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7 May 2012

Volume 100, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 100, 191901 (2012); http://dx.doi.org/10.1063/1.4709436 (4 pages)

Muamer Kadic, Tiemo Bückmann, Nicolas Stenger, Michael Thiel, and Martin Wegener
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Study of electromagnetic enhancement for surface enhanced Raman spectroscopy of SiC graphene

Jing Niu, Viet Giang Truong, Han Huang, Sudhiranjan Tripathy, Caiyu Qiu, Andrew T. S. Wee, Ting Yu, and Hyunsoo Yang

Appl. Phys. Lett. 100, 191601 (2012); http://dx.doi.org/10.1063/1.4712054 (4 pages) | Cited 2 times

Online Publication Date: 9 May 2012

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The electromagnetic enhancement for surface enhanced Raman spectroscopy (SERS) of graphene is studied by inserting a layer of Al2O3 between epitaxial graphene and Au nanoparticles. Different excitation lasers are utilized to study the relationship between laser wavelength and SERS. The theoretical calculation shows that the extinction spectrum of Au nanoparticles is modulated by the presence of graphene. The experimental results of the relationship between the excitation laser wavelength and the enhancement factor fit well with the calculated results. An exponential relationship is observed between the enhancement factor and the thickness of the spacer layer.
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78.30.-j Infrared and Raman spectra
78.66.-w Optical properties of specific thin films
78.68.+m Optical properties of surfaces
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)

Bandgap and band discontinuity in wurtzite/zincblende GaAs homomaterial heterostructure

Ron Gurwitz, Asa Tavor, Liran Karpeles, Ilan Shalish, Wei Yi, Georgiy Seryogin, and Venkatesh Narayanamurti

Appl. Phys. Lett. 100, 191602 (2012); http://dx.doi.org/10.1063/1.4712562 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2012

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A wurtzite GaAs epilayer grown on a zincblende GaAs substrate by metalorganic chemical vapor deposition is studied by surface photovoltage spectroscopy. The wurtzite structure of the epilayer is disclosed by scanning electron microscope images of surface pits, where the pits are seen to change their structure from a rectangular into a hexagonal shape. The wurtzite phase is also revealed in x-ray diffraction showing a 〈0002〉 diffraction alongside the main (200) diffraction, suggesting a “c” lattice constant of 0.668 nm. A comparison of room temperature surface photovoltage spectra taken from the epilayer sample and from an epilayer-etched substrate suggests a type II heterostructure with valence band difference of about 15 meV and bandgap difference of about 70 meV between the zincblende and the wurtzite GaAs polytypes.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology
68.55.ag Semiconductors
61.66.-f Structure of specific crystalline solids
71.20.Nr Semiconductor compounds
72.40.+w Photoconduction and photovoltaic effects

Extremely low surface recombination velocities in black silicon passivated by atomic layer deposition

Martin Otto, Matthias Kroll, Thomas Käsebier, Roland Salzer, Andreas Tünnermann, and Ralf B. Wehrspohn

Appl. Phys. Lett. 100, 191603 (2012); http://dx.doi.org/10.1063/1.4714546 (4 pages) | Cited 3 times

Online Publication Date: 9 May 2012

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We investigate the optical and opto-electronic properties of black silicon (b-Si) nanostructures passivated with Al2O3. The b-Si nanostructures significantly improve the absorption of silicon due to superior anti-reflection and light trapping properties. By coating the b-Si nanostructures with a conformal layer of Al2O3 by atomic layer deposition, the surface recombination velocity can be effectively reduced. We show that control of plasma-induced subsurface damage is equally important to achieve low interface recombination. Surface recombination velocities of Seff<13 cm/s have been measured for an optimized structure which, like the polished reference, exhibits lifetimes in the millisecond range.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Cy Elemental semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
81.65.Rv Passivation
52.77.-j Plasma applications

Surface oxide on thin films of yttrium hydride studied by neutron reflectometry

T. Mongstad, C. Platzer-Björkman, J. P. Mæhlen, B. C. Hauback, S. Zh. Karazhanov, and F. Cousin

Appl. Phys. Lett. 100, 191604 (2012); http://dx.doi.org/10.1063/1.4714517 (3 pages) | Cited 1 time

Online Publication Date: 10 May 2012

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The applicability of standard methods for compositional analysis is limited for H-containing films. Neutron reflectometry is a powerful, non-destructive method that is especially suitable for these systems due to the large negative scattering length of H. In this work, we demonstrate how neutron reflectometry can be used to investigate thin films of yttrium hydride. Neutron reflectometry gives a strong contrast between the film and the surface oxide layer, enabling us to estimate the oxide thickness and oxygen penetration depths. A surface oxide layer of 5–10 nm thickness was found for unprotected yttrium hydride films.
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81.65.Mq Oxidation
82.80.-d Chemical analysis and related physical methods of analysis
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.jd Thickness
68.55.Nq Composition and phase identification
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