APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

20 Jul 1998

Volume 73, Issue 3, pp. 279-419

Page 2 of 2 Pages Previous Page | Jump to Page
back to top
RSS Feeds

Observation of spin splitting in single InAs self-assembled quantum dots in AlAs

A. S. G. Thornton, T. Ihn, P. C. Main, L. Eaves, and M. Henini

Appl. Phys. Lett. 73, 354 (1998); http://dx.doi.org/10.1063/1.121832 (3 pages) | Cited 44 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using magneto-tunneling spectroscopy, we observe the Zeeman spin splitting of the ground state of a single InAs quantum dot grown within AlAs. We obtain values for the g factor of different quantum dots between +0.52±0.08 and +1.6±0.2, with magnetic field applied in the plane of the dot. This value for the g factor is considerably different from that of bulk InAs (g = −14.8), and we explain this using a simple three band k⋅p calculation. Using the spin split states of the dot as a probe, we observe the complete spin polarization of the emitter accumulation layer. © 1998 American Institute of Physics.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
78.20.Ls Magneto-optical effects

Hybrid ferromagnetic/semiconductor Hall effect device

J. Reijniers and F. M. Peeters

Appl. Phys. Lett. 73, 357 (1998); http://dx.doi.org/10.1063/1.121833 (3 pages) | Cited 28 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The diffusive classical transport of a two-dimensional electron gas (2DEG) in a Hall cross, subjected to a locally inhomogeneous magnetic field resulting from an in plane magnetized ferromagnetic film deposited above the 2DEG, is investigated. The magnetic field profile in the 2DEG is obtained analytically and the Hall resistance is calculated for various configurations. Our results are in good agreement with the recent experimental results of Johnson et al. [Appl. Phys. Lett. 71, 974 (1997)] on a novel magnetoelectronic device. The output of the device scales inversely with both the size of the voltage and the current probes. © 1998 American Institute of Physics.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.40.Ns Metal-nonmetal contacts
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
75.70.Ak Magnetic properties of monolayers and thin films

Floating low-temperature radio-frequency plasma oxidation of polycrystalline silicon-germanium

Zhineng Fan, Gang Zhao, Paul K. Chu, Zhonghe Jin, Hoi S. Kwok, and Man Wong

Appl. Phys. Lett. 73, 360 (1998); http://dx.doi.org/10.1063/1.121834 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Low temperature oxide formation is an important process in the fabrication of thin-film transistors (TFT) used in active-matrix liquid crystal displays. However, low temperature oxide is prone to have defects at the SiO2/polycrystalline–SiGe interfaces. We have recently developed a novel rf (radio frequency) plasma oxidation method for polycrystalline SiGe (poly-SiGe) materials. The poly-SiGe wafers are oxidized in an oxygen rf plasma with the samples electrically floating. That is, the sample voltage is the same as the sheath potential of the floating wall and is always negative with respect to the bulk of the plasma since electrons have higher mobility than ions. The slightly negative potential on the wafers attracts low energy oxygen ions from the plasma and the resulting damage on the wafers is thus lower than that induced by the more commonly used and energetic electron cyclotron resonance (ECR) source. No deliberate heating is applied during oxidation since the samples are heated spontaneously by the plasma, but the temperature is measured to be below 100 °C throughout the entire process. The oxidation rate is comparable to that of ECR plasma oxidation. Depth profiles are acquired by Auger electron spectroscopy and the interfaces are examined by x-ray photoelectron spectroscopy. The n-channel metal oxide silicon device fabricated on the as-grown gate oxide shows good electrical characteristics. The process is thus compatible with inexpensive large-area, low-temperature fabrication of TFTs on glass substrates. © 1998 American Institute of Physics.
Show PACS
81.05.Hd Other semiconductors
81.65.Mq Oxidation
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
79.60.Jv Interfaces; heterostructures; nanostructures
79.20.Fv Electron impact: Auger emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Spontaneous splitting of ferromagnetic (Ga, Mn)As valence band observed by resonant tunneling spectroscopy

H. Ohno, N. Akiba, F. Matsukura, A. Shen, K. Ohtani, and Y. Ohno

Appl. Phys. Lett. 73, 363 (1998); http://dx.doi.org/10.1063/1.121835 (3 pages) | Cited 91 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Current–voltage characteristics of AlAs/GaAs/AlAs double barrier resonant tunneling diodes with ferromagnetic p-type (Ga, Mn)As on one side and p-type GaAs on the other have been studied. A series of resonant peaks have been observed in both polarities, i.e., injecting holes from p-type GaAs and from (Ga, Mn)As. When holes are injected from the (Ga, Mn)As side, spontaneous resonant peak splitting has been observed below the ferromagnetic transition temperature of (Ga, Mn)As without magnetic field. The temperature dependence of the splitting is explained by the the spontaneous spin splitting in the valence band of ferromagnetic (Ga, Mn)As. © 1998 American Institute of Physics.
Show PACS
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.Kk Junction diodes
73.20.At Surface states, band structure, electron density of states

Electron and hole tunneling in a moderate density quantum dot ensemble with shallow confinement potentials

D. L. Huffaker and D. G. Deppe

Appl. Phys. Lett. 73, 366 (1998); http://dx.doi.org/10.1063/1.121836 (3 pages) | Cited 24 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Data are presented on InAlGaAs quantum dot ensembles that possess different degrees of lateral tunnel coupling for electrons and holes. Atomic force microscope images show that even for moderate densities ( ∼ 4.8×1010 cm−2), but with shallow potentials, many dots of an ensemble can be in such close proximity that tunneling is expected for both electrons and holes. On average, however, holes remain confined while electrons freely tunnel. Even with electron tunneling, single dot emission is observed for small area light emitting diodes. © 1998 American Institute of Physics.
Show PACS
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.)
73.40.Gk Tunneling
85.60.Jb Light-emitting devices

Resistivity anisotropy in ordered InxGa1−xP grown at 640 °C

J. Novák, S. Hasenöhrl, R. Kúdela, M. Kučera, D. Wüllner, and H.-H. Wehmann

Appl. Phys. Lett. 73, 369 (1998); http://dx.doi.org/10.1063/1.121837 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The anisotropy of electrical properties in ordered InxGa1−xP epitaxial layers was studied. These samples were prepared by a low-pressure metalorganic chemical vapor phase epitaxy technique at the growth temperature of 640 °C. Resistivity measurements using a four-point-probe method have shown that samples with a low misfit value (0–1.5×10−3) are electrically uniform. For samples with higher misfit the anisotropy of resistivity markedly increases up to a maximum of 950. Comparing the results obtained from x-ray diffraction, low temperature photoluminescence, and atomic force microscopy experiments, we have shown that lattice mismatch can support the evolution and extension of the ordering effect in the InxGa1−xP layers. © 1998 American Institute of Physics.
Show PACS
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Nondestructive evaluation of carrier concentration in the channel layer of In0.5Ga0.5P/In0.2Ga0.8As/GaAs heterostructure field-effect transistors by Raman scattering

Gako Araki, Takumi Nittono, Tomofumi Furuta, and Fumiaki Hyuga

Appl. Phys. Lett. 73, 372 (1998); http://dx.doi.org/10.1063/1.121838 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Carrier concentration (N) in the channel layers of pseudomorphic In0.5Ga0.5P/In0.2Ga0.8As/GaAs heterostructure field-effect transistors (HFETs) is evaluated by Raman scattering measurements. The coupled mode between the InGaAs longitudinal optical phonons and electrons in the InGaAs channel shifts continuously to a low wave number with an increasing N in the InGaAs channel. Preliminary calculation indicates that N can be determined with an error of less than 0.35×1018/cm3 in the 1018/cm3 order range, which corresponds to a 100 mV HFET threshold voltage. Raman scattering measurement is nondestructive and has a high spatial resolution as small as 1 μm in diameter. Thus, this measurement is promising in HFET wafer selection. © 1998 American Institute of Physics.
Show PACS
85.30.Tv Field effect devices
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
63.20.K- Phonon interactions
06.60.Mr Testing and inspecting procedures

Broadening of near-band-gap photoluminescence in n-GaN films

E. Iliopoulos, D. Doppalapudi, H. M. Ng, and T. D. Moustakas

Appl. Phys. Lett. 73, 375 (1998); http://dx.doi.org/10.1063/1.121839 (3 pages) | Cited 46 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This letter addresses the broadening mechanism of the near-band-gap photoluminescence in GaN films doped n type with silicon. The films were produced by plasma assisted molecular beam epitaxy and their carrier concentration was varied systematically from 1015 to 1020 cm−3. The photoluminescence was excited with a 10 mW He–Cd laser at 77 K. At low carrier concentration (<1017 cm−3) the photoluminescence peak has a full width at half maximum of about 18 meV, while at high carrier concentration (>1018 cm−3) the full width at half maximum increases monotonically with carrier concentration up to about 120 meV. The broadening of the line at high carrier concentration is attributed to tailing of the density of states caused by potential fluctuations due to randomly distributed impurities. The data were quantitatively analyzed, as a function of carrier concentration and compensation ratio, using the impurity band broadening model of Morgan [Phys. Rev. 139, A343 (1965)], and the agreement between model and experimental data supports the model’s validity and suggests a potential method of determining the compensation in degenerate nitride semiconductors. © 1998 American Institute of Physics.
Show PACS
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds
back to top
RSS Feeds

Imaging of vortices in superconductors by electron beam scanning

J. Martin, R. P. Huebener, J. B. le Grand, C. A. Mears, S. E. Labov, and A. T. Barfknecht

Appl. Phys. Lett. 73, 378 (1998); http://dx.doi.org/10.1063/1.121840 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Abrikosov vortices trapped in a superconducting tunnel junction and oriented perpendicular to the barrier plane were imaged by electron beam scanning at 1.6 K. We have used NbAlOxNb junctions. As an important feature, the top Nb electrode was covered with a SiO2 film of 300 nm thickness, absorbing most of the 5 keV beam energy. The signal generating the image is explained by a model, assuming that the beam-induced electronic excitations in the SiO2 overlay film are trapped in the local magnetic field protruding from a vortex, resulting in an increased recombination rate. In addition to providing a novel approach to the imaging of the vortices in superconductors, our results are important for understanding quasiparticle losses in tunnel junction detectors. © 1998 American Institute of Physics.
Show PACS
74.50.+r Tunneling phenomena; Josephson effects
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Growth of HgBa2Ca2Cu3O8 thin films using stable Re0.1Ba2Ca2Cu3Ox precursor by pulsed laser deposition

W. N. Kang, R. L. Meng, and C. W. Chu

Appl. Phys. Lett. 73, 381 (1998); http://dx.doi.org/10.1063/1.121841 (3 pages) | Cited 20 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High quality c-axis oriented HgBa2Ca2Cu3O8 thin films have been fabricated with the stable Re-doped Ba2Ca2Cu3Ox precursor powder by pulsed laser deposition followed by postannealing without any special handling. As-grown films on (100) SrTiO3 exhibit a zero-resistance transition (Tc,zero) at ∼131 K with a narrow transition width ΔT ∼ 1.5 K after oxygen annealing at 340 °C for 12 h. The critical current densities are observed 1.1×107 A/cm2 at 10 K and 1.2×105 A/cm2 at 120 K in zero field. The x-ray diffraction pattern indicates highly c-axis oriented thin films normal to the substrate plane containing a minor HgBa2CaCu2O6 phase. The scanning electron microscopy analysis shows that the surface morphology of the film is well connected platelike crystals but reveals Ba–Cu–Ox impurities are uniformly scattered across the film surface. © 1998 American Institute of Physics.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
81.15.Fg Pulsed laser ablation deposition
74.25.Sv Critical currents
74.62.-c Transition temperature variations, phase diagrams
68.35.B- Structure of clean surfaces (and surface reconstruction)
back to top
RSS Feeds

High conductance small area magnetoresistive tunnel junctions

P. K. Wong, J. E. Evetts, and M. G. Blamire

Appl. Phys. Lett. 73, 384 (1998); http://dx.doi.org/10.1063/1.121842 (3 pages) | Cited 3 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fe–Al2O3–CoFe mesa junctions with micron scale areas have been fabricated from dc sputtered whole wafer heterostructures by standard photolithographic processing. The junctions showed magnetoresistances (JMRs) of 6.2% at room temperature and 9.2% at 77 K. Resistance-area (RA) products as small as 9.6×10−10 Ω m2, suitable for device applications, were obtained. A JMR/RA ratio of 6.5×109% Ω−1 m−2 was also achieved. The fabrication processes we used provide a useful basis for manufacturing ferromagnetic tunnel devices for MR sensor applications. © 1998 American Institute of Physics.
Show PACS
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Cd Deposition by sputtering
73.40.Rw Metal-insulator-metal structures
75.50.Bb Fe and its alloys
73.40.Gk Tunneling
75.70.Ak Magnetic properties of monolayers and thin films

Uniaxial magnetic anisotropy of submicron MnAs ferromagnets in GaAs semiconductors

K. Ando, A. Chiba, and H. Tanoue

Appl. Phys. Lett. 73, 387 (1998); http://dx.doi.org/10.1063/1.121843 (3 pages) | Cited 23 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Submicron (100–500 nm) room-temperature ferromagnets of MnAs have been successfully incorporated into GaAs semiconductor substrates by Mn+ ion implantation and subsequent heat treatment at 920 °C for 1 s in a nitrogen gas. Atomic force microscopy indicates an epitaxial relation of [0001] oriented hexagonal MnAs crystallites on (001) GaAs substrates: [11 math0]MnAs∥[110]GaAs. A stronger shape anisotropy along [110]GaAs is observed for the smaller crystallites. Magnetic characterizations by superconducting quantum interference device reveal uniaxial in-plane magnetic anisotropy of the sample. Magnetic force microscopy imaging shows that the uniaxial magnetic anisotropy comes from the alignment of magnetic dipoles along the magnetic easy [11 20] axis of MnAs, which is parallel to [110]GaAs. © 1998 American Institute of Physics.
Show PACS
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Gw Magnetic anisotropy
61.72.uj III-V and II-VI semiconductors
75.50.Tt Fine-particle systems; nanocrystalline materials
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
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Tunable magnetocaloric effect in ceramic perovskites

X. Bohigas, J. Tejada, E. del Barco, X. X. Zhang, and M. Sales

Appl. Phys. Lett. 73, 390 (1998); http://dx.doi.org/10.1063/1.121844 (3 pages) | Cited 66 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A large entropy variation (magnetocaloric effect) has been discovered in ceramic perovskites with the formulas La0.65Ca0.35Ti1−xMnxO3−z and La0.5+x+yLi0.5−3yTi1−3xMn3xO3−z. Both Curie temperature and entropy change were studied from 4.2 to 400 K for different stoichiometric compositions and applied magnetic fields. Our conclusion is that these materials are excellent candidates for working materials in magnetic refrigeration and liquefaction devices in a wide temperature range. © 1998 American Institute of Physics.
Show PACS
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials

Observation of perpendicular magnetic anisotropy in Ni/Pt multilayers at room temperature

Sung-Chul Shin, G. Srinivas, Young-Seok Kim, and Mu-Gyeom Kim

Appl. Phys. Lett. 73, 393 (1998); http://dx.doi.org/10.1063/1.121845 (3 pages) | Cited 26 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the experimental observation of room-temperature perpendicular magnetic anisotropy in Ni/Pt multilayers having 7–26 Å Ni and 2.3–4.6 Å Pt layer thicknesses, prepared by dc magnetron sputtering on glass substrates at 7 mTorr Ar sputtering pressure. Perpendicular magnetic anisotropy was found to be sensitively dependent on both Ni- and Pt-layer thicknesses, and a maximum anisotropy energy of 1.74×105 erg/cm3 was obtained for (16 Å Ni/2.3 Å Pt)30 multilayer. Interestingly, magnetization measurements revealed that about two atomic layers of Ni at the interface were magnetically dead in our samples. © 1998 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
75.50.Cc Other ferromagnetic metals and alloys
81.15.Cd Deposition by sputtering

Large low-field magnetoresistance over a wide temperature range induced by weak-link grain boundaries in La0.7Ca0.3MnO3

X. L. Wang, S. X. Dou, H. K. Liu, M. Ionescu, and B. Zeimetz

Appl. Phys. Lett. 73, 396 (1998); http://dx.doi.org/10.1063/1.121846 (3 pages) | Cited 86 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Polycrystalline bulk porous samples with a large number of weak-link grain boundaries and high density polycrystalline bulk samples with strong-link boundaries were synthesized by conventional solid-state reaction and a partial melting technique. The weak-link samples showed large magnetoresistance (MR,Δρ/ρH = [ρ0−ρH]/ρ0), 20–30%, at a low magnetic field of 300 mT and over a wide temperature range from the magnetic transition at 235 to 77 K. The partially melted samples exhibited the same magnetoresistance behavior as that of single crystals with a maximum peak MR of 15% at a narrow temperature range around the ferromagnetic transition. It is suggested that grain boundaries are necessary but not sufficient to account for the MR at low field over a large temperature range. Weak-link grain boundaries rather than strong-link boundaries are responsible for the MR at low field over a large temperature range. © 1998 American Institute of Physics.
Show PACS
75.47.De Giant magnetoresistance
73.61.At Metal and metallic alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.15.Gd Galvanomagnetic and other magnetotransport effects
61.72.Mm Grain and twin boundaries
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Dd Nonmetallic ferromagnetic materials

Single crystal Fe films grown on InAs(100) by molecular beam epitaxy

Y. B. Xu, E. T. M. Kernohan, M. Tselepi, J. A. C. Bland, and S. Holmes

Appl. Phys. Lett. 73, 399 (1998); http://dx.doi.org/10.1063/1.121847 (3 pages) | Cited 27 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Thin Fe films have been grown on InAs(100) by molecular beam epitaxy, and studied using in situ magneto-optical Kerr effect (MOKE), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM). Despite the large lattice mismatch between Fe and InAs, the growth of Fe on InAs at 175 °C was found to be epitaxial with the orientation relationship Fe(100)〈001〉‖InAs(100)〈001〉, as evidenced by LEED. STM images indicate that growth proceeds via a 3D Volmer–Weber mode. The magnetic hysteresis loops measured using in situ MOKE show a distinct cubic anisotropy with the easy axis along 〈001〉, the easy axis of bulk bcc Fe, which further confirms that well ordered single crystal Fe films have been stabilized on the InAs(100) substrate. Current–voltage measurements in the temperature range of 2.5–304 K show that Fe forms an ohmic contact on InAs. We propose that Fe/InAs is a suitable heterostructure for magnetoelectronic devices as, unlike Fe/GaAs, there is no Schottky barrier to electron transport. © 1998 American Institute of Physics.
Show PACS
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
73.40.Ns Metal-nonmetal contacts
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.66.Bz Metals and metallic alloys

Tunneling and enhanced magnetoresistance in Nd2/3Sr1/3MnO3 thin films with microcracks

K. M. Satyalakshmi, B. Fisher, L. Patlagan, G. Koren, E. Sheriff, R. Prozorov, and Y. Yeshurun

Appl. Phys. Lett. 73, 402 (1998); http://dx.doi.org/10.1063/1.121848 (3 pages) | Cited 17 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We found that microcracks in thin Nd2/3Sr1/3MnO3 films create a series of intrinsic break junctions which are ideal for investigating tunneling phenomena in this system. A comparison of films with and without cracks, which have similar ferromagnetic Curie temperature (Tc) of 140–150 K, shows that the cracked film has a lower insulator to metal transition temperature TM (97 K vs 140 K), three orders of magnitude higher resistivity at TM, and two times larger magnetoresistance at 1 T near TM. At T>TM we observed that ln ραT−1/4 in the uncracked film while in the cracked film a ln ραT−1/2 dependence was found. This indicates that the conductivity in the first case is due to variable range hopping in three dimension, while in the second case it is dominated by thermally activated tunneling across the insulating barriers (the microcracks). © 1998 American Institute of Physics.
Show PACS
73.61.At Metal and metallic alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
72.15.Gd Galvanomagnetic and other magnetotransport effects
62.20.M- Structural failure of materials
72.60.+g Mixed conductivity and conductivity transitions
back to top
RSS Feeds

Piezoelectric surface barrier lowering applied to InGaN/GaN field emitter arrays

Robert D. Underwood, P. Kozodoy, S. Keller, S. P. DenBaars, and U. K. Mishra

Appl. Phys. Lett. 73, 405 (1998); http://dx.doi.org/10.1063/1.121849 (3 pages) | Cited 14 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A method of lowering the surface barrier for field emission by using the piezoelectric effect is presented. The piezoelectric effect produces a surface dipole that decreases the surface barrier, which in turn decreases the turn-on voltage of the field emitter. Calculations show that significant reduction of the tunneling barrier can be effected with relatively thin layers of strained InGaN on GaN field emitter arrays. Dramatic reduction of the turn-on voltage from 450 V (GaN field emitter array) to 70 V (InGaN/GaN field emitter array) was observed and can be attributed partly to surface barrier lowering. © 1998 American Institute of Physics.
Show PACS
73.61.Ey III-V semiconductors
85.45.Db Field emitters and arrays, cold electron emitters
73.40.Cg Contact resistance, contact potential
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Imaging of photogenerated acid in a chemically amplified photoresist

S. J. Bukofsky, G. D. Feke, Q. Wu, R. D. Grober, P. M. Dentinger, and J. W. Taylor

Appl. Phys. Lett. 73, 408 (1998); http://dx.doi.org/10.1063/1.121850 (3 pages) | Cited 15 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Chemically amplified photoresists are widely used throughout the semiconductor industry due to the need for high throughput in the lithography process. Knowledge of the location of acid molecules in chemically amplified resists is of paramount importance for the process control of the image formation of almost all the lithographic techniques used in the semiconductor industry today. We have demonstrated a technique based on pH-dependent fluorescence which can measure directly the spatial distribution of the photoacid in photoresist films without the need of any other subsequent process after exposure. By adding a small amount of fluorescent material to the resist, a latent image can be formed when photogenerated acid molecules quench the fluorescence in exposed areas. We demonstrate images formed after exposure of SAL605 resist films to x-ray radiation, with no post-exposure bake, and show that the optical contrast is a function of dose. We also show that the same technique can be utilized for rapid evaluation of photoacid generator efficiency. © 1998 American Institute of Physics.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Radio frequency photoinjector using LaB6 cathode and a nitrogen drive laser

P. G. O’Shea, J. A. Lancaster, R. Sachtschale, and C. R. Jones

Appl. Phys. Lett. 73, 411 (1998); http://dx.doi.org/10.1063/1.121851 (3 pages) | Cited 1 time

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the successful operation of an inexpensive, simple, and reliable 2.856 GHz radio frequency photoinjector using a rugged LaB6 cathode and a nitrogen drive laser operating at a wavelength of 337 nm. The cathode was operated at a vacuum of ≈ 10−8 Torr, and produced excellent beam quality. The device produces a 1 ns long pulse containing 0.1 nC of charge. The photoelectrons have been accelerated to 270 MeV in traveling-wave linear accelerator. © 1998 American Institute of Physics.
Show PACS
29.25.Bx Electron sources
07.77.Ka Charged-particle beam sources and detectors
41.75.Lx Other advanced accelerator concepts
29.20.-c Accelerators

Ferroelectric properties of c-oriented YMnO3 films deposited on Si substrates

Takeshi Yoshimura, Norifumi Fujimura, and Taichiro Ito

Appl. Phys. Lett. 73, 414 (1998); http://dx.doi.org/10.1063/1.122269 (3 pages) | Cited 34 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have proposed the use of RMnO3 (R: rare earth elements) films for metal–ferroelectric–semiconductor field effect transistor (MFSFET)-type ferroelectric random access memories (ferroelectric RAMs). This reports the production of YMnO3 films on Si substrates for MFSFET with confirmation of the distinct ferroelectricity by P–E hysteresis and capacitance–voltage (C–V) measurement. (0001)-oriented YMnO3 films were obtained on a (111)Si substrate using a pulsed-laser deposition method. Although the Pt/YMnO3/Si structure exhibits a very small remnant polarization of 1.2 nC/cm2, it has clear ferroelectric polarization switching type C–V characteristics with a memory window of 1.1 V. The dielectric constant and the dissipation factor were 27.8 and 0.035, respectively. The polarization switching characteristics are discussed. © 1998 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.Fm Switching phenomena
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
81.15.Fg Pulsed laser ablation deposition
85.30.Tv Field effect devices

Biomolecular recognition using submicron laser lithography

G. V. Shivashankar and A. Libchaber

Appl. Phys. Lett. 73, 417 (1998); http://dx.doi.org/10.1063/1.121852 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Direct beam biomolecular patterning on gold-coated glass substrates, using diffraction limited near infrared laser spot, is used for DNA recognition and specific ligand-receptor interactions. Using a microscope objective lens, a near infrared laser beam is focused onto a glass slide coated with 50-Å gold film. Localized laser absorption results in partial melting and ablation of gold. Spatially moving the laser spot, a stable etched gold pattern is obtained at submicron resolution. During the process, submicron particles in suspension aggregate along the melted gold film. The submicron particles are themselves coated with specific biomolecules, like the protein avidin or single stranded DNA oligomers, for specific biomolecular recognition. This opens many possibilities for biomolecular networks, biochip microfabrication, and bioelectronic circuitry. © 1998 American Institute of Physics.
Show PACS
87.15.M- Spectra of biomolecules
85.65.+h Molecular electronic devices
87.50.W- Optical/infrared radiation effects
87.80.-y Biophysical techniques (research methods)
Page 2 of 2 Pages Previous Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close