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29 Aug 2005

Volume 87, Issue 9, Articles (09xxxx)

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Appl. Phys. Lett. 87, 093109 (2005); http://dx.doi.org/10.1063/1.2035332 (3 pages)

J. Noborisaka, J. Motohisa, S. Hara, and T. Fukui
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Photoluminescence in erbium doped amorphous silicon oxycarbide thin films

Spyros Gallis, Mengbing Huang, Harry Efstathiadis, Eric Eisenbraun, Alain E. Kaloyeros, Ei Ei Nyein, and Uwe Hommerich

Appl. Phys. Lett. 87, 091901 (2005); http://dx.doi.org/10.1063/1.2032600 (3 pages) | Cited 15 times

Online Publication Date: 22 August 2005

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Photoluminescence (PL) in Er-doped amorphous silicon oxycarbide (a-SiCxOy:Er) thin films, synthesized via thermal chemical vapor deposition, was investigated for carbon and oxygen concentrations in the range of 0–1.63. Intense room-temperature PL was observed at 1540 nm, with the PL intensity being dependent on the carbon and oxygen content. The strongest PL intensity was detected for a-SiC0.53O0.99:Er when pumped at 496.5 nm, with ∼ 20 times intensity enhancement as compared to a-SiO2:Er. Broadband excitation in the visible was observed for a-SiC0.53O0.99:Er. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses suggest that the formation of Si–C–O networks plays an important role in enhancing the Er optical activity in a-SiCxOy:Er films.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
78.66.Nk Insulators
78.55.Qr Amorphous materials; glasses and other disordered solids
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
79.60.Dp Adsorbed layers and thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth

Plasma hydrogenation of strained Si/SiGe/Si heterostructure for layer transfer without ion implantation

Lin Shao, Yuan Lin, J. K. Lee, Q. X. Jia, Yongqiang Wang, M. Nastasi, Phillip E. Thompson, N. David Theodore, Paul K. Chu, T. L. Alford, J. W. Mayer, Peng Chen, and S. S. Lau

Appl. Phys. Lett. 87, 091902 (2005); http://dx.doi.org/10.1063/1.2032602 (3 pages) | Cited 18 times

Online Publication Date: 22 August 2005

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We have developed an innovative approach without the use of ion implantation to transfer a high-quality thin Si layer for the fabrication of silicon-on-insulator wafers. The technique uses a buried strained SiGe layer, a few nanometers in thickness, to provide H trapping centers. In conjunction with H plasma hydrogenation, lift-off of the top Si layer can be realized with cleavage occurring at the depth of the strained SiGe layer. This technique avoids irradiation damage within the top Si layer that typically results from ion implantation used to create H trapping regions in the conventional ion-cut method. We explain the strain-facilitated layer transfer as being due to preferential vacancy aggregation within the strained layer and subsequent trapping of hydrogen, which lead to cracking in a well controlled manner.
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81.05.Cy Elemental semiconductors
81.65.-b Surface treatments
61.72.uf Ge and Si
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.J- Point defects and defect clusters
52.77.-j Plasma applications
68.35.Ct Interface structure and roughness

Growth of high-quality ZnMgO epilayers and ZnO/ZnMgO quantum well structures by radical-source molecular-beam epitaxy on sapphire

S. Sadofev, S. Blumstengel, J. Cui, J. Puls, S. Rogaschewski, P. Schäfer, Yu. G. Sadofyev, and F. Henneberger

Appl. Phys. Lett. 87, 091903 (2005); http://dx.doi.org/10.1063/1.2034113 (3 pages) | Cited 51 times

Online Publication Date: 22 August 2005

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We report on a specific growth procedure combining low-temperature growth of ZnMgO and postgrowth annealing at intermediate temperatures. Despite the large lattice misfit induced by the sapphire substrate, layer-by-layer growth is accomplished up to the phase-separation limit found at a c-lattice constant of 0.5136 nm and Mg mole fraction of 0.40. The procedure allows us to grow quantum wells with atomically smooth interfaces in a wide range of structural designs exhibiting prominent emission features up to room temperature.
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81.05.Dz II-VI semiconductors
81.07.St Quantum wells
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Hf II-VI semiconductors
78.67.De Quantum wells
61.72.Cc Kinetics of defect formation and annealing
61.66.Fn Inorganic compounds
64.75.-g Phase equilibria

Ultrahigh strength and high ductility of bulk nanocrystalline copper

Khaled M. Youssef, Ronald O. Scattergood, K. Linga Murty, Joseph A. Horton, and Carl. C. Koch

Appl. Phys. Lett. 87, 091904 (2005); http://dx.doi.org/10.1063/1.2034122 (3 pages) | Cited 115 times

Online Publication Date: 22 August 2005

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We have synthesized artifact-free bulk nanocrystalline copper samples with a narrow grain size distribution (mean grain size of 23 nm) that exhibited tensile yield strength about 11 times higher than that of conventional coarse-grained copper, while retaining a 14% uniform tensile elongation. In situ dynamic straining transmission electron microscope observations of the nanocrystalline copper are also reported, which showed individual dislocation motion and dislocation pile-ups. This suggests a dislocation-controlled deformation mechanism that allows for the high strain hardening observed. Trapped dislocations are observed in the individual nanograins.
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81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.46.-w Structure of nanoscale materials

Intersubband transitions in proton irradiated InGaAs/GaAs multiple quantum dots

Ying Chao Chua, E. A. Decuir, M. O. Manasreh, and B. D. Weaver

Appl. Phys. Lett. 87, 091905 (2005); http://dx.doi.org/10.1063/1.2035877 (3 pages) | Cited 1 time

Online Publication Date: 24 August 2005

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The optical absorbance spectra of the intersubband transition in 3 MeV proton irradiated In0.3Ga0.7As/GaAs multiple quantum dot samples, cut from the same wafer, were investigated as a function of irradiation dose. The intensity of the intersubband transition is observed to decrease as the irradiation dose is increased. The behavior of the intersubband transition in irradiated In0.3Ga0.7As/GaAs multiple quantum dot samples is compared to those of intersubband transitions in irradiated GaAs/AlGaAs and InGaAs/InAlAs multiple quantum well samples. The intersubband transition absorbance spectrum was completely depleted in a multiple quantum dot sample irradiated with 5×1014 cm−2. Post-irradiation thermal annealing was performed on the latter sample where thermal annealing recovery of the depleted intersubband transition was not observed. Instead, a broadband with a peak at 5 μm is observed after annealing the sample at 500 °C for 15 min. The absence of the broadband in an unirradiated sample that was subject to the same annealing conditions suggests that this band may be related to irradiation-induced defects.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
78.67.De Quantum wells
78.30.Fs III-V and II-VI semiconductors

Super-elastic titanium alloy with unstable plastic deformation

Y. L. Hao, S. J. Li, S. Y. Sun, C. Y. Zheng, Q. M. Hu, and R. Yang

Appl. Phys. Lett. 87, 091906 (2005); http://dx.doi.org/10.1063/1.2037192 (3 pages) | Cited 51 times

Online Publication Date: 24 August 2005

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Here we report a non-toxic β-type titanium alloy exhibiting unstable elastic and plastic deformation behavior. Elastic instability leads to remarkable elastic softening, i.e., the decrease of incipient Young’s modulus with slight pre-straining. In spite of partial recovery during room-temperature aging, a stable modulus of 33 GPa matching that of human bone can be maintained. Plastic instability causes highly-localized deformation which is very effective in grain refinement but contributes little to strength. We thus obtain soft nanostructured metallic materials (NMMs): The flow stress increases by only ∼ 5.5% as coarse grains are reduced to below 50 nm, in contrast with several times increase for previously-reported NMMs.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity
62.20.F- Deformation and plasticity

Subwavelength imaging by a flat cylindrical lens using optimized negative refraction

Zhaolin Lu, Caihua Chen, Christopher A. Schuetz, Shouyuan Shi, Janusz A. Murakowski, Garrett J. Schneider, and Dennis W. Prather

Appl. Phys. Lett. 87, 091907 (2005); http://dx.doi.org/10.1063/1.2035317 (3 pages) | Cited 11 times

Online Publication Date: 25 August 2005

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We experimentally demonstrate subwavelength imaging by a “flat cylindrical” lens using negative refraction. A two-dimensional photonic crystal whose dispersion at the second band provides group velocity opposite to the phase velocity for electromagnetic waves is employed to realize the flat lens, and the working frequency is chosen so that the effective refractive index is approximately equal to −1.0. Experiment demonstrated the imaging of a point source in both amplitude and phase in the millimeter-wave regime. By measuring the field distributions in the object plane and image plane, we observed amplification of evanescent waves and subwavelength size image. The image of two incoherent sources with subwavelength distance showed two resolvable spots, which served to further verify subwavelength resolution.
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42.79.Bh Lenses, prisms and mirrors
42.70.Qs Photonic bandgap materials

High-quality thin single-crystal γ-Al2O3 films grown on Si (111)

S. Y. Wu, M. Hong, A. R. Kortan, J. Kwo, J. P. Mannaerts, W. C. Lee, and Y. L. Huang

Appl. Phys. Lett. 87, 091908 (2005); http://dx.doi.org/10.1063/1.2037205 (3 pages) | Cited 13 times

Online Publication Date: 25 August 2005

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Single-crystal Al2O3 films have been epitaxially grown on Si (111) substrates despite a lattice mismatch of more than 30%. The oxide was electron-beam evaporated from a high-purity sapphire source. The structural and morphological studies carried out by x-ray diffraction, x-ray reflectivity, atomic force microscopy, and transmission electron microscopy, with the initial epitaxial growth observed by in situ reflection high-energy electron diffraction show that the oxide films as thin as 3.8 nm have the cubic γ-phase with a very uniform thickness and a high structural perfection. The film surface is very smooth with a roughness of 0.12 nm and the oxide/Si interface is atomically sharp. The γ-Al2O3 films are well aligned with Si substrate with an orientation relationship of Si(111)//Al2O3(222), Si[220]//Al2O3[440].
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Gh Oxide surfaces
68.55.-a Thin film structure and morphology
68.35.Ct Interface structure and roughness
68.37.Ps Atomic force microscopy (AFM)
68.37.Lp Transmission electron microscopy (TEM)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Germanium n-type shallow junction activation dependences

Chi On Chui, Leonard Kulig, Jean Moran, Wilman Tsai, and Krishna C. Saraswat

Appl. Phys. Lett. 87, 091909 (2005); http://dx.doi.org/10.1063/1.2037861 (3 pages) | Cited 47 times

Online Publication Date: 25 August 2005

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A few of the recent unsatisfactory germanium n-channel metal-oxide-semiconductor field-effect transistor MOSFET experimentations are believed to stem from the poor source and drain n+‐p junction formations. In order to explain the primary cause and suggest rectifying solutions, we have examined the activation of common n-type dopants in germanium and the related dependences. These dependences include thermal anneal budget, impurity species, and implantation dosage. Low thermal budgets are generally preferred to activate shallow junctions to simultaneously annihilate defects and suppress fast dopant diffusion. Injecting dopants over the solid-solubility limitation into shallow junctions would only generate more implantation damage but could not however lower the junction sheet resistance.
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61.72.uf Ge and Si
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Ei Rectification
66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
64.75.-g Phase equilibria

Interaction of nitrogen with vacancy defects in N+-implanted ZnO studied using a slow positron beam

Z. Q. Chen, M. Maekawa, A. Kawasuso, R. Suzuki, and T. Ohdaira

Appl. Phys. Lett. 87, 091910 (2005); http://dx.doi.org/10.1063/1.2037847 (3 pages) | Cited 7 times

Online Publication Date: 26 August 2005

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ZnO crystals were implanted with N+, O+, and Al+, and co-implanted with O+/N+ and Al+/N+ ions. Positron annihilation measurements indicate introduction of vacancy clusters upon implantation. In the N+-implanted and Al+/N+ co-implanted samples, these vacancy clusters are only partially annealed at 800 °C, as compared with their entire recovery in the O+- and Al+-implanted samples at 800–900 °C, suggesting a strong interaction between nitrogen and vacancy clusters. However, in the O+/N+ co-implanted sample, most vacancy clusters disappear at 800 °C. Probably oxygen scavenges nitrogen to enhance the annealing of the vacancy clusters. Upon further annealing at 1000–1100 °C, nitrogen also forms stable complexes with thermally generated vacancies. These nitrogen-related vacancy complexes need high-temperature annealing at 1200–1250 °C to be fully removed.
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61.72.J- Point defects and defect clusters
61.80.Jh Ion radiation effects
78.70.Bj Positron annihilation
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
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