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17 Jul 2000

Volume 77, Issue 3, pp. 313-459

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In-plane magnetophotoluminescence studies of modulation-doped GaAs/AlGaAs coupled double quantum wells

Yongmin Kim, C. H. Perry, J. A. Simmons, and J. F. Klem

Appl. Phys. Lett. 77, 388 (2000); http://dx.doi.org/10.1063/1.126985 (3 pages) | Cited 3 times

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In-plane magnetic-field photoluminescence spectra from a series of n-type modulation-doped GaAs/Al0.3Ga0.7As coupled double quantum wells show distinctive doublet structures related to the tunnel-split ground sublevel states. The magnetic-field behavior of the upper transition from the antisymmetric state strongly depends on sample mobility. In a lower mobility sample, the transition energy displays an N-type kink with field (namely, a maximum followed by a minimum), whereas higher mobility samples have a linear dependence. The former is attributed to a coupling mechanism due to homogeneous broadening of the electron and hole states. The results are in good agreement with recent theoretical calculations. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.20.Ls Magneto-optical effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors

Atomic-force-microscopy investigation of the formation and evolution of Ge islands on GexSi1−x strained layers

C. J. Huang, D. Z. Li, Z. Yu, B. W. Cheng, J. Z. Yu, and Q. M. Wang

Appl. Phys. Lett. 77, 391 (2000); http://dx.doi.org/10.1063/1.126986 (3 pages) | Cited 3 times

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A constant amount of Ge was deposited on strained GexSi1−x layers of approximately the same thickness but with different alloy compositions, ranging from x = 0.06 to x = 0.19. From their atomic-force-microscopy images, we found that both the size and density of Ge islands increased with the Ge composition of the strained layer. By conservation of mass, this implies that these islands must incorporate material from the underlying strained layer. © 2000 American Institute of Physics.
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68.55.Nq Composition and phase identification
68.60.Bs Mechanical and acoustical properties
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

Statistical analysis of near-field photoluminescence spectra of single ultrathin layers of CdSe/ZnSe

G. von Freymann, E. Kurtz, C. Klingshirn, and M. Wegener

Appl. Phys. Lett. 77, 394 (2000); http://dx.doi.org/10.1063/1.126987 (3 pages) | Cited 17 times

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The statistical analysis of thousands of near-field photoluminescence spectra of single ultrathin CdSe layers at 20 K exhibits a strong positive correlation peak around 20 meV energy with a width of 5 meV. Our data are consistent with individual spectra which consist of sets of many pairs of lines. In each pair, the two lines must have comparable strength. We speculate about the origin of these pairs. © 2000 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Room temperature InAsSb photovoltaic midinfrared detector

A. Rakovska, V. Berger, X. Marcadet, B. Vinter, G. Glastre, T. Oksenhendler, and D. Kaplan

Appl. Phys. Lett. 77, 397 (2000); http://dx.doi.org/10.1063/1.126988 (3 pages) | Cited 23 times

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An InAs0.91Sb0.09 p-i-n photovoltaic midinfrared detector grown by molecular beam epitaxy and operating at room temperature is presented. An R0A of 1.05 Ω cm2 at 250 K and 0.12 Ω cm2 at 295 K has been achieved, resulting in a detectivity of 4.5×109 cmmath/W at 3.39 μm and 250 K. The quality of the active region material ensures a sufficiently low generation-recombination current. Room temperature performances are limited by the diffusion of holes from the active region through the confining barriers. © 2000 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
73.50.Pz Photoconduction and photovoltaic effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
85.60.Dw Photodiodes; phototransistors; photoresistors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors

Minority carrier diffusion, defects, and localization in InGaAsN, with 2% nitrogen

Steven R. Kurtz, A. A. Allerman, C. H. Seager, R. M. Sieg, and E. D. Jones

Appl. Phys. Lett. 77, 400 (2000); http://dx.doi.org/10.1063/1.126989 (3 pages) | Cited 79 times

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Electron and hole transport in compensated InGaAsN ( ≈ 2% N) are examined through Hall mobility, photoconductivity, and solar cell photoresponse measurements. Short minority carrier diffusion lengths, photoconductive-response spectra, and doping dependent, thermally activated Hall mobilities reveal a broad distribution of localized states. At this stage of development, lateral carrier transport appears to be limited by large scale (≫ mean free path) material inhomogeneities, not a random alloy-induced mobility edge. © 2000 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.My Galvanomagnetic and other magnetotransport effects
72.40.+w Photoconduction and photovoltaic effects
72.20.Ee Mobility edges; hopping transport
84.60.Jt Photoelectric conversion

Improved thermal stability of GaN{0001} surfaces by adsorbed C60 molecules

Hermann Nienhaus, Carsten Schepers, Stefan P. Grabowski, and Winfried Mönch

Appl. Phys. Lett. 77, 403 (2000); http://dx.doi.org/10.1063/1.126990 (3 pages) | Cited 2 times

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Adsorption and desorption of C60 molecules on GaN{0001}-1×1 surfaces as well as the surface decomposition by heating were investigated with Auger electron spectroscopy. The first monolayer of C60 forms strong chemical bonds to the substrate atoms. A seven-step annealing procedure at temperatures up to 1275 K is presented which completely removes the adsorbed carbon without decomposing the surface. If the process is applied to clean, uncovered GaN{0001}-1×1 surfaces thermal etching with a significant Ga atom loss is observed. The results indicate that adsorbed C60 increases the thermal stability of the surfaces considerably and that thermal etching begins at defects or steps at the surface where the molecules are most strongly bound. © 2000 American Institute of Physics.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
78.66.Tr Fullerenes and related materials
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.60.Dv Thermal stability; thermal effects
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
79.20.Fv Electron impact: Auger emission
81.65.Cf Surface cleaning, etching, patterning

Mobility enhancement in conjugated polymer field-effect transistors through chain alignment in a liquid-crystalline phase

H. Sirringhaus, R. J. Wilson, R. H. Friend, M. Inbasekaran, W. Wu, E. P. Woo, M. Grell, and D. D. C. Bradley

Appl. Phys. Lett. 77, 406 (2000); http://dx.doi.org/10.1063/1.126991 (3 pages) | Cited 326 times

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A method is demonstrated by which liquid-crystalline self-organization in rigid-rod nematic conjugated polymers can be used to control the microstructure of the active semiconducting layer in solution-processed polymer thin-film transistors (TFTs). Enhanced charge carrier mobilities of 0.01–0.02 cm2/V s and good operating stability have been achieved in polyfluorene copolymer TFTs by preparing the polymer in a nematic glassy state and by aligning the polymer chains parallel to the transport direction with the help of an alignment layer. Mobility anisotropies of 5–8 for current flow parallel and perpendicular to the alignment direction have been observed that are of the same order of magnitude as optical dichroic ratios. © 2000 American Institute of Physics.
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85.65.+h Molecular electronic devices
85.30.Tv Field effect devices
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
61.41.+e Polymers, elastomers, and plastics

Strain relaxation and segregation effects during self-assembled InAs quantum dots formation on GaAs(001)

J. M. García, J. P. Silveira, and F. Briones

Appl. Phys. Lett. 77, 409 (2000); http://dx.doi.org/10.1063/1.126992 (3 pages) | Cited 56 times

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In segregation effects during InAs growth on GaAs(001) and critical thickness for InAs self-assembled quantum dots are studied using a real time, in situ technique capable of measuring accumulated stress during growth. Due to a large ( ∼ 50%) surface In segregation of floating In, self-assembled dot formation takes place when less than one monolayer of InAs is pseudomorphically grown on GaAs. A picture of the growth process is discussed on the basis of the equilibrium between InAs and floating In dominated by the stress energy. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.35.Dv Composition, segregation; defects and impurities
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties

Nanoscale characterization of stresses in semiconductor devices by quantitative electron diffraction

J. Demarest, R. Hull, K. T. Schonenberg, and K. G. F. Janssens

Appl. Phys. Lett. 77, 412 (2000); http://dx.doi.org/10.1063/1.126993 (3 pages) | Cited 9 times

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By using transmission electron microscopy and focused ion beam technology in conjunction with finite element and electron diffraction contrast simulations, we have been able to quantitatively measure stresses in semiconductor devices with a spatial resolution on the order of tens of nanometers and a sensitivity on the order of tens of mega pascals. Examples of measuring stresses around shallow isolation trenches in semiconductor device structures are presented. © 2000 American Institute of Physics.
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85.30.De Semiconductor-device characterization, design, and modeling
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.10.Lw Balance systems, tensile machines, etc.
85.30.Pq Bipolar transistors
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Crosstalk canceling for laser-assisted magnetic recording

M. Hamamoto, K. Kojima, J. Sato, H. Katayama, and Y. Murakami

Appl. Phys. Lett. 77, 415 (2000); http://dx.doi.org/10.1063/1.126994 (3 pages) | Cited 5 times

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A promising method of crosstalk canceling is proposed for laser-assisted magnetic recording, which makes it possible to record and read with a narrow track pitch limited to nearly the size of a focused laser spot. In this method, a track pitch narrower than the laser spot size is obtained by utilizing the canceling of the leakage flux from an adjacent track. We achieved a crosstalk of −24 dB or less with a 0.7 μm track pitch in laser-assisted magnetic recording by using a laser spot size of 1.07 μm in diameter and a magnetoresistive head with a track width of 1.4 μm. © 2000 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Magnetocaloric effect in Gd2PdSi3

E. V. Sampathkumaran, I. Das, R. Rawat, and Subham Majumdar

Appl. Phys. Lett. 77, 418 (2000); http://dx.doi.org/10.1063/1.126995 (3 pages) | Cited 25 times

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The influence of the application of a magnetic field (H) on the temperature (T) dependence of heat capacity and isothermal magnetization has been investigated in Gd2PdSi3, a compound ordering antiferromagnetically below (TN = )21 K in zero H. Among other findings, the one to be emphasized is the observation of significant magnetocaloric effect (MCE) over about a 30 K range with a peak in the vicinity of TN. This finding suggests that this material could be useful for magnetic refrigeration below 50 K. The results also establish that either of the two experimental methods—heat capacity or magnetization—can be applied to identify materials with large MCE. © 2000 American Institute of Physics.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics

Sm(Co, Fe, Cu, Zr)z magnets fabricated by simple processing

W. Tang, Y. Zhang, and G. C. Hadjipanayis

Appl. Phys. Lett. 77, 421 (2000); http://dx.doi.org/10.1063/1.126996 (2 pages) | Cited 13 times

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Optimization studies in Sm(Co, Cu, Fe, Zr)z magnets for high-temperature applications led to some compositions which develop their high coercivity with simple processing. Homogenized magnets with higher Cu and Zr content acquire a coercivity of above 20 kOe after a short aging (3 h) at 850 °C without the traditional slow cooling to 400 °C which is required for the commercial magnets. Microstructure studies showed that the homogenized magnets consist of a mixture of Sm(Co, Cu)5 precipitates in a disordered 2:17 matrix as compared to a uniform and featureless microstructure of the traditional homogenized magnets. Because of this, the time required for the full development of uniform cellular and lamellar structures with the right microchemistry is much shorter in the magnets. © 2000 American Institute of Physics.
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75.50.Ww Permanent magnets
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.05.Bx Metals, semimetals, and alloys
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
81.30.Mh Solid-phase precipitation
75.50.Bb Fe and its alloys

Magnetization reversal of ferromagnetic/antiferromagnetic bilayers

Zhanjie Li and Shufeng Zhang

Appl. Phys. Lett. 77, 423 (2000); http://dx.doi.org/10.1063/1.126997 (3 pages) | Cited 28 times

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By incorporating random interfacial exchange interaction into the Landau–Lifshitz–Gilbert equation, we show that magnetization reversal of exchange-biased films possesses unique hysteresis features. A detail magnetization reversal process for different ferromagnetic layer thickness is analyzed. © 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
75.30.Et Exchange and superexchange interactions
75.70.Kw Domain structure (including magnetic bubbles and vortices)

Thermally stable, soft FeXN thin films

Yi-Kuang Liu and M. H. Kryder

Appl. Phys. Lett. 77, 426 (2000); http://dx.doi.org/10.1063/1.126998 (3 pages) | Cited 13 times

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Significant improvement of the thermal stability in FeXN (X=Al, Zr, Ta,…) thin films is reported. Sputtered at the reduced target–substrate spacing of 38 mm, 200-nm-thick thermally stable FeXN thin films are obtained. They have hard-axis coercivity ≈ 0.1–2.0 Oe, easy-axis coercivity ≈1.5–3.0 Oe, Hk ≈ 8–16 Oe, and Bs ≈ 19–20 kG. Results of transverse-field annealing experiments in a uniform field of 700 Oe show no significant change of magnetic properties at 150 °C for 3 h. At 150 °C for 24 h Hk decreases by 2–4 Oe. Their easy/hard axes do not rotate and the coercivity remains almost unchanged. This superior thermal stability of FeXN films is very promising for high-moment write heads. © 2000 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Rs Electrical and magnetic properties related to treatment conditions
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
81.15.Cd Deposition by sputtering

Submillimeter spectroscopy of tilted Nd1.85Ce0.15CuO4−δ films: Observation of a mixed ac-plane excitation

A. Pimenov, A. V. Pronin, A. Loidl, A. P. Kampf, S. I. Krasnosvobodtsev, and V. S. Nozdrin

Appl. Phys. Lett. 77, 429 (2000); http://dx.doi.org/10.1063/1.126999 (3 pages) | Cited 3 times

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The anisotropic conductivity of a series of tilted Nd1.85Ce0.15CuO4−δ thin films was measured by quasioptical spectroscopy in the frequency range 6 cm−1<ν<40 cm−1. Two characteristic features have been observed in the low-temperature transmission spectra. The first one at ν = 12 cm−1 was shown to reflect the c-axis plasma frequency of Nd1.85Ce0.15CuO4−δ. The second feature represents a mixed ab-plane/c-axis excitation. The frequency of this resonance may be changed in a controllable way by rotating the polarization of the incident radiation. © 2000 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
78.70.Gq Microwave and radio-frequency interactions
74.25.F- Transport properties

Superconducting quantum wells for the detection of submillimeter wave electromagnetic radiation

Faiz Rahman and Trevor Thornton

Appl. Phys. Lett. 77, 432 (2000); http://dx.doi.org/10.1063/1.127000 (3 pages) | Cited 2 times

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We propose the use of superconducting quantum well structures for use as detectors of submillimeter wave radiation. The energy levels formed due to quantum confinement by superconducting barriers provide a useful system for radiation sensing. The well width could be readily altered by varying the temperature or the strength of an applied magnetic field so that the levels can be shifted in energy. This provides a means of tuning the detector over a range of frequencies in the terahertz range, enabling both photometric and spectroscopic observations. Also, the structure of the device should permit use of cofabricated antennas allowing efficient radiation coupling into the active region of the device. The geometry also allows the possibility of implementing one- and two-dimensional arrays. © 2000 American Institute of Physics.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
84.40.Ba Antennas: theory, components and accessories
07.60.Dq Photometers, radiometers, and colorimeters
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Electric field dependence of ferroelectric phase transition in epitaxial SrTiO3 films on SrRuO3 and La0.5Sr0.5CoO3

K. C. Park and J. H. Cho

Appl. Phys. Lett. 77, 435 (2000); http://dx.doi.org/10.1063/1.127001 (3 pages) | Cited 24 times

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We report on the electric field dependence of ferroelectric phase transition in epitaxial SrTiO3 (STO) thin films grown by the pulsed-laser ablation deposition method. Metallic oxides SrRuO3 (SRO) and La0.5Sr0.5CoO3 (LSCO) were used as the bottom electrodes, and the bottom electrodes influence the dielectric properties of STO films. The change in the dielectric properties originates from the different work functions and the lattice mismatches among STO film, the bottom electrode, and the substrate. However, the field-induced ferroelectric phase transition temperatures of the STO/SRO/(100) STO and the STO/LSCO/(100) LaAlO3 systems are proportional to the applied electric field, indicating a field-induced first-order ferroelectric phase transition. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)

Role of substrate on the dielectric and piezoelectric behavior of epitaxial lead magnesium niobate-lead titanate relaxor thin films

V. Nagarajan, S. P. Alpay, C. S. Ganpule, B. K. Nagaraj, S. Aggarwal, E. D. Williams, A. L. Roytburd, and R. Ramesh

Appl. Phys. Lett. 77, 438 (2000); http://dx.doi.org/10.1063/1.127002 (3 pages) | Cited 54 times

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The effect of various substrates on the electrical and electromechanical properties of 100-nm-thick epitaxial 0.9[Pb(Mg1/3Nb2/3)O3]–0.1[PbTiO3](0.9PMN–0.1PT) thin films is investigated. (001) 0.9PMN–0.1PT films are grown on (001)LaAlO3(LAO), (La, Sr)(Al, Ta)O3(LSAT), SrTiO3(STO), and MgO substrates with 40-nm-thick top and bottom La0.5Sr0.5CoO3 electrodes by pulsed laser deposition. X-ray diffraction results indicate that the films on LAO, LSAT, and STO are stressed biaxially in compression in the film-substrate interface whereas the films on MgO are stressed in tension. A decrease in the temperature of dielectric maximum (Tm) together with an increase in the dielectric constant and the longitudinal piezomodulus is observed with decreasing in-plane epitaxial stresses for LAO, LSAT, and STO substrates. The films on MgO substrates have the highest dielectric constant and piezomodulus with Tm below room temperature. The variation in Tm may be attributed to the shift in the transformation temperature from the paraelectric state to the relaxor state due to internal stresses in the film-substrate interface. Electrical and electromechanical properties should depend strongly on internal stresses in the vicinity of the phase transformation, which is reflected in our experimental observations. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.65.Bn Piezoelectric and electrostrictive constants
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Fg Pulsed laser ablation deposition
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
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Random telegraph signals of tetrahedral-shaped recess field-effect transistor memory cell with a hole-trapping floating quantum dot gate

Masashi Shima, Yoshiki Sakuma, Yuji Awano, and Naoki Yokoyama

Appl. Phys. Lett. 77, 441 (2000); http://dx.doi.org/10.1063/1.127003 (3 pages) | Cited 2 times

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An AlGaAs/InGaAs heterojunction field-effect transistor (FET) memory cell in a tetrahedral-shaped recess (TSR) on the (111)B GaAs substrate was fabricated and investigated. The TSR–FET memory cell has a channel on the (111)A facet surfaces of the recess and a hole-trapping quantum dot (QD) as a floating gate at the bottom. Memory operations were achieved at temperatures up to 130 K, and random telegraph signals (RTSs) with a temperature dependence were observed in the retention characteristics. After our analysis of RTSs, the activation energy of hole capture and emission processes in the TSR QD were estimated to be 260 and 190 meV, respectively. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
84.30.Sk Pulse and digital circuits
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.50.Td Noise processes and phenomena
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Metal–semiconductor–metal GaN ultraviolet photodetectors on Si(111)

Z. M. Zhao, R. L. Jiang, P. Chen, D. J. Xi, Z. Y. Luo, R. Zhang, B. Shen, Z. Z. Chen, and Y. D. Zheng

Appl. Phys. Lett. 77, 444 (2000); http://dx.doi.org/10.1063/1.127004 (3 pages) | Cited 19 times

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GaN metal–semiconductor–metal photoconductive detectors have been fabricated on Si(111) substrates. The GaN epitaxial layers were grown on Si substrates by means of metalorganic chemical-vapor deposition. These detectors exhibited a sharp cutoff at the wavelength of 363 nm and a high responsivity at a wavelength from 360 to 250 nm. A maximum responsivity of 6.9 A/W was achieved at 357 nm with a 5 V bias. The relationship between the responsivity and the bias voltage was measured. The responsivity saturated when the bias voltage reached 5 V. The response time of 4.8 ms was determined by the measurements of photocurrent versus modulation frequency. © 2000 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.61.Ey III-V semiconductors

Superconducting device with transistor-like properties including large current amplification

G. P. Pepe, G. Ammendola, G. Peluso, A. Barone, L. Parlato, E. Esposito, R. Monaco, and N. E. Booth

Appl. Phys. Lett. 77, 447 (2000); http://dx.doi.org/10.1063/1.127005 (3 pages) | Cited 10 times

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We have fabricated and studied a stacked superconducting double tunnel junction device with transistor-like properties. The intermediate electrode is a bilayer consisting of a Nb film together with an Al film that acts as a quasiparticle trap. Large current gains of more than 50 are observed at 4.2 K when the Al layer is normal. The operation is highly directional. Results are explained on the basis of trapping of quasiparticles from a superconductor into a normal metal, together with a conversion of relaxation energy into electronic excitations. Similar devices should have wide applications in low-temperature measurement and detection systems. © 2000 American Institute of Physics.
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85.25.Cp Josephson devices
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Mechanical resonant immunospecific biological detector

B. Ilic, D. Czaplewski, H. G. Craighead, P. Neuzil, C. Campagnolo, and C. Batt

Appl. Phys. Lett. 77, 450 (2000); http://dx.doi.org/10.1063/1.127006 (3 pages) | Cited 176 times

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We have demonstrated high-sensitivity detection of bacteria using an array of bulk micromachined resonant cantilevers. The biological sensor is a micromechanical oscillator that consists of an array of silicon-nitride cantilevers with an immobilized antibody layer on the surface of the resonator. Measured resonant frequency shift as a function of the additional cell loading was observed and correlated to the mass of the specifically bound Escherichia coli O157:H7 cells. Deposition and subsequent detection of E. coli cells was achieved under ambient conditions. © 2000 American Institute of Physics.
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87.85.Va Micromachining
87.85.Ng Biological signal processing
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Generation of terahertz pulses by photoionization of electrically biased air

T. Löffler, F. Jacob, and H. G. Roskos

Appl. Phys. Lett. 77, 453 (2000); http://dx.doi.org/10.1063/1.127007 (3 pages) | Cited 42 times

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We present an experimental demonstration of the generation of far-infrared (terahertz) pulses by photoionization of electrically biased air with amplified laser pulses. The current surge following photoionization of the air with an applied bias field of 10.6 kV/cm leads to the emission of THz pulses with an intensity which can be almost as high as that of THz pulses radiated from a large-area intrinsic-field GaAs emitter. The spectra peak at higher frequency than those of biased large-area GaAs emitters. © 2000 American Institute of Physics.
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51.70.+f Optical and dielectric properties

Metal–insulator–semiconductor tunneling microscope: two-dimensional dopant profiling of semiconductors with conducting atomic-force microscopy

S. Richter, M. Geva, J. P. Garno, and R. N. Kleiman

Appl. Phys. Lett. 77, 456 (2000); http://dx.doi.org/10.1063/1.127008 (3 pages) | Cited 16 times

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A method for two-dimensional carrier profiling is presented, based on tunneling from a conducting atomic-force microscope (AFM) probe tip to a semiconductor sample. Current–voltage data are taken during the AFM scan on a cross-sectioned sample consisting of epitaxial InP multilayers. The results show a clear dependence of the current–voltage characteristics on the carrier concentration and different behavior for n-and p-type InP. Modeling of the data enables one to use this method as a quantitative tool for high-resolution two-dimensional dopant profiling. © 2000 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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
61.72.S- Impurities in crystals
73.61.Ey III-V semiconductors
73.40.Gk Tunneling
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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Erratum: “Ultrashort laser pulse induced deformation of silver nanoparticles in glass” [Appl. Phys. Lett. 74, 1200 (1999)]

M. Kaempfe, T. Rainer, K.-J. Berg, G. Seifert, and H. Graener

Appl. Phys. Lett. 77, 459 (2000); http://dx.doi.org/10.1063/1.127010 (1 page) | Cited 3 times

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Abstract Unavailable
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78.20.Fm Birefringence
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
61.46.-w Structure of nanoscale materials
61.82.-d Radiation effects on specific materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
99.10.Cd Errata
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