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23 May 2011

Volume 98, Issue 21, Articles (21xxxx)

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Appl. Phys. Lett. 98, 212504 (2011); http://dx.doi.org/10.1063/1.3593371 (3 pages)

K. Okumura, T. Ishikura, M. Soda, T. Asaka, H. Nakamura, Y. Wakabayashi, and T. Kimura
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Electronic structure of Pt based topological Heusler compounds with C1b structure and “zero band gap”

Siham Ouardi, Chandra Shekhar, Gerhard H. Fecher, Xeniya Kozina, Gregory Stryganyuk, Claudia Felser, Shigenori Ueda, and Keisuke Kobayashi

Appl. Phys. Lett. 98, 211901 (2011); http://dx.doi.org/10.1063/1.3592834 (3 pages) | Cited 13 times

Online Publication Date: 23 May 2011

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Besides of their well-known wide range of properties it was recently shown that many of the heavy Heusler semiconductors with 1:1:1 composition and C1b structure exhibit a zero band gap behavior and are topological insulators induced by their inverted band structure. In the present study, the electronic structure of the Heusler compounds PtYSb and PtLaBi was investigated by bulk sensitive hard x-ray photoelectron spectroscopy. The measured valence band spectra are clearly resolved and in well agreement to the first-principles calculations of the electronic structure of the compounds. The experimental results give clear evidence for the zero band gap state.
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71.20.Gj Other metals and alloys
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Polarized photoluminescence from single wurtzite InP/InAs/InP core-multishell nanowires

Yasuaki Masumoto, Yuuki Hirata, Premila Mohan, Junichi Motohisa, and Takashi Fukui

Appl. Phys. Lett. 98, 211902 (2011); http://dx.doi.org/10.1063/1.3592855 (3 pages) | Cited 2 times

Online Publication Date: 23 May 2011

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The photoluminescence from single InP/InAs/InP core-multishell nanowires (CMNs) was highly linearly polarized in perpendicular to the nanowire long axis. Taking account of dielectric confinement of light field, we found the internal optical dipole squared perpendicular to the nanotube long axis d0x2 is larger than that parallel to the axis d0z2 by two orders of magnitude. With the increase in the thickness of InAs nanotubes, the ratio β = d0x2/d0z2 increases. This strong anisotropy in β comes from nearly perfect wurtzite structure of InP/InAs/InP CMNs and small inclusion of pz-character into the Γ7(B)-hole state.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.67.Uh Nanowires
77.22.Ej Polarization and depolarization

Enhanced visible-light photocatalytic activity of anatase TiO2 through N and S codoping

Lichao Jia, Congcong Wu, Yuanyuan Li, Song Han, Zongbao Li, Bo Chi, Jian Pu, and Li Jian

Appl. Phys. Lett. 98, 211903 (2011); http://dx.doi.org/10.1063/1.3593147 (3 pages) | Cited 13 times

Online Publication Date: 23 May 2011

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The density of states and optical properties of N, S, and (N, S)-doped anatase TiO2 are calculated based on the density functional theory. The results indicate that the doping S atoms occupy the Ti-atom sites in anatase TiO2 lattice. The mixing of O 2p, N 2p, S 3p, and Ti 3d states in the forbidden gap of (N, S)-codoped TiO2 can result in the higher visible-light photocatalytic activities than those monodoped TiO2. For comparison, (N, S)-codoped TiO2 was also synthesized by one-step hydrothermal method, and the optical absorption spectra obtained by experiments verified the reliability of our calculation.
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78.40.Fy Semiconductors
71.20.Nr Semiconductor compounds
82.50.Hp Processes caused by visible and UV light
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
81.05.Hd Other semiconductors
81.10.Dn Growth from solutions
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Interfacial mixing during annealing of zinc oxide nanoparticle junctions

Ming Hu, Konstantinos P. Giapis, and Dimos Poulikakos

Appl. Phys. Lett. 98, 211904 (2011); http://dx.doi.org/10.1063/1.3593487 (3 pages) | Cited 1 time

Online Publication Date: 23 May 2011

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The process of forming a junction between crystalline zinc oxide (ZnO) nanoparticles during pulsed thermal annealing in liquid tetradecane is studied using molecular dynamics simulation. Pairs of equal and unequal size particles are considered with emphasis on neck growth and atom mixing. The contact area and interface width of the junction are found to increase with heat pulse power albeit at different rates. The results suggest that it is possible to increase the junction area without significant mixing of atoms across the junction interface by tailoring the heat pulse power.
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81.07.Wx Nanopowders
61.72.Cc Kinetics of defect formation and annealing
81.05.Dz II-VI semiconductors
64.75.Ef Mixing
68.35.Ct Interface structure and roughness
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Generation of high spatial frequency ripples on silicon under ultrashort laser pulses irradiation

R. Le Harzic, D. Dörr, D. Sauer, F. Stracke, and H. Zimmermann

Appl. Phys. Lett. 98, 211905 (2011); http://dx.doi.org/10.1063/1.3593493 (3 pages) | Cited 6 times

Online Publication Date: 23 May 2011

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Periodic high spatial frequency ripples structures have been generated in silicon under femtosecond laser pulses irradiation. The period of the ripples is wavelength dependent. It increases from 110 up to 160 nm when the wavelength varies from 700 to 950 nm, respectively. We propose a refined model of the second harmonic generation ripples spacing theory Λ = λ/2nλ∗ taking into account the modified femtosecond laser excited silicon refractive index n∗ related to the Drude model. Good agreement is found between experimental results and the presented revisited model.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

The grain size and temperature dependence of the thermal conductivity of polycrystalline, tetragonal yttria-stabilized zirconia

Andi M. Limarga and David R. Clarke

Appl. Phys. Lett. 98, 211906 (2011); http://dx.doi.org/10.1063/1.3593383 (3 pages) | Cited 5 times

Online Publication Date: 24 May 2011

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The thermal conductivity of optically transparent, yttria-stabilized tetragonal zirconia having a range of grain sizes from 100 to 180 nm has been measured from just below its approximate Debye temperature up to 1000 °C. It is found that the grain size dependence is most marked at room temperature, decreasing with increasing temperature until being indistinguishable at the highest temperatures. The Kapitza thermal resistance of the grain boundaries is found to be almost independent of temperature, with a value of Rk = 4.5±0.5×10−9 m2K/W and an estimated grain boundary phonon transparency of ∼ 0.9.
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66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
61.72.Mm Grain and twin boundaries
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Observation of anomalous acoustic phonon dispersion in SrTiO3 by broadband stimulated Brillouin scattering

S. Brivio, D. Polli, A. Crespi, R. Osellame, G. Cerullo, and R. Bertacco

Appl. Phys. Lett. 98, 211907 (2011); http://dx.doi.org/10.1063/1.3593488 (3 pages) | Cited 2 times

Online Publication Date: 25 May 2011

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Femtosecond laser pulses have been used to generate and detect longitudinal acoustic phonons along the [001] direction of SrTiO3 single crystals coated with a thin absorbing layer. Two-dimensional maps of the reflectivity as a function of probe wavelength and time delay display persistent oscillations, from which the frequency-dependent group velocity of the photoinduced strain pulse can be directly measured. By applying the theory of stimulated Brillouin scattering we found that the longitudinal sound speed varies from 7900 to 7520 m/s in the 60–74 rad μm−1 wave vector range, thus indicating a clear deviation from a linear phonon dispersion relationship.
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63.20.dd Measurements
62.65.+k Acoustical properties of solids
78.20.Pa Photoacoustic effects
78.35.+c Brillouin and Rayleigh scattering; other light scattering
42.65.Es Stimulated Brillouin and Rayleigh scattering
78.40.Ha Other nonmetallic inorganics

Narrow-band acoustic attenuation measurements in vitreous silica at frequencies between 20 and 400 GHz

C. Klieber, E. Peronne, K. Katayama, J. Choi, M. Yamaguchi, T. Pezeril, and Keith A. Nelson

Appl. Phys. Lett. 98, 211908 (2011); http://dx.doi.org/10.1063/1.3595275 (3 pages) | Cited 5 times

Online Publication Date: 26 May 2011

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Acoustic attenuation rates in vitreous silica in the 20–400 GHz frequency range have been measured using a multiple-pulse optical technique for generation of tunable multicycle acoustic waves that are detected interferometrically after traversal of the sample. The results connect the frequency ranges of several measurement methods, yielding a consistent description of the acoustic behavior.
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62.65.+k Acoustical properties of solids
61.43.-j Disordered solids

In situ investigation of hydrogen interacting with Si(100)

Sebastian Brückner, Henning Döscher, Peter Kleinschmidt, and Thomas Hannappel

Appl. Phys. Lett. 98, 211909 (2011); http://dx.doi.org/10.1063/1.3593195 (3 pages) | Cited 5 times

Online Publication Date: 27 May 2011

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Silicon surfaces are subject to intense interaction with hydrogen ambient common in vapor phase epitaxy. We distinguish characteristic configurations of vicinal Si(100) by in situ reflectance anisotropy spectroscopy: covered by protective oxides, cleaned by thermal annealing, and the formation of monohydrides during cooling. Even above 1000 K, most dangling bonds of the (2×1)-reconstructed surface are saturated by hydrogen, while stability of Si–H bonds in the process gas ambient requires temperatures well below 750 K. Adjustment of hydrogen coverage employing alternative process gases provides experimental access to hydrogen adsorption and desorption characteristics valid for annealing in vapor phase epitaxy ambient.
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81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing
71.55.Cn Elemental semiconductors
68.43.Mn Adsorption kinetics
68.43.Nr Desorption kinetics
78.30.Am Elemental semiconductors and insulators
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