of a single molecule on the surface of a spherical microcavity

D. J. Norris, M. Kuwata-Gonokami, and W. E. Moerner

Appl. Phys. Lett. 71, 297 (1997); http://dx.doi.org/10.1063/1.119554 (3 pages) | Cited 19 times

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We use the optical resonance of a spherical microcavity (quality factor ∼ 106) to excite a single molecule. By attaching a p-terphenyl crystal doped with pentacene and terrylene molecules to a dielectric sphere, we detect individual molecules excited by the near field of the cavity. A low-temperature optical microscope is utilized to image the emission from the single molecule, determine its position on the sphere surface, and measure its absorption linewidth. These results demonstrate the feasibility of single-molecule cavity quantum electrodynamics. © 1997 American Institute of Physics.
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12.20.Fv Experimental tests
31.50.Df Potential energy surfaces for excited electronic states

Wavelength switching in multicavity lasers

A. P. Kanjamala and A. F. J. Levi

Appl. Phys. Lett. 71, 300 (1997); http://dx.doi.org/10.1063/1.119555 (3 pages) | Cited 2 times

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By controlling optical loss in a multiple cavity laser, it is possible to sequentially switch the lasing wavelength with a mode suppression ratio greater than −35 dB. Our experiments use an antireflection coated semiconductor laser diode with optical feedback from Bragg gratings embedded in a single mode fiber. Residual reflectivity from the antireflection coating plays a critical role in determining device operation. © 1997 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
84.32.Dd Connectors, relays, and switches
85.30.-z Semiconductor devices

Crystal growth, spectroscopic characterization, and laser performance of a new efficient laser material Nd:Ba5(PO4)3F

G. B. Loutts, C. Bonner, C. Meegoda, H. Ries, M. A. Noginov, N. Noginova, M. Curley, P. Venkateswarlu, A. Rapaport, and M. Bass

Appl. Phys. Lett. 71, 303 (1997); http://dx.doi.org/10.1063/1.119556 (3 pages) | Cited 15 times

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High quality single crystals of neodymium doped barium fluorapatite have been grown by the Czochralski technique and evaluated as an optical gain medium. A product of the emission cross section and lifetime of Nd3+ luminescence of more than 1.8×10−22 cm2 s at 1055 nm, and laser performance with slope efficiency up to 65% have been obtained. © 1997 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
81.10.Fq Growth from melts; zone melting and refining
78.55.Hx Other solid inorganic materials

Photothermal measurements at picowatt resolution using uncooled micro-optomechanical sensors

J. Varesi, J. Lai, T. Perazzo, Z. Shi, and A. Majumdar

Appl. Phys. Lett. 71, 306 (1997); http://dx.doi.org/10.1063/1.120440 (3 pages) | Cited 43 times

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Deflections of bimaterial microcantilever beams were optically detected with 400 fm resolution at room temperature. This enabled photothermal radiation detection with resolutions of 40 pW for power and 10 fJ for energy. The resolution was improved by an order of magnitude by optimizing the thickness ratio of the two beam materials, as well as by modulating the incident radiation at sufficiently high frequency to be in the range of the thermal white noise limit of the cantilever vibrations. Radiative power was detected with a noise spectral density of and 250 pW/math and detectivity, D∗, of 4.6×107 cm math/W. © 1997 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Optical control of electric field poling in LiTaO3

Graeme W. Ross, Peter G. R. Smith, and Robert W. Eason

Appl. Phys. Lett. 71, 309 (1997); http://dx.doi.org/10.1063/1.119557 (3 pages) | Cited 5 times

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A room temperature technique is presented for optically inducing periodic domain-inverted structures in bulk (0.2 mm thick) LiTaO3. By simultaneous application of an electric field and patterned illumination using UV wavelengths (351 and 364 nm), we demonstrate modulation of the resulting domain profile. We discuss the origins of the observed optical effect and describe our results from repeated domain switching, by cycling the electric field. © 1997 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena

Improvement of the lasing performance of copper vapor laser by adding Sc atoms as energy donors

Hironobu Kimura, Masaru Chinen, Takuya Nayuki, and Hiroshi Saitoh

Appl. Phys. Lett. 71, 312 (1997); http://dx.doi.org/10.1063/1.119558 (3 pages) | Cited 2 times

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The lasing performance of a copper vapor laser with a 60 mm diameter and 2000 mm discharge length has been improved by adding Sc atoms. As a typical result, a 28% increase of output power and electrical-optical conversion efficiency has been obtained. The result was qualitatively but reasonably interpreted as indicating that the upper laser level was enhanced by the collisional energy transfer from a response of Sc atoms to a resonance-excited state of Cu atoms. © 1997 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers

Second harmonic generation of the output of an AlGaAs diode oscillator amplifier system in critically phase matched LiB3O5 and β-BaB2O4

B. Beier, D. Woll, M. Scheidt, K.-J. Boller, and R. Wallenstein

Appl. Phys. Lett. 71, 315 (1997); http://dx.doi.org/10.1063/1.119559 (3 pages) | Cited 15 times

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Blue 403 nm laser light is generated by frequency doubling the radiation of an AlGaAs diode laser oscillator amplifier system in critically phase matched LiB3O5 (LBO) and β-BaB2O4 (BBO) crystals. The laser system emits 400 mW of single frequency 806 nm radiation in an almost diffraction limited beam. For optimum doubling efficiency the laser radiation is enhanced by a resonant external ring cavity. The nonlinear crystal is placed at a resonator internal focus. Using a 16-mm-long LBO crystal a diode laser power of 387 mW generated 98 mW of second harmonic radiation, corresponding to a conversion efficiency of 25%. The same power was obtained in a 12- mm-long BBO crystal with a laser power of 417 mW. The measured conversion efficiencies are in good agreement with the values calculated for critically phase matched conversion in these nonlinear materials. © 1997 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes

Dielectric fluid motors

Yasufumi Otsubo and Kazuya Edamura

Appl. Phys. Lett. 71, 318 (1997); http://dx.doi.org/10.1063/1.119560 (3 pages) | Cited 15 times

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On the application of high electric fields to a dielectric fluid, a convective motion of the fluid is induced. By controlling the fluid motion in nonuniform dc fields, a new type of fluid motor is developed. An angular velocity of more than 15 s−1 (150 rpm) can be achieved at a dc voltage of 5 kV for a motor with a rotor radius of 10 mm. The efficiency of energy transformation from electric to kinetic energy is about 4%. Since magnetic fields and switching circuits are not required, the advantage of the fluid motor will be enhanced by size reduction. The dielectric fluid motor is attractive as a source of mechanical energy in a micromachine. © 1997 American Institute of Physics.
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84.50.+d Electric motors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
47.65.-d Magnetohydrodynamics and electrohydrodynamics
47.27.T- Turbulent transport processes

Resonance Raman and photoluminescence investigations of micro-twins in homoepitaxially grown chemical vapor deposited diamond

Yogesh K. Vohra, Andrew Israel, and Shane A. Catledge

Appl. Phys. Lett. 71, 321 (1997); http://dx.doi.org/10.1063/1.119561 (3 pages) | Cited 9 times

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Resonance Raman and photoluminescence (PL) investigations of the {100}〈111〉 penetration twin that forms during homoepitaxial diamond growth on (100) diamond substrates by microwave plasma chemical vapor deposition is reported on. A homoepitaxially grown diamond film of 0.13 mm thickness and 1.6 mm diameter was studied with blue (457.9 nm), green (514.5 nm), and red (647.1 nm) laser excitation. The amorphous carbon incorporated in the twin crystal shows resonance Raman enhancement with 647.1 nm excitation. PL spectroscopy reveals increased incorporation of nitrogen-vacancy (N-V) and nitrogen di-vacancy (N-V2) defects in the twin as well as a new defect not observed in the bulk of the film. The present studies show that once the micro-twins are nucleated they form a preferential site for the incorporation of amorphous carbon and other nitrogen-based defects. © 1997 American Institute of Physics.
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81.05.Cy Elemental semiconductors
78.55.Ap Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
81.05.ub Fullerenes and related materials
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Mm Grain and twin boundaries
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.J- Point defects and defect clusters

Fabrication of amorphous-carbon-nitride field emitters

Eung Joon Chi, Jae Yeob Shim, Hong Koo Baik, and Sung Man Lee

Appl. Phys. Lett. 71, 324 (1997); http://dx.doi.org/10.1063/1.119562 (3 pages) | Cited 46 times

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To improve silicon field emitters, an amorphous-carbon-nitride (a-CN) coating was applied by helical resonator plasma-enhanced chemical vapor deposition. By this process, a-CN was very uniformly coated on silicon tips without any damage. Microstructural and electrical investigation of the silicon and a-CN coated field emitters were performed. a-CN coating lowered turn-on voltage and increased emission current. Negative electron affinity of carbon nitride is suggested for enhancing emission current. © 1997 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.05.Cy Elemental semiconductors
85.45.Db Field emitters and arrays, cold electron emitters
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.)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Hydrogen complexes in epitaxial BaTiO3 thin films

Gyu-Chul Yi, Bruce A. Block, and Bruce W. Wessels

Appl. Phys. Lett. 71, 327 (1997); http://dx.doi.org/10.1063/1.119529 (3 pages) | Cited 6 times

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Hydrogen complexes in epitaxial BaTiO3 thin films are investigated using Fourier transform infrared spectroscopy. Both undoped and Er-doped layers were grown using low-pressure metal–organic chemical vapor deposition. From the infrared spectra of the undoped and Er-doped films grown at 750–800 °C, infrared absorption was observed at 3486 cm−1. The absorption peak is attributed to a vibrational mode of O–H in BaTiO3. Moreover, the Er-doped layers showed additional absorption peaks at 2905 and 2964 cm−1. The peaks are ascribed to the vibrational modes of C–H complexes in the Er-doped layers. © 1997 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Nk Insulators
77.55.-g Dielectric thin films
78.30.Hv Other nonmetallic inorganics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.40.Ha Other nonmetallic inorganics

Local structural order around dopant atoms in Fe- and Co-doped ternary alloys based on γ′-Ni3Al

Mahalingam Balasubramanian, Rex Lyver, Joseph I. Budnick, and Douglas M. Pease

Appl. Phys. Lett. 71, 330 (1997); http://dx.doi.org/10.1063/1.119919 (3 pages) | Cited 1 time

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We have utilized x-ray absorption fine structure (XAFS) to study the local structural order of dopants in ternary alloys of the composition Ni75(Fe/Co)xAl25−x. In γ′-Ni75Al25, the first coordination shell around Al consists of 12 Ni atoms, whereas Ni is surrounded by 8 Ni and 4 Al atoms. Cobalt absorbers exclusively occupy the Ni sublattice, yet the Co XAFS shows only Co–Ni bond contributions in the first peak of the Fourier transform, with the Al backscattering being either completely absent or so weak that it is masked by the strong Ni backscattering background. A model based on a highly distorted Al sublattice, created by dopant atoms occupying the Ni sublattice, gives a possible explanation for the absence of Al backscattering contributions, and furnishes an explanation for our results on Fe dopants in γ′-Ni3Al, as well as results from similar studies by others on doped γ′ nickel aluminides. © 1997 American Institute of Physics.
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61.66.Dk Alloys
78.70.Dm X-ray absorption spectra

Structural limitation to the material strength of electrorheological fluids

Xiao-Dong Pan and Gareth H. McKinley

Appl. Phys. Lett. 71, 333 (1997); http://dx.doi.org/10.1063/1.119530 (3 pages) | Cited 7 times

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The variation of the dynamic modulus of a model electrorheological fluid with strain amplitude is shown to closely resemble that of traditional physical gels. Comparison of the in-phase stress component in each system indicates that the material strength of electrorheological fluids in shear is limited by the small strain amplitude to structural failure. An anisotropic network model is proposed for electrorheological fluids, in which the primary structure consists of chains of particles spanning the electrode gap along the field direction, while many-body interactions form a secondary structure of short chains tilted with respect to the field direction and interconnecting the primary chains. A geometrical argument shows that the tensile strain in the secondary structure can be an order of magnitude larger than that in the primary chains. This nonuniform strain distribution poses an inherent structural limitation on the shear material strength of electrorheological fluids. © 1997 American Institute of Physics.
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83.80.Gv Electro- and magnetorheological fluids
83.60.Np Effects of electric and magnetic fields
62.10.+s Mechanical properties of liquids

Dielectric properties of silicon nitride films deposited by microwave electron cyclotron resonance plasma chemical vapor deposition at low temperature

Chao Ye, Zhaoyuan Ning, Mingrong Shen, Hao Wang, and Zhaoqiang Gan

Appl. Phys. Lett. 71, 336 (1997); http://dx.doi.org/10.1063/1.119531 (2 pages) | Cited 6 times

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The dielectric properties of amorphous silicon nitride (SiNx) films that were prepared by microwave electron cyclotron resonance plasma chemical vapor deposition at low temperature in the frequency range 5 Hz–1 MHz have been investigated. The dielectric dispersion in the frequency range exhibits two fractional power laws of (ϵ′−ϵ∞′)∝ω−p1 and (ϵ′−ϵ∞′)∝ωn1−1 with p1 = 0.12–0.18 and n1 = 0.95–0.96. These are close to the result predicted by the many-cluster anomalous conduction theory of fractal structure. © 1997 American Institute of Physics.
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77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.61.Ng Insulators
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.)

Photoreflectance study of the substrate-film interface of GaAs homoepitaxial structures with different in situ substrate surface cleaning processes

Máximo López-López, Miguel Meléndez-Lira, and Shigeo Goto

Appl. Phys. Lett. 71, 338 (1997); http://dx.doi.org/10.1063/1.119564 (3 pages) | Cited 7 times

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The substrate-film interface of GaAs homoepitaxial structures prepared by molecular beam epitaxy, employing three different in situ treatments for the substrate surface preparation: (1) cleaning by hydrogen radicals (H∗), (2) exposure to trisdimethylaminoarsine (TDMAAs), and (3) the usual thermal cleaning under an arsenic flux have been studied. The concentrations of interfacial residual impurities of C and O were measured by secondary ion mass spectroscopy (SIMS). These impurities pin the Fermi level producing an interfacial electric field, whose strength was evaluated by photoreflectance spectroscopy. For semi-insulating substrates, the usual thermal cleaning process resulted in very high concentrations of C (2×1019 atoms/cm3) and O (1.3×1018 atoms/cm3) at the interface, producing a large electric field (1.3×106 V/m). The impurities were drastically diminished to below the SIMS detection limit by using the H∗ cleaning, and as a result the electric field was effectively reduced. On the other hand, we observed higher concentrations of impurities, and larger interfacial electric fields on Si-doped substrates. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness
81.65.Cf Surface cleaning, etching, patterning
78.66.Fd III-V semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.-e Optical properties of bulk materials and thin films

Preconditioning of c-plane sapphire for GaN epitaxy by radio frequency plasma nitridation

Christian Heinlein, Jostein Grepstad, Torunn Berge, and Henning Riechert

Appl. Phys. Lett. 71, 341 (1997); http://dx.doi.org/10.1063/1.119532 (3 pages) | Cited 29 times

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The crystalline quality of molecular beam epitaxy grown layers of GaN on sapphire is generally improved by nitridation of the substrate. In this study, we use x-ray photoelectron spectroscopy, low energy electron diffraction, and atomic force microscopy to examine the case for nitridation of c-plane sapphire upon exposure to rf plasma generated nitrogen radicals. We find that a monolayer of surface nitride is formed after ∼ 300 min exposure with the substrate at 400 °C. Extended exposure causes growth of protrusions from the c-plane sapphire and thus leads to a rough surface morphology. Moreover, we report removal of adventitious surface carbon upon heat treatment at 300 °C in nitrogen plasma, albeit with reduced efficiency compared with hydrogen plasma cleaning. © 1997 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
79.60.Jv Interfaces; heterostructures; nanostructures
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
81.40.Gh Other heat and thermomechanical treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation

Fabrication of dry etched CdZnSe/ZnSe quantum wires by thermally assisted electron cyclotron resonance etching

T. Kümmell, G. Bacher, A. Forchel, J. Nürnberger, W. Faschinger, G. Landwehr, B. Jobst, and D. Hommel

Appl. Phys. Lett. 71, 344 (1997); http://dx.doi.org/10.1063/1.119533 (3 pages) | Cited 3 times

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A low damage dry etch technology suitable for in situ processing was developed for the fabrication of ZnSe-based nanostructures. Thermally assisted electron cyclotron resonance etching combines plasma etching at low ion energies with process temperatures between 80°C and 210°C. Due to a variation of the process parameters, i.e., plasma power and sample temperature, a transition from partially physical to prevailing chemical etch properties is obtained. Therefore an accurate control of etch profile, surface morphology, and etch rate is possible. Optically active CdZnSe/ZnSe quantum wires with lateral sizes down to 20 nm were realized, indicating a significantly reduced influence of optically inactive layers compared to conventionally dry etched nanostructures. In narrow wires, a systematic blue shift of the photoluminescence signal with decreasing wire width clearly demonstrates lateral carrier confinement effects. © 1997 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.65.Cf Surface cleaning, etching, patterning
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.23.-b Electronic transport in mesoscopic systems

On the kinetics of growth of highly defective GaN epilayers and the origin of the deep trap responsible for yellow-band luminescence

H. Liu, J. G. Kim, M. H. Ludwig, and R. M. Park

Appl. Phys. Lett. 71, 347 (1997); http://dx.doi.org/10.1063/1.119971 (3 pages) | Cited 14 times

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The kinetics of growth of GaN/(0001) sapphire heteroepitaxial films have been examined in the relatively low substrate temperature range, 560–640 °C, using the reflection high energy electron diffraction (RHEED) specular reflection intensity monitoring technique. In particular, an alternate element exposure method of growth was employed in which Ga and N atoms were supplied separately (rather than simultaneously, as in conventional molecular beam epitaxy) to the substrate with the inclusion of a time delay between successive Ga flux and N flux exposures. We interpret the observed time dependent recovery of the RHEED specular reflection intensity during the time delay phases to be associated with Ga–N surface molecule migration on Ga-terminated surfaces and the activation energy for this migration process was determined to be 1.45±0.25 eV. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.35.Fx Diffusion; interface formation
61.72.J- Point defects and defect clusters
61.72.Lk Linear defects: dislocations, disclinations
61.72.Yx Interaction between different crystal defects; gettering effect

Optical investigation of strain and defects in (100) CdTe/Ge/Si and ZnTe/Ge/Si grown by molecular beam epitaxy

J. W. Hutchins, B. J. Skromme, Y. P. Chen, S. Sivananthan, and J. B. Posthill

Appl. Phys. Lett. 71, 350 (1997); http://dx.doi.org/10.1063/1.119534 (3 pages) | Cited 4 times

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Low temperature (1.7 K) reflectance and photoluminescence (PL) have been used to assess residual strain and impurities in molecular beam epitaxial (100) CdTe/Ge/Si and (100) ZnTe/Ge/Si. Both types of samples exhibit residual biaxial tensile thermal strain as expected from differences in previous thermal expansion data, but the measured magnitudes (0.72×10−3 for CdTe/Ge/Si and 1.5×10−3 for ZnTe/Ge/Si) are smaller than predicted. The results are consistent with either residual lattice mismatch stress or partial relaxation of the thermal strain during cooling. Residual acceptors in the CdTe include Cu and a frequently observed 49 meV level, whose PL peaks lack the previously reported linear polarization. However, a new series of linearly polarized bound exciton lines is reported in CdTe. © 1997 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
68.35.Ct Interface structure and roughness
68.35.Gy Mechanical properties; surface strains
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Db Elemental semiconductors and insulators
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Si single electron tunneling transistor with nanoscale floating dot stacked on a Coulomb island by self-aligned process

Anri Nakajima, Toshiro Futatsugi, Kinjiro Kosemura, Tetsu Fukano, and Naoki Yokoyama

Appl. Phys. Lett. 71, 353 (1997); http://dx.doi.org/10.1063/1.119535 (3 pages) | Cited 28 times

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We fabricated a Si single electron tunneling transistor which has a nanoscale floating dot gate stacked on a Coulomb island by a self-aligned process. This device exhibits drain current (Id) oscillations due to the Coulomb blockade effect and quantized threshold voltage (Vth) shifts resulting from a single electron tunneling from the channel to the floating dot gate. The high on/off current ratio of the Id oscillation combined with the quantized Vth shifts leads to the possibility of developing ultralow power consumption memory. © 1997 American Institute of Physics.
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85.35.Gv Single electron devices
73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Ds Quantum interference devices

La0.5Sr0.5CoO3/Pb(Nb0.04Zr0.28Ti0.68)O3/La0.5Sr0.5CoO3 thin film heterostructures on Si using TiN/Pt conducting barrier

B. Yang, S. Aggarwal, A. M. Dhote, T. K. Song, R. Ramesh, and J. S. Lee

Appl. Phys. Lett. 71, 356 (1997); http://dx.doi.org/10.1063/1.119536 (3 pages) | Cited 40 times

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A high density ferroelectric memory process flow requires the integration of conducting barrier layers to connect the drain of the pass-gate transistor to the bottom electrode of the ferroelectric stack. We are studying the effect of crystallinity of the TiN/Pt barrier layer with Si wafers on the ferroelectric properties of La0.5Sr0.5CoO3/Pb(Nb0.04Zr0.28Ti0.68)O3/La0.5Sr0.5CoO3 (LSCO/PNZT/LSCO) capacitors. Structural studies indicate complete phase purity (i.e., fully perovskite) in both epitaxial and polycrystalline materials. The polycrystalline capacitors show lower remnant polarization and coercive voltages. However, the retention, fatigue, and imprint characteristics are similar, indicating minimal influence of crystalline quality on the ferroelectric properties. © 1997 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
68.35.Ct Interface structure and roughness
77.22.Ej Polarization and depolarization

Ex situ ellipsometry characterization of excimer laser annealed amorphous silicon thin films grown by low pressure chemical vapor deposition

Chau-Hong Kuo, In-Cha Hsieh, Dieter K. Schroder, George N. Maracas, Sheau Chen, and Thomas W. Sigmon

Appl. Phys. Lett. 71, 359 (1997); http://dx.doi.org/10.1063/1.119537 (3 pages) | Cited 5 times

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Spectroscopic ellipsometry was used to monitor excimer laser annealed thin ( ∼ 100 nm) amorphous silicon (a-Si) films grown on quartz substrates by low pressure chemical vapor deposition (LPCVD). The peak position of the imaginary part of the complex dielectric function ϵ2 was used to determine the degree of crystallization of the a-Si. The amplitude of ϵ2 at the Si E1 transition energy is found to be a good indicator of the polycrystalline silicon (poly-Si) grain size after laser annealing with good correlation between ex situ ellipsometric data and poly-Si grain sizes being observed. Spectroscopic ellipsometry provides a contactless, nondestructive, and simple technique for monitoring laser annealing both in situ during the annealing process or ex situ after annealing. © 1997 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
77.22.Ch Permittivity (dielectric function)
64.70.K- Solid-solid transitions

Atomic-scale nature of the (3×3)-ordered GaAs(001):N surface prepared by plasma-assisted molecular-beam epitaxy

S. Gwo, H. Tokumoto, and S. Miwa

Appl. Phys. Lett. 71, 362 (1997); http://dx.doi.org/10.1063/1.119538 (3 pages) | Cited 22 times

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In situ scanning tunneling microscopy and time-resolved reflection high-energy electron diffraction measurements were performed to study the nitridation process of the As-terminated GaAs(001)-(2×4) surface by using electron cyclotron resonance plasma-assisted molecular-beam epitaxy. We report the real-space atomic structure of the coherently strained (3×3)-ordered GaN monolayer on GaAs(001) after a limited-exposure nitridation process and the atomically smooth morphology of this nitrided surface. The unique (3×3) phase is found consisting of nitrogen dimers and a regular array of missing nitrogen rows in both [110] and [110] directions.© 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
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation

The effect of the boron doping level on the thermal behavior of end-of-range defects in silicon

C. Bonafos, A. Claverie, D. Alquier, C. Bergaud, A. Martinez, L. Laânab, and D. Mathiot

Appl. Phys. Lett. 71, 365 (1997); http://dx.doi.org/10.1063/1.119563 (3 pages) | Cited 18 times

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The effect of the doping level on the formation and growth of end-of-range (EOR) defects is studied. Transmission electron microscopy observations have been performed on boron doped Si wafers (from 1015 to 1020 atom3) preamorphized with germanium and subjected to rapid thermal annealing. When increasing the doping level up to a few 1018 atom3, a delay in the coarsening process encountered by the loops is observed while above this threshold the EOR defects quickly disappear. These results are interpreted by considering three possibly concomitant phenomena: the formation of boron/Si-interstitial clusters, the gettering of boron at the loop periphery, and a change from the intrinsic to the extrinsic regime for self-diffusion. Moreover, an estimate of the effective trapping efficiency of boron is reached and gives about 1±0.3 Si interstitial per boron atom, a value consistent with the one obtained from studies of B transient enhanced diffusion. © 1997 American Institute of Physics.
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61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.Yx Interaction between different crystal defects; gettering effect

Surface morphology of GaN films determined from quantitative x-ray reflectivity

D. Lederman, Zhonghai Yu, T. H. Myers, and M. R. Richards-Babb

Appl. Phys. Lett. 71, 368 (1997); http://dx.doi.org/10.1063/1.119539 (3 pages) | Cited 4 times

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The surface of two GaN films grown under Ga-rich conditions by molecular beam epitaxy was characterized using x-ray reflectivity, assuming a self-affine/fractal surface morphology. The surface height fluctuations were similar for both samples at the largest lateral length scales at which the fractal description is valid, although this lateral length was significantly greater and the “jaggedness” significantly smaller for the sample grown under higher Ga flux. Previous atomic force microscopy images revealed a higher density of large features on the surface for the sample grown under lower Ga flux. The lateral size of the features are dominated by a convolution of the atomic force microscopy tip shape and the actual features on the surface, which precludes an accurate determination of the surface structure at length scales smaller than the tip radius. This study illustrates the importance of using different techniques to evaluate the film surface morphology at different length scales. © 1997 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.05.cm X-ray reflectometry (surfaces, interfaces, films)
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