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16 Oct 2006

Volume 89, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 164101 (2006); http://dx.doi.org/10.1063/1.2362602 (3 pages)

Yen-Wen Lu and Chang-Jin(CJ) Kim
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Carrier recombination near threading dislocations in GaN epilayers by low voltage cathodoluminescence

N. Pauc, M. R. Phillips, V. Aimez, and D. Drouin

Appl. Phys. Lett. 89, 161905 (2006); http://dx.doi.org/10.1063/1.2357881 (3 pages) | Cited 17 times

Online Publication Date: 16 October 2006

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The authors present a low voltage cathodoluminescence (CL) study of as grown GaN and GaN:Si epilayers on sapphire. At 1 kV they resolve individual threading dislocations on the sample surface at low temperature (5 K), which appear as correlated dark spots. Analysis of CL intensity profiles across individual dislocation cores provides a direct measurement of the exciton and minority carrier diffusion lengths. Using this approach at 5 K, an exciton diffusion length of 62±28 nm was found for GaN:Si ( ∼ 3×1018 cm−3) compared with 81±20 nm for a nominally undoped n-type GaN ( ∼ 1×1016 cm−3).
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78.66.Fd III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
71.35.-y Excitons and related phenomena
66.30.-h Diffusion in solids
78.60.Hk Cathodoluminescence, ionoluminescence

Structural stability and elastic property of the L12 ordered Co3(Al,W) precipitate

Q. Yao, H. Xing, and J. Sun

Appl. Phys. Lett. 89, 161906 (2006); http://dx.doi.org/10.1063/1.2362574 (3 pages) | Cited 15 times

Online Publication Date: 17 October 2006

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The method of augmented plane wave plus local orbitals within the generalized gradient approximation has been employed to investigate the structural stability and elastic properties of the ternary Co3(Al,W) precipitate. The results showed that the stable Co3(Al,W) compound has L12 ordered structure. The calculated results of elastic properties show that the L12 Co3(Al,W) precipitate has a strengthening effect in the disordered fcc cobalt matrix, owing to the larger modulus differences between Co3(Al,W) and cobalt matrix. The theoretical calculations also show that the Co3(Al,W) compound is brittle in nature.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.66.Dk Alloys
81.30.Mh Solid-phase precipitation
62.20.D- Elasticity
62.20.M- Structural failure of materials

Direct strain measurement in a 65 nm node strained silicon transistor by convergent-beam electron diffraction

Peng Zhang, Andrei A. Istratov, Eicke R. Weber, Christian Kisielowski, Haifeng He, Chris Nelson, and John C. H. Spence

Appl. Phys. Lett. 89, 161907 (2006); http://dx.doi.org/10.1063/1.2362978 (3 pages) | Cited 21 times

Online Publication Date: 17 October 2006

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Using the energy-filtered convergent-beam electron diffraction (CBED) technique in a transmission electron microscope, the authors report here a direct measurement of the lattice parameters of uniaxially strained silicon as close as 25 nm below the gate in a 65 nm node p-type metal-oxide-semiconductor field-effect transistor with SiGe source and drain. It is found that the dominant strain component (0.58%) is compressive along the source-drain direction. The compressive stress is 1.1 GPa along this direction. These findings demonstrate that CBED can serve as a strain metrology technique for the development of strained silicon device technology.
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85.30.Tv Field effect devices
07.10.Lw Balance systems, tensile machines, etc.

Effect of uniaxial strain on anisotropic diffusion in silicon

Ming-Jer Chen and Yi-Ming Sheu

Appl. Phys. Lett. 89, 161908 (2006); http://dx.doi.org/10.1063/1.2362980 (3 pages) | Cited 3 times

Online Publication Date: 17 October 2006

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A physical model is directly extended from the thermodynamic framework to deal with anisotropic diffusion in uniaxially stressed silicon. With the anisotropy of the uniaxial strain induced activation energy as input, two fundamental material parameters, the activation volume and the migration strain anisotropy, can be quantitatively determined. When applied to boron, a process-device coupled simulation is performed on a p-type metal-oxide-semiconductor field-effect transistor undergoing uniaxial stress in a manufacturing process. The resulting material parameters have been found to be in satisfactory agreement with values presented in the literature.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
85.30.Tv Field effect devices

Nanocluster formation in Fe implanted GaN

G. Talut, H. Reuther, A. Mücklich, F. Eichhorn, and K. Potzger

Appl. Phys. Lett. 89, 161909 (2006); http://dx.doi.org/10.1063/1.2363960 (3 pages) | Cited 15 times

Online Publication Date: 17 October 2006

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The formation of Fe clusters in wurtzite GaN implanted with 200 keV math ions at 350 °C was investigated. Cluster sizes from few nanometers up to several 100 nm depending on ion fluence, implantation, and annealing temperature have been observed for ion fluences between 4×1016 and 1.6×1017 cm−2. A clear epitaxial relation between Fe and GaN was determined. X-ray diffraction, conversion electron Mössbauer spectroscopy, transmission electron microscopy, and Auger electron spectroscopy were used for the characterization of the implanted samples. Mössbauer spectroscopy shows that precipitation of Fe occurs already during implantation.
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81.07.Bc Nanocrystalline materials
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
81.16.-c Methods of micro- and nanofabrication and processing
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

Rapid solid-phase crystallization of high-rate, hot-wire chemical-vapor-deposited hydrogenated amorphous silicon

David L. Young, Paul Stradins, Yueqin Xu, Lynn Gedvilas, Bob Reedy, A. H. Mahan, Howard M. Branz, Qi Wang, and D. L. Williamson

Appl. Phys. Lett. 89, 161910 (2006); http://dx.doi.org/10.1063/1.2361163 (3 pages) | Cited 7 times

Online Publication Date: 17 October 2006

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Solid-phase crystallization of hydrogenated amorphous silicon thin films deposited by hot-wire (HW) and plasma-enhanced (PE) chemical vapor deposition was studied using in situ optical monitoring. HW films crystallized at least five times faster than PE films, independent of H and O concentration, deposition rate (2–110 Å/s), and nanovoid density due to reduced enthalpy barriers to both nucleation and final crystallization, which may be related to the presence of larger regions of highly ordered Si in the films.
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81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
64.70.K- Solid-solid transitions
61.43.Dq Amorphous semiconductors, metals, and alloys
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth

Thermal conductivity contrast measurement of fused silica exposed to low-energy femtosecond laser pulses

Yves Bellouard, Mark Dugan, Ali A. Said, and Philippe Bado

Appl. Phys. Lett. 89, 161911 (2006); http://dx.doi.org/10.1063/1.2363957 (3 pages) | Cited 8 times

Online Publication Date: 18 October 2006

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Femtosecond laser irradiation has various noticeable effects on fused silica. Of particular interest, pulses with energy levels below the ablation threshold can locally increase the refractive index and the material etching selectivity to hydrofluoric acid. The mechanism responsible for these effects is not yet fully understood. In this letter, the authors report on local thermal conductivity mapping of laser-affected zones. It is found that these zones exhibit a lower thermal conductivity at room temperature.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
78.47.-p Spectroscopy of solid state dynamics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
79.20.Ds Laser-beam impact phenomena
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Room temperature photoluminescence from ZnO quantum wells grown on (0001) sapphire using buffer assisted pulsed laser deposition

P. Misra, T. K. Sharma, S. Porwal, and L. M. Kukreja

Appl. Phys. Lett. 89, 161912 (2006); http://dx.doi.org/10.1063/1.2360222 (3 pages) | Cited 25 times

Online Publication Date: 19 October 2006

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Efficient room temperature (RT) photoluminescence (PL) is achieved on ZnO multiple quantum wells (MQWs) grown on sapphire by pulsed laser deposition using a buffer assisted growth scheme. Absorption spectra of these MQWs at RT showed the excitonic features entwined with the band edges, which pointed to the excitonic nature of the PL transitions. At RT the band edge of these MQWs shifted from ∼ 3.36 to 3.78 eV on decreasing the well layer thickness from ∼ 4 to 1 nm. In the range from 10 K to RT, the PL spectral linewidth increased and the peak shifted monotonically towards red with increasing temperature.
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78.67.De Quantum wells
78.55.Et II-VI semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
81.15.Fg Pulsed laser ablation deposition
68.65.Fg Quantum wells
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Dephasing of Bloch oscillating electrons in GaAs-based superlattices due to interface roughness scattering

T. Unuma, N. Sekine, and K. Hirakawa

Appl. Phys. Lett. 89, 161913 (2006); http://dx.doi.org/10.1063/1.2360911 (3 pages) | Cited 7 times

Online Publication Date: 19 October 2006

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We have investigated dephasing mechanisms of Bloch oscillating electrons in GaAs-based superlattices (SLs) by time-domain terahertz electro-optic sampling method. It was found that dephasing time τr for GaAs/AlAs SLs in the Wannier-Stark regime rapidly becomes shorter with decreasing well width Lw as τr∝Lw3−5. The observed strong Lw dependence of τr indicates that the dominant dephasing mechanism is interface roughness scattering, which was indeed confirmed by quantitative comparison between theory and experiment. It was also found that alloy disorder scattering is negligibly weak even in the case of GaAs/Al0.3Ga0.7As SLs.
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73.63.-b Electronic transport in nanoscale materials and structures
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
68.35.Ct Interface structure and roughness
78.20.Jq Electro-optical effects

Gas-phase synthesis of magnesium nanoparticles: A high-resolution transmission electron microscopy study

B. J. Kooi, G. Palasantzas, and J. Th. M. De Hosson

Appl. Phys. Lett. 89, 161914 (2006); http://dx.doi.org/10.1063/1.2358860 (3 pages) | Cited 22 times

Online Publication Date: 19 October 2006

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Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg{10math0} facets. Oxidation of Mg yields a MgO shell ( ∼ 3 nm thick), which has an orientation relation with the Mg. Inhomogeneous facet oxidation influences their growth kinetics resulting in a relatively broad size and shape distribution. Faceted voids between Mg and MgO shells indicate a fast outward diffusion of Mg and vacancy rearrangement into voids. The faceting of polar {220} planes is assisted by electron irradiation.
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81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
81.16.Pr Micro- and nano-oxidation
81.65.Mq Oxidation
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Indium adsorption on GaN under metal-organic chemical vapor deposition conditions

F. Jiang, R.-V. Wang, A. Munkholm, S. K. Streiffer, G. B. Stephenson, P. H. Fuoss, K. Latifi, and Carol Thompson

Appl. Phys. Lett. 89, 161915 (2006); http://dx.doi.org/10.1063/1.2364060 (3 pages) | Cited 8 times

Online Publication Date: 19 October 2006

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Real-time synchrotron grazing-incidence x-ray fluorescence is employed to study indium adsorption on the GaN (0001) surface under typical process conditions for InGaN metal-organic chemical vapor deposition. An indium condensation boundary is mapped as a function of trimethylindium pressure, substrate temperature, and carrier gas composition. Below the condensation boundary, indium surface coverage reaches a maximum of ∼ 1/4 ML. The addition of 8% H2 to the carrier gas is found to have a significant effect on both condensation and adsorption of indium.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.43.Mn Adsorption kinetics
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
64.70.F- Liquid-vapor transitions

Mechanisms and control of phase transition in thermally grown aluminas

B. W. Veal, A. P. Paulikas, and R. C. Birtcher

Appl. Phys. Lett. 89, 161916 (2006); http://dx.doi.org/10.1063/1.2364124 (3 pages) | Cited 9 times

Online Publication Date: 19 October 2006

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The oxidation rate of β-NiAl, at 1100 °C in air, can be slowed by means of a mechanical polish with α-Al2O3 grit. Particles embedded during polishing act as nucleation sites for conversion of the initially formed θ-Al2O3 to the stable α-Al2O3 phase. Since θ-phase growth is much faster than α-phase growth, accelerated θ→α conversion results in a thinner oxide when conversion is complete. A model is presented to quantitatively describe this behavior.
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64.70.K- Solid-solid transitions
81.65.Mq Oxidation
81.65.Ps Polishing, grinding, surface finishing
64.60.Q- Nucleation

Effect of the surface coating on the magnetic nanoparticle smectic-A liquid crystal interaction

L. J. Martínez-Miranda, Kevin McCarthy, L. K Kurihara, Jason J. Harry, and Alexis Noel

Appl. Phys. Lett. 89, 161917 (2006); http://dx.doi.org/10.1063/1.2359430 (3 pages) | Cited 10 times

Online Publication Date: 19 October 2006

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The behavior of smectic-A liquid crystals with magnetic particles has not been very well characterized. The authors have studied the interaction of a smectic-A liquid crystal with magnetic nanoparticles. They concentrate on the effect of the particles’ surface coating or functionalization compound. The surface coating in a nanoparticle is used to avoid phase separation and in biological applications to identify a particular cell or protein. Thus it is important to see how the surface coating interacts with the liquid crystal in conjunction with the magnetic nanoparticles. They have found out that depending on the surface coating the interaction of the nanoparticles with the liquid crystal varies. This variation is related to how the surface coating aligns the liquid crystal, how it contributes to the relative concentration of the nanoparticles in the liquid crystal-nanoparticle mixture, and how it affects the magnetic energy of the system.
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75.50.Tt Fine-particle systems; nanocrystalline materials
61.30.-v Liquid crystals

Molded electromechanical shift register memories

Gary M. McClelland and Bayu Atmaja

Appl. Phys. Lett. 89, 161918 (2006); http://dx.doi.org/10.1063/1.2364458 (3 pages) | Cited 1 time

Online Publication Date: 20 October 2006

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Synchronous, nonvolatile, shift register memories storing >1000 data bits can be constructed of a series of bistable mechanical levers, interacting electrostatically and actuated by a single electrode. An entire memory can be formed by a single molding step. A working laboratory-scale model has been constructed, and two submicron designs have been modeled. In one design using conducting levers, momentum briefly carries information. In another design using charged levers, information is passed between primary and secondary portions of a memory cell. Input and output, error propagation, fabrication tolerance, and memory integration are discussed.
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84.30.Sk Pulse and digital circuits
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Band gap and band parameters of InN and GaN from quasiparticle energy calculations based on exact-exchange density-functional theory

P. Rinke, M. Scheffler, A. Qteish, M. Winkelnkemper, D. Bimberg, and J. Neugebauer

Appl. Phys. Lett. 89, 161919 (2006); http://dx.doi.org/10.1063/1.2364469 (3 pages) | Cited 58 times

Online Publication Date: 20 October 2006

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The authors have studied the electronic structure of InN and GaN employing G0W0 calculations based on exact-exchange density-functional theory. For InN their approach predicts a gap of 0.7 eV. Taking the Burnstein-Moss effect into account, the increase of the apparent quasiparticle gap with increasing electron concentration is in good agreement with the observed blueshift of the experimental optical absorption edge. Moreover, the concentration dependence of the effective mass, which results from the nonparabolicity of the conduction band, agrees well with recent experimental findings. Based on the quasiparticle band structure the parameter set for a 4×4 k∙p Hamiltonian has been derived.
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71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
78.20.Bh Theory, models, and numerical simulation

Temperature dependence of Raman scattering in GaMnN

L. L. Guo, Y. H. Zhang, and W. Z. Shen

Appl. Phys. Lett. 89, 161920 (2006); http://dx.doi.org/10.1063/1.2364472 (3 pages) | Cited 7 times

Online Publication Date: 20 October 2006

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A detailed investigation of temperature-dependent Raman scattering has been carried out on ion-implanted GaMnN with different Mn doses. The observed frequency downshift and linewidth broadening with increasing temperature can be well described by a model taking into account the contributions of the thermal expansion and decay of optical phonons into two and three phonons of lower energy. The authors have demonstrated clear dependence of the phonon frequency, linewidth, and decay process on the Mn concentration in GaMnN, which is found to be closely related to the crystal structure.
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78.30.Fs III-V and II-VI semiconductors
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
65.40.De Thermal expansion; thermomechanical effects

Thermal conductivity of diamond-like carbon films

M. Shamsa, W. L. Liu, A. A. Balandin, C. Casiraghi, W. I. Milne, and A. C. Ferrari

Appl. Phys. Lett. 89, 161921 (2006); http://dx.doi.org/10.1063/1.2362601 (3 pages) | Cited 45 times

Online Publication Date: 20 October 2006

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The authors report the thermal conductivity (K) of a variety of carbon films ranging from polymeric hydrogenated amorphous carbons (a-C:H) to tetrahedral amorphous carbon (ta-C). The measurements are performed using the 3ω method. They show that thermal conduction is governed by the amount and structural disorder of the sp3 phase. If the sp3 phase is amorphous, K scales linearly with the C–C sp3 content, density, and elastic constants. Polymeric and graphitic films have the lowest K (0.2–0.3 W/mK), hydrogenated ta-C:H has K ∼ 1 W/mK, and ta-C has the highest K (3.5 W/mK). If the sp3 phase orders, even in small grains such as in micro- or nanodiamond, a strong K increase occurs for a given density, Young’s modulus, and sp3 content.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.55.-a Thin film structure and morphology
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
62.25.-g Mechanical properties of nanoscale systems
68.60.Bs Mechanical and acoustical properties

Cracking of III-nitride layers with strain gradients

A. E. Romanov, G. E. Beltz, P. Cantu, F. Wu, S. Keller, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 89, 161922 (2006); http://dx.doi.org/10.1063/1.2352043 (3 pages) | Cited 8 times

Online Publication Date: 20 October 2006

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Experimental results are demonstrated for the cracking of nominally compressed AlyGa1−yN layers grown on AlxGa1−xN buffer layers with smaller lattice constants (y<x). The authors present a theoretical analysis showing that the inclination of pure edge threading dislocation lines effectively reduces the compressive stress, causing relaxation, and after reaching a certain thickness begins to generate the tensile stress gradient responsible for cracking. The critical layer thickness for crack nucleation in such a gradient elastic field has been found. The results of the modeling are in good agreement with experimental observations of crack onset in nominally compressed nitride layers.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
68.55.A- Nucleation and growth
68.60.Bs Mechanical and acoustical properties

Formation of a body-centered-cubic Fe-based alloy at the Fe/GaAs(001) interface

P. Schieffer, A. Guivarc’h, C. Lallaizon, B. Lépine, D. Sébilleau, P. Turban, and G. Jézéquel

Appl. Phys. Lett. 89, 161923 (2006); http://dx.doi.org/10.1063/1.2364063 (3 pages) | Cited 6 times

Online Publication Date: 20 October 2006

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The room temperature epitaxial growth of Fe films on the As-rich GaAs(001)-(2×4) surface is studied using x-ray photoelectron spectroscopy as well as reflection high-energy electron diffraction and photoelectron diffraction. Interdiffusion mechanisms take place between Fe and GaAs during the deposition of the first 4 ML (0.7 nm) Fe. The authors find that an Fe-based substitutional alloy with a body-centered-cubic structure confined on several atomic planes and containing 30% of foreign species (Ga and As atoms) sits at the Fe/GaAs(001) interface. This intermixed layer is then buried by an almost pure Fe layer.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.Fx Diffusion; interface formation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
79.60.Jv Interfaces; heterostructures; nanostructures

In situ observation of the grain growth of the copper electrodeposits for ultralarge scale integration

Hyo-Jong Lee, Heung Nam Han, Do Hyun Kim, Ui-hyoung Lee, Kyu Hwan Oh, and Pil-Ryung Cha

Appl. Phys. Lett. 89, 161924 (2006); http://dx.doi.org/10.1063/1.2364119 (3 pages) | Cited 3 times

Online Publication Date: 20 October 2006

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The grain growth which occurs during the self-annealing in copper electrodeposits was investigated by in situ observation with an electron backscattered diffraction technique. From these observations, it was found that a newly created twin was initiated on the front interface of growing twin and that the transverse direction for the growth was ⟨110⟩. Most of the twins had the Σ3 twin boundary of {111}⟨110⟩. The formation of the twin and its peculiar growth direction could be explained quite well based on the hypothesis that the growth front interface is one of the {111} planes.
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82.45.Mp Thin layers, films, monolayers, membranes
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
82.45.Qr Electrodeposition and electrodissolution
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.40.Gh Other heat and thermomechanical treatments
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Growth of long wavelength InxGa1−xAsySb1−y layers on GaAs from liquid phase

A. Kumar and P. S. Dutta

Appl. Phys. Lett. 89, 162101 (2006); http://dx.doi.org/10.1063/1.2360899 (3 pages) | Cited 2 times

Online Publication Date: 16 October 2006

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Lattice mismatched layers of InxGa1−xAsySb1−y with band edge corresponding to a wavelength of 10.9 μm have been grown on GaAs substrates using a self-graded compositionally organized near-equilibrium growth process based on quaternary melt thermochemistry. A variable composition quaternary acts as a buffer layer between the GaAs substrate and the final layer of uniform composition. Layers of a constant composition with thicknesses as high as 100 μm have been achieved. The dislocation densities in the layers are as low as 8×105 cm−2 even for a lattice mismatch of 13.08%. van der Pauw measurements showed room temperature electron mobility as high as 1.4×104 cm2/V s and carrier concentration of 4.2×1016 cm−3. With further optimization in the growth conditions and improvements in the material quality, the grown layers are expected to be suitable for infrared optoelectronics, high speed electronic devices, and magnetoresistive sensors.
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68.55.A- Nucleation and growth
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
73.61.Ey III-V semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
82.60.-s Chemical thermodynamics
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

High resolution photoemission spectroscopy: Evidence for strong chemical interaction between Mg and 3,4,9,10-perylene-tetracarboxylic dianhydride

G. Gavrila, D. R. T. Zahn, and W. Braun

Appl. Phys. Lett. 89, 162102 (2006); http://dx.doi.org/10.1063/1.2356305 (3 pages) | Cited 4 times

Online Publication Date: 16 October 2006

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The interface formation between Mg and 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) was investigated by high resolution soft x-ray photoemission spectroscopy. The interface chemistry was obtained after fitting the core level spectra as a function of Mg thickness. At the initial stage of deposition, a strong chemical interaction between Mg and the single bonded oxygen atoms of PTCDA is observed leading to the formation of MgO and a modified organic molecule. Based on the experimental evidence, the molecular structure of the modified molecule is proposed. Moreover, the changes observed in the measured C1s core level spectra are supported by density functional theory calculations.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Jv Interfaces; heterostructures; nanostructures
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
73.20.-r Electron states at surfaces and interfaces
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Magnetotransport properties of Ge channels with extremely high compressive strain

K. Sawano, Y. Kunishi, Y. Shiraki, K. Toyama, T. Okamoto, N. Usami, and K. Nakagawa

Appl. Phys. Lett. 89, 162103 (2006); http://dx.doi.org/10.1063/1.2354467 (3 pages) | Cited 3 times

Online Publication Date: 17 October 2006

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Ge channel structures with extremely high compressive strain up to 2.8% were fabricated and their magnetotransport properties were evaluated. It was found that at the same hole density the sample with the higher strain showed the lower hole effective mass and that the compressive strain effectively reduced the effective mass. The Dingle ratios obtained were very high (>5) for all samples, indicating that remote impurity scattering was a dominant scattering mechanism rather than high angle scatterings caused by degradation of the channel layers. This result strongly suggests that Ge channels with extremely high strain are very promising for high performance complementary-metal-oxide-semiconductor applications.
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81.05.Cy Elemental semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Cw Elemental semiconductors
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Electron transport in semiconducting chiral carbon nanotubes

M. Z. Kauser and P. P. Ruden

Appl. Phys. Lett. 89, 162104 (2006); http://dx.doi.org/10.1063/1.2362973 (3 pages) | Cited 4 times

Online Publication Date: 17 October 2006

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The authors report on electron transport characteristics for semiconducting, single wall, chiral carbon nanotubes. The Boltzmann transport equation is solved indirectly by the ensemble Monte Carlo method. The basis for the transport calculations is provided by electronic structure calculations in the framework of a simple tight binding model. Scattering mechanisms considered are due to the electron-phonon interactions involving longitudinal acoustic, longitudinal optic, and radial breathing mode phonons. Due to the smaller Brillouin zone, Umklapp scattering processes occur with much greater frequency in chiral carbon nanotubes than in achiral nanotubes. The transient and steady-state transport characteristics are found to be dependent on the chirality for semiconducting carbon nanotubes with similar diameters.
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73.63.Fg Nanotubes
61.46.Fg Nanotubes
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
73.22.-f Electronic structure of nanoscale materials and related systems
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
71.38.-k Polarons and electron-phonon interactions

Improved memory window for Ge nanocrystals embedded in SiON layer

Chun-Hao Tu, Ting-Chang Chang, Po-Tsun Liu, Hsin-Chou Liu, Simon M. Sze, and Chun-Yen Chang

Appl. Phys. Lett. 89, 162105 (2006); http://dx.doi.org/10.1063/1.2362972 (3 pages) | Cited 17 times

Online Publication Date: 18 October 2006

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The formation of germanium (Ge) nanocrystals embedded in silicon oxygen nitride (SiON) is proposed for charge storage elements in this work. The Ge nanocrystals can be nucleated after the oxidation process of silicon germanium nitride (SiGeN) layer at high temperatures. Compared to the control samples of Ge nanocrystals/SiO2/Si structure and SiON/Si stack memory, the proposed Ge nanocrystals/SiON/Si memory obtained superior memory window, even larger than the typical sum of both. It is considered that the extra interface trap states between Ge and SiON film were generated as Ge nanocrystals were embedded in SiON layer.
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73.40.Ty Semiconductor-insulator-semiconductor structures
81.65.Mq Oxidation
73.20.At Surface states, band structure, electron density of states
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