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

27 Sep 2004

Volume 85, Issue 13, pp. 2451-2664

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 2619 (2004); http://dx.doi.org/10.1063/1.1802384 (3 pages)

R. Basu, N. P. Guisinger, M. E. Greene, and M. C. Hersam
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Exchange bias and the origin of magnetism in Mn-doped ZnO tetrapods

R. K. Zheng, H. Liu, X. X. Zhang, V. A. L. Roy, and A. B. Djurišić

Appl. Phys. Lett. 85, 2589 (2004); http://dx.doi.org/10.1063/1.1795366 (3 pages) | Cited 43 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Wurtzite-type ZnO tetrapod nanostructures were prepared by evaporating Zn metal under humid argon flow. After the fabrication, Mn was doped into ZnO nanostructures by diffusion at 600 °C. The average concentration of Mn was determined to be 8.4 mol % by x-ray fluorescence. X-ray diffraction patterns obtained from the doped and undoped samples are almost the same. High-resolution transmission electron microscopy observations reveal the existence of surface layers. Magnetic measurements show that the sample has a very large coercivity HC=5500 Oe at 5.5 K and a Curie temperature TC=43 K, which may suggest that ferrimagnetic (Zn,Mn)Mn2O4 exists at the surface. Exchange bias is clearly observed below 22 K. Exchange bias is attributed to the exchange interaction between ferrimagnetic (Zn,Mn)Mn2O4 and spin-glass-like (or antiferromagnetic) phase in manganese oxides.
Show PACS
75.50.Pp Magnetic semiconductors
75.50.Gg Ferrimagnetics
75.50.Ee Antiferromagnetics
75.30.Et Exchange and superexchange interactions
81.05.Dz II-VI semiconductors
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.uj III-V and II-VI semiconductors
61.72.S- Impurities in crystals
66.30.J- Diffusion of impurities
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.70.En X-ray emission spectra and fluorescence
68.37.Lp Transmission electron microscopy (TEM)

Redistribution dynamics of optically generated charges in In(Ga)As∕GaAs self-assembled quantum dots

Y. Ducommun, M. Kroutvar, M. Reimer, M. Bichler, D. Schuh, G. Abstreiter, and J. J. Finley

Appl. Phys. Lett. 85, 2592 (2004); http://dx.doi.org/10.1063/1.1784040 (3 pages) | Cited 4 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigate a quantum-dot-based field-effect device allowing selective optical charging (electrons or holes) of a sub-ensemble of InGaAs∕GaAs self-assembled quantum dots using resonant excitation. The dynamics of the photogenerated charge distribution is studied as a function of excitation energy and lattice temperature. Thermally activated redistribution of charge among the quantum dot ensemble is shown to occur, over a microsecond time scale, only at elevated (T∼100 K) temperatures. An activation energy analysis demonstrates that the two-dimensional wetting layer is the main charge redistribution channel and provides information about the single-particle energy structure of the quantum dots.
Show PACS
85.30.Tv Field effect devices
73.21.La Quantum dots
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Pq Charged excitons (trions)
85.30.Kk Junction diodes
85.60.Dw Photodiodes; phototransistors; photoresistors

Memory characteristics of Pt nanocrystals self-assembled from reduction of an embedded PtOx ultrathin film in metal-oxide-semiconductor structures

Jiun-Yi Tseng, Cheng-Wei Cheng, Sheng-Yu Wang, Tai-Bor Wu, Kuang-Yeu Hsieh, and Rich Liu

Appl. Phys. Lett. 85, 2595 (2004); http://dx.doi.org/10.1063/1.1795976 (3 pages) | Cited 21 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The nonvolatile memory characteristics of metal-oxide-semiconductor structures containing Pt nanocrystals in SiO2 gate oxide were studied. The Pt nanocrystals of 2–3 nm in diameter were self-assembled from reduction of an ultrathin PtOx layer embedded in the SiO2 by vacuum annealing at 425°C. A large hysteresis loop was found in the capacitance–voltage (C–V) relation indicating this significant memory effect. However, two different charge storage mechanisms were found for the Pt nanocrystals in devices with different tunnel oxide thickness. A counterclockwise C–V hysteresis was induced from substrate injection for the devices made with a thin tunnel oxide layer 2.5–5.0 nm thick. Contrast, a clockwise behavior attributed to the electron transfer from charged defects in the gate oxide was found for the devices having a tunnel oxide layer 7.5 nm thick. The relatively stable memory characteristics of Pt nanocrystals resulted from substrate injection were also demonstrated.
Show PACS
85.30.Tv Field effect devices
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
72.20.Fr Low-field transport and mobility; piezoresistance

High-resolution Raman microscopy of curled carbon nanotubes

Hyunhyub Ko, Yuri Pikus, Chaoyang Jiang, Andrea Jauss, Olaf Hollricher, and Vladimir V. Tsukruk

Appl. Phys. Lett. 85, 2598 (2004); http://dx.doi.org/10.1063/1.1795981 (3 pages) | Cited 18 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Patterned carbon nanotube assemblies with bent nanotube bundles were investigated with combined atomic force microscopy and confocal Raman imaging spectroscopy to identify conditions of carbon nanotubes in the bent state. We showed that the tangential G mode on Raman spectra systematically shifts downward upon nanotube bending as was predicted earlier. This lower frequency shift is attributed to the tensile stress, which results in the loosening of C–C bonds in the outer nanotube walls.
Show PACS
78.30.Na Fullerenes and related materials
61.46.-w Structure of nanoscale materials
68.37.Ps Atomic force microscopy (AFM)
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Role of thin Fe catalyst in the synthesis of double- and single-wall carbon nanotubes via microwave chemical vapor deposition

Y. Y. Wang, S. Gupta, and R. J. Nemanich

Appl. Phys. Lett. 85, 2601 (2004); http://dx.doi.org/10.1063/1.1796529 (3 pages) | Cited 44 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Synthesis of vertically aligned small diameter (single- and double-wall) carbon nanotube films on thermally oxidized n+-Si(001) wafers, with acetylene diluted with ammonia gas mixture using a microwave plasma-assisted chemical vapor deposition technique, is reported. Experiments show that by continuous reduction in the thickness of the iron catalyst film to ∼0.3–0.5 nm, or alternately, smaller catalyst particles produces hollow concentric tubes with a fewer number of walls. Double- and single-wall carbon nanotubes with diameters ranging from 1 to 5 nm were identified using transmission electron microscopy and Raman spectroscopy. A relatively higher deposition temperature (∼850°C) in conjunction with a controlled catalyst and rapid growth (<40 s) allowed for the growth of well-graphitized, high areal density (∼1012-1013∕cm2) nanotubes with reduced amorphous carbon and iron. Our results also indicate that the base growth is the most appropriate model to describe the growth mechanism for the nanotube films.
Show PACS
81.07.De Nanotubes
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.37.Lp Transmission electron microscopy (TEM)
78.66.Tr Fullerenes and related materials
78.67.Ch Nanotubes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.30.Na Fullerenes and related materials
81.16.Hc Catalytic methods

Virus detection using nanoelectromechanical devices

B. Ilic, Y. Yang, and H. G. Craighead

Appl. Phys. Lett. 85, 2604 (2004); http://dx.doi.org/10.1063/1.1794378 (3 pages) | Cited 116 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have used a resonating mechanical cantilever to detect immunospecific binding of viruses, captured from liquid. As a model virus, we used a nonpathogenic insect baculovirus to test the ability to specifically bind and detect small numbers of virus particles. Arrays of surface micromachined, antibody-coated polycrystalline silicon nanomechanical cantilever beams were used to detect binding from various concentrations of baculoviruses in a buffer solution. Because of their small mass, the 0.5 μm×6 μm cantilevers have mass sensitivities on the order of 10−19 g∕Hz, enabling the detection of an immobilized AcV1 antibody monolayer corresponding to a mass of about 3×10−15 g. With these devices, we can detect the mass of single-virus particles bound to the cantilever. Resonant frequency shift resulting from the adsorbed mass of the virus particles distinguished solutions of virus concentrations varying between 105 and 107 pfu∕ml. Control experiments using buffer solutions without baculovirus showed small amounts (<50 attograms) of nonspecific adsorption to the antibody layer.
Show PACS
87.85.Va Micromachining
87.15.B- Structure of biomolecules
87.85.Qr Nanotechnologies-design
87.85.Rs Nanotechnologies-applications
87.80.-y Biophysical techniques (research methods)
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Receiving and transmitting light-like radio waves: Antenna effect in arrays of aligned carbon nanotubes

Y. Wang, K. Kempa, B. Kimball, J. B. Carlson, G. Benham, W. Z. Li, T. Kempa, J. Rybczynski, A. Herczynski, and Z. F. Ren

Appl. Phys. Lett. 85, 2607 (2004); http://dx.doi.org/10.1063/1.1797559 (3 pages) | Cited 54 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present optical measurements of random arrays of aligned carbon nanotubes, and show that the response is consistent with conventional radio antenna theory. We first demonstrate the polarization effect, the suppression of the reflected signal when the electric field of the incoming radiation is polarized perpendicular to the nanotube axis. Next, we observe the interference colors of the reflected light from an array, and show that they result from the length matching antenna effect. This antenna effect could be used in a variety of optoelectronic devices, including THz and IR detectors.
Show PACS
78.67.Ch Nanotubes

Cantilever effects on electrostatic force gradient microscopy

G. M. Sacha and J. J. Sáenz

Appl. Phys. Lett. 85, 2610 (2004); http://dx.doi.org/10.1063/1.1797539 (3 pages) | Cited 32 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effects of the cantilever on electrostatic force microscopy are discussed. Numerical calculations of the electrostatic potential distribution and force gradient for typical experimental geometries are presented. A simple analytical relation between the calculated force gradients with and without cantilever is found. The main effect of the cantilever is to reduce the electric field in the tip–sample gap and, as a consequence, the force gradient can be strongly reduced. This effect can be very important for dielectric films while it can be neglected for metallic samples.
Show PACS
07.79.-v Scanning probe microscopes and components
68.35.B- Structure of clean surfaces (and surface reconstruction)

Morphological variation of multiwall carbon nanotubes in supercritical water oxidation

Jia-Yaw Chang, Bertrand Lo, Meili Jeng, Shin-Hwa Tzing, and Yong-Chien Ling

Appl. Phys. Lett. 85, 2613 (2004); http://dx.doi.org/10.1063/1.1798393 (3 pages) | Cited 4 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Multiwall carbon nanotubes (MWNTs) with different morphology were prepared using supercritical water (SCW) oxidation and investigated by transmission electron microscope (TEM) and electron energy-loss spectroscopy (EELS). TEM results indicate that the peeling and sharpening of MWNTs are influenced by the etching process in SCW oxidation, of which oxidation time and amount of oxygen used is crucial. A simplified etching model is proposed, which indicates that the difference of mean etching rate between two adjoining blocks causes the morphological variation of MWNTs. The EELS results show change in characteristic energy-loss peaks as a function of total shell numbers along longitudinal axis of individual peeled tube.
Show PACS
81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
81.16.Pr Micro- and nano-oxidation
79.20.Uv Electron energy loss spectroscopy
81.65.Cf Surface cleaning, etching, patterning
81.65.Mq Oxidation
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Lp Transmission electron microscopy (TEM)

Spin interferometry with electrons in nanostructures: A road to spintronic devices

U. Zülicke

Appl. Phys. Lett. 85, 2616 (2004); http://dx.doi.org/10.1063/1.1794861 (3 pages) | Cited 12 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The wave nature of electrons in semiconductor nanostructures results in spatial interference effects similar to those exhibited by coherent light. The presence of spin–orbit coupling renders interference in spin space and in real space interdependent, making it possible to manipulate the electron’s spin state by addressing its orbital degree of freedom. This suggests the utility of electronic analogs of optical interferometers as blueprints for new spintronics devices. We demonstrate the usefulness of this concept using the Mach–Zehnder interferometer as an example. Its spin-dependent analog realizes a spin-controlled field-effect transistor without magnetic contacts and may be used as a quantum logical gate.
Show PACS
85.30.De Semiconductor-device characterization, design, and modeling
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
72.25.Dc Spin polarized transport in semiconductors
73.63.Bd Nanocrystalline materials
75.47.Pq Other materials

Room temperature nanofabrication of atomically registered heteromolecular organosilicon nanostructures using multistep feedback controlled lithography

R. Basu, N. P. Guisinger, M. E. Greene, and M. C. Hersam

Appl. Phys. Lett. 85, 2619 (2004); http://dx.doi.org/10.1063/1.1802384 (3 pages) | Cited 34 times

Online Publication Date: 28 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ultrahigh vacuum scanning tunneling microscopy is employed for the nanofabrication and characterization of atomically registered heteromolecular organosilicon nanostructures at room temperature. In the first fabrication step, feedback controlled lithography (FCL) is used to pattern individual 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) free radical molecules at opposite ends of the same dimer row on the Si(100)‐2×1:H surface. In atomic registration with the first pattern, FCL is subsequently applied for the removal of a single hydrogen atom. The resulting dangling bond templates the spontaneous growth of a styrene chain that is oriented along the underlying dimer row. The styrene chain growth is bounded by the originally patterned TEMPO molecules, thus resulting in a heteromolecular organosilicon nanostructure. The demonstration of multistep FCL suggests that this approach can be widely used for fundamental studies and fabricating prototype devices that require atomically registered organic molecules mounted on silicon surfaces.
Show PACS
81.16.Nd Micro- and nanolithography
81.16.Ta Atom manipulation
61.46.-w Structure of nanoscale materials
71.55.Cn Elemental semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close