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20 Oct 2008

Volume 93, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 93, 161101 (2008); http://dx.doi.org/10.1063/1.3000630 (3 pages)

E. Mujagić, L. K. Hoffmann, S. Schartner, M. Nobile, W. Schrenk, M. P. Semtsiv, M. Wienold, W. T. Masselink, and G. Strasser
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Optical properties of MoO3 containing tellurite glasses

Rajan Jose, Yusuke Arai, and Yasutake Ohishi

Appl. Phys. Lett. 93, 161901 (2008); http://dx.doi.org/10.1063/1.2976133 (3 pages) | Cited 1 time

Online Publication Date: 20 October 2008

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It was observed that P2O5 generates TeO5+δ groups in tellurite glasses that have a profound influence on their optical properties. The presence of TeO5+δ groups in phosphotellurite glass made MoO3 behave in a different way compared to other tellurite glass systems that do not contain P2O5. The refractive index measurements and Raman spectroscopy were combined to show that the addition of MoO3 in a phosphotellurite glass generates TeO3+1 polyhedron, whereas it generates TeO3 trigonal bipyramids in other glass systems. The MoO3 system showed absorption bands corresponding to Mo5+ ion in phosphotellurite glasses, whereas no similar bands were observed for other glasses.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Time scale for point-defect equilibration in nanostructures

Paul C. Millett, Dieter Wolf, Tapan Desai, and Vesselin Yamakov

Appl. Phys. Lett. 93, 161902 (2008); http://dx.doi.org/10.1063/1.3005175 (3 pages) | Cited 3 times

Online Publication Date: 20 October 2008

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Molecular dynamics simulations of high-temperature annealing are performed on nanostructured materials enabling direct observation of vacancy emission from planar defects (i.e., grain boundaries and free surfaces) to populate the initially vacancy-free grain interiors on a subnanosecond time scale. We demonstrate a universal time-length scale correlation that governs these re-equilibration processes, suggesting that nanostructures are particularly stable against perturbations in their point-defect concentrations, caused for example by particle irradiation or temperature fluctuations.
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61.43.Bn Structural modeling: serial-addition models, computer simulation
61.72.jd Vacancies
61.72.Mm Grain and twin boundaries
61.72.Cc Kinetics of defect formation and annealing
61.80.Az Theory and models of radiation effects
61.82.Rx Nanocrystalline materials

Tunable transmission and harmonic generation in nonlinear metamaterials

Ilya V. Shadrivov, Alexander B. Kozyrev, Daniel W. van der Weide, and Yuri S. Kivshar

Appl. Phys. Lett. 93, 161903 (2008); http://dx.doi.org/10.1063/1.2999634 (3 pages) | Cited 28 times

Online Publication Date: 21 October 2008

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We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.-e Optical elements, devices, and systems
42.70.-a Optical materials

Study of nanoprecipitates in a nickel-based superalloy using small-angle neutron scattering and transmission electron microscopy

E-Wen Huang, Peter K. Liaw, Lionel Porcar, Yun Liu, Yee-Lang Liu, Ji-Jung Kai, and Wei-Ren Chen

Appl. Phys. Lett. 93, 161904 (2008); http://dx.doi.org/10.1063/1.3002288 (3 pages) | Cited 7 times

Online Publication Date: 21 October 2008

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Small-angle neutron scattering (SANS) experiments were performed on a Ni-based nanoprecipitate-strengthened superalloy. A theoretical model for SANS absolute intensity distribution I(Q) was presented to extract the structural properties. During the deformation process, a change in the morphology of precipitates was discovered. However, the average interprecipitate distance and the average volume of precipitates were found to remain invariant. This microstructural information resolved by SANS is in good agreement with the results obtained from the quantitative transmission-electron-microscopy image analysis.
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64.70.Nd Structural transitions in nanoscale materials
61.05.fg Neutron scattering (including small-angle scattering)

Violet-light spontaneous and stimulated emission from ultrathin In-rich InGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition

Ho-Sang Kwack, Bong-Joon Kwon, Jin-Soo Chung, Yong-Hoon Cho, Soon-Yong Kwon, Hee Jin Kim, and Euijoon Yoon

Appl. Phys. Lett. 93, 161905 (2008); http://dx.doi.org/10.1063/1.3002300 (3 pages) | Cited 1 time

Online Publication Date: 21 October 2008

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We investigated the spontaneous and stimulated emission properties of violet-light-emitting ultrathin In-rich InGaN/GaN multiple quantum wells (MQWs) with indium content of 60%–70%. The Stokes shift was smaller than that of In-poor InGaN MQWs, and the emission peak position at 3.196 eV was kept constant with increasing pumping power, indicating negligible quantum confined Stark effect in ultrathin In-rich InGaN MQWs despite of high indium content. Optically pumped stimulated emission performed at room temperature was observed at 3.21 eV, the high-energy side of spontaneous emission, when the pumping power density exceeds ∼ 31 kW/cm2.
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78.67.De Quantum wells
78.45.+h Stimulated emission

Electron diffraction with ten nanometer beam size for strain analysis of nanodevices

A. Armigliato, S. Frabboni, and G. C. Gazzadi

Appl. Phys. Lett. 93, 161906 (2008); http://dx.doi.org/10.1063/1.3003581 (3 pages) | Cited 5 times

Online Publication Date: 21 October 2008

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A method to perform nanobeam diffraction (NBD) in a transmission electron microscope with high spatial resolution and low convergence angle is proposed. It is based on the use of a properly fabricated condenser aperture of 1 μm in diameter, which allows an electron beam about 10 nm in size to be focused on the sample, with a convergence angle in the 0.1 mrad range. Examples of NBD patterns taken in an untilted ⟨110⟩ cross section of a silicon device are shown. Their quality is adequate for spot position determination and hence to obtain, in principle, quantitative strain information.
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85.35.-p Nanoelectronic devices
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Efficient oxygen gettering in Si by coimplantation of hydrogen and helium

Xin Ou, Reinhard Kögler, Arndt Mücklich, Wolfgang Skorupa, Wolfhard Möller, Xi Wang, Jürgen W. Gerlach, and Bernd Rauschenbach

Appl. Phys. Lett. 93, 161907 (2008); http://dx.doi.org/10.1063/1.3005595 (3 pages) | Cited 3 times

Online Publication Date: 21 October 2008

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Hydrogen preimplantation performed in addition to helium implantation efficiently shrinks the width of the gettering layer in Si and increases the empty volume fraction as well as the internal surface area per unit volume. The gettering efficiency for oxygen is significantly enhanced compared to the single helium implantation, and the helium implantation dose can be strongly reduced. The gas-filled bubble layer induced by the coimplantation of hydrogen and helium has the highest gettering efficiency for the oxygen accumulation. Direct evidence for oxygen gettering at the internal wall of the cavity is demonstrated by cross-sectional transmission electron microscopy.
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61.72.uf Ge and Si
81.65.Tx Gettering
68.47.Fg Semiconductor surfaces
61.80.Jh Ion radiation effects
68.37.Og High-resolution transmission electron microscopy (HRTEM)

Anisotropic in-plane strains in nonpolar AlN and AlGaN (11math0) films grown on SiC (11math0) substrates

Tetsuya Akasaka, Yasuyuki Kobayashi, and Makoto Kasu

Appl. Phys. Lett. 93, 161908 (2008); http://dx.doi.org/10.1063/1.2995994 (3 pages) | Cited 2 times

Online Publication Date: 22 October 2008

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Nonpolar Al1−xGaxN (0 ≤ x ≤ 0.196) (11math0) films were grown on 4H-SiC (11math0) substrates by metal organic vapor phase epitaxy. Al1−xGaxN (0 ≤ x ≤ 0.057) films grew almost pseudomorphically on the substrates due to balanced in-plane stresses along [0001] and [1math00], while Al1−xGaxN (0.057<x) films were strained along [0001] but partially relaxed along [1math00] due to the absence of the balance. The crystal tilts of the films toward [0001] decreased monotonically with increasing Ga composition due to the correspondence between the (0001) plane distances of the films and the (0002) plane distance of substrates and due to a decrease in the in-plane strain along [0001].
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81.05.Ea III-V semiconductors
71.55.Eq III-V semiconductors
68.55.ag Semiconductors
68.60.Bs Mechanical and acoustical properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Ge dangling bonds at the (100)Ge/GeO2 interface and the viscoelastic properties of GeO2

M. Houssa, G. Pourtois, M. Caymax, M. Meuris, M. M. Heyns, V. V. Afanas’ev, and A. Stesmans

Appl. Phys. Lett. 93, 161909 (2008); http://dx.doi.org/10.1063/1.3006320 (3 pages) | Cited 46 times

Online Publication Date: 23 October 2008

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The electronic energy band structure of a (100)Ge/GeO2 interface with a Ge3 ≡ Ge• center (Ge dangling bond) is calculated using the density functional theory. The defect level associated with this dangling bond is found to lie near the middle of the Ge band gap. Consequently, the Ge dangling bond at this interface should be paramagnetic when the Fermi level is near the midgap, and it should thus be observed by electron spin resonance (ESR), which appears to be in contradiction with the results reported by [ Afanas’ev et al., Appl. Phys. Lett. 87, 032107 (2005) ]. We point out that the density of Ge3 ≡ Ge• centers at the (100)Ge/GeO2 interface is possibly at/below the ESR detection limit due to the viscoelastic properties of GeO2, owing to a better stress relaxation at/near the interface, compared to its silicon counterpart.
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68.35.Gy Mechanical properties; surface strains
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
76.30.Mi Color centers and other defects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Splitting of valance subbands in the wurtzite c-plane InGaN/GaN quantum well structure

Yu Song, Dong Chen, Lai Wang, Hongtao Li, Guangyi Xi, and Yang Jiang

Appl. Phys. Lett. 93, 161910 (2008); http://dx.doi.org/10.1063/1.3007985 (3 pages) | Cited 1 time

Online Publication Date: 24 October 2008

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Peak splitting in the low temperature photoluminescence (PL) spectra of c-plane InGaN/GaN single quantum well samples was observed. For the k∥c configuration, the splitting peaks show a variation in relative intensity as the excitation power is tuned. For the k⊥c configuration, a strong polarization dependence of the luminescence distribution and intensity was spotted. The PL spectra was analyzed with a calculation model based on the k⋅p effective mass theory, and the splitting peaks were identified as free-exciton transitions between the conduction subband C1 and two groups of valence subbands, the {HH1,LH1} and the {HH2,LH2,CH1}, respectively.
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73.20.-r Electron states at surfaces and interfaces
71.20.Nr Semiconductor compounds
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.15.-m Methods of electronic structure calculations
78.55.Cr III-V semiconductors

Two-dimensional photonic crystals with anisotropic unit cells imprinted from poly(dimethylsiloxane) membranes under elastic deformation

Xuelian Zhu, Ying Zhang, Dinesh Chandra, Shih-Chieh Cheng, James M. Kikkawa, and Shu Yang

Appl. Phys. Lett. 93, 161911 (2008); http://dx.doi.org/10.1063/1.3006061 (3 pages) | Cited 11 times

Online Publication Date: 24 October 2008

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We study structural symmetries of two-dimensional (2D) photonic crystals with anisotropic unit cells, including square- and rectangular-lattices with orientationally modulated elliptic motifs, and a compound structure consisting of circles with sixfold rotational symmetry and elliptical lines with twofold symmetry, which are created through elastic deformation of a single elastomeric membrane with circular pores. We then investigate the photonic bandgap (PBG) properties of the corresponding 2D Si posts and their tolerance to the structural deviation. We find that in the compound structure the overall PBGs are dominated by the sublattice with a higher symmetry, while the total symmetry is determined by the one with a lower symmetry.
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42.70.Qs Photonic bandgap materials
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Sr induced striped surface reconstructions formed on Si(111)

S. Teys, B. Olshanetsky, R. Zhachuk, S. Pereira, and G. Norga

Appl. Phys. Lett. 93, 161912 (2008); http://dx.doi.org/10.1063/1.3005594 (3 pages) | Cited 3 times

Online Publication Date: 24 October 2008

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Surface structures induced by submonolayer Sr adsorption on Si(111) surface were investigated by scanning tunneling microscopy (STM). Depending on the sample temperature and Sr coverage the following reconstructions on Si(111) surface could be directly resolved: 3×2, n×1 (n = 5,7,9), 2math×math, 4math×4math, and math×2 with increasing Sr coverage. The 3×2 and 2math×math striped structures cover large surface areas and are found to have stripe-to-stripe separations of 1.00 and 1.34 nm, respectively. The surface structures and respective rotational and antiphase domains reported here can explain all the previously suggested reconstructions except 2×1, which was not found. It is also demonstrated that diffraction data may lead to ambiguous results regarding the structure periodicity, when structural antiphase domains with sizes below the coherence length are present, highlighting the importance of complementary real space STM analysis.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Origin of tensile stress in the Si substrate induced by TiN/HfO2 metal gate/high-k dielectric gate stack

J. G. Wang, Jiyoung Kim, Chang Yong Kang, Byoung Hun Lee, Raj Jammy, Rino Choi, and M. J. Kim

Appl. Phys. Lett. 93, 161913 (2008); http://dx.doi.org/10.1063/1.3009572 (3 pages)

Online Publication Date: 24 October 2008

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The tensile stress induced by the metal TiN film in the atomic layer deposited HfO2/TiN stacks has been found from the crystallite coalescence mechanism of the Volmer–Weber-type growth mode at the early stage of the TiN film formation. The higher tensile stress induced by 3 nm TiN film than that by the 20 nm TiN film resulted from the smaller grain size and the [200] orientation of the TiN layer. Electron energy loss spectrum profile shows that there is no significant elemental interdiffusion between HfO2 and TiN, which could contribute to stress relaxation.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
79.20.Uv Electron energy loss spectroscopy
66.30.Ny Chemical interdiffusion; diffusion barriers
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