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10 Sep 2012

Volume 101, Issue 11, Articles (11xxxx)

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Appl. Phys. Lett. 101, 113302 (2012); http://dx.doi.org/10.1063/1.4749791 (4 pages)

Chang-Hoon Shim, Shuzo Hirata, Juro Oshima, Tomohiko Edura, Reiji Hattori, and Chihaya Adachi
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Black silicon with controllable macropore array for enhanced photoelectrochemical performance

Xianyu Ao, Xili Tong, Dong Sik Kim, Lianbing Zhang, Mato Knez, Frank Müller, Sailing He, and Volker Schmidt

Appl. Phys. Lett. 101, 111901 (2012); http://dx.doi.org/10.1063/1.4752231 (4 pages)

Online Publication Date: 10 September 2012

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Macroporous silicon with multiscale texture for reflection suppression and light trapping was achieved through a controllable electrochemical etching process. It was coated with TiO2 by atomic layer deposition, and used as the photoanode in photocatalytic water splitting. A conformal pn-junction was also built-in in order to split water without external bias. A 45% enhancement in photocurrent density was observed after black silicon etching. In comparison with nano-structured silicon, the etching process here has neither metal contamination nor requirement of vacuum facilities.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.45.Fk Electrodes

High pressure phase determination and electronic properties of lithiumamidoborane

M. Ramzan, T. Hussain, and R. Ahuja

Appl. Phys. Lett. 101, 111902 (2012); http://dx.doi.org/10.1063/1.4752237 (4 pages)

Online Publication Date: 10 September 2012

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In this study we report on the high pressure phase of the promising hydrogen storage material lithiumamidoborane (LiNH2BH3), on the basis of density functional theory calculations with generalized gradient approximation. We take the five possible candidate structures, Pbca, Pbcn, Pcca, Pnma, and Pnnm for the high pressure study of LiNH2BH3. The corresponding structures are relaxed with respect to fractional atomic coordinates and cell parameters, with the use of fully self-consistent ab initio electronic structure calculations to get the equilibrium parameters and total energies. Then we compare the energies of these phases and find that Pbcn is the most favorable phase at ≈ 100 GPa. Then we calculate the structural parameters of this phase. Finally, we calculate the density of states, Bader charge analysis, and corresponding electron density of this phase.
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62.50.-p High-pressure effects in solids and liquids
88.30.R- Hydrogen storage
71.15.-m Methods of electronic structure calculations
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Ps Other inorganic compounds
71.15.Nc Total energy and cohesive energy calculations

Visible photoluminescence in polycrystalline terbium doped aluminum nitride (Tb:AlN) ceramics with high thermal conductivity

A. T. Wieg, Y. Kodera, Z. Wang, T. Imai, C. Dames, and J. E. Garay

Appl. Phys. Lett. 101, 111903 (2012); http://dx.doi.org/10.1063/1.4751856 (5 pages) | Cited 1 time

Online Publication Date: 11 September 2012

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Thermal management continues to be one of the major challenges in the development of high powered light sources such as solid state lasers. In particular, the relatively low thermal conductivity of standard photoluminescent (PL) materials limits the overall power output and/or duty cycle. We present a method based on current activated pressure assisted densification for the fabrication of high thermal conductivity PL materials: rare earth doped polycrystalline bulk aluminum nitride. Specifically, the ceramics are translucent and are doped with Tb3+, allowing for emission in the visible. Remarkably, the ceramics have a room temperature thermal conductivity of 94 W/(m K) which is almost seven times higher than that of the state of the art host material, Nd-doped yttrium aluminum garnet. These light emitting properties coupled with very high thermal conductivity should enable the development of a wide variety of more powerful light sources.
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78.55.Cr III-V semiconductors
66.70.Df Metals, alloys, and semiconductors
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.05.Ea III-V semiconductors

Strain effect on lattice vibration, heat capacity, and thermal conductivity of graphene

F. Ma, H. B. Zheng, Y. J. Sun, D. Yang, K. W. Xu, and Paul K. Chu

Appl. Phys. Lett. 101, 111904 (2012); http://dx.doi.org/10.1063/1.4752010 (4 pages) | Cited 1 time

Online Publication Date: 11 September 2012

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First-principle calculation based on density functional theory is performed to study the lattice vibration, heat capacity, and thermal conductivity of graphene under strain. Two degenerate optical branches in the phonon dispersion curves split near the G points due to the reduced crystal symmetry, and the frequencies of the optical phonon modes shift down thus inducing more phonon modes at a given temperature. The heat capacity is increased, but the thermal conductivity is reduced because of enhanced Umklapp scattering among more phonons. This phenomenon should be considered when determining the heat management of graphene-based devices.
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65.40.Ba Heat capacity
72.80.Vp Electronic transport in graphene
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
63.22.Rc Phonons in graphene
66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.

Blue shift induced by extrinsic spin-orbit coupling on monolayer graphene

A. Phirouznia, S. Safari Shateri, J. Poursamad Bonab, and K. Jamshidi-Ghaleh

Appl. Phys. Lett. 101, 111905 (2012); http://dx.doi.org/10.1063/1.4752101 (4 pages)

Online Publication Date: 12 September 2012

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The effect of substrate induced spin-orbit (SO) interaction on the transverse dielectric function of a single plane of graphene has been investigated. The Lindhard model approach was then employed to obtain the transverse dielectric function. The dependence of dielectric function on the SO coupling of the graphene sheet with the substrate was theoretically studied. Numerical results show that increasing the Rashba coupling strength results in a blue shift of the van Hove singularities in the linear dielectric response function. Controllable blue shift opens up ways for a variety of device applications.
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78.67.Wj Optical properties of graphene
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Temperature dependence of chemical-vapor deposition of pure boron layers from diborane

V. Mohammadi, W. B. de Boer, and L. K. Nanver

Appl. Phys. Lett. 101, 111906 (2012); http://dx.doi.org/10.1063/1.4752109 (4 pages) | Cited 2 times

Online Publication Date: 12 September 2012

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Surface reaction mechanisms are investigated to determine the activation energies of pure boron (PureB) layer deposition at temperatures from 350 °C to 850 °C when using chemical-vapor deposition from diborane in a commercial Si/SiGe epitaxial reactor with either hydrogen or nitrogen as carrier gas. Three distinguishable regions are identified to be related to the dominance of specific chemical reaction mechanisms. Activation energies in H2 are found to be 28 kcal/mol below 400 °C and 6.5 kcal/mol from 400 °C to 700 °C. In N2, the value decreases to 2.1 kcal/mol for all temperatures below 700 °C. The rate of hydrogen desorption is decisive for this behavior.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.Nr Desorption kinetics
68.43.Mn Adsorption kinetics

Charge dynamics and electronic structures of monolayer graphene with molecular doping

C. C. Shen, C. T. Lin, L. J. Li, and H. L. Liu

Appl. Phys. Lett. 101, 111907 (2012); http://dx.doi.org/10.1063/1.4752131 (4 pages)

Online Publication Date: 13 September 2012

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THz absorption and spectroscopic ellipsometry were used to investigate the charge dynamics and electronic structures of monolayer graphene with doping by triazine. The absorption spectrum of the triazine-doped film shows an optical excitation near 5.1 eV that is blue shifted compared with that of undoped analog. THz conductivity displays a coherent response of itinerant charge carriers at zero frequency and a disorder-induced finite frequency peak around 155 cm−1. Drude plasma frequency (∼4400 cm−1) decreases with decreasing temperature while carrier relaxation time (∼13 fs) is almost temperature independent, implying the semiconducting behavior with thermal activation energy of 3 meV.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.70.Gq Microwave and radio-frequency interactions
71.20.Mq Elemental semiconductors
73.61.Cw Elemental semiconductors
73.22.Pr Electronic structure of graphene
73.61.Wp Fullerenes and related materials

Self-sustaining oxidation initiated by rapid formation reactions in multilayer foils

H. Joress, S. C. Barron, K. J. T. Livi, N. Aronhime, and T. P. Weihs

Appl. Phys. Lett. 101, 111908 (2012); http://dx.doi.org/10.1063/1.4752133 (4 pages)

Online Publication Date: 13 September 2012

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Here we report that a self-sustaining oxidation of a multilayer foil can be ignited by an intermetallic formation reaction, releasing ∼4× the energy of the formation reaction. We examine foils with overall chemistries of 3Al:2Ni, 3Al:Zr, and Al:Zr and find that only the latter experiences significant oxidation. The Al:Zr samples initially react to form intermetallics and reach ∼1500 K in <10 ms. The samples then oxidize in air, absorbing ∼30 at. % O and remaining at ∼1400 K for >2.0 s. The phases within the Al:Zr foils are characterized and temperature-time profiles are examined to predict the heat generated by the oxidation reaction.
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82.30.-b Specific chemical reactions; reaction mechanisms
82.60.Cx Enthalpies of combustion, reaction, and formation
68.65.Ac Multilayers
82.33.Vx Reactions in flames, combustion, and explosions

Electronic structure and optical properties of β-FeSi2(100)/Si(001) interface at high pressure

L. Z. Liu, X. L. Wu, X. X. Liu, J. C. Shen, T. H. Li, and Paul K. Chu

Appl. Phys. Lett. 101, 111909 (2012); http://dx.doi.org/10.1063/1.4752154 (4 pages)

Online Publication Date: 13 September 2012

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The electronic structure and optical absorption properties of the β-FeSi2(100)/Si(001) interface are investigated by first-principle calculation at high pressure. As the pressure increases, the optical gap decreases sharply, reaches a minimum, and then increases slowly. Structural analysis reveals that the Si(001) slab partially offsets the pressure exerted on the β-FeSi2 (100) interface, thus downshifting the lowest unoccupied electronic states of the interface and decreasing the optical gap. As the pressure increases further, this offsetting effect weakens and the optical gap increases again gradually. Hence, a high pressure plays an important role in the optical behavior.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Ps Other inorganic compounds
61.66.Fn Inorganic compounds
71.15.-m Methods of electronic structure calculations
62.50.-p High-pressure effects in solids and liquids

Effect of Pd on the Ni2Si stress relaxation during the Ni-silicide formation at low temperature

M. Putero and D. Mangelinck

Appl. Phys. Lett. 101, 111910 (2012); http://dx.doi.org/10.1063/1.4752716 (5 pages)

Online Publication Date: 14 September 2012

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The thermally induced solid-state reaction between a 50-nm-thick Ni(6%Pd) layer and a Si(100) substrate was investigated using in situ and simultaneous x-ray diffraction and sheet resistance. The reaction begins with the growth of the stressed δ-Ni2Si phase, and the transient θ-Ni2Si. At the end of the θ-Ni2Si consumption, a NiSi seed is formed. Then, the δ-Ni2Si relaxation occurs simultaneously with its subsequent growth and the Pd out diffusion from the unreacted Ni(Pd) layer. It is suggested that the driving force for the Pd diffusion out of the metal layer is linked to both the higher solubility of Pd in NiSi compared to Ni2Si and to the Ni2Si 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
68.60.Bs Mechanical and acoustical properties
64.75.Bc Solubility
81.15.Cd Deposition by sputtering
68.55.aj Insulators

Electron backscatter diffraction on femtosecond laser sulfur hyperdoped silicon

Thomas Gimpel, Ingmar Höger, Fritz Falk, Wolfgang Schade, and Stefan Kontermann

Appl. Phys. Lett. 101, 111911 (2012); http://dx.doi.org/10.1063/1.4752454 (3 pages) | Cited 1 time

Online Publication Date: 14 September 2012

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This paper analyzes the impact of femtosecond laser pulse irradiation on the crystallinity of silicon wafers by means of electron backscatter diffraction (EBSD) measurements. EBSD based image quality maps and orientation imaging microscopy maps are correlated to the grade of the silicon crystallinity. We analyze the impact of accumulated net laser irradiation originating from a laser spot overlap that is necessary to process macroscopic areas, e.g., for sulfur doping of semiconductor devices. Furthermore, we demonstrate that post processing annealing recovers crystallinity and therefore allows fs-laser processed silicon to be used in semiconductor device manufacturing.
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81.16.-c Methods of micro- and nanofabrication and processing
42.62.-b Laser applications
81.05.Cy Elemental semiconductors
79.20.Kz Other electron-impact emission phenomena
78.47.J- Ultrafast spectroscopy (<1 psec)
61.72.Cc Kinetics of defect formation and annealing

Convergent beam electron-diffraction investigation of lattice mismatch and static disorder in GaAs/GaAs1−xNx intercalated GaAs/GaAs1−xNx:H heterostructures

S. Frabboni, V. Grillo, G. C. Gazzadi, R. Balboni, R. Trotta, A. Polimeni, M. Capizzi, F. Martelli, S. Rubini, G. Guzzinati, and F. Glas

Appl. Phys. Lett. 101, 111912 (2012); http://dx.doi.org/10.1063/1.4752464 (4 pages)

Online Publication Date: 14 September 2012

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Hydrogen incorporation in diluted nitride semiconductors dramatically modifies the electronic and structural properties of the crystal through the creation of nitrogen-hydrogen complexes. We report a convergent beam electron-diffraction characterization of diluted nitride semiconductor-heterostructures patterned at a sub-micron scale and selectively exposed to hydrogen. We present a method to determine separately perpendicular mismatch and static disorder in pristine and hydrogenated heterostructures. The roles of chemical composition and strain on static disorder have been separately assessed.
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61.66.Fn Inorganic compounds
61.72.J- Point defects and defect clusters
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