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6 Aug 2007

Volume 91, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 063118 (2007); http://dx.doi.org/10.1063/1.2768861 (3 pages)

Douglas C. Meier, Steve Semancik, Bradley Button, Evgheni Strelcov, and Andrei Kolmakov
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Interference method for the determination of the complex refractive index of thin polymer layers

Adam J. Moulé and Klaus Meerholz

Appl. Phys. Lett. 91, 061901 (2007); http://dx.doi.org/10.1063/1.2767232 (3 pages) | Cited 12 times

Online Publication Date: 6 August 2007

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The optical properties of thin-film layers are described by the complex index-of-refraction (N) and are commonly measured using spectroscopic ellipsometry. Once determined, they can be used to predict the optical reflection and transmission from films of any thickness. Fitting of the spectroscopic ellipsometry data for thin-film polymers and polymer-blends is difficult because numerous numerical assumptions are necessary and optical birefringence must be accounted for. Ellipsometric fitting techniques fail for thin films with strong absorption and high surface roughness. The authors present a simple method to measure N, perpendicular to the sample plane, of optically homogeneous films using a UV/Vis spectrometer and partial transmission substrates.
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78.66.Qn Polymers; organic compounds
78.40.Me Organic compounds and polymers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Fm Birefringence
68.35.B- Structure of clean surfaces (and surface reconstruction)

Anomalous tunneling effect on photoluminescence of asymmetric coupled double InGaN/GaN quantum wells

Y. Wang, X. J. Pei, Z. G. Xing, L. W. Guo, H. Q. Jia, H. Chen, and J. M. Zhou

Appl. Phys. Lett. 91, 061902 (2007); http://dx.doi.org/10.1063/1.2757091 (3 pages) | Cited 3 times

Online Publication Date: 6 August 2007

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Tunneling-assisted carrier transfer in coupled double InGaN/GaN quantum wells (QWs) has been studied by temperature-dependent photoluminescence (PL) at varied excitation density. It is found that the carriers captured by the wide (“deep”) well are efficiently transferred to the adjacent narrow (“shallow”) one by resonant tunneling, which results in anomalous temperature dependence of PL intensity and significantly enhanced luminescent efficiency for the narrow well. This is disparate from those conventional tunneling-assisted behaviors in coupled double QWs constructed by zinc-blende materials without polarization effect, where the carriers are always tunneling from the narrow (“shallow”) well to the wide (“deep”) one.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.65.Fg Quantum wells
73.40.Gk Tunneling

Optical investigation of p-type ZnO epilayers doped with different phosphorus concentrations by radio-frequency magnetron sputtering

B. J. Kwon, H. S. Kwack, S. K. Lee, Y. H. Cho, D. K. Hwang, and S. J. Park

Appl. Phys. Lett. 91, 061903 (2007); http://dx.doi.org/10.1063/1.2767993 (3 pages) | Cited 15 times

Online Publication Date: 6 August 2007

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Optical properties of p-type ZnO epilayers doped with different amounts of phosphorus by radio-frequency magnetron sputtering are investigated by x-ray diffraction, temperature dependent photoluminescence (PL), and time-resolved PL techniques. Bound exciton, free electrons-to-acceptors, donor-to-acceptor pair, and deep-level emissions are observed at about 3.356, 3.32, 3.24, and 2.4 eV at 10 K for p-type ZnO, respectively. The crystal quality and luminescence efficiency are improved with increasing phosphorus doping concentration. These results show that phosphorus doping plays an important role both in reducing native defects and in generating shallow acceptors in ZnO, leading to a good p-type conductivity in ZnO.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
61.72.uj III-V and II-VI semiconductors
73.61.Ga II-VI semiconductors
81.05.Dz II-VI semiconductors

Lifetime modeling for stress-induced voiding in integrated circuit interconnections

Cher Ming Tan and Yuejin Hou

Appl. Phys. Lett. 91, 061904 (2007); http://dx.doi.org/10.1063/1.2766695 (3 pages) | Cited 3 times

Online Publication Date: 6 August 2007

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By considering the stress-induced voiding (SIV) as a result of strain energy relief in the presence of flaws, an analytical lifetime model for SIV is derived from the energy perspective. The SIV lifetime is strongly dependent on the passivation integrity of the cap layer, effective bulk modulus of the interconnect system, diffusivities of the interconnect atoms in the dominant diffusion paths, stress free temperature, and temperature of the interconnection. The calculated SIV lifetime and the critical temperature are found to be consistent with the experimental values.
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85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Ultrastiff carbides uncovered in first principles

Zhouwen Chen, Mingxia Gu, Chang Q. Sun, Xinyu Zhang, and Riping Liu

Appl. Phys. Lett. 91, 061905 (2007); http://dx.doi.org/10.1063/1.2766860 (3 pages) | Cited 25 times

Online Publication Date: 6 August 2007

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The authors have computationally designed ultraincompressible materials, namely, rhenium carbide, in the WC and NiAs structures with a very high shear modulus. The corresponding calculated bulk modulus is comparable with that of diamond. Especially for the WC-typed rhenium carbide (ReC), the incompressibility along the c axis is demonstrated to exceed the linear incompressibility of diamond. The unique mechanical properties would make it suitable for applications under extreme conditions.
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62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Friction of partially embedded vertically aligned carbon nanofibers inside elastomers

Burak Aksak, Metin Sitti, Alan Cassell, Jun Li, Meyya Meyyappan, and Phillip Callen

Appl. Phys. Lett. 91, 061906 (2007); http://dx.doi.org/10.1063/1.2767997 (3 pages) | Cited 18 times

Online Publication Date: 7 August 2007

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Vertically aligned carbon nanofibers partially embedded inside polyurethane (eVACNFs) are proposed as a robust high friction fibrillar material with a compliant backing. Carbon nanofibers with 50–150 nm in diameter and 20–30 μm in length are vertically grown on silicon and transferred completely inside an elastomer by vacuum molding. By using time controlled and selective oxygen plasma etching, fibers are partially released up to 5 μm length. Macroscale friction experiments show that eVACNFs exhibit reproducible effective friction coefficients up to 1. Besides high friction, the proposed fabrication method improves fiber-substrate bond strength, and enables uniform height nanofibers with a compliant backing.
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62.25.-g Mechanical properties of nanoscale systems
81.40.Pq Friction, lubrication, and wear
68.35.Af Atomic scale friction
81.16.-c Methods of micro- and nanofabrication and processing
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Influence of the compressive stress on the infrared absorption of sp2-bonded boron nitride in cubic boron nitride thin films

Hangsheng Yang, Yan Zhang, Xiaobin Zhang, and Yabo Xu

Appl. Phys. Lett. 91, 061907 (2007); http://dx.doi.org/10.1063/1.2768199 (3 pages) | Cited 5 times

Online Publication Date: 7 August 2007

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Cubic BN films with a pure cubic phase upper layer were prepared by plasma-enhanced chemical vapor deposition. Infrared spectroscopy was applied to analyze the content of initial sp2-bonded BN layer in cubic BN thin films under compressive stress. It was found that the peak intensity near 1380 cm−1 attributed to the B–N stretching vibration of sp2-bonded BN was suppressed by the compressive stress in cubic BN films. The deviation between the measured and calculated peak intensities was found to be linear with the compressive stress when the upper layer of the film is a pure cubic phase layer.
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78.30.Fs III-V and II-VI semiconductors
68.60.Bs Mechanical and acoustical properties
78.66.Fd III-V semiconductors

Optimal crystal surface for efficient channeling in the new generation of hadron machines

S. Baricordi, V. Guidi, A. Mazzolari, G. Martinelli, A. Carnera, D. De Salvador, A. Sambo, G. Della Mea, R. Milan, A. Vomiero, and W. Scandale

Appl. Phys. Lett. 91, 061908 (2007); http://dx.doi.org/10.1063/1.2768200 (3 pages) | Cited 14 times

Online Publication Date: 7 August 2007

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The new generation of hadron machines may profitably take advantage of channeling for steering and collimation of high-energy particle beams. In that case, the requirements on the quality of the crystal surface are rather stringent in terms of both lattice perfection and roughness. Here, the authors show the structural and morphological characterizations of crystals fabricated through a method to achieve a surface that fulfills all needed specifications for application in hadron machines.
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61.85.+p Channeling phenomena (blocking, energy loss, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Vanadia-based equilibrium-thickness amorphous films on anatase (101) surfaces

Haijun Qian and Jian Luo

Appl. Phys. Lett. 91, 061909 (2007); http://dx.doi.org/10.1063/1.2768315 (3 pages) | Cited 14 times

Online Publication Date: 7 August 2007

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Nanometer-thick, surficial amorphous films are found to form in a model “monolayer” catalyst system: vanadia on TiO2 anatase (101) surfaces. These films exhibit a self-selecting or “equilibrium” thickness; once a thermodynamic equilibrium is reached, the film thickness, which corresponds to the Gibbsian surface excess of vanadia adsorbates, is independent of synthesis methods, the fraction of secondary vanadia phase, and the heat treatment history. These (multilayer) adsorbate films are largely amorphous (quasiliquid) at subeutectic temperatures, where analogies to premelting and prewetting phenomena are made. Reversible film thickness versus temperature (with a hysteresis loop) is observed and explained from a force-balance model.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.55.-a Thin film structure and morphology
61.43.-j Disordered solids
68.43.Mn Adsorption kinetics

Strain-induced formation of carbon and boron clusters in boron carbide during dynamic indentation

Dipankar Ghosh, Ghatu Subhash, Chee Huei Lee, and Yoke Khin Yap

Appl. Phys. Lett. 91, 061910 (2007); http://dx.doi.org/10.1063/1.2768316 (3 pages) | Cited 9 times

Online Publication Date: 7 August 2007

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The authors found that the level of amorphization or structural disorder in boron carbide is higher when induced by dynamic indentation compared to static indentation. Visible and uv Raman spectroscopies indicate that sp2-bonded aromatic carbon clusters were formed, consistent with the detected photoluminescence spectra. Infrared absorption shows that amorphous boron clusters were created by dynamic indentation which has strain rates ∼ 108 order higher than that introduced by static indentation. The decreased intensity of infrared stretching mode of carbon-boron-carbon (CBC) chains also suggests that amorphization is due to the collapse of B11C(CBC) unit cells, which reorganize into the energetically favorite carbon and boron clusters.
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61.43.Hv Fractals; macroscopic aggregates (including diffusion-limited aggregates)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
78.40.Pg Disordered solids
78.30.Hv Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials

Ultratransparent glass ceramics: The structure factor and the quenching of the Rayleigh scattering

M. Mattarelli, M. Montagna, and P. Verrocchio

Appl. Phys. Lett. 91, 061911 (2007); http://dx.doi.org/10.1063/1.2768642 (3 pages) | Cited 9 times

Online Publication Date: 8 August 2007

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Glass ceramics with nanocrystals present a transparency higher than that expected from the theory of Rayleigh scattering. This ultratransparency is attributed to the spatial correlation of the nanoparticles. The structure factor is calculated for a simple model system, the random sequential addition of equal spheres, at different volume filling factor. The spatial correlation given by the constraint that particles cannot superimpose produces a diffraction peak with a low S(q) in its low-q tail, which is relevant for light scattering. The physical mechanism producing high transparency in glass ceramics is demonstrated to be the low density fluctuation in the number of scatterers.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Direct observation of dislocation plasticity in 100 nm scale Au/Cu multilayers

Y. P. Li, G. P. Zhang, J. Tan, and B. Wu

Appl. Phys. Lett. 91, 061912 (2007); http://dx.doi.org/10.1063/1.2768888 (3 pages) | Cited 3 times

Online Publication Date: 8 August 2007

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Dislocation plasticity of Au/Cu multilayer with 100 nm scale was investigated by three-point bending tests. The authors found directly that clear slip lines appeared inside the grains ranging from 60 to 190 nm. The finding implies that the potential dislocation plasticity is still the dominant deformation mechanism in the material. Statistical evaluation of the mean spacing between slip lines reveals the effect of the length scale on homogeneity of plastic deformation. The critical length scale for dislocation-dominated deformation of the nanoscale material is found to be ∼ 15 nm.
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62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.65.Ac Multilayers
68.60.Bs Mechanical and acoustical properties

Self-assembled monolayers for reduced temperature direct metal thermocompression bonding

X. F. Ang, F. Y. Li, W. L. Tan, Z. Chen, C. C. Wong, and J. Wei

Appl. Phys. Lett. 91, 061913 (2007); http://dx.doi.org/10.1063/1.2768869 (3 pages) | Cited 5 times

Online Publication Date: 8 August 2007

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A reduction in the bonding temperature required for direct gold-gold (Au–Au) thermocompression bonding is observed by coating a monolayer of dodecanethiol on gold surfaces prior to bonding. The results show that Au–Au bonded joints of 26.9 g per bump strength can be achieved at a temperature as low as 160 °C. The temperature drop becomes more apparent when both coated and blank gold samples are exposed in air over some time before bonding. The authors propose that self-assembled monolayers passivate metal surface by obviating the adsorption of surface contaminants, in particular, carbon and oxygen but get desorbed just before bonding takes place.
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81.65.Rv Passivation
68.55.A- Nucleation and growth
68.43.Mn Adsorption kinetics
68.47.De Metallic surfaces
68.55.-a Thin film structure and morphology

Surface studies of hydrogen etched 3C-SiC(001) on Si(001)

C. Coletti, C. L. Frewin, S. E. Saddow, M. Hetzel, C. Virojanadara, and U. Starke

Appl. Phys. Lett. 91, 061914 (2007); http://dx.doi.org/10.1063/1.2768870 (3 pages) | Cited 10 times

Online Publication Date: 8 August 2007

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The morphology and structure of 3C-SiC(001) surfaces, grown on Si(001) and prepared via hydrogen etching, are studied using atomic force microscopy (AFM), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). On the etched samples, flat surfaces with large terraces and atomic steps are revealed by AFM. In ultrahigh vacuum a sharp LEED pattern with an approximate (5×1) periodicity is observed. AES studies reveal a “bulklike” composition up to the near surface region and indicate that an overlayer consisting of a weakly bound silicon oxide monolayer is present.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning
68.37.Ps Atomic force microscopy (AFM)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Quantification of In clustering in InGaN/GaN multi-quantum-wells by analysis of x-ray diffraction data

M. Krysko and M. Leszczynski

Appl. Phys. Lett. 91, 061915 (2007); http://dx.doi.org/10.1063/1.2764112 (3 pages) | Cited 2 times

Online Publication Date: 9 August 2007

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The authors developed a method of quantification of lateral indium content fluctuations in InGaN/GaN multi-quantum-wells (MQWs) grown on bulk GaN substrates. The method is based on comparison of intensities of the substrate and the MQW zeroth order peaks in 2θ-ω high resolution x-ray diffraction scans. They use a simulation program based on the kinematical theory of diffraction to fit simulated curves to the measured ones. The program uses the indium composition fluctuation amplitude as a fitting parameter.
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64.75.-g Phase equilibria
68.65.Fg Quantum wells

Dynamic process of dendrite fragmentation in solidification from undercooled Si melt using time-resolved x-ray diffraction

K. Nagashio, K. Nozaki, K. Kuribayashi, and Y. Katayama

Appl. Phys. Lett. 91, 061916 (2007); http://dx.doi.org/10.1063/1.2764114 (3 pages) | Cited 1 time

Online Publication Date: 9 August 2007

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The spontaneous dendrite fragmentation in solidification from undercooled Si melt was analyzed by time-resolved two-dimensional x-ray diffractometry. For the sample solidified at ΔT = 261 K, several spots appeared at 1 ms after recalescence and the subsequent transition from spots to rings occurred within ∼ 25 ms, which suggests that the fragmentation occurred after recalescence but just at the initial stage of the plateau period. Although the present experiment supported that the driving force for the fragmentation is a capillarity effect at the plateau period, the time scale for the fragmentation differed from the current quantitative prediction.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
81.05.Cy Elemental semiconductors
81.10.Fq Growth from melts; zone melting and refining
81.30.Fb Solidification
64.70.D- Solid-liquid transitions
61.72.-y Defects and impurities in crystals; microstructure

Modulation spectroscopic investigation on lattice polarity of gallium nitride

Ryuji Katayama, Kentaro Onabe, Hiroyuki Yaguchi, Tomonori Matsushita, and Takashi Kondo

Appl. Phys. Lett. 91, 061917 (2007); http://dx.doi.org/10.1063/1.2764115 (3 pages) | Cited 6 times

Online Publication Date: 9 August 2007

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A lattice polarity determination method for GaN is demonstrated, which is based on a capability of modulation spectroscopy for the assignment of electric-field directions performed nondestructively using simple optical setups. A strong spontaneous polarization induces an upward band bending toward +c surfaces and a downward but weaker bending toward −c surfaces for typical films with small residual strains and electron densities. This difference is distinguishable in terms of the spectral-phase flip, utilizing photoreflectance, and electroreflectance. Quantitative analysis revealed the exciton dissociation at a high-field region of +c surfaces consistent with the band profile derived as a solution of Poisson equation.
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78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.35.-y Excitons and related phenomena
71.20.Nr Semiconductor compounds

Texture memory and strain-texture mapping in a NiTi shape memory alloy

B. Ye, B. S. Majumdar, and I. Dutta

Appl. Phys. Lett. 91, 061918 (2007); http://dx.doi.org/10.1063/1.2768899 (3 pages) | Cited 5 times

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The authors report on the near-reversible strain hysteresis during thermal cycling of a polycrystalline NiTi shape memory alloy at a constant stress that is below the yield strength of the martensite. In situ neutron diffraction experiments are used to demonstrate that the strain hysteresis occurs due to a texture memory effect, where the martensite develops a texture when it is cooled under load from the austenite phase and is thereafter “remembered.” Further, the authors quantitatively relate the texture to the strain by developing a calculated strain-texture map or pole figure for the martensite phase, and indicate its applicability in other martensitic transformations.
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81.05.Bx Metals, semimetals, and alloys
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Broadband optical amplification in Bi-doped germanium silicate glass

Shifeng Zhou, Huafang Dong, Heping Zeng, Gaofeng Feng, Hucheng Yang, Bin Zhu, and Jianrong Qiu

Appl. Phys. Lett. 91, 061919 (2007); http://dx.doi.org/10.1063/1.2768914 (3 pages) | Cited 44 times

Online Publication Date: 9 August 2007

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Bi-doped germanium silicate glass is prepared and their optical properties are investigated. The glass sample shows broadband and flat emission characteristics compared with germanate glass. The single-pass optical amplification was measured on a traditional two-wave mixing configuration. Ultrabroadband optical amplification at 1272 and 1560 nm is observed simultaneously. The highest gain at 1272 nm of germanium silicate glass reaches to 6.73 dB excited with single commercially available 980 nm laser diode. The glass is promising for optical amplification covering almost all the O, E, S, C, and L bands.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.55.Wd Fiber lasers
61.43.Fs Glasses
78.55.Hx Other solid inorganic materials

Structure and magnetic properties of FePt/B4C multilayer thin films: Role of the compositional elements intermixing

M. J. Zhou, Quan Li, F. J. Yang, H. B. Wang, H. Wang, and D. Tang

Appl. Phys. Lett. 91, 061920 (2007); http://dx.doi.org/10.1063/1.2757597 (3 pages) | Cited 5 times

Online Publication Date: 9 August 2007

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FePt/B4C multilayer thin films were deposited using magnetron sputtering with different boron carbide layer thicknesses. Experimental results suggest that the B4C layers effectively serve as spacers to separate the FePt layers, making the multilayer configuration stable even after film annealing at elevated temperatures. On the other hand, B and C are found to incorporate into the FePt layer, which is responsible for the FePt grain growth confinement and grain separation, and eventually affects the magnetic properties of the composite film.
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68.65.Ac Multilayers
68.55.-a Thin film structure and morphology
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Vv High coercivity materials

Method to analyze electromechanical stability of dielectric elastomers

Xuanhe Zhao and Zhigang Suo

Appl. Phys. Lett. 91, 061921 (2007); http://dx.doi.org/10.1063/1.2768641 (3 pages) | Cited 73 times

Online Publication Date: 10 August 2007

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Subject to an electric voltage, a layer of a dielectric elastomer reduces its thickness, so that the voltage induces a high electric field. The positive feedback may cause the elastomer to thin down drastically, resulting in an electrical breakdown. The authors show that the electromechanical instability occurs when the Hessian of the free-energy function ceases to be positive definite. Their calculation shows that the stability of the actuator is markedly enhanced by prestresses, agreeing with existing experimental observations.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.22.Jp Dielectric breakdown and space-charge effects

Infrared reflection-absorption spectroscopy of Alq3 thin film on silver surface using synchrotron radiation

Yoko Sakurai, Shin-ichi Kimura, and Kazuhiko Seki

Appl. Phys. Lett. 91, 061922 (2007); http://dx.doi.org/10.1063/1.2768912 (3 pages) | Cited 3 times

Online Publication Date: 10 August 2007

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Infrared reflection-absorption spectra of Alq3 film on Ag surface have been measured as a function of thickness in the wave number region from 300 to 500 cm−1 using synchrotron radiation to determine which of the geometrical isomers of Alq3 is dominant. The observed spectra of the Al–N stretching modes of Alq3 indicate that Alq3 film predominantly consists of the meridional isomer including the first monolayer adsorbed on the Ag surface. In the spectrum of the monolayer Alq3, the Al–N stretching mode was observed to be located at wave number slightly lower than that of multilayer Alq3 probably due to the charge transfer between Alq3 and the Ag surface.
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78.66.Qn Polymers; organic compounds
78.30.Jw Organic compounds, polymers
63.20.-e Phonons in crystal lattices

Plasma ehnancement of metalorganic chemical vapor deposition and properties of Er2O3 nanostructured thin films

Maria M. Giangregorio, Maria Losurdo, Alberto Sacchetti, Pio Capezzuto, Giovanni Bruno, Graziella Malandrino, Ignazio L. Fragalà, Raffaella Lo Nigro, Lidia Armelao, Davide Barreca, and Eugenio Tondello

Appl. Phys. Lett. 91, 061923 (2007); http://dx.doi.org/10.1063/1.2768915 (3 pages) | Cited 2 times

Online Publication Date: 10 August 2007

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An O2 remote plasma metal organic chemical vapor deposition (RP-MOCVD) route is presented for tailoring the structural, morphological, and optical properties of Er2O3 thin films grown on Si(100) using the tris(isopropylcyclopentadienyl)erbium precursor. The RP-MOCVD approach produced highly (100)-oriented, dense, and mechanically stable Er2O3 films with columnar structure.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
52.77.-j Plasma applications
81.16.Be Chemical synthesis methods
77.55.-g Dielectric thin films

Incipient plasticity in metallic glass modulated nanolaminates

Y. M. Wang, A. V. Hamza, and T. W. Barbee, Jr.

Appl. Phys. Lett. 91, 061924 (2007); http://dx.doi.org/10.1063/1.2768939 (3 pages) | Cited 6 times

Online Publication Date: 10 August 2007

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The plastic deformation in copper-zirconium nanocrystalline-amorphous nanolaminates is investigated by means of stress-relaxation experiments at a range of initial stress levels. Progressive multistep relaxation cycles reveal that the onset of plastic deformation occurs at a much lower stress level in nanocrystalline-amorphous nanolaminate than in crystalline-crystalline nanolaminates or other nanostructured materials. The derived activation volumes and strain rate sensitivities imply interfacial dislocation mechanisms, consistent with the observations from postmorterm transmission electron microscopy. This indicates that the crystalline-amorphous interfaces may be the preferred source for dislocation nucleation and/or emission.
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68.35.Gy Mechanical properties; surface strains
81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.35.Ct Interface structure and roughness

Identification of sub-band-gap absorption features at the HfO2/Si(100) interface via spectroscopic ellipsometry

J. Price, P. S. Lysaght, S. C. Song, Hong-Jyh Li, and A. C. Diebold

Appl. Phys. Lett. 91, 061925 (2007); http://dx.doi.org/10.1063/1.2769389 (3 pages) | Cited 14 times

Online Publication Date: 10 August 2007

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Spectroscopic ellipsometry is used to characterize charge trapping defect states in thin HfO2 gate dielectric films deposited by atomic layer deposition on chemically oxidized p-type Si (100) substrates. The intensity of specific absorption features detected below the band gap of HfO2 at 2.9 and 4.75 eV is clearly distinguished from the Si critical points; however, repeating this spectroscopic evaluation for identical HfO2 films deposited and annealed on fused silica substrates results in no defect features detected. The HfO2/Si(100) results, therefore, suggest these oxygen deficient defects are not intrinsic to HfO2 but reside primarily at the interface with the silicon substrate. The feasibility of utilizing spectroscopic ellipsometry to identify stoichiometric variations at the SiO2/Si(100) interface and the corresponding changes associated with the electrical performance is presented.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
71.55.Ht Other nonmetals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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