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

9 Dec 2002

Volume 81, Issue 24, pp. 4499-4663

Page 2 of 3 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Magnetic properties of self-assembled interacting nanoparticles

D. Kechrakos and K. N. Trohidou

Appl. Phys. Lett. 81, 4574 (2002); http://dx.doi.org/10.1063/1.1528290 (3 pages) | Cited 18 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The temperature-dependent magnetization and the hysteresis properties (remanence and coercivity) of magnetic nanoparticle arrays are studied by Monte Carlo simulations. An oscillatory variation of the remanence with layer coverage and accompanying peaks in the coercive field are predicted at low temperatures, due to dipolar interparticle interactions. The blocking temperature of the arrays decreases with the inverse cube of the interparticle spacing (Tb ∼ d−3) and it remains almost unchanged with film thickness above one monolayer. Our results are compared with recent experiments on self-assembled Co nanoparticle arrays. © 2002 American Institute of Physics.
Show PACS
75.75.-c Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.40.Mg Numerical simulation studies
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys

Significant enhancement of irreversibility field in clean-limit bulk MgB2

V. Braccini, L. D. Cooley, S. Patnaik, D. C. Larbalestier, P. Manfrinetti, A. Palenzona, and A. S. Siri

Appl. Phys. Lett. 81, 4577 (2002); http://dx.doi.org/10.1063/1.1528289 (3 pages) | Cited 37 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Low resistivity MgB2 bulk samples annealed in Mg vapor show an increase in irreversibility field μ0H∗(T) by a factor of ∼2 in both transport and magnetic measurements. The best sample displayed a magnetic irreversibility field μ0HM∗>14 T at 4.2 K and ∼6 T at 20 K. These changes were accompanied by an increase of the 40 K resistivity from 1 to 18 μΩ cm and a lowering of the resistivity ratio from 15 to 3, while the critical temperature Tc decreased by only 1–2 K. These results show that systematic processing changes can make MgB2 attractive for magnet applications. © 2002 American Institute of Physics.
Show PACS
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.25.Ha Magnetic properties including vortex structures and related phenomena
back to top
RSS Feeds

Cooling-rate-dependent dielectric properties of (Pb(Mg1/3Nb2/3)O3)0.67(PbTiO3)0.33 single crystals in ferroelectric phase

Feng Yan, Peng Bao, Yening Wang, Helen L. W. Chan, and Chung Loong Choy

Appl. Phys. Lett. 81, 4580 (2002); http://dx.doi.org/10.1063/1.1527701 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The dielectric properties of (Pb(Mg1/3Nb2/3)O3)0.67(PbTiO3)0.33 single crystals in the temperature range from room temperature to 250 °C have been studied. A very sharp change of dielectric permittivity due to the spontaneous relaxor–ferroelectric phase transition was observed. The most interesting result is that the dielectric permittivity in ferroelectric phase is strongly dependent on the cooling rate across the relaxor–ferroelectric phase transition. We assume that the cooling rate can influence the grain size of ferroelectric subdomains in ferroelectric phase and can therefore influence the dielectric properties. © 2002 American Institute of Physics.
Show PACS
77.22.Ch Permittivity (dielectric function)
77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis

Electrical properties of SrBi2Ta2O9 ferroelectric thin films at low temperature

Pingxiong Yang, David L. Carroll, John Ballato, and Robert W. Schwartz

Appl. Phys. Lett. 81, 4583 (2002); http://dx.doi.org/10.1063/1.1527700 (3 pages) | Cited 24 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The temperature dependence of electrical properties for SrBi2Ta2O9 thin film capacitors with platinum electrodes (Pt/SBT/Pt) on silicon wafers was studied from 10 to 300 K. With a decrease in temperature from 300 to 200 K, the remanent polarization of the thin films shows about an 11% reduction from its 300 K value; however, it is reduced by about 87% reduction from its 200 K value when the temperature drops from 200 to 100 K. With a decrease to 200 K, the polarization fatigue was significant, and the capacitor shows an approximate 29% reduction in polarization from its initial value following 1010 cycles. The dielectric response and leakage current of the thin films were also studied over the same lower temperature region. These results are helpful in the understanding of the fatigue-free behavior observed in SrBi2Ta2O9 thin films at room temperature and provide additional insight into their use for ferroelectric memory applications. © 2002 American Institute of Physics.
Show PACS
77.80.-e Ferroelectricity and antiferroelectricity
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
back to top
RSS Feeds

Simple catalyst for the growth of small-diameter carbon nanotubes

P. M. Campbell, E. S. Snow, and J. P. Novak

Appl. Phys. Lett. 81, 4586 (2002); http://dx.doi.org/10.1063/1.1528735 (3 pages) | Cited 14 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We describe a simple technique to grow small (approximately 1–4 nm) diam carbon nanotubes both in and out of the plane of a silicon substrate using the decomposition of ethylene and a nickel–iron thin film catalyst. This procedure can be used to produce nanotubes for ultrasharp atomic force microscope probes as well as for nanotube-based electronic devices. The technique is compatible with the patterned growth of nanotubes and with standard device microfabrication processes. © 2002 American Institute of Physics.
Show PACS
81.07.De Nanotubes
81.16.Hc Catalytic methods
61.46.-w Structure of nanoscale materials
68.37.Ps Atomic force microscopy (AFM)

Single-electron tunneling to insulator surfaces detected by electrostatic force

L. J. Klein and C. C. Williams

Appl. Phys. Lett. 81, 4589 (2002); http://dx.doi.org/10.1063/1.1525886 (3 pages) | Cited 17 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The detection of single-electron tunneling events between a metallic scanning probe tip and an insulating surface is demonstrated by an electrostatic force method. When a voltage-biased oscillating atomic force microscopy tip is placed within tunneling range of the surface of an insulator, single-electron tunneling events are observed between the tip and electronic states at the surface. The events cause an abrupt reduction in cantilever oscillation amplitude, due to the instantaneous reduction of the force gradient at the tip. In most cases, only a single electron tunnels to or from the surface. Experimental data show that no physical contact is made during the tunneling events. © 2002 American Institute of Physics.
Show PACS
73.23.Hk Coulomb blockade; single-electron tunneling
07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Ns Metal-nonmetal contacts
73.40.Gk Tunneling
73.20.At Surface states, band structure, electron density of states
85.35.Gv Single electron devices

Synthesis and magnetic behavior of an array of nickel-filled carbon nanotubes

Jianchun Bao, Quanfa Zhou, Jianming Hong, and Zheng Xu

Appl. Phys. Lett. 81, 4592 (2002); http://dx.doi.org/10.1063/1.1526461 (3 pages) | Cited 35 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Highly-ordered arrays of Ni-filled carbon nanotubes have been fabricated by a second-order template method. First, an array of aligned carbon nanotubes was generated in a porous alumina membrane by catalytic pyrolysis of acetylene. The desired material, such as nickel, was then filled into the aligned carbon nanotubes by electrodeposition. The remarkable features of this method are: (i) high yield of metal-filled carbon nanotubes, and (ii) the wall thickness of the carbon nanotubes, and the length, diameter, and structure of the metal nanowires in the carbon nanotubes are controllable via changing experimental conditions. This method should be applicable for preparation of other metal- and alloy-filled carbon nanotubes, and allow the reliable technological application in nanoelectronic devices, high-density magnetic memories, electrochemical energy storages and sensors, etc. © 2002 American Institute of Physics.
Show PACS
81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
75.75.-c Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
75.50.Tt Fine-particle systems; nanocrystalline materials

Single-electron transistors and memory cells with Au colloidal islands

C. S. Wu, C. D. Chen, S. M. Shih, and W. F. Su

Appl. Phys. Lett. 81, 4595 (2002); http://dx.doi.org/10.1063/1.1527236 (3 pages) | Cited 12 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this study, single-electron transistors and memory cells with Au colloidal islands linked by C60 derivatives have been fabricated by hybridization of top–down advanced electron-beam lithography and bottom–up nanophased-material synthesis techniques. Low-temperature transport measurements exhibit clear Coulomb-blockade-type current–voltage characteristics and hysteretic-type gate-modulated current. The hysteresis is attributed to the presence of electrically isolated charge–storage islands. With the guidance provided by Monte Carlo simulation, we propose a circuit model and give an estimate of the sample parameters. © 2002 American Institute of Physics.
Show PACS
85.35.Gv Single electron devices
85.65.+h Molecular electronic devices
85.40.Hp Lithography, masks and pattern transfer
85.30.De Semiconductor-device characterization, design, and modeling
81.16.Be Chemical synthesis methods

Magnetic properties and magnetoresistance in small iron oxide cluster assemblies

D. L. Peng, T. Asai, N. Nozawa, T. Hihara, and K. Sumiyama

Appl. Phys. Lett. 81, 4598 (2002); http://dx.doi.org/10.1063/1.1528725 (3 pages) | Cited 25 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the magnetic properties and magnetoresistance (MR) in small iron oxide (Fe3−xO4 and Fe3O4) cluster assemblies. Half-metallic Fe3O4 cluster assembly with grain size of 10–15 nm is shown to exhibit a MR value of about 8% at T = 30 K and a peak around the Verwey transition temperature Tv = 115 K which is a little lower than the Tv value ( ∼ 120 K) of single crystal specimens. Even at T = 5 K, the magnetization is not saturated in fields up to 50 kOe. The MR behaviors of a Fe3−xO4-coated iron cluster assembly and a sample which was prepared by embedding the Fe3−xO4-coated iron clusters into a MgO matrix are also studied for comparison. The MR value of the latter is over one time larger than that of the former and is also larger than those of the Fe3O4 cluster assembly at various temperatures. It suggests that the barrier layer is important for enhancing the MR effect at high temperatures. © 2002 American Institute of Physics.
Show PACS
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Dd Nonmetallic ferromagnetic materials
75.75.-c Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.60.+g Mixed conductivity and conductivity transitions

Retardation of oxidation in Co nanocolumns: Scanning tunneling microscopy study

J. P. Singh, G.-R. Yang, T.-M. Lu, and G.-C. Wang

Appl. Phys. Lett. 81, 4601 (2002); http://dx.doi.org/10.1063/1.1527980 (3 pages) | Cited 5 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The oxidation of Co nanocolumns grown by the glancing angle deposition technique was studied ex situ using scanning tunneling microscopy and spectroscopy. The normalized conductance (dI/dV)/(I/V) of a single nanocolumn shows a nonoxidized Co peak at about −0.7 eV corresponding to the 3d valence electrons which was absent in the conventional film. It is argued that a retardation of the oxidation occurred in the Co nanocolumn due to the lack of grain boundaries in the isolated nanocolumns. © 2002 American Institute of Physics.
Show PACS
81.65.Mq Oxidation
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.16.Pr Micro- and nano-oxidation
61.46.-w Structure of nanoscale materials
FREE

Visible spectrum (654 nm) room temperature continuous wave InP quantum dot coupled to InGaP quantum well InP–InGaP–In(AlGa)P–InAlP heterostructure laser

G. Walter, N. Holonyak, R. D. Heller, and R. D. Dupuis

Appl. Phys. Lett. 81, 4604 (2002); http://dx.doi.org/10.1063/1.1526454 (3 pages) | Cited 10 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Data are presented demonstrating the cw 300 K visible spectrum (654 nm) laser operation of a single 7.5 monolayer InP quantum dot (QD) layer coupled by a 20 Å In0.5Al0.3Ga0.2P barrier to an auxiliary 70 Å In0.5Ga0.5P quantum well (QW) that, via resonant tunneling, assists carrier collection, thermalization, and lateral rearrangement in the QDs. The simple stripe-geometry (530 μm×10 μm) InP QD+InGaP QW heterostructure laser, enhanced by the QW and operating on an upper QD state (42% quantum efficiency), is capable of over 10 mW/facet cw 300 K operation in spite of the weak heat sinking of probe operation. © 2002 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.Fg Quantum wells
73.21.La Quantum dots

Creation of a gradient polymer-fullerene interface in photovoltaic devices by thermally controlled interdiffusion

M. Drees, K. Premaratne, W. Graupner, J. R. Heflin, R. M. Davis, D. Marciu, and M. Miller

Appl. Phys. Lett. 81, 4607 (2002); http://dx.doi.org/10.1063/1.1522830 (3 pages) | Cited 32 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Efficient polymer-fullerene photovoltaic devices require close proximity of the two materials to ensure photoexcited electron transfer from the semiconducting polymer to the fullerene acceptor. We describe studies in which a bilayer system consisting of spin-cast 2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene copolymer (MEH-PPV) and sublimed C60 is heated above the MEH-PPV glass transition temperature in an inert environment, inducing an interdiffusion of the polymer and the fullerene layers. With this process, a controlled, bulk, gradient heterojunction is created bringing the fullerene molecules within the exciton diffusion radius of the MEH-PPV throughout the film to achieve highly efficient charge separation. The interdiffused devices show a dramatic decrease in photoluminescence and concomitant increase in short circuit currents, demonstrating the improved interface. © 2002 American Institute of Physics.
Show PACS
66.30.Ny Chemical interdiffusion; diffusion barriers
85.60.-q Optoelectronic devices
81.05.ub Fullerenes and related materials
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
73.61.Wp Fullerenes and related materials
78.66.Tr Fullerenes and related materials
68.35.Ct Interface structure and roughness
68.35.Fx Diffusion; interface formation
73.61.Ph Polymers; organic compounds
78.66.Qn Polymers; organic compounds
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states
61.46.-w Structure of nanoscale materials
66.30.Pa Diffusion in nanoscale solids
81.07.Bc Nanocrystalline materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.63.Bd Nanocrystalline materials
78.55.-m Photoluminescence, properties and materials
73.50.Pz Photoconduction and photovoltaic effects
72.40.+w Photoconduction and photovoltaic effects
81.16.-c Methods of micro- and nanofabrication and processing

Formation of oriented nanocrystals in an amorphous alloy by focused-ion-beam irradiation

R. Tarumi, K. Takashima, and Y. Higo

Appl. Phys. Lett. 81, 4610 (2002); http://dx.doi.org/10.1063/1.1526922 (3 pages) | Cited 24 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Structural changes of a Ni–P amorphous alloy under focused-ion-beam (FIB) irradiation have been examined using transmission electron microscopy. On the irradiated plane, the formation of crystallographically orientated nanosized crystals (NCs), with the particle size of approximately 10 nm, was observed. A series of electron diffraction analyses have revealed that NCs have a face-centered-cubic (fcc) structure and the following orientation relationships between the NCs and the FIB direction were found. These are, irradiated plane//(111)fcc and FIB direction//〈110〉fcc. © 2002 American Institute of Physics.
Show PACS
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
61.80.Jh Ion radiation effects
61.82.Bg Metals and alloys

Fabrication of nanometer-spaced electrodes using gold nanoparticles

Saiful I. Khondaker and Zhen Yao

Appl. Phys. Lett. 81, 4613 (2002); http://dx.doi.org/10.1063/1.1528285 (3 pages) | Cited 46 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A simple and highly reproducible technique is demonstrated for the fabrication of metallic electrodes with nanometer separation. Commercially available bare gold colloidal nanoparticles are first trapped between prefabricated large-separation electrodes to form a low-resistance bridge by an ac electric field. A large dc voltage is then applied to break the bridge via electromigration at room temperature, which consistently produces gaps in the sub-10 nm range. The technique is readily applied to prefabricated electrodes with separation up to 1 μm, which can be defined using optical lithography. The simple fabrication scheme will facilitate electronic transport studies of individual nanostructures made by chemical synthesis. As an example, measurement of a thiol-coated gold nanoparticle showing a clear Coulomb staircase is presented. © 2002 American Institute of Physics.
Show PACS
81.07.Bc Nanocrystalline materials
73.23.Hk Coulomb blockade; single-electron tunneling
61.46.-w Structure of nanoscale materials
82.70.Dd Colloids
66.30.Qa Electromigration

Laterally doped heterostructures for III–N lasing devices

S. M. Komirenko, K. W. Kim, V. A. Kochelap, and J. M. Zavada

Appl. Phys. Lett. 81, 4616 (2002); http://dx.doi.org/10.1063/1.1527985 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
To achieve a high-density electron-hole plasma in group-III nitrides for efficient light emission, we propose a planar two-dimensional (2D) p-i-n structure that can be formed in the quantum well layers due to efficient activation of donors and acceptors in the laterally, selectively doped barriers. We show that strongly nonequilibrium 2D electron-hole plasma with density above 1012 cm−2 can be realized in the i region of the laterally biased p-i-n structure, enabling the formation of interband population inversion and stimulated emission from such a lateral current pumped emitter (LACE). We suggest that implementation of the lateral p-i-n structures provides an efficient way of utilizing potential-profile-enhanced doping of superlattices and quantum wells for electric pumping of nitride-based lasers. © 2002 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Pseudo-digital quantum bits

Mark Friesen, Robert Joynt, and M. A. Eriksson

Appl. Phys. Lett. 81, 4619 (2002); http://dx.doi.org/10.1063/1.1527692 (3 pages) | Cited 10 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Quantum computers are analog devices; thus they are highly susceptible to accumulative errors arising from classical control electronics. Fast operation—as necessitated by decoherence—makes gating errors very likely. In most current designs for scalable quantum computers, it is not possible to satisfy both the requirements of low decoherence errors and low gating errors. Here, we introduce a hardware-based technique for pseudo-digital gate operation. We perform self-consistent simulations of semiconductor quantum dots, finding that pseudo-digital techniques reduce operational error rates by more than two orders of magnitude, thus facilitating fast operation. © 2002 American Institute of Physics.
Show PACS
03.67.Lx Quantum computation architectures and implementations

Thermal spike analysis of interface mixing induced by swift heavy ions

G. Szenes

Appl. Phys. Lett. 81, 4622 (2002); http://dx.doi.org/10.1063/1.1528303 (3 pages) | Cited 3 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Interface mixing induced by energetic ions is discussed, applying the author’s thermal spike model. Diffusion in the ion-induced melt is assumed. An expression is derived for the variation of the mixing rate k with the electronic stopping power Se. The experimental results recently reported by the Stuttgart group on NiO, ZnO, CuO, and Cu2O layers on SiO2 substrate are analyzed and good agreement is found with the predictions of the model for k and for the threshold of Se for melt formation. Average diffusion coefficients in the spike are estimated, and Dd ≈ 0.053, 0.03, and 0.004 cm2/s are obtained for Zn, Ni, and Cu ions, respectively. © 2002 American Institute of Physics.
Show PACS
61.80.Jh Ion radiation effects
66.10.C- Diffusion and thermal diffusion
64.70.D- Solid-liquid transitions
61.82.Ms Insulators

Electrical resistivity of polypyrrole nanotube measured by conductive scanning probe microscope: The role of contact force

J. G. Park, S. H. Lee, B. Kim, and Y. W. Park

Appl. Phys. Lett. 81, 4625 (2002); http://dx.doi.org/10.1063/1.1528281 (3 pages) | Cited 40 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Polypyrrole (PPy) nanotubes were synthesized using the pores of track-etched polycarbonate membrane as a template. Its size depends on the pore diameter of template, range from 50 to 200 nm. Direct I–V measurements of PPy nanotube (diameter of 120 nm) deposited on Au were done using a metal-coated tapping-mode atomic-force-microscope tip. Linear I–V characteristics are observed, and the resistance is decreased as the contact force is increased. Using the Hertz model, the elastic modulus E and electrical resistivity ρ are estimated to be E ∼ 1 GPa and ρ ∼ 1 Ωcm. These values are consistent with those obtained in bulk PPy film. © 2002 American Institute of Physics.
Show PACS
73.63.Fg Nanotubes
81.07.De Nanotubes
62.20.D- Elasticity
81.16.Ta Atom manipulation
back to top
RSS Feeds

Backilluminated ultraviolet photodetector based on GaN/AlGaN multiple quantum wells

S. K. Zhang, W. B. Wang, F. Yun, L. He, H. Morkoç, X. Zhou, M. Tamargo, and R. R. Alfano

Appl. Phys. Lett. 81, 4628 (2002); http://dx.doi.org/10.1063/1.1527994 (3 pages) | Cited 11 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The operation of backilluminated ultraviolet (UV) photodetector based on GaN/Al0.27Ga0.73N multiple quantum wells (MQWs) is reported. The MQW structure was deposited on a 1-μm-thick Al0.35Ga0.65N buffer layer which was epitaxied on a sapphire substrate. Coplanar Ohmic contacts were made on the top side of the MQW structure. By illuminating the Ohmic contact positions from the backside of the detector, a flat and narrow band spectral response is achieved in the UV wavelength range from 297 nm to 352 nm. The electron-heavy hole absorption in the MQW region produces the sharp long-wavelength cutoff at 352 nm and the band-to-band absorption of the Al0.35Ga0.65N buffer layer introduces the sharp short-wavelength cutoff at 297 nm. The polarization-induced electric fields result in a redshift of the long-wavelength cutoff. The response time is measured to be RC limited and determined to be 5 μs at a 50 Ω load. © 2002 American Institute of Physics.
Show PACS
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Thermal activation and reversal time in antiferromagnetically coupled media

D. T. Margulies, A. Moser, M. E. Schabes, and Eric. E. Fullerton

Appl. Phys. Lett. 81, 4631 (2002); http://dx.doi.org/10.1063/1.1526464 (3 pages) | Cited 7 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The thermally-activated magnetization reversal process of the lower layer in antiferromagnetically coupled media is investigated. The temperature dependence of the hysteresis loops is used to determine the magnetic parameters of the lower layer and to predict its reversal time. We discuss this reversal time both with and without transitions recorded in the media, and present an experimental technique that demonstrates thermally activated writing of the lower layer. © 2002 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Single-crystalline Si on insulator in confined structures fabricated by two-step metal-induced crystallization of amorphous Si

Yaocheng Liu, Michael D. Deal, Krishna C. Saraswat, and James D. Plummer

Appl. Phys. Lett. 81, 4634 (2002); http://dx.doi.org/10.1063/1.1527977 (3 pages) | Cited 2 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a technology and its mechanism to obtain single-crystalline Si pillars on SiO2 using a two-step Ni-induced crystallization process on amorphous Si pillars with confined sizes. The amorphous Si pillars with a Ni cap were first annealed at 400 °C for 15 h so that a single-crystalline NiSi2 template was formed on top of each pillar. In the second step, they were annealed at 550 °C for 2 h, during which single-crystalline Si pillars were formed by NiSi2-mediated solid-phase epitaxy. These single-crystalline Si pillars can be used for advanced vertical metal–oxide–semiconductor transistors and surround-gate structures, especially where low-temperature processing is required. © 2002 American Institute of Physics.
Show PACS
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing
81.15.Np Solid phase epitaxy; growth from solid phases

Resonant detection of subterahertz and terahertz radiation by plasma waves in submicron field-effect transistors

W. Knap, Y. Deng, S. Rumyantsev, and M. S. Shur

Appl. Phys. Lett. 81, 4637 (2002); http://dx.doi.org/10.1063/1.1525851 (3 pages) | Cited 95 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the experiments on resonant photoresponse of the gated two-dimensional electron gas to the terahertz radiation. The visible-light-induced, metastable increase of the carrier density in the transistor channel shifts the resonance position to the higher gate voltages, in agreement with plasma wave detection theory. In this way, an unambiguous proof of the origin of the observed resonant detection is provided. The visible light illumination also leads to an increase of the electron mobility and, as a result, to an increase of the resonant detection quality factor. Resonant detection of the harmonics of the Gunn diode-based emission system is demonstrated up to 1.2 THz. © 2002 American Institute of Physics.
Show PACS
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.Tv Field effect devices
81.05.Ea III-V semiconductors

Hole transport in amorphous-crystalline-mixed and amorphous pentacene thin-film transistors

M. H. Choo, Jae Hoon Kim, and Seongil Im

Appl. Phys. Lett. 81, 4640 (2002); http://dx.doi.org/10.1063/1.1527993 (3 pages) | Cited 24 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the hole transport behavior in amorphous-crystalline-mixed and amorphous pentacene thin-film transistors. Five organic thin-film transistors (OTFTs) were fabricated by evaporating the pentacene films at rates of 1, 3, 5, and 7 Å/s at 25 °C (RT), and 7 Å/s at 60 °C. The field-effect mobility increased with the deposition rate even though the crystalline quality of the pentacene film degraded from an amorphous-crystalline-mixed phase to an amorphous phase. With our optimum deposition rate of 5 Å/s at RT, we obtained a saturation current (ID-SAT) of about 4 μA at a gate bias of −40 V, the field-effect mobility of 0.1 cm2/V s, and the on/off current ratio of 105. For the OTFT prepared with a deposition rate of 7 Å/s at 60 °C, an amorphous pentacene channel layer with a high mobility of ∼0.3 cm2/V s and the on/off current ratio of 104 were observed. © 2002 American Institute of Physics.
Show PACS
85.30.Tv Field effect devices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
72.20.Ee Mobility edges; hopping transport

Humidity sensors based on pentacene thin-film transistors

Zheng-Tao Zhu, Jeffrey T. Mason, Rüdiger Dieckmann, and George G. Malliaras

Appl. Phys. Lett. 81, 4643 (2002); http://dx.doi.org/10.1063/1.1527233 (3 pages) | Cited 150 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
When a pentacene thin-film transistor is exposed to humidity, its saturation current decreases. This decrease was found to be reversible and can therefore be used to measure the amount of relative humidity in atmosphere. The sensitivity was found to depend on the thickness of the pentacene layer. The microscopic origin of the sensing mechanism is discussed. © 2002 American Institute of Physics.
Show PACS
07.07.Vx Hygrometers; hygrometry
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
72.80.Le Polymers; organic compounds (including organic semiconductors)
73.61.Ph Polymers; organic compounds

Influence of carrier mobility and contact barrier height on the electrical characteristics of organic transistors

A. Bolognesi, A. Di Carlo, and P. Lugli

Appl. Phys. Lett. 81, 4646 (2002); http://dx.doi.org/10.1063/1.1527983 (3 pages) | Cited 34 times

Online Publication Date: 3 December 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated the electrical properties of organic thin-film transistors by way of two-dimensional drift-diffusion simulations. The dependence of the electrical characteristics on the mobility model and on the Schottky barrier height of the contacts is analyzed. We found that both the field dependence of the carrier mobility and the barrier height of the contacts are responsible for the nonlinearity of the output characteristics in the low bias region. We have then extracted the mobility from the simulated characteristics using standard metal–oxide–semiconductor analytic relations and compared to the mobility used in the simulation. The discrepancy found between the two mobilities is mainly induced by the presence of the contact barrier. © 2002 American Institute of Physics.
Show PACS
85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
73.30.+y Surface double layers, Schottky barriers, and work functions
Page 2 of 3 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close