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14 Feb 2005

Volume 86, Issue 7, Articles (07xxxx)

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Appl. Phys. Lett. 86, 071101 (2005); http://dx.doi.org/10.1063/1.1862756 (3 pages)

Robert Horvath, Henrik C. Pedersen, Nina Skivesen, David Selmeczi, and Niels B. Larsen
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Intrinsic and extrinsic contributions to the lattice parameter of GaMnAs

L. X. Zhao, C. R. Staddon, K. Y. Wang, K. W. Edmonds, R. P. Campion, B. L. Gallagher, and C. T. Foxon

Appl. Phys. Lett. 86, 071902 (2005); http://dx.doi.org/10.1063/1.1864238 (3 pages) | Cited 24 times

Online Publication Date: 7 February 2005

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We report on measurements of the crystal structure and hole density in a series of as-grown and annealed GaMnAs samples. The measured hole densities are used to obtain the fraction of incorporated Mn atoms occupying interstitial and substitutional sites. This allows us to make a direct comparison of the measured lattice parameters with recent density-functional theory (DFT) predictions. We find that the decrease in lattice constant observed on annealing is smaller than that predicted due to the out-diffusion of interstitial Mn during annealing. The measured lattice parameters after annealing are still significantly larger than that of GaAs even in samples with very low compensation. This indicates that the intrinsic lattice parameter of GaMnAs is significantly larger than that of GaAs, in contradiction to the DFT prediction.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
66.30.Lw Diffusion of other defects
72.20.Fr Low-field transport and mobility; piezoresistance
61.72.Cc Kinetics of defect formation and annealing

X-ray diffraction measurements of internal strain in Si nanowires fabricated using a self-limiting oxidation process

Takayoshi Shimura, Kiyoshi Yasutake, Masataka Umeno, and Masao Nagase

Appl. Phys. Lett. 86, 071903 (2005); http://dx.doi.org/10.1063/1.1864245 (3 pages) | Cited 5 times

Online Publication Date: 7 February 2005

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We demonstrate x-ray diffraction measurements of internal strain in Si nanowires that were fabricated using a self-limiting oxidation process. Rod-shaped scattering around the 111 Bragg point due to interference effects from the Si nanowires were observed, which are robust reflections for incoherent displacement of the wires. From the shifts of the scattering in reciprocal space, the strain was estimated to be 1.0–1.5×10−3 for the sample oxidized at 800 °C for 300 min.
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81.05.Cy Elemental semiconductors
81.07.Bc Nanocrystalline materials
62.25.-g Mechanical properties of nanoscale systems
81.16.Pr Micro- and nano-oxidation
61.46.-w Structure of nanoscale materials
81.65.Mq Oxidation

Formation and evolution of epitaxial Co5Ge7 on Ge(001) surface by reactive deposition inside an ultrahigh-vacuum transmission electron microscope

H. P. Sun, Y. B. Chen, X. Q. Pan, D. Z. Chi, R. Nath, and Y. L. Foo

Appl. Phys. Lett. 86, 071904 (2005); http://dx.doi.org/10.1063/1.1862331 (3 pages) | Cited 6 times

Online Publication Date: 7 February 2005

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Cobalt was deposited on single-crystal Ge(001) surface at ∼ 350 °C by electron-beam evaporation in an ultrahigh-vacuum transmission electron microscope. The deposited Co reacts with Ge to form nanosized islands with the cobalt germanide Co5Ge7 phase. The Co5Ge7 islands show square and rectangular shapes. Two epitaxial orientation relationships between Co5Ge7 and Ge were observed: Co5Ge7 〈110〉(001)‖Ge〈100〉(001) and Co5Ge7〈001〉(110)‖Ge〈100〉(001).
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Lp Transmission electron microscopy (TEM)

Direct observation and theoretical interpretation of strongly enhanced lateral diffusion of photogenerated carriers in InGaN/GaN quantum well structures

S. J. Xu, Y. J. Wang, Q. Li, X. H. Zhang, W. Liu, and S. J. Chua

Appl. Phys. Lett. 86, 071905 (2005); http://dx.doi.org/10.1063/1.1862774 (3 pages) | Cited 2 times

Online Publication Date: 8 February 2005

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Strongly enhanced lateral diffusion of photogenerated carriers was directly observed in the luminescent image of the InGaN/GaN quantum wells. Such an effect was quantitatively modeled using diffusion equation and the ambipolar diffusion coefficient derived by K. H. Gulden and his co-workers [Phys. Rev. Lett. 66, 373 (1991) ]. Our simulation shows that the vertical piezoelectric field existing in strained InGaN/GaN quantum wells is the original “driving force” for the enhancement of lateral diffusion. Influence of the density of photogenerated carriers and their average mobility on the enhancement was discussed.
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73.63.Hs Quantum wells
78.67.De Quantum wells
66.30.Dn Theory of diffusion and ionic conduction in solids
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Dn Low-field transport and mobility; piezoresistance
78.55.Cr III-V semiconductors

Ferromagnetic nanoclusters formed by Mn implantation in GaAs

O. D. D. Couto, M. J. S. P. Brasil, F. Iikawa, C. Giles, C. Adriano, J. R. R. Bortoleto, M. A. A. Pudenzi, H. R. Gutierrez, and I. Danilov

Appl. Phys. Lett. 86, 071906 (2005); http://dx.doi.org/10.1063/1.1863436 (3 pages) | Cited 15 times

Online Publication Date: 8 February 2005

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Ferromagnetic clusters were incorporated into GaAs samples by Mn implantation and subsequent annealing. The composition and structural properties of the Mn-based nanoclusters formed at the surface and buried into the GaAs sample were analyzed by x-ray and microscopic techniques. Our measurements indicate the presence of buried MnAs nanoclusters with a structural phase transition around 40 °C, in accord with the first-order magneto-structural phase transition of bulk MnAs. We discuss the structural behavior of these nanoclusters during their formation and phase transition, which is an important point for technological applications.
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61.46.-w Structure of nanoscale materials
61.72.uj III-V and II-VI semiconductors
75.50.Cc Other ferromagnetic metals and alloys
68.35.B- Structure of clean surfaces (and surface reconstruction)
64.70.K- Solid-solid transitions
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
61.72.Cc Kinetics of defect formation and annealing
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
68.37.Ps Atomic force microscopy (AFM)
68.37.Lp Transmission electron microscopy (TEM)

Temperature-dependent luminescent properties of Eu–Tb complexes synthesized in situ in gel glass

Yan Liu, Guodong Qian, Zhiyu Wang, and Minquan Wang

Appl. Phys. Lett. 86, 071907 (2005); http://dx.doi.org/10.1063/1.1864233 (3 pages) | Cited 15 times

Online Publication Date: 8 February 2005

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The chelates of europium and terbium with hexafluoroacetylacetone (HFA) and triphenylphoshine oxide (TPPO), Eu/Tb(HFA)3(TPPO)2, have been synthesized in situ in gel glasses with various concentrations of Eu3+ and Tb3+ ions. The photoluminescence spectra have been measured and the characteristic transitions of Tb3+ and Eu3+ have been observed. Due to the variance of energy transfer efficiencies from Tb3+ to Eu3+, the intensity ratios of europium luminescent band to terbium band vary remarkably with measurement temperatures. In addition, the Förster mechanism has been proved to be responsible for the energy transfer between Eu3+ and Tb3+. The materials doped with Eu/Tb(HFA)3(TPPO)2 are promising for being used as a temperature detector and thermal-sensitive probe of optical fiber sensor.
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81.05.Kf Glasses (including metallic glasses)
78.55.Qr Amorphous materials; glasses and other disordered solids
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
42.81.Pa Sensors, gyros

Photoconductivity decay in metamorphic InAsP/InGaAs double heterostructures grown on InAsyP1−y compositionally step-graded buffers

Y. Lin, M. K. Hudait, S. W. Johnston, R. K. Ahrenkiel, and S. A. Ringel

Appl. Phys. Lett. 86, 071908 (2005); http://dx.doi.org/10.1063/1.1866645 (3 pages) | Cited 4 times

Online Publication Date: 9 February 2005

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Lattice-mismatched InAs0.32P0.68/In0.68Ga0.32As/InAs0.32P0.68 double heterostructures (DH) were grown on compositionally graded InAsyP1−y/InP substrates by solid-source molecular-beam epitaxy (MBE) out to a misfit of ∼ 1%. The kinetics of carrier recombination were investigated in the nearly totally relaxed MBE-grown DH structures using photoconductivity decay (PCD) measurements. High minority carrier lifetimes of 4–5 μs close to the radiation limit were measured, indicating the ability of MBE-grown InAsyP1−y buffers in achieving high-electronic-quality, low-band-gap mismatched InGaAs layers. Analysis suggests that very low interface recombination velocities are achieved. A photogenerated carrier diffusion model is presented to explain the initial nonlinear decays observed in PCD data for these heterostructures.
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73.50.Pz Photoconduction and photovoltaic effects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

High efficiency visible electroluminescence from silicon nanocrystals embedded in silicon nitride using a transparent doping layer

Kwan Sik Cho, Nae-Man Park, Tae-Youb Kim, Kyung-Hyun Kim, Gun Yong Sung, and Jung H. Shin

Appl. Phys. Lett. 86, 071909 (2005); http://dx.doi.org/10.1063/1.1866638 (3 pages) | Cited 78 times

Online Publication Date: 9 February 2005

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We have fabricated light-emitting diodes with a transparent doping layer on silicon nanocrystals (nc-Si) embeded in silicon nitride matrix formed by plasma-enhanced chemical vapor deposition. Under forward biased condition, orange electroluminescence (EL) with its peak wavelength at about 600 nm was observed at room temperature. The peak position of the EL is very similar to that of the photoluminescence (PL) and the emitted EL intensity is proportional to the current density passing through the device. We suggest that the observed EL is originated from electron-hole pair recombination in nc-Si. By using indium tin oxide and n-type SiC layer combination as a transparent doping layer, we obtained high external quantum efficiency greater than 1.6%.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Ap Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.up Other materials

On the crystalline structure, stoichiometry and band gap of InN thin films

K. M. Yu, Z. Liliental-Weber, W. Walukiewicz, W. Shan, J. W. Ager, S. X. Li, R. E. Jones, E. E. Haller, Hai Lu, and William J. Schaff

Appl. Phys. Lett. 86, 071910 (2005); http://dx.doi.org/10.1063/1.1861513 (3 pages) | Cited 51 times

Online Publication Date: 9 February 2005

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Detailed transmission electron microscopy, x-ray diffraction (XRD), and optical characterization of a variety of InN thin films grown by molecular-beam epitaxy under both optimized and nonoptimized conditions is reported. Optical characterization by absorption and photoluminescence confirms that the bandgap of single-crystalline and polycrystalline wurtzite InN is 0.70±0.05 eV. Films grown under optimized conditions with an AlN nucleation layer and a GaN buffer layer are stoichiometric, single-crystalline wurtzite structure with dislocation densities not exceeding mid-1010 cm−2. Nonoptimal films can be polycrystalline and display an XRD diffraction feature at 2θ ≈ 33°; this feature has been attributed by others to the presence of metallic In clusters. Careful indexing of wide-angle XRD scans and selected area diffraction patterns shows that this peak is in fact due to the presence of polycrystalline InN grains; no evidence of metallic In clusters was found in any of the studied samples.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
78.55.Cr III-V semiconductors
73.20.At Surface states, band structure, electron density of states
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)

Thermal lens study of the OH− influence on the fluorescence efficiency of Yb3+-doped phosphate glasses

C. Jacinto, S. L. Oliveira, L. A. O. Nunes, T. Catunda, and M. J. V. Bell

Appl. Phys. Lett. 86, 071911 (2005); http://dx.doi.org/10.1063/1.1861960 (3 pages) | Cited 23 times

Online Publication Date: 9 February 2005

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In this work, the thermal lens (TL) technique is used to determine the fluorescence quantum efficiency (η) of Yb3+-doped phosphate glasses. The role of nonradiative processes such as energy migration among Yb ions and the interaction with OH− radicals are presented and discussed. Two sets of samples with the same Yb concentrations were prepared, one at ambient conditions (set A) and the other in N2 atmosphere (set N). The TL technique was shown to be very sensitive to the amount of OH radicals. Moreover, the η values obtained from the TL method are in good agreement with the calculate ones (based on lifetime measurements). The results indicate that TL can be a valuable technique to evaluate the quantum efficiency and nonradiative rates in ion-doped materials.
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78.55.Qr Amorphous materials; glasses and other disordered solids
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
61.43.Fs Glasses

Transformation-induced plasticity and cascading structural changes in hexagonal boron nitride under high pressure and shear

Valery I. Levitas, Yanzhang Ma, and Javad Hashemi

Appl. Phys. Lett. 86, 071912 (2005); http://dx.doi.org/10.1063/1.1866226 (3 pages) | Cited 7 times

Online Publication Date: 9 February 2005

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In situ x-ray diffraction study and modeling of the degree of disorder, s, and phase transformation (PT) in hexagonal hBN were performed. It was proven that changes in s are strain-induced and that s can be used to quantify plastic strain. During the strain-induced hBN→wurtzitic wBN PT, the transformation-induced plasticity (TRIP) was exposed and quantified. TRIP exceeds conventional plasticity by a factor of 20. Cascading structural changes were revealed. Strain-induced disorder explains why PT under hydrostatic and nonhydrostatic conditions started at the same pressure ∼ 10 GPa. For the same disorder, plastic shear reduces PT pressure by a factor of 3–4.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
64.70.K- Solid-solid transitions
62.50.-p High-pressure effects in solids and liquids
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

High-resolution x-ray diffraction and transmission electron microscopy of multiferroic BiFeO3 films

Xiaoding Qi, Ming Wei, Yuan Lin, Quanxi Jia, Dan Zhi, Joonghoe Dho, Mark G. Blamire, and Judith L. MacManus-Driscoll

Appl. Phys. Lett. 86, 071913 (2005); http://dx.doi.org/10.1063/1.1866214 (3 pages) | Cited 46 times

Online Publication Date: 9 February 2005

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High-resolution x-ray diffraction and transmission electron microscopy (TEM) have been used to study BiFeO3 thin films grown on the bare and SrRuO3 buffered (001) SrTiO3 substrates. Reciprocal space mapping (RSM) around (002) and (103) reflections revealed that BFO films with a thickness of about 200 nm were almost fully relaxed and had a rhombohedral structure. Cross-sectional, high-resolution TEM showed that the films started to relax at a very early stage of growth, which was consistent with the RSM results. A thin intermediate layer of about 2 nm was observed at the interface, which had a smaller lattice than the overgrown film. Twist distortions about the c axis to release the shear strain introduced by the growth of rhombic (001) BiFeO3 on cubic (001) SrTiO3 were also observed. The results indicate that a strained, coherent BiFeO3 film on (001) SrTiO3 is very difficult to maintain and (111) STO substrates are preferable.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.55.-a Thin film structure and morphology
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.60.Bs Mechanical and acoustical properties
68.37.Lp Transmission electron microscopy (TEM)

Planck blackbody emissive power in particulate media

Ravi Prasher

Appl. Phys. Lett. 86, 071914 (2005); http://dx.doi.org/10.1063/1.1866218 (3 pages) | Cited 3 times

Online Publication Date: 9 February 2005

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Modifications of the Planck blackbody intensity and emissive power are proposed due to the modifications of the photon energy transport velocity and the density of states in particulate media. These modifications result from the multiple scattering of photons. These modifications affect the heat flux and temperature predictions in particulate media. Results show that current methods of predicting heat flux and temperature can lead to erroneous conclusions in a multiple-scattering radiative system.
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65.90.+i Other topics in thermal properties of condensed matter (restricted to new topics in section 65)
44.40.+a Thermal radiation

High-resolution three-dimensional imaging of flat objects by synchrotron-radiation computed laminography

L. Helfen, T. Baumbach, P. Mikulík, D. Kiel, P. Pernot, P. Cloetens, and J. Baruchel

Appl. Phys. Lett. 86, 071915 (2005); http://dx.doi.org/10.1063/1.1854735 (3 pages) | Cited 25 times

Online Publication Date: 10 February 2005

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Computed laminography with synchrotron radiation is developed and carried out for three-dimensional imaging of flat, laterally extended objects with high spatial resolution. Particular experimental conditions of a stationary synchrotron source have been taken into account by a scanning geometry different from that employed with movable conventional laboratory x-ray sources. Depending on the mechanical precision of the sample manipulation system, high spatial resolution down to the scale of 1 μm can be attained nondestructively, even for objects of large lateral size. Furthermore, high beam intensity and the parallel-beam geometry enables easy use of monochromatic radiation for optimizing contrast and reducing imaging artifacts. Simulations and experiments on a test object demonstrate the feasibility of the method. Application to the inspection of solder joints in a flip-chip bonded device shows the potential for quality assurance of microsystem devices.
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87.59.bd Computed radiography
87.63.-d Non-ionizing radiation equipment and techniques
81.70.Tx Computed tomography
07.85.Qe Synchrotron radiation instrumentation

Consequences of strong coupling between excitons and microcavity leaky modes

Maxime Richard, Robert Romestain, Régis André, and Le Si Dang

Appl. Phys. Lett. 86, 071916 (2005); http://dx.doi.org/10.1063/1.1861979 (3 pages) | Cited 12 times

Online Publication Date: 10 February 2005

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Semiconductor microcavities are known to exhibit the so-called leaky modes due to the Bragg structure of the cavity mirrors. In case of microcavities operating in the strong coupling regime, the leaky modes are usually considered as a perturbation for the polariton modes. Using microcavities based on II–VI compounds we observed that leaky modes and excitons can be strongly coupled and lead to complex multimode polaritons. The consequences for photoluminescence under nonresonant excitation and potential applications are discussed in terms of polariton state occupancy and photonic weight.
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73.21.Fg Quantum wells
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.67.De Quantum wells
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.55.Et II-VI semiconductors

High optical quality GaN nanopillar arrays

Y. D. Wang, S. J. Chua, S. Tripathy, M. S. Sander, P. Chen, and C. G. Fonstad

Appl. Phys. Lett. 86, 071917 (2005); http://dx.doi.org/10.1063/1.1861984 (3 pages) | Cited 20 times

Online Publication Date: 10 February 2005

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GaN nanopillar arrays have been fabricated by inductively coupled plasma etching of GaN films using anodic aluminum oxide film as an etch mask. The average diameter and length of these pillars are 60–65 nm and 350–400 nm, respectively. Ultraviolet microphotoluminescence measurements indicate high photoluminescence intensity and stress relaxation in these GaN nanopillars as compared to the starting epitaxial GaN films. Evidence of good crystalline quality is also observed by micro-Raman measurements, wherein a redshift of the E2high mode from GaN nanopillars suggests partial relaxation of the compressive strain. In addition, breakdown of the polarization selection rules led to the appearance of symmetry-forbidden and quasipolar modes.
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81.07.Bc Nanocrystalline materials
81.05.Ea III-V semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.40.Tv Optical and dielectric properties related to treatment conditions
78.55.Cr III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
61.46.-w Structure of nanoscale materials
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Vertical order in stacked layers of self-assembled In(Ga)As quantum rings on GaAs (001)

D. Granados, J. M. García, T. Ben, and S. I. Molina

Appl. Phys. Lett. 86, 071918 (2005); http://dx.doi.org/10.1063/1.1866228 (3 pages) | Cited 45 times

Online Publication Date: 10 February 2005

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Stacked layers of self-assembled In(Ga)As quantum rings on GaAs grown by solid source molecular beam epitaxy are studied by ex situ atomic force microscopy (AFM), low temperature photoluminescence (PL) and cross-sectional transmission electron microscopy (XTEM). The influence of the strain field and InAs segregation on the surface morphology, optical properties and vertical ordering of three quantum ring layers is analyzed for GaAs spacers between layers from 1.5 to 14 nm. AFM and PL results show that samples with spacers >6 nm have surface morphology and optical properties similar to single layers samples. XTEM results on samples with 3 and 6 nm GaAs spacers show that the rings are preserved after capping with GaAs, and evidence the existence of vertically ordered quantum rings.
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68.65.Hb Quantum dots (patterned in quantum wells)
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
68.35.Dv Composition, segregation; defects and impurities
68.37.Lp Transmission electron microscopy (TEM)
68.37.Ps Atomic force microscopy (AFM)

Antioxidation properties of Ti0.83Al0.17N prepared using plasma-enhanced atomic layer deposition

Yong Ju Lee and Sang-Won Kang

Appl. Phys. Lett. 86, 071919 (2005); http://dx.doi.org/10.1063/1.1861119 (3 pages) | Cited 2 times

Online Publication Date: 11 February 2005

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The high-temperature antioxidation behavior of Ti0.83Al0.17N prepared using plasma-enhanced atomic layer deposition (PEALD) with TiCl4, AlCl3, N2∕H2∕Ar, and NH3∕H2∕Ar radicals were studied. One cycle for depositing Ti0.83Al0.17N consisted of eight TiN cycles followed by two AlN cycles. After forming a 30-nm-thick Ti0.83Al0.17N film, the film was oxidized in ambient O2 at 650 °C for 30 min. The Ti0.83Al0.17N thin film showed good oxidation-resistance properties as compared with the pure TiN film prepared by PEALD. This is attributed to the Al2O3 layer formed on the surface of the Ti0.83Al0.17N. The Al2O3 layer serves as a barrier to oxygen diffusion, and protects the remaining nitride layer from being oxidized further.
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68.55.A- Nucleation and growth
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.65.Mq Oxidation
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology
82.45.Bb Corrosion and passivation

Fracture toughness of polycrystalline silicon carbide thin films

J. J. Bellante, H. Kahn, R. Ballarini, C. A. Zorman, M. Mehregany, and A. H. Heuer

Appl. Phys. Lett. 86, 071920 (2005); http://dx.doi.org/10.1063/1.1864246 (3 pages) | Cited 11 times

Online Publication Date: 11 February 2005

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Thin film polycrystalline silicon carbide (poly-SiC) doubly clamped microtensile specimens were fabricated using standard micromachining processes, and precracked using microindentation. The poly-SiC had been deposited on Si wafers by atmospheric pressure chemical vapor deposition, a process which leads to residual tensile stresses in the poly-SiC thin films; we measured the residual stress adjacent each specimen via a micromachined strain gauge. The stress intensity factor, KI, at the crack tip in each specimen depends on the magnitude of these residual stresses and the precrack length. Upon release, those precracks whose stress intensity exceeded a critical value, KIc, propagated to failure, whereas no crack growth was observed in those precracks with K<KIc. The fracture toughness so determined was 2.8 ⩽ KIc ⩽ 3.4 MPa m1/2. Our technique also allowed us to assess any susceptibility to moisture-assisted stress corrosion cracking, which proved to be essentially absent in poly-SiC.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.55.A- Nucleation and growth
68.60.Bs Mechanical and acoustical properties
68.35.Gy Mechanical properties; surface strains
62.20.M- Structural failure of materials
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Crystallinity of Li-doped Gd2O3:Eu3+ thin-film phosphors grown on Si (100) substrate

Soung Soo Yi, Jong Seong Bae, Byung Kee Moon, Jung Hyun Jeong, and Jung Hwan Kim

Appl. Phys. Lett. 86, 071921 (2005); http://dx.doi.org/10.1063/1.1868864 (3 pages) | Cited 10 times

Online Publication Date: 11 February 2005

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Gd2O3:Eu3+ and Li-doped Gd2O3:Eu3+ luminescent thin films have been grown on Si (100) substrates using pulsed-laser deposition. The films grown at different deposition conditions show different microstructural and luminescent characteristics. Both cubic and monoclinic crystalline structures were observed in both Gd2O3:Eu3+ and Li-doped Gd2O3:Eu3+ films, but the cubic phase becomes more dominant and the ratio of peak values IC(222)/IM(−402) increases rapidly for Li-doped Gd2O3:Eu3+ films. The photoluminescence brightness data obtained from Li-doped Gd2O3:Eu3+ films indicate that Si (100) is a promising substrate for growth of high-quality Li-doped Gd2O3:Eu3+ thin-film red phosphor. In particular, the incorporation of Li+ ions into the Gd2O3 lattice induced changes of crystallinity, surface roughness, and photoluminescence. The highest emission intensity was observed with Gd1.84Li0.08Eu0.08O3, whose brightness was a factor of 2.1 larger than that from Gd2O3:Eu3+ films. This phosphor is promising for applications in flat-panel displays.
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42.70.Mp Nonlinear optical crystals
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
78.55.Hx Other solid inorganic materials
81.15.Fg Pulsed laser ablation deposition
78.66.Nk Insulators
68.55.A- Nucleation and growth
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Photoinduced resistivity changes in Bi0.4Ca0.6MnO3 thin films

V. N. Smolyaninova, M. Rajeswari, R. Kennedy, M. Overby, S. E. Lofland, L. Z. Chen, and R. L. Greene

Appl. Phys. Lett. 86, 071922 (2005); http://dx.doi.org/10.1063/1.1868869 (3 pages) | Cited 17 times

Online Publication Date: 11 February 2005

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We report charge-ordered Bi0.4Ca0.6MnO3 thin films with charge-ordering temperature near room temperature, and observation of large photoinduced resistivity changes in these films associated with melting of the charge ordering by visible light. Films grown under small compressive strain exhibit the largest photoinduced resistivity changes. The lifetime of the photoinduced low-resistance state is on the order of half a minute. These photoinduced resistivity changes in thin films of Bi0.4Ca0.6MnO3 make them very promising for photonic device application.
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73.61.Ng Insulators
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.82.Ms Insulators
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Ballistic emission spectroscopy and imaging of a buried metal∕organic interface

Cedric Troadec, Linda Kunardi, and N. Chandrasekhar

Appl. Phys. Lett. 86, 072101 (2005); http://dx.doi.org/10.1063/1.1862789 (3 pages) | Cited 12 times

Online Publication Date: 8 February 2005

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The silver∕polyparaphenylene interface is investigated using ballistic electron emission microscopy (BEEM). Multiple injection barriers and spatial nonuniformity of carrier injection over nanometer length scales are observed. No unique injection barrier is found. Physical reasons for these features are discussed. BEEM current images and the surface topography of the silver film are uncorrelated.
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73.30.+y Surface double layers, Schottky barriers, and work functions
68.35.Ct Interface structure and roughness
68.37.Vj Field emission and field-ion microscopy
73.20.At Surface states, band structure, electron density of states
73.40.Ns Metal-nonmetal contacts
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Magnetoresistance in Ag2+δSe with high silver excess

M. von Kreutzbruck, B. Mogwitz, F. Gruhl, L. Kienle, C. Korte, and J. Janek

Appl. Phys. Lett. 86, 072102 (2005); http://dx.doi.org/10.1063/1.1866642 (3 pages) | Cited 16 times

Online Publication Date: 9 February 2005

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In the present study, we investigated the galvanomagnetic transport properties of polycrystalline AgxSe thin films with silver excess in the range from x = 1.5 to 18. The results prove that the silver excess controls the transition from linear magnetoresistance (MR) behavior to the quadratic ordinary MR and the temperature for the metal–semiconductor transition. Analyzing the MR effect by Kohler’s rule and comparing the results with the field-free resistivity we observe for 2<x<2.3 a steep rise of the product of mean free path and electron concentration (λ·n2/3). We interpret this result as a consequence of the percolation of nanoscale silver networks within the semiconducting matrix, i.e., as a consequence of the two-phase character of the system.
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75.50.Pp Magnetic semiconductors
75.20.Ck Nonmetals
75.70.Ak Magnetic properties of monolayers and thin films
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.Le Other inorganic semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
72.60.+g Mixed conductivity and conductivity transitions

Dielectric breakdown and Poole–Frenkel field saturation in silicon oxynitride thin films

S. Habermehl and R. T. Apodaca

Appl. Phys. Lett. 86, 072103 (2005); http://dx.doi.org/10.1063/1.1865338 (3 pages) | Cited 9 times

Online Publication Date: 9 February 2005

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Dielectric breakdown is studied in silicon oxynitride thin films varying in composition from SiN1.33 to SiO0.60N0.93. The films are observed to exhibit Poole–Frenkel emission as the dominant charge transport mechanism, with a compositionally dependent ionization potential ranging from 1.22 to 1.51 eV. The barrier lowering energy at the point of dielectric breakdown is independently determined to be likewise compositionally dependent, with the energies correlated to within ∼ 2 kT of the ionization potential. Field saturation-induced trap ionization is discussed as a means to negate carrier scattering from bulk traps as an impediment to impact ionization and dielectric breakdown.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.22.Jp Dielectric breakdown and space-charge effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
73.50.Fq High-field and nonlinear effects

Structural influence on atomic hopping and electronic states of Pd-based bulk metallic glasses

X.-P. Tang, Jörg F. Löffler, R. B. Schwarz, William L. Johnson, and Yue Wu

Appl. Phys. Lett. 86, 072104 (2005); http://dx.doi.org/10.1063/1.1866217 (3 pages) | Cited 2 times

Online Publication Date: 9 February 2005

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Atomic motion and electronic structures of Pd–Ni–Cu–P bulk metallic glasses were investigated using math nuclear magnetic resonance. The hopping rate of P atoms was determined by the stimulated echo technique. Significant hopping was observed in all alloys well below the glass transition temperature. Increasing the Cu content to above 25 at. % increases P hopping significantly, consistent with the previous finding that the openness of the structure increases with Cu content. In contrast, P hopping is not influenced by changes of local electronic states at P sites, induced by the substitution of Ni by Cu.
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76.60.Lz Spin echoes
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.43.Fs Glasses
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