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24 Jul 2000

Volume 77, Issue 4, pp. 463-603

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Biexciton emission from high-quality ZnO films grown on epitaxial GaN by plasma-assisted molecular-beam epitaxy

H. J. Ko, Y. F. Chen, T. Yao, K. Miyajima, A. Yamamoto, and T. Goto

Appl. Phys. Lett. 77, 537 (2000); http://dx.doi.org/10.1063/1.127036 (3 pages) | Cited 77 times

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We have investigated the optical and structural properties of high-quality ZnO films grown on epitaxial GaN (epi-GaN) by plasma-assisted molecular-beam epitaxy employing low-temperature buffer layers. High-resolution x-ray diffraction for both symmetric and asymmetric reflexes shows that crystalline defects in ZnO films have a similarity to epi-GaN used as a substrate. The quality of ZnO epilayers grown on epi-GaN is basically determined by epi-GaN. The photoluminescence (PL) spectrum at 10 K exhibits very sharp exciton emission with a linewidth of 1.5 meV, while deep-level emission is negligible, indicative of small residual strain. At 77 K, PL is dominated by a free-exciton emission line in the low-excitation regime, while it is overtaken by a new emission band due to biexcitons at its low-energy side as the excitation intensity increases. This biexciton emission band emerges even under the intermediate excitation regime of 100 W/cm2, which is 100 times smaller than the previously reported threshold for bulk ZnO. The biexciton binding energy is estimated to be 15 meV, in agreement with previous results. At the higher excitation regime, the emission line due to exciton–exciton scattering dominates the PL spectrum. © 2000 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
68.55.-a Thin film structure and morphology
61.72.-y Defects and impurities in crystals; microstructure
71.35.-y Excitons and related phenomena

Real-time measurements of the pseudodielectric function of low-temperature-grown GaAs

Donald A. Gajewski, Jonathan E. Guyer, and Joseph G. Pellegrino

Appl. Phys. Lett. 77, 540 (2000); http://dx.doi.org/10.1063/1.127037 (3 pages) | Cited 1 time

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We present real-time in situ spectroscopic ellipsometry (SE) measurements of the pseudodielectric function of low-temperature-grown GaAs as a function of growth temperature Tg, As2:Ga flux ratio R, and thickness. We show that the interband critical point E1 amplitude and sharpness decrease monotonically with decreasing Tg and/or increasing R for layers thinner than the critical epitaxial thickness hepi. We used in situ SE to reveal distinct signatures of the onset of polycrystalline or amorphous growth above hepi, which depends strongly on Tg. We revealed these systematic trends using in situ SE in conjunction with diffuse reflectance spectroscopy for active feedback temperature control. © 2000 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
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Charge noise analysis of an AlGaAs/GaAs quantum dot using transmission-type radio-frequency single-electron transistor technique

Toshimasa Fujisawa and Yoshiro Hirayama

Appl. Phys. Lett. 77, 543 (2000); http://dx.doi.org/10.1063/1.127038 (3 pages) | Cited 40 times

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Radio-frequency (rf)-operated single-electron transistors (SETs) are high-sensitivity, fast-response electrometers, which are valuable for developing new insights into single-charge dynamics. We investigate high-frequency (up to 1 MHz) charge noise in an AlGaAs/GaAs quantum dot using a transmission-type rf SET technique. The electron capture and emission kinetics on a trap in the vicinity of the quantum dot are dominated by a Poisson process. The maximum bandwidth for measuring single trapping events is about 1 MHz, which is the same as that required for observing single-electron tunneling oscillations in a measurable current ( ∼ 0.1 pA). © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.68.+m Photography, photographic instruments; xerography
85.35.Gv Single electron devices
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Photoelectric properties of the 0.44 eV deep level-to-band transition in gallium nitride investigated by optical admittance spectroscopy

A. Krtschil, H. Witte, M. Lisker, J. Christen, A. Krost, U. Birkle, S. Einfeldt, D. Hommel, F. Scholz, J. Off, and M. Stutzmann

Appl. Phys. Lett. 77, 546 (2000); http://dx.doi.org/10.1063/1.127039 (3 pages) | Cited 5 times

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In GaN layers grown by molecular beam epitaxy and metalorganic vapor phase epitaxy on c-axis oriented sapphire, a defect-to-band transition at a photon energy of 0.44 eV was found by optical admittance spectroscopy. This transition was investigated as a function of temperature and modulation frequency. The height of the corresponding optical admittance peak shows a thermally activated quenching with an activation energy of 0.4±0.1 eV caused by a thermal carrier emission from the same defect state to the conduction band at higher temperatures. Based on this thermal quenching, the 0.44 eV level is assigned to an electron trap located in the upper half of the gap. The spectral photoionization cross section was determined, resulting in a photoionization energy at 80 K estimated to be below 0.425 eV. The omnipresence of the 0.44 eV electron trap in GaN layers grown by various epitaxial techniques and in different reactors implicates its intrinsic nature. © 2000 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
71.55.Eq III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Spectroscopic measurements on the Andreev reflection probability as a function of temperature

J. Appenzeller, M. Jakob, H. Stahl, J. Knoch, and B. Lengeler

Appl. Phys. Lett. 77, 549 (2000); http://dx.doi.org/10.1063/1.127040 (3 pages)

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The temperature dependence of the Andreev reflection coefficient A(E,T) at a superconductor/normal-metal interface is a key issue for the critical current in a Josephson field-effect transistor at finite temperature. In this letter, we discuss our experimental observations of A(E,T) as a function of temperature determined by point contact spectroscopy. In addition, we point out major discrepancies between our findings and predictions from different theoretical models. © 2000 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects

Two-dimensional delineation of ultrashallow junctions obtained by ion implantation and excimer laser annealing

Vittorio Privitera, Corrado Spinella, Guglielmo Fortunato, and Luigi Mariucci

Appl. Phys. Lett. 77, 552 (2000); http://dx.doi.org/10.1063/1.127041 (3 pages) | Cited 19 times

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Junctions shallower than 100 nm, obtained by ion implantation and excimer laser annealing, have been characterized in two dimensions by transmission electron microscopy (TEM) on chemically treated samples. The chemical treatment selectively removes silicon as a function of the B concentration, making thinner the regions where B is present in the cross section of the sample, with respect to the n-type substrate. Both secondary ion mass spectrometry and spreading resistance profiling measurements have been performed, in order to quantify the contour line obtained by TEM in terms of B concentration. The results achieved by the two-dimensional technique show interesting features, related to the particular redistribution of B occurring when silicon is melted by excimer laser annealing irradiation. In particular, a rectangular shape of the doped region obtained by laser annealing could be evidenced, caused by the fast diffusion in the melted material, completely different from the typical half-moon-shaped, thermally annealed, two-dimensional B profile. The feasibility of ultrashallow junctions by laser annealing, with depths below 100 nm and high electrical activation, is demonstrated. However, a huge lateral diffusion in the melted silicon is also to be taken into account when considering excimer laser treatments as an alternative to standard rapid thermal annealing. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.S- Impurities in crystals
66.30.J- Diffusion of impurities

Oxide thinning percolation statistical model for soft breakdown in ultrathin gate oxides

Ming-Jer Chen, Ting-Kuo Kang, Chuan-Hsi Liu, Yih J. Chang, and Kuan-Yu Fu

Appl. Phys. Lett. 77, 555 (2000); http://dx.doi.org/10.1063/1.127042 (3 pages) | Cited 7 times

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An existing cell-based percolation model with parameter correlation can find its potential applications in assessing soft-breakdown (BD) statistics as long as the oxide thinning due to the localized physical damage near the SiO2/Si interface is accounted for. The resulting model is expressed explicitly with the critical trap number per cell nBD and the remaining oxide thickness tox′ both as parameters. Reproduction of time-to-bimodal (soft- and hard-) breakdown statistical data from 3.3-nm-thick gate-oxide samples yields nBD of 3 and 4 for soft and hard breakdown, respectively. The extracted tox′ of 1.0 nm for soft breakdown, plus the transition layer thickness of 0.5 nm in the model, is fairly comparable with literature values from current–voltage fitting. The dimension and area of the localized physically damaged region or percolation path (cell) are quantified as well. Based on the work, the origins of soft and hard breakdown are clarified in the following: (i) soft breakdown behaves intrinsically as hard breakdown, that is, they share the same defect (neutral trap) generation process and follow Poisson random statistics; (ii) both are independent events corresponding to different tox′ requirements; and (iii) hard breakdown takes place in a certain path located differently from that for the first soft breakdown. © 2000 American Institute of Physics.
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77.22.Jp Dielectric breakdown and space-charge effects
85.30.Tv Field effect devices
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Single-crystalline silicon lift-off films for metal–oxide–semiconductor devices on arbitrary substrates

A. Tilke, M. Rotter, R. H. Blick, H. Lorenz, and J. P. Kotthaus

Appl. Phys. Lett. 77, 558 (2000); http://dx.doi.org/10.1063/1.127043 (3 pages) | Cited 3 times

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We present a technique to mount single-crystalline silicon thin films on arbitrary substrates. We demonstrate in detail the preparation of a 190-nm-thin silicon metal–oxide–semiconductor field-effect transistor (MOSFET) on a silicon-on-insulator film lifted from its substrate and bonded to quartz. Functioning of this hybrid MOSFET on a rigid surface at room temperature is demonstrated. © 2000 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
85.30.Tv Field effect devices
73.61.Cw Elemental semiconductors
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.55.-a Thin film structure and morphology

Electrical properties of in situ phosphorus- and boron-doped polycrystalline SiGeC films

I. M. Anteney, G. J. Parker, P. Ashburn, and H. A. Kemhadjian

Appl. Phys. Lett. 77, 561 (2000); http://dx.doi.org/10.1063/1.127044 (3 pages) | Cited 4 times

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The sheet resistance, effective carrier concentration, and Hall mobility of in situ boron- and phosphorus-doped polycrystalline Si0.82−yGe0.18Cy films are presented for carbon contents between 0% and 4%. Phosphorus and boron doping levels of 4×1019 and 2×1020 cm−3 were achieved for the n- and p-type layers, respectively, and remained largely unaffected by carbon content. The phosphorus-doped films showed a dramatic increase in sheet resistivity and a corresponding drop in effective carrier concentration and Hall mobility. In contrast, the boron-doped films showed only a minor increase in resistivity. This is attributed to interstitial carbon increasing the defect density and also shifting the defect energy levels at the grain boundaries towards the valence band. This causes an increase in the grain-boundary energy barrier in n-type layers, but leaves the p-type layers largely unaffected. © 2000 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
81.05.Hd Other semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.80.Jc Other crystalline inorganic semiconductors
61.72.Mm Grain and twin boundaries
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Ht Other nonmetals
61.72.J- Point defects and defect clusters

Evidence for ferroelectric border traps near the SrBi2Ta2O9/Si interface through capacitance–voltage measurement

W. P. Li, R. Zhang, J. Shen, Y. M. Liu, B. Shen, P. Chen, Y. G. Zhou, J. Li, X. L. Yuan, Z. Z. Chen, Y. Shi, Z. G. Liu, and Y. D. Zheng

Appl. Phys. Lett. 77, 564 (2000); http://dx.doi.org/10.1063/1.127045 (3 pages) | Cited 7 times

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A metal–ferroelectric–semiconductor (MFS) structure has been developed by depositing SrBi2Ta2O9 (SBT) films directly on n-type (100) Si by pulsed laser deposition. In the MFS structure, evidence for ferroelectric border traps in the SBT film has been obtained by high-frequency capacitance–voltage (C–V) measurement. When the ramp rate of voltage is higher than 200 mV/s, typical ferroelectric C–V hysteresis loops with the counterclockwise direction are obtained in C–V plots. When the ramp rate is lower than 80 mV/s, the ferroelectric hysteresis loops are replaced by the trap-induced ones with the clockwise direction. This pronounced change results from the fact that more and more border traps in SBT can communicate with the underlying Si. The border-trap density at the ramp rate of 10 mV/s is as high as 1.8×1012 cm−2. Moreover, the width of the hysteresis loops changes linearly with the logarithmic decrease in ramp rate, which is consistent with the ferroelectric border traps communicating with Si by tunneling or a thermally activated process. © 2000 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
77.80.Dj Domain structure; hysteresis
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Fg Pulsed laser ablation deposition
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Transfer function and noise properties of YBa2Cu3O7−δ direct-current superconducting-quantum-interference-device magnetometers with resistively shunted inductances

F. Kahlmann, W. E. Booij, M. G. Blamire, P. F. McBrien, E. J. Tarte, N. H. Peng, C. Jeynes, E. J. Romans, and C. M. Pegrum

Appl. Phys. Lett. 77, 567 (2000); http://dx.doi.org/10.1063/1.127046 (3 pages) | Cited 6 times

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We have investigated resistively shunted direct-coupled high-Tc dc superconducting quantum interference device (SQUID) magnetometers with four different inductances (50, 100, 150, and 200 pH). The SQUIDs were based on 200 nm thick YBa2Cu3O7−δ films deposited on bicrystal substrates with a 24° misorientation angle, and the shunt resistors were fabricated by masked ion damage. At T = 77 K, good quantitative agreement was observed between the measured maximum voltage modulation depth ΔV and calculated values based on the theoretical predictions by Enpuku et al., whereas the white magnetic flux noise math at 10 kHz of all four devices was found to be a factor of 2.3 higher than predicted. The lowest white magnetic field noise of 153 fT/math was obtained for the magnetometer with a SQUID inductance of 100 pH with an outer dimension of the pickup loop of just 2 mm. © 2000 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
07.50.Hp Electrical noise and shielding equipment
07.55.Ge Magnetometers for magnetic field measurements
07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements

Surface electronic phase transition in colossal magnetoresistive manganese perovskites: La0.65Sr0.35MnO3

Hani Dulli, E. W. Plummer, P. A. Dowben, Jaewu Choi, and S.-H. Liou

Appl. Phys. Lett. 77, 570 (2000); http://dx.doi.org/10.1063/1.127047 (3 pages) | Cited 28 times

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We have observed a distinct surface phase transition for an important class of giant magnetoresistance materials [La1−xSrxMnO3(x = 0.35)]. The surface phase transition occurs at 240 K compared to 370 K for the bulk and is fundamentally different. In the bulk, a ferromagnetic metal to paramagnetic bad-metal transition occurs, while the lower-temperature surface transition is from an insulator to a semimetal. The surface of this manganese perovskite is electronically and compositionally quite different from the bulk with important implications for the behavior of artificially grown layered transition-metal oxides and for the use of surface sensitive techniques to probe the bulk. © 2000 American Institute of Physics.
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71.30.+h Metal-insulator transitions and other electronic transitions
75.47.Gk Colossal magnetoresistance
72.15.Gd Galvanomagnetic and other magnetotransport effects
72.60.+g Mixed conductivity and conductivity transitions
73.25.+i Surface conductivity and carrier phenomena
73.20.At Surface states, band structure, electron density of states

Engineering coercivity in epitaxially grown (110) films of DyFe2–YFe2 superlattices

M. Sawicki, G. J. Bowden, P. A. J. de Groot, B. D. Rainford, J. M. L. Beaujour, R. C. C. Ward, and M. R. Wells

Appl. Phys. Lett. 77, 573 (2000); http://dx.doi.org/10.1063/1.127048 (3 pages) | Cited 11 times

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Molecular beam epitaxial methods have been used to grow single crystal Laves phase DyFe2–YFe2 superlattice samples with a (110) growth direction. It is shown that it is possible, in principle, to engineer a desired coercivity between the limits KDyFe2 ⩽ K ⩽ ∞. This can be achieved by adjusting the relative thickness of the individual DyFe2 and YFe2 layers, in multilayer films This novel feature is illustrated, using the superlattice films [x Å DyFe2/(100-x) Å YFe2]×40, with x = 80, 60, 50, and 45. It is found that the measured coercivity is in semiquantitative agreement with a simple theoretical expression, for the nucleation fields in both bilayer and multilayer compounds. However, in practice, exchange spring penetration into the DyFe2 layers can set a limit to the maximum coercivity that can be achieved. © 2000 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.30.Et Exchange and superexchange interactions
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
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Analysis of the activation energy of the subthreshold current in laser- and solid-phase-crystallized polycrystalline silicon thin-film transistors

L. Pichon, A. Mercha, R. Carin, O. Bonnaud, T. Mohammed-Brahim, Y. Helen, and R. Rogel

Appl. Phys. Lett. 77, 576 (2000); http://dx.doi.org/10.1063/1.127049 (3 pages) | Cited 17 times

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Analysis of the thermal and gate-voltage dependences of the current in the subthreshold region is performed on both low-temperature laser-crystallized and solid-phase-crystallized polycrystalline silicon (polysilicon) thin-film transistors (TFTs). Temperature measurements are made at first in order to extract the variations of the activation energy EA of the drain current with the gate voltage. The plot of the subthreshold current versus the measured activation energy leads to an apparent activation energy EA/n, where the n factor is extracted from the slope of this plot. The n factor is close to 1 for laser-crystallized polysilicon TFTs while it is rather close to 2 for solid-phase-crystallized ones. These two values can be attributed to a different defect distribution in the two differently crystallized TFTs polysilicon active layers. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
81.05.Cy Elemental semiconductors
85.30.Tv Field effect devices
68.55.-a Thin film structure and morphology
61.43.Dq Amorphous semiconductors, metals, and alloys
81.15.Aa Theory and models of film growth
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors

Correlation of mobile and fixed charge creation in protonated field-effect transistors

R. A. B. Devine, K. Vanheusden, and G. V. Herrera

Appl. Phys. Lett. 77, 579 (2000); http://dx.doi.org/10.1063/1.127050 (3 pages) | Cited 2 times

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Protons have been introduced into the 40 nm gate oxides of n-channel metal–oxide–semiconductor field-effect transistors, resulting in the creation of mobile and fixed positive charge. Transistor gate lengths in the range from 5 to 70 μm have been studied. Hysteresis in the threshold voltage as large as −18 V has been measured. An inverse linear relationship has been found between the quantity of mobile and fixed charge generated. The inversion channel electron mobility is found to lie in the range 310–530 cm2 V−1 s−1. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
61.72.Cc Kinetics of defect formation and annealing
73.20.-r Electron states at surfaces and interfaces
85.30.De Semiconductor-device characterization, design, and modeling
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Piconewton regime dynamic force microscopy in liquid

Javier Tamayo, Andrew D. L. Humphris, and Mervyn J. Miles

Appl. Phys. Lett. 77, 582 (2000); http://dx.doi.org/10.1063/1.127051 (3 pages) | Cited 65 times

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In this work, a cantilever in a fluid is driven by a mixed signal composed of a standard driving signal and a feedback signal consisting of the amplified and phase shifted oscillation signal. This mimics the oscillation of a cantilever with a quality factor up to three orders of magnitude higher than its natural Q ( ∼ 1). This technique allows the identification of the resonance frequency of the cantilever by mechanical excitation of the fluid. The improved sensitivity has been checked by imaging a very soft sample of 1% agarose gel in the dynamic mode. A force smaller than 50 pN could be applied to the sample, improving the spatial resolution and the phase contrast significantly. This technique provides a major improvement in atomic force microscopy/spectroscopy in liquids. © 2000 American Institute of Physics.
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07.79.Lh Atomic force microscopes
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Analysis of a photon assisted field emission device

K. L. Jensen, Y. Y. Lau, and D. S. McGregor

Appl. Phys. Lett. 77, 585 (2000); http://dx.doi.org/10.1063/1.127052 (3 pages) | Cited 13 times

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A field emitter array held at the threshold of emission by a dc gate potential from which current pulses are triggered by the application of a laser pulse on the backside of the semiconductor may produce electron bunches (“density modulation”) at gigahertz frequencies. We develop an analytical model of such optically controlled emission from a silicon tip using a modified Wentzel–Kramers–Brillouin and Airy function approach to solving Schrödinger’s equation. Band bending and an approximation to the exchange-correlation effects on the image charge potential are included for an array of hyperbolic emitters with a distribution in tip radii and work function. For a simple relationship between the incident photon flux and the resultant electron density at the emission site, an estimation of the tunneling current is made. An example of the operation and design of such a photon-assisted field emission device is given. © 2000 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
73.30.+y Surface double layers, Schottky barriers, and work functions

Significant improvement of the emission property of Spindt-type platinum field emitters by operation in carbon monoxide ambient

Y. Gotoh, D. Nozaki, H. Tsuji, J. Ishikawa, T. Nakatani, T. Sakashita, and K. Betsui

Appl. Phys. Lett. 77, 588 (2000); http://dx.doi.org/10.1063/1.127053 (3 pages) | Cited 9 times

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The emission property of a Spindt-type platinum field emitter was greatly improved by operating in carbon monoxide ambient with appropriate operating parameters. After sufficient aging, the emitter was operated in carbon monoxide ambient up to 10−3 Pa, at the emission current of 1 μA. The emission current first decreased in accordance with the gas introduction, but turned to show rapid increase when the gas pressure was increased to 10−3 Pa. The current stability, as well as the operating voltage, was improved by this treatment. The apex of the emitter was examined with the Seppen–Katamuki analysis technique, in which detailed information on the emission area and effective work function can be read from the diagram plotted with the intercept and slope of a Fowler–Nordheim plot. The analysis suggested reduction of the effective work function is a major reason for the improvement of the emission property. © 2000 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.05.Bx Metals, semimetals, and alloys
73.30.+y Surface double layers, Schottky barriers, and work functions

Near-field microscope probe for far infrared time domain measurements

O. Mitrofanov, I. Brener, M. C. Wanke, R. R. Ruel, J. D. Wynn, A. J. Bruce, and J. Federici

Appl. Phys. Lett. 77, 591 (2000); http://dx.doi.org/10.1063/1.127054 (3 pages) | Cited 27 times

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A near-field probe fabrication technique for far-infrared frequencies based on photoconducting antennas is developed. A subwavelength-size field source is accomplished by means of an aperture and protruding high refractive index tip. The near-field probe is tested by using free space traveling electromagnetic pulses with a broadband spectrum in the range of 0.3–1.5 THz. A spatial resolution of 60 μm is achieved for a 50 μm aperture. The described probe may be used for near-field transmission microscopy in illumination and collection modes. Resolution may be further improved by means of a smaller aperture. © 2000 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.60.Hv Refractometers and reflectometers

Cathodoluminescent properties at nanometer resolution through Z-contrast scanning transmission electron microscopy

H.-J. Gao, G. Duscher, M. Kim, S. J. Pennycook, D. Kumar, K. G. Cho, and R. K. Singh

Appl. Phys. Lett. 77, 594 (2000); http://dx.doi.org/10.1063/1.127055 (3 pages) | Cited 3 times

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We report the observation of porous structures in laser-ablation-deposited Y2O3:Eu thin films and their correlation with luminescent properties by a combination of transmission electron microscopy and Z-contrast scanning transmission electron microscopy (Z-STEM). Depending on growth conditions, a large density of voids is incorporated into the films, which leads to a much increased surface area. Cathodoluminescence imaging in the STEM directly reveals a 5 nm “dead layer” around each void, which is responsible for the observed reduction in luminescence efficiency. © 2000 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Nk Insulators
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
61.43.Gt Powders, porous materials
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Ultrafast dynamics microscopy

M. Dyba, T. A. Klar, S. Jakobs, and S. W. Hell

Appl. Phys. Lett. 77, 597 (2000); http://dx.doi.org/10.1063/1.127056 (3 pages) | Cited 16 times

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We report the three-dimensional imaging of the vibrational, solvent, orientational, and electronic relaxation in organic fluorescent samples at 200–500 nm spatial resolution. This is achieved in steady-state recordings by exciting the fluorophore with a femtosecond pulse and subsequent quenching with a time-delayed, redshifted femtosecond pulse through stimulated emission. Temporal resolution of 380 fs is solely determined by the pulse widths and is further reducible. Images of submicron structures revealing vibrational and solvent relaxation gradients are shown. Furthermore, we introduce contrast modes based on stimulated emission depletion and apply them to cellular imaging. © 2000 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
78.55.Bq Liquids
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
07.60.Pb Conventional optical microscopes
63.50.-x Vibrational states in disordered systems
78.45.+h Stimulated emission
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Comment on “Lattice deformation and magnetic properties in epitaxial thin films of Sr1−xBaxRuO3” [Appl. Phys. Lett. 73, 1200 (1998)]

J. Lettieri, I. W. Scrymgeour, D. G. Schlom, M. K. Lee, and C. B. Eom

Appl. Phys. Lett. 77, 600 (2000); http://dx.doi.org/10.1063/1.127057 (2 pages) | Cited 5 times

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62.20.F- Deformation and plasticity
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
68.60.Bs Mechanical and acoustical properties
81.40.Lm Deformation, plasticity, and creep
61.66.Fn Inorganic compounds
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Response to “Comment on ‘Lattice deformation and magnetic properties in epitaxial thin films of Sr1−xBaxRuO3’ ” [Appl. Phys. Lett. 77, 600 (2000)]

Noburu Fukushima, Kenya Sano, Tatsuo Schimizu, Kazuhide Abe, Shuichi Komatsu, and Shiro Takeno

Appl. Phys. Lett. 77, 602 (2000); http://dx.doi.org/10.1063/1.127058 (2 pages)

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Show Abstract
Show PACS
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
68.60.Bs Mechanical and acoustical properties
62.20.F- Deformation and plasticity
61.66.Fn Inorganic compounds
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