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11 Jul 2011

Volume 99, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 023102 (2011); http://dx.doi.org/10.1063/1.3567932 (3 pages)

Shadi A. Dayeh, Nathan H. Mack, Jian Yu Huang, and S. T. Picraux
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Transparent conductive oxides: Plasmonic materials for telecom wavelengths

M. A. Noginov, Lei Gu, J. Livenere, G. Zhu, A. K. Pradhan, R. Mundle, M. Bahoura, Yu. A. Barnakov, and V. A. Podolskiy

Appl. Phys. Lett. 99, 021101 (2011); http://dx.doi.org/10.1063/1.3604792 (3 pages) | Cited 13 times

Online Publication Date: 11 July 2011

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We show that despite of low loss, silver and gold are not suitable for a variety of nanoplasmonic applications in the infrared range, which require compact modes in single-interface plasmonic waveguides. At the same time, degenerate wide-band-gap semiconductors can serve as high-quality plasmonic materials at telecom wavelengths, combining fairly high compactness and relatively low loss. Their plasmonic properties in the near-infrared can be compared to those of gold in the visible range. The same materials can be used in a variety of non-plasmonic metamaterials applications, including transformation optics and invisibility cloaking.
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81.05.Hd Other semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.40.Fy Semiconductors
78.30.Hv Other nonmetallic inorganics
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Temperature dependence of 4.1 μm mid-infrared type II “W” interband cascade lasers

B. A. Ikyo, I. P. Marko, A. R. Adams, S. J. Sweeney, C. L. Canedy, I. Vurgaftman, C. S. Kim, M. Kim, W. W. Bewley, and J. R. Meyer

Appl. Phys. Lett. 99, 021102 (2011); http://dx.doi.org/10.1063/1.3606533 (3 pages)

Online Publication Date: 13 July 2011

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The thermal properties of 5-stage “W” Interband-Cascade Lasers emitting at 4.1 μm at room temperature (RT) are investigated by measuring the lasing and spontaneous emission properties as a function of temperature and hydrostatic pressure up to 1 GPa. Experiments show that at RT more than 90% of threshold current of these devices is due to non-radiative loss processes. We also find that the threshold current density dependence on temperature can be fitted with a single exponential function over a wide temperature range with a characteristic temperature, T0, of 45 K. The relatively high temperature sensitivity in these devices is attributable to the large non-radiative current contribution coupled with non-pinning of the carrier density above threshold.
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42.55.Px Semiconductor lasers; laser diodes
42.72.Ai Infrared sources

Optical properties of self assembled GaN polarity inversion domain boundary

M.-C. Liu, Y.-J. Cheng, J.-R. Chang, S.-C. Hsu, and C.-Y. Chang

Appl. Phys. Lett. 99, 021103 (2011); http://dx.doi.org/10.1063/1.3610449 (3 pages)

Online Publication Date: 13 July 2011

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We report the fabrication of GaN lateral polarity inversion heterostructure with self assembled crystalline inversion domain boundaries (IDBs). The sample was fabricated by two step molecular-beam epitaxy (MBE) with microlithography patterning in between to define IDBs. Despite the use of circular pattern, hexagonal crystalline IDBs were self assembled from the circular pattern during the second MBE growth. Both cathodoluminescent (CL) and photoluminescent (PL) measurements show a significant enhanced emission at IDBs and in particular at hexagonal corners. The ability to fabricate self assembled crystalline IDBs and its enhanced emission property can be useful in optoelectronic applications.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors

Highly efficient Si-nanorods/organic hybrid core-sheath heterojunction solar cells

Lining He, Changyun Jiang, Rusli, Donny Lai, and Hao Wang

Appl. Phys. Lett. 99, 021104 (2011); http://dx.doi.org/10.1063/1.3610461 (3 pages) | Cited 16 times

Online Publication Date: 14 July 2011

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We report a hybrid solar cell based on well-aligned crystalline silicon nanorods (SiNRs) and an organic semiconductor, 2,2′,7,7′-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD), in a core-sheath heterojunction structure. The device is formed by spin coating Spiro-OMeTAD on SiNRs array fabricated by electroless chemical etching. A silver grid on a conductive poly (3,4-ethylene-dioxythiophene): polystyrenesulfonate layer is used as the top transparent anode. A power conversion efficiency of 10.3% has been obtained for a 1-cm2 cell with 0.35-µm long SiNRs. The high efficiency and simple solution process used suggest that such devices are promising for developing low cost and high efficiency SiNRs/organic solar cells.
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88.40.jp Multijunction solar cells
88.40.jr Organic photovoltaics
81.65.Cf Surface cleaning, etching, patterning
88.40.hj Efficiency and performance of solar cells

Laser writing of the electronic activity of N- and H-atoms in GaAs

N. Balakrishnan, A. Patanè, O. Makarovsky, A. Polimeni, M. Capizzi, F. Martelli, and S. Rubini

Appl. Phys. Lett. 99, 021105 (2011); http://dx.doi.org/10.1063/1.3610464 (3 pages) | Cited 2 times

Online Publication Date: 14 July 2011

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We use a focussed laser beam to control the electronic activity of N- and H-atoms in a dilute nitride Ga(AsN)/GaAs quantum well. Our approach yields submicron resolution in the spatial manipulation of the electronic properties and can provide an alternative method to masking techniques for H-defect engineering and in-plane patterning of the band gap energy.
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73.21.Fg Quantum wells
81.07.St Quantum wells
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer

Submillisecond-response polymer network liquid crystal phase modulators at 1.06-μm wavelength

Jie Sun, Haiqing Xianyu, Yuan Chen, and Shin-Tson Wu

Appl. Phys. Lett. 99, 021106 (2011); http://dx.doi.org/10.1063/1.3611031 (3 pages) | Cited 9 times

Online Publication Date: 15 July 2011

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A fast-response and scattering-free polymer network liquid crystal (PNLC) light modulator is demonstrated at λ = 1.06 μm wavelength. A decay time of 117 μs for 2π phase modulation is obtained at 70 °C, which is ∼ 650 × faster than that of the host nematic LCs. The major tradeoff is the increased operating voltage. Potential applications include spatial light modulators and adaptive optics.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Kr Display devices, liquid-crystal devices
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Dye-sensitized solar cell with a titanium-oxide-modified carbon nanotube transparent electrode

A. K. K. Kyaw, H. Tantang, T. Wu, L. Ke, C. Peh, Z. H. Huang, X. T. Zeng, H. V. Demir, Q. Zhang, and X. W. Sun

Appl. Phys. Lett. 99, 021107 (2011); http://dx.doi.org/10.1063/1.3610488 (3 pages) | Cited 12 times

Online Publication Date: 15 July 2011

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Transparent and conductive carbon-based materials are promising for window electrodes in solid-state optoelectronic devices. However, the catalytic activity to redox reaction limits their application as a working electrode in a liquid-type dye-sensitized solar cell (DSSC). In this letter, we propose and demonstrate a transparent carbon nanotubes (CNTs) film as the working electrode in a DSSC containing iodide/triiodide redox couples. This implementation is realized by inhibiting the charge-transfer kinetics at CNT/redox solution interface with an aid of thin titanium oxide film that facilitates the unidirectional flow of electrons in the cell without sacrificing the electrical and optical properties of CNT.
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88.40.jr Organic photovoltaics
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Impact of phase lag on uniformity in pulsed capacitively coupled plasmas

Ankur Agarwal, Shahid Rauf, and Ken Collins

Appl. Phys. Lett. 99, 021501 (2011); http://dx.doi.org/10.1063/1.3610466 (3 pages) | Cited 1 time

Online Publication Date: 12 July 2011

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Process uniformity of macro-scale parameters such as electron and ion densities is critical during any plasma process. Pulsed operation of multiple frequency capacitively coupled plasmas (CCPs) has been shown to improve profile characteristics of features during plasma etching. In this work, we consider pulsing of both power sources in a dual frequency CCP. The impact of phase lag between the high frequency and low frequency power pulses on plasma uniformity is examined using a two-dimensional computational plasma model. Results for Ar/CF4 gas mixture indicate that phase lag allows one to control plasma uniformity by modulating the time for which the high or low frequency source is on.
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52.50.Dg Plasma sources
52.65.Kj Magnetohydrodynamic and fluid equation
52.77.Bn Etching and cleaning
52.80.Pi High-frequency and RF discharges
52.25.-b Plasma properties

Vacuum electron heating by surface plasma wave

Pawan Kumar and V. K. Tripathi

Appl. Phys. Lett. 99, 021502 (2011); http://dx.doi.org/10.1063/1.3609784 (3 pages) | Cited 2 times

Online Publication Date: 14 July 2011

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Vacuum heating of electrons by a large amplitude surface plasma wave (SPW) over a metal surface due to the Brunel effect is studied. The surface plasma wave has large normal component of electric vector. The normal field pulls the electrons away from the plasma during the half cycle. Each electron sees, besides the E⊥ of the surface plasma wave, a static space charge field. As the electron returns back to the interface, it possesses kinetic energy that is deposited into the plasma, leading to plasma heating.
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52.50.-b Plasma production and heating
52.25.Fi Transport properties
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams

Phase-independent generation of relativistic electron sheets

H.-C. Wu

Appl. Phys. Lett. 99, 021503 (2011); http://dx.doi.org/10.1063/1.3609872 (3 pages) | Cited 2 times

Online Publication Date: 14 July 2011

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A uniform and stable relativistic electron sheet can be generated by the two-layer target scheme, where a linearly polarized drive laser is originally employed. The energy and density of the electron layer are found to be sensitive to carrier-envelope phases of few-cycle laser pulses. To circumvent this problem, the present letter proposes to use a circularly polarized laser. The produced electron layer becomes completely independent of the phase of the laser, avoiding the rigorous requirement for phase stabilization in an ultra-intense few-cycle laser system. The improved scheme makes coherent x-ray sources based on relativistic electron sheets more attainable.
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41.75.Ht Relativistic electron and positron beams
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
41.60.Cr Free-electron lasers
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Depth dependency of indentation hardness during solid-state phase transition of shape memory alloys

Abbas Amini, Wenyi Yan, and Qingping Sun

Appl. Phys. Lett. 99, 021901 (2011); http://dx.doi.org/10.1063/1.3603933 (3 pages) | Cited 4 times

Online Publication Date: 11 July 2011

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We conducted the measurement of the hardness-depth relationship of NiTi shape memory alloy with a sharp Berkovich indenter. Different from most ductile metals, NiTi reacts to the mechanical load of indentation through phase transition underneath the indentation tip. We found that the hardness decreases rapidly with the increase of the indentation depth and eventually approaches a constant. To understand the depth dependency, we performed energy analysis involving the bulk and the interface energies of the transformation zone. We derived the hardness-depth relationship which well explains the experimental results. The finding is useful in hardness measurement of materials involving solid-state phase transitions.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
64.70.kd Metals and alloys
62.20.fg Shape-memory effect; yield stress; superelasticity
81.40.Lm Deformation, plasticity, and creep
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Existence of modulated structure and negative magnetoresistance in Ga excess Ni-Mn-Ga

Sanjay Singh, R. Rawat, and S. R. Barman

Appl. Phys. Lett. 99, 021902 (2011); http://dx.doi.org/10.1063/1.3604015 (3 pages) | Cited 5 times

Online Publication Date: 11 July 2011

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Ni2−xMnGa1+x (0.4 ≤ x ≤ 0.9) show the existence of modulated crystal structure at room temperature (RT) in the martensite phase, exhibit ferromagnetic behavior and have high martensitic transition temperature. The saturation magnetic moment decreases as Ga content increases, and this is related to antisite defects between Mn and Ga atoms leading to Mn-Mn nearest neighbor antiferromagnetic interaction. Negative magnetoresistance is observed at RT that increases linearly with magnetic field. These properties of Ga excess Ni-Mn-Ga show that it is a potential candidate for technological applications.
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61.66.Dk Alloys
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.30.Cr Saturation moments and magnetic susceptibilities
81.30.Kf Martensitic transformations
61.72.J- Point defects and defect clusters
64.70.kd Metals and alloys

Synchrotron-based photoluminescence excitation spectroscopy applied to investigate the valence band splittings in AlN and Al0.94Ga0.06N

Martin Feneberg, Marcus Röppischer, Norbert Esser, Christoph Cobet, Benjamin Neuschl, Tobias Meisch, Klaus Thonke, and Rüdiger Goldhahn

Appl. Phys. Lett. 99, 021903 (2011); http://dx.doi.org/10.1063/1.3610469 (3 pages)

Online Publication Date: 12 July 2011

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We demonstrate that synchrotron-based photoluminescence excitation (PLE) spectroscopy is a versatile tool for determining valence band splittings of AlN and high aluminum content AlGaN. PLE results are independently confirmed by synchrotron-based spectroscopic ellipsometry. The splittings between the ordinary and the extraordinary absorption edges are found to be −240 meV and −170 meV for AlN and Al0.94Ga0.06N, respectively. These values differ from the crystal field energy due to residual strain.
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78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds
78.40.Fy Semiconductors

Mesoscopic scale description of nucleation processes in glasses

Olivier Dargaud, Laurent Cormier, Nicolas Menguy, Gilles Patriarche, and Georges Calas

Appl. Phys. Lett. 99, 021904 (2011); http://dx.doi.org/10.1063/1.3610557 (3 pages) | Cited 4 times

Online Publication Date: 13 July 2011

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Mesoscale ordering of a Zr-bearing aluminosilicate glass is determined using high-angle annular dark field scanning transmission microscopy, corrected from aberration. This method reveals evidences for the presence of nanometer-size inhomogeneities in a macroscopically isotropic glass, with regions enriched in Zr. The nucleation step is largely overcome by the initial glass organization and can be understood as a local aggregation process, made easier as a result from the intrinsic heterogeneous organization of the initial glass structure.
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61.43.Fs Glasses
64.60.qj Studies of nucleation in specific substances
61.46.Hk Nanocrystals

Eliminating stacking faults in semi-polar GaN by AlN interlayers

A. Dadgar, R. Ravash, P. Veit, G. Schmidt, M. Müller, A. Dempewolf, F. Bertram, M. Wieneke, J. Christen, and A. Krost

Appl. Phys. Lett. 99, 021905 (2011); http://dx.doi.org/10.1063/1.3610467 (3 pages) | Cited 5 times

Online Publication Date: 13 July 2011

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We report on the elimination of stacking faults by the insertion of low-temperature AlN interlayers in nearly (10math6) and (1math04) oriented semi-polar GaN grown by metalorganic vapor phase epitaxy on Si(112) and Si(113), respectively. The elimination of these defects is visualized by cathodoluminescence (CL) as well as scanning transmission electron microscopy (STEM) and STEM-CL. A possible annihilation mechanism is discussed which leads to the conclusion that the elimination mechanism is most likely valid for all layers with (1math01) surfaces, enabling heteroepitaxial semi- and non-polar GaN free from stacking faults.
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61.72.Nn Stacking faults and other planar or extended defects
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors

Atom probe tomography assessment of the impact of electron beam exposure on InxGa1−xN/GaN quantum wells

Samantha E Bennett, David W Saxey, Menno J Kappers, Jonathan S Barnard, Colin J Humphreys, George DW Smith, and Rachel A Oliver

Appl. Phys. Lett. 99, 021906 (2011); http://dx.doi.org/10.1063/1.3610468 (3 pages) | Cited 5 times

Online Publication Date: 13 July 2011

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This study addresses the ongoing debate concerning the distribution of indium in InxGa1−xN quantum wells (QWs) using a combination of atom probe tomography (APT) and transmission electron microscopy (TEM). APT analysis of InxGa1−xN QWs, which had been exposed to the electron beam in a TEM, revealed an inhomogeneous indium distribution which was not observed in a control sample which had not been exposed to the electron beam. These data validate the effectiveness of APT in detecting subtle compositional inhomogeneities in the nitrides.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
68.37.Lp Transmission electron microscopy (TEM)
68.37.Vj Field emission and field-ion microscopy
79.20.Kz Other electron-impact emission phenomena

Synchrotron x-ray photoelectron spectroscopy study on thermally grown SiO2/4H-SiC(0001) interface and its correlation with electrical properties

Heiji Watanabe, Takuji Hosoi, Takashi Kirino, Yusuke Kagei, Yusuke Uenishi, Atthawut Chanthaphan, Akitaka Yoshigoe, Yuden Teraoka, and Takayoshi Shimura

Appl. Phys. Lett. 99, 021907 (2011); http://dx.doi.org/10.1063/1.3610487 (3 pages) | Cited 9 times

Online Publication Date: 13 July 2011

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The correlation between atomic structure and the electrical properties of thermally grown SiO2/4H-SiC(0001) interfaces was investigated by synchrotron x-ray photoelectron spectroscopy together with electrical measurements of SiC-MOS capacitors. We found that the oxide interface was dominated by Si-O bonds and that there existed no distinct C-rich layer beneath the SiC substrate despite literature. In contrast, intermediate oxide states in Si core-level spectra attributable to atomic scale roughness and imperfection just at the oxide interface increased as thermal oxidation progressed. Electrical characterization of corresponding SiC-MOS capacitors also indicated an accumulation of both negative fixed charges and interface defects, which correlates well with the structural change in the oxide interface and provides insight into the electrical degradation of thermally grown SiC-MOS devices.
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79.60.Jv Interfaces; heterostructures; nanostructures
84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Surface-related two-photon absorption and refraction of CdSe quantum dots

B. H. Zhu, H. C. Zhang, J. Y. Zhang, Y. P. Cui, and Z. Q. Zhou

Appl. Phys. Lett. 99, 021908 (2011); http://dx.doi.org/10.1063/1.3610561 (3 pages) | Cited 6 times

Online Publication Date: 14 July 2011

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Colloidal CdSe quantum dots (QDs), whose surface traps are controlled with the purification process, are measured with a Z-scan technique using an 80 femtosecond pulse duration laser source. Their two-photon absorption coefficient and refractive index are decreased more than one order of magnitude with the increase of the density of surface traps, indicating that the surface states are involved in the two-photon process.
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78.67.Hc Quantum dots
81.07.Ta Quantum dots
73.20.At Surface states, band structure, electron density of states
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Dz II-VI semiconductors
79.20.Ds Laser-beam impact phenomena

Evaluation of the interface of thin GaN layers on c- and m-plane ZnO substrates by Rutherford backscattering

Y. Izawa, T. Oga, T. Ida, K. Kuriyama, A. Hashimoto, H. Kotake, and T. Kamijoh

Appl. Phys. Lett. 99, 021909 (2011); http://dx.doi.org/10.1063/1.3610958 (3 pages) | Cited 1 time

Online Publication Date: 14 July 2011

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Lattice distortion at the interfaces between thin GaN layers with ∼400 nm in thickness and ZnO substrates with non-polar m-plane (10-10) and polar c-plane (0001) is studied using Rutherford backscattering/ion channeling techniques. The interface between GaN/m-plane ZnO is aligned clearly to m-axis, indicating no lattice distortion, while between GaN/c-plane ZnO causes the lattice distortion in the GaN layer due to the piezoelectric field. The range of distortion exceeds ∼90 nm from the interface of GaN/c-plane ZnO. These results are confirmed by x-ray diffraction and reflection high energy electron diffraction studies.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
68.35.Ct Interface structure and roughness
68.47.Fg Semiconductor surfaces
68.55.-a Thin film structure and morphology
77.65.-j Piezoelectricity and electromechanical effects

Drop size control in electro-coflow

N. Vilanova, V. R. Gundabala, and A. Fernandez-Nieves

Appl. Phys. Lett. 99, 021910 (2011); http://dx.doi.org/10.1063/1.3610949 (3 pages) | Cited 1 time

Online Publication Date: 15 July 2011

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We introduce electro-coflow as a way to generate emulsion drops with an average size that can be larger, comparable, and smaller than the smallest geometric feature of the device. The method relies on using three immiscible liquids, two of them having a finite electrical conductivity. There are three regimes of operation that allow the steady generation of drops: dripping, electro-dripping, and an electrically dominated regime. We transit from one to the other by increasing the applied voltage and describe the changes in drop size by balancing the relevant forces in each regime.
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47.65.-d Magnetohydrodynamics and electrohydrodynamics
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
64.75.Bc Solubility
47.55.D- Drops and bubbles
47.57.Bc Foams and emulsions

Formation of hollow structures through diffusive phase transition across a membrane

Luca Pasquini, Amelia Montone, Elsa Callini, Marco Vittori Antisari, and Ennio Bonetti

Appl. Phys. Lett. 99, 021911 (2011); http://dx.doi.org/10.1063/1.3610973 (3 pages) | Cited 3 times

Online Publication Date: 15 July 2011

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We report on the formation of hollow structures driven by a phase transition that proceeds via diffusion through a membrane. The mechanism is demonstrated for Mg/MgO core/shell nanoparticles: When they undergo successive metal-hydride transitions at sufficiently high temperature, the core material progressively diffuses outward and evaporates, leaving a hollow shell with the original shape and thickness. This phenomenon might become a general approach to the design of materials with controlled porosity.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
64.70.Nd Structural transitions in nanoscale materials
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions

Coherent hypersonic closed-pipe organ like modes in supported polymer films

A. V. Akimov, E. S. K. Young, J. S. Sharp, V. Gusev, and A. J. Kent

Appl. Phys. Lett. 99, 021912 (2011); http://dx.doi.org/10.1063/1.3605567 (3 pages) | Cited 3 times

Online Publication Date: 15 July 2011

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Hypersonic wavepackets were injected into polymer films of various thicknesses on a crystalline substrate, and quantized vibrational modes were detected. The acoustic spectrum showed up to six localized modes with frequencies determined by the boundary conditions for acoustic modes similar to those obtained in closed organ pipes. The decay rate of the modes was found to increase linearly with frequency in the gigahertz range.
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61.41.+e Polymers, elastomers, and plastics
82.35.Gh Polymers on surfaces; adhesion
63.50.-x Vibrational states in disordered systems
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Ab initio calculation of effective work functions for a TiN/HfO2/SiO2/Si transistor stack

Pierre-Yves Prodhomme, Fabien Fontaine-Vive, Abram Van Der Geest, Philippe Blaise, and Jacky Even

Appl. Phys. Lett. 99, 022101 (2011); http://dx.doi.org/10.1063/1.3609869 (3 pages) | Cited 5 times

Online Publication Date: 11 July 2011

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Ab initio techniques are used to calculate the effective work function (Weff) of a TiN/HfO2/SiO2/Si stack representing a metal-oxide-semiconductor (MOS) transistor gate taking into account first order many body effects. The required band offsets were calculated at each interface varying its composition. Finally, the transitivity of local density approximation (LDA) calculated bulk band lineups were used and completed by many body perturbation theory (MBPT) bulk corrections for the terminating materials (Si and TiN) of the MOS stack. With these corrections the ab initio calculations predict a Weff of a TiN metal gate on HfO2 to be close to 5.0 eV.
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85.30.Tv Field effect devices

Efficient thermoelectric van der Pauw measurements

Johannes de Boor and Volker Schmidt

Appl. Phys. Lett. 99, 022102 (2011); http://dx.doi.org/10.1063/1.3609325 (3 pages) | Cited 3 times

Online Publication Date: 12 July 2011

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The development of powerful thermoelectric materials requires fast and simple characterization techniques. We combine three measurements to obtain a complete thermoelectric characterization. The electrical conductivity is measured by the van der Pauw method, while ZT is determined directly by means of a Harman measurement. Finally, exploiting the analogy between electrical and thermal physics, a thermal van der Pauw measurement is performed and the sample Seebeck coefficient and thermal conductivity can be determined. No temperature differences need to be measured; all quantities can be deduced from voltage measurements concurrently on the same sample which allows for quick and convenient material screening.
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72.20.Pa Thermoelectric and thermomagnetic effects

Influence of SrTiO3 substrate miscut angle on the transport properties of LaAlO3/SrTiO3 interfaces

T. Fix, F. Schoofs, Z. Bi, A. Chen, H. Wang, J. L. MacManus-Driscoll, and M. G. Blamire

Appl. Phys. Lett. 99, 022103 (2011); http://dx.doi.org/10.1063/1.3609785 (3 pages) | Cited 2 times

Online Publication Date: 12 July 2011

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A free charge layer forms at the LaAlO3/SrTiO3 interface. We show the influence of the SrTiO3 (001) substrate miscut angle on its electronic and transport properties. Highly miscut substrates lead to a substantial mobility enhancement and a carrier density decrease at low temperature consistent with a two-carrier type model.
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73.40.-c Electronic transport in interface structures
72.20.Fr Low-field transport and mobility; piezoresistance
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