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1 Mar 2010

Volume 96, Issue 9, Articles (09xxxx)

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Appl. Phys. Lett. 96, 091102 (2010); http://dx.doi.org/10.1063/1.3332591 (3 pages)

A. Schropp, P. Boye, J. M. Feldkamp, R. Hoppe, J. Patommel, D. Samberg, S. Stephan, K. Giewekemeyer, R. N. Wilke, T. Salditt, J. Gulden, A. P. Mancuso, I. A. Vartanyants, E. Weckert, S. Schöder, et al.
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An efficient, simple, and precise way to map strain with nanometer resolution in semiconductor devices

Christoph T. Koch, V. Burak Özdöl, and Peter A. van Aken

Appl. Phys. Lett. 96, 091901 (2010); http://dx.doi.org/10.1063/1.3337090 (3 pages) | Cited 14 times

Online Publication Date: 1 March 2010

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We report on the development of the dark-field inline electron holography technique and its application to map strain in technologically relevant structures, using as an example the strain-engineered gate channel in a 45 nm metal-oxide semiconductor field-effect transistor structure. We show that this technique combines a large field of view of several micrometers with high precision (better than 0.01%), high spatial resolution (better than 1 nm), and very loose experimental requirements not possible with any other technique currently available.
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85.30.Tv Field effect devices
42.40.-i Holography

Doping behavior of phosphorus in ZnO thin films: Effects of doping concentration and postgrowth thermal annealing

H. F. Liu and S. J. Chua

Appl. Phys. Lett. 96, 091902 (2010); http://dx.doi.org/10.1063/1.3337099 (3 pages) | Cited 9 times

Online Publication Date: 1 March 2010

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Effects of phosphorus concentration, [P], and postgrowth annealing on the x-ray diffraction and Raman scattering from ZnO:P thin films are presented. The ZnO (0002) diffraction peak exhibits a large monotonic angular shift with increasing [P] up to 5.1×1019 cm−3 while its shift upon annealing is dependent on [P]. No extrinsic phases were detected for the samples studied. Raman spectra reveal disorder-activated vibrational modes, around 276, 510, 582, and 643 cm−1, with increasing [P]. They also reveal local vibrational modes corresponding to PO ( ∼ 370 cm−1) and PZn ( ∼ 482 cm−1) upon annealing. The intensity evolution of the Raman features, together with the x-ray diffraction results, indicates that phosphorus substituting for zinc is favored at low annealing temperatures while increasing annealing temperature tends to convert phosphorus doping configurations from PZn to PO.
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61.72.uj III-V and II-VI semiconductors
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
68.55.ag Semiconductors
78.30.Fs III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

Observation of space charge limited current by Cu ion drift in porous low-k/Cu interconnects

L. S. Chen, W. H. Bang, Young-Joon Park, E. Todd Ryan, Sean King, and Choong-Un Kim

Appl. Phys. Lett. 96, 091903 (2010); http://dx.doi.org/10.1063/1.3337102 (3 pages) | Cited 1 time

Online Publication Date: 1 March 2010

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This letter reports the observation of the space charge limited current (SCLC) induced by injection and drift of Cu ions into porous low-k dielectrics. The SCLC, characterized by the momentary rise and fall of current with time, is found in all Cu interconnects having defective Ta barrier while it is absent in interconnects with intact barrier. This observation, combined with existing model on SCLC, leads to the conclusion that Cu ions can be injected through defects in Ta barrier and drift under electric field with the mobility as high as an order of 10−13 cm2/sec V at room temperature.
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77.22.Jp Dielectric breakdown and space-charge effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Optical anisotropies of Si grown on step-graded SiGe(110) layers

R. E. Balderas-Navarro, L. F. Lastras-Martínez, K. Arimoto, R. Castro-García, O. Villalobos-Aguilar, A. Lastras-Martínez, K. Nakagawa, K. Sawano, Y. Shiraki, N. Usami, and K. Nakajima

Appl. Phys. Lett. 96, 091904 (2010); http://dx.doi.org/10.1063/1.3339881 (3 pages) | Cited 2 times

Online Publication Date: 1 March 2010

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Macroreflectance and microreflectance difference spectroscopies have been used to measure the strain induced optical anisotropies of semiconductor structures comprised of strained Si(110) thin films deposited on top of step-graded SiGe virtual substrates. The stress relaxation mechanism mainly occurs by the introduction of microtwin formation, whose fluctuation depends strongly on growth conditions. Correlations of such optical diagnostics with x-ray diffraction measurements and atomic force microscopy images, allow for the in situ study of the strain within both the top Si layer and the SiGe underneath with an spatial resolution of at least 5 μm.
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78.66.Db Elemental semiconductors and insulators
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Hexagonal BaTi1−xCoxO3 phase stabilized by Co dopants

Yuanyuan Li, Qinghua Liu, Tao Yao, Zhiyun Pan, Zhihu Sun, Yong Jiang, Hong Zhang, Zijia Pan, Wensheng Yan, and Shiqiang Wei

Appl. Phys. Lett. 96, 091905 (2010); http://dx.doi.org/10.1063/1.3337110 (3 pages) | Cited 5 times

Online Publication Date: 2 March 2010

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The phase transition from tetragonal to hexagonal of crystalline BaTi1−xCoxO3 (0.01 ≤ x ≤ 0.20) powders prepared by solid state reaction has been studied by x-ray diffraction and x-ray absorption fine structure (XAFS). At the low Co doping level of x ≤ 0.03, the structure of the samples is tetragonal, and it is transformed gradually to a hexagonal structure upon increasing Co content to ≥ 0.05. The detailed analysis of Co K-edge XAFS indicated unambiguously that the doped Co ions are substantially incorporated into the BaTiO3 host and likely serve as a trigger in leading the structure transition. On the basis of the formation energy calculations, we find that there exists a critical Co concentration in the x range of 0.027–0.055 for inducing the tetragonal-to-hexagonal structure transition of BaTi1−xCoxO3, in good agreement with the experimental observations.
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64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
61.72.U- Doping and impurity implantation
78.70.Dm X-ray absorption spectra

Magneto-optical properties of cobalt slanted columnar thin films

Daniel Schmidt, Tino Hofmann, Craig M. Herzinger, Eva Schubert, and Mathias Schubert

Appl. Phys. Lett. 96, 091906 (2010); http://dx.doi.org/10.1063/1.3340913 (3 pages) | Cited 6 times

Online Publication Date: 2 March 2010

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Magneto-optical properties of ferromagnetic slanted columnar thin films from cobalt made by electron-beam glancing angle deposition are reported. Magneto-optic ellipsometry in the polar Kerr effect configuration was employed to determine the field- and wavelength-dependent complex magneto-optic polarizability parameter within the spectral range from 0.74 to 3.0 eV. Kerr effect measurements and calculations reveal a strong azimuthal dependence for the incident linear polarization with peak Kerr rotation one order of magnitude larger than what has been reported for solid Co thin films.
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78.20.Ls Magneto-optical effects
75.50.Cc Other ferromagnetic metals and alloys
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys

Highly polarized Raman scattering anisotropy in single GaN nanowires

E. O. Schäfer-Nolte, T. Stoica, T. Gotschke, F. Limbach, E. Sutter, P. Sutter, and R. Calarco

Appl. Phys. Lett. 96, 091907 (2010); http://dx.doi.org/10.1063/1.3343347 (3 pages) | Cited 9 times

Online Publication Date: 3 March 2010

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Single GaN nanowires and larger GaN ensembles are investigated by Raman spectroscopy. Spectra of nanowire ensembles prove the high crystal quality and are in agreement with selection rules for the wurtzite structure. Single nanowires are studied with a spatial resolution of the order of 400 nm for different polarization directions of the incident laser beam relative to the nanowire axis. In the single wire spectrum, only the A1(TO) was observed and the Raman intensity was suppressed for perpendicular polarization. These results confirm that Raman scattering in isolated GaN nanowires is governed by size effects.
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78.30.Fs III-V and II-VI semiconductors
68.65.La Quantum wires (patterned in quantum wells)
81.05.Ea III-V semiconductors

Towards second-harmonic generation micropatterning of glass surface

Aurelien Delestre, Michel Lahaye, Evelyne Fargin, Matthieu Bellec, Arnaud Royon, Lionel Canioni, Marc Dussauze, Frederic Adamietz, and Vincent Rodriguez

Appl. Phys. Lett. 96, 091908 (2010); http://dx.doi.org/10.1063/1.3350895 (3 pages) | Cited 2 times

Online Publication Date: 3 March 2010

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Thermal poling of sodium borophosphate niobium glasses, previously coated with a thin silver layer micropatterned by femtosecond laser irradiation, is demonstrated. The field-assisted ion-exchange process for fabricating planar surface in this glass substrate is analyzed. Inside the silver ablated lines obtained by femtosecond laser irradiation, we clearly observe a change in the distribution of the frozen electrostatic field that is modulated by the Ag+/Na+ ion-exchange process during the thermal poling.
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42.70.Ce Glasses, quartz
42.79.Wc Optical coatings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
77.22.Ej Polarization and depolarization

A surface locking instability for atomic intercalation into a solid electrode

Hamed Haftbaradaran, Huajian Gao, and W. A. Curtin

Appl. Phys. Lett. 96, 091909 (2010); http://dx.doi.org/10.1063/1.3330940 (3 pages) | Cited 13 times

Online Publication Date: 3 March 2010

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By introducing a coupling between internal stresses and activation energy for diffusion in the classical theory of diffusion induced stresses, a class of nonconventional solutions has been found for atomic intercalation into a solid electrode, indicative of a surface locking instability once the product between electrode dimension and charging rate exceeds a critical value. This finding may have important implications for the lithium ion battery technology.
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82.47.Aa Lithium-ion batteries
66.30.-h Diffusion in solids
82.45.Fk Electrodes

Solid fraction in dendritic solidification of a liquid

Lasse Makkonen

Appl. Phys. Lett. 96, 091910 (2010); http://dx.doi.org/10.1063/1.3306728 (3 pages) | Cited 2 times

Online Publication Date: 4 March 2010

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When a liquid is cooled below its equilibrium solidification temperature the solidification takes place as growing dendrites of microscopic scale. An essential feature of the material formed this way is its solid fraction f, which is less than unity due to liquid entrapped between the solid dendrites. In this letter, f in directional solidification of a pure liquid is solved analytically showing that f is independent of the growth conditions. In this sense, this solidification process is self-regulating and f is a material parameter. For water, as an example, the ice fraction is 70% in agreement with experimental data.
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64.70.D- Solid-liquid transitions
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
81.30.Fb Solidification

Anharmonic decay of g-process longitudinal optical phonons in silicon

Z. Aksamija and U. Ravaioli

Appl. Phys. Lett. 96, 091911 (2010); http://dx.doi.org/10.1063/1.3350894 (3 pages) | Cited 1 time

Online Publication Date: 4 March 2010

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We study phonons produced by transitions between the equivalent X valleys in silicon. We use the Monte Carlo method first to select stochastically the time between phonon collisions, and then to select a final-state pair of phonons from the probability distribution for anharmonic decay. Our results show that g-process phonons decay into one near-equilibrium transverse acoustic phonon and another intermediate longitudinal phonon either on the acoustic or optical branch. This second phonon has energies between 40 and 50 meV and undergoes further decay before turning into a pair of near-equilibrium transverse acoustic phonons, presenting a potential additional bottleneck.
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63.20.kg Phonon-phonon interactions
63.20.kd Phonon-electron interactions
02.50.Fz Stochastic analysis

The response of mechanical and electronic properties of graphane to the elastic strain

M. Topsakal, S. Cahangirov, and S. Ciraci

Appl. Phys. Lett. 96, 091912 (2010); http://dx.doi.org/10.1063/1.3353968 (3 pages) | Cited 32 times

Online Publication Date: 4 March 2010

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Based on first-principles calculations, we resent a method to reveal the elastic properties of recently synthesized monolayer hydrocarbon, graphane. The in-plane stiffness and Poisson’s ratio values are found to be smaller than those of graphene, and its yielding strain decreases in the presence of various vacancy defects and also at high ambient temperature. We also found that the band gap can be strongly modified by applied strain in the elastic range.
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68.18.-g Langmuir-Blodgett films on liquids
61.72.jd Vacancies
46.25.-y Static elasticity
62.20.dq Other elastic constants

Photoluminescence and positron annihilation studies on Mg-doped nitrogen-polarity semipolar (10mathmath) GaN heteroepitaxial layers grown by metalorganic vapor phase epitaxy

T. Onuma, A. Uedono, H. Asamizu, H. Sato, J. F. Kaeding, M. Iza, S. P. DenBaars, S. Nakamura, and S. F. Chichibu

Appl. Phys. Lett. 96, 091913 (2010); http://dx.doi.org/10.1063/1.3337098 (3 pages) | Cited 4 times

Online Publication Date: 4 March 2010

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The influences of enhanced stacking fault (SF) formation, which is peculiar to nitrogen-(N-) polarity growth and lattice-mismatched semipolar heteroepitaxy, on the electrical properties of (10mathmath) Mg-doped GaN (GaN:Mg) epilayers were investigated. Although the residual donor concentration was higher than (0001) GaN because of N-polar growth, comparatively low Mg doping (3×1019 cm−3) gave a hole concentration approximately 1.5×1018 cm−3, which was an order of magnitude higher than (0001) GaN:Mg. As the acceptor ionization energy estimated from low temperature photoluminescence was quite similar for (10mathmath) and (0001) GaN:Mg, the high Mg activation seems to result with the aid of high density SFs. Because the Doppler broadening S parameter for the positron annihilation measurement, which reflects the concentration or size of negatively charged cation vacancies, of (10mathmath) GaN:Mg was smaller than (0001) case, (10mathmath) orientation is well suited to Mg-doping.
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78.66.Fd III-V semiconductors
61.72.uj III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.70.Bj Positron annihilation
78.55.-m Photoluminescence, properties and materials

Roles of carbon in light emission of ZnO

Y. H. Lu, Z. X. Hong, Y. P. Feng, and S. P. Russo

Appl. Phys. Lett. 96, 091914 (2010); http://dx.doi.org/10.1063/1.3340934 (3 pages) | Cited 7 times

Online Publication Date: 4 March 2010

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The origin of green light emission of ZnO has been a controversial topic. First-principles electronic structure calculations so far failed to provide useful evidence due to severe underestimation of band gap and ambiguous defect energy levels. In this work, we carried out first-principles electronic structure calculations on defected ZnO with a hybrid density functional. It was found that carbon, which cannot be completely avoided in fabricating processes, plays an important role in the commonly observed green emission, and could be the origin of green emission of ZnO. We also propose a method for the selection of emission by controlling defect types and ratio in ZnO.
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71.15.Mb Density functional theory, local density approximation, gradient and other corrections
81.05.Dz II-VI semiconductors
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