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15 Dec 2010

Volume 108, Issue 12, Articles (12xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 108, 121101 (2010); http://dx.doi.org/10.1063/1.3503505 (12 pages)

J. Martin, T. Tritt, and C. Uher
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back to top Structural, Mechanical, Thermodynamic, and Optical Properties of Condensed Matter

Scale-dependent vibration analysis of prestressed carbon nanotubes undergoing rotation

T. Murmu and S. Adhikari

J. Appl. Phys. 108, 123507 (2010); http://dx.doi.org/10.1063/1.3520404 (7 pages) | Cited 6 times

Online Publication Date: 20 December 2010

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Understanding the dynamic behavior of rotating nanostructures is important for practical development of nanomachines. At the nanoscale, the nonlocal effects often become prominent. In this study, we investigate the nonlocal effects in bending-vibration of an initially prestressed single-walled carbon nanotube via nonlocal elasticity. The carbon nanotube is assumed to be attached to a molecular hub and is undergoing rotation. Nonlocal Euler–Bernoulli beam theory is employed to formulate the governing equations. Differential quadrature method is being utilized and the nonlocal bending frequencies of the rotating system are determined. The effects of the initial preload on vibration characteristics of rotating carbon nanotube are examined. Further, influence of (a) nonlocal effects (b) angular velocities, (c) hub radii and (d) higher mode frequencies are studied. It is explicitly shown that the bending vibration of a rotating carbon nanotube is significantly influenced by the existence of a preload, angular velocity and the nonlocal parameter.
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62.25.Jk Mechanical modes of vibration
62.23.St Complex nanostructures, including patterned or assembled structures
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep

Interferometric imaging of surface acoustic waves on a glass sphere

P. H. Otsuka, O. Matsuda, M. Tomoda, and O. B. Wright

J. Appl. Phys. 108, 123508 (2010); http://dx.doi.org/10.1063/1.3517076 (5 pages) | Cited 1 time

Online Publication Date: 20 December 2010

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We use an ultrafast optical pump and probe technique to investigate the propagation of subgigahertz surface acoustic waves on a 1 mm diameter glass sphere with an aluminum coating. A fiber-based pump setup generates the surface waves and a common-path interferometer images them in the time domain over the sphere surface as they pass through the pole opposite the source of excitation. Fourier analysis allows the acoustic spectrum of the acoustic source to be extracted and waves traveling in opposite directions to be isolated.
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43.35.Pt Surface waves in solids and liquids
68.35.Iv Acoustical properties
78.47.J- Ultrafast spectroscopy (<1 psec)

Adhesion and cyclic stretching of Au thin film on poly(dimethyl-siloxane) for stretchable electronics

Onobu Akogwu, David Kwabi, Auxillia Munhutu, Tiffany Tong, and W. O. Soboyejo

J. Appl. Phys. 108, 123509 (2010); http://dx.doi.org/10.1063/1.3510488 (6 pages) | Cited 3 times

Online Publication Date: 21 December 2010

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This paper presents the results of an experimental study of the effects of cyclic damage and adhesion on nanoscale Au thin films deposited on a flexible poly(dimethyl-siloxane) substrate. The deformation and cracking mechanisms are elucidated as functions of film thickness. The implications of the results are also discussed for the design of stretchable electronic structures.
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68.60.Bs Mechanical and acoustical properties
68.55.jd Thickness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.40.Lm Deformation, plasticity, and creep
68.35.Np Adhesion

Distribution of structural domains in MnAs layers grown on GaAs substrates

Y. Takagaki, J. Lähnemann, B. Jenichen, J. Herfort, C. Herrmann, and U. Jahn

J. Appl. Phys. 108, 123510 (2010); http://dx.doi.org/10.1063/1.3520654 (7 pages)

Online Publication Date: 21 December 2010

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Electron backscatter diffraction is utilized to determine the distribution of coexisting structural domains in MnAs layers prepared on GaAs substrates. In a layer grown on a GaAs(111)B substrate using solid phase epitaxy, the structural domains roughly correspond to the morphological features of the surface. The domains are, in contrast, considerably larger in size than the surface roughness when the substrate is GaAs(113)A. We examine the role of the freedom in in-plane crystalline alignment for causing such a difference using a numerical model. In a layer grown at an extraordinary high temperature (600 °C) on a GaAs(111)B substrate, (0001) and (1math0l) orientations are interwoven. While the (0001) component is present mainly as thin flat films, a mixture of all the components forms thick elongated islands in the surrounding of the films. Consequences of such an inhomogeneity on the magnetic and electrical properties of the layer are discussed.
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68.55.J- Morphology of films
81.15.Np Solid phase epitaxy; growth from solid phases
73.61.Ey III-V semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.ag Semiconductors

Nickel-affected silicon crystallization and silicidation on polyimide by multipulse excimer laser annealing

A. Alberti, A. La Magna, M. Cuscunà, G. Fortunato, C. Spinella, and V. Privitera

J. Appl. Phys. 108, 123511 (2010); http://dx.doi.org/10.1063/1.3531562 (6 pages)

Online Publication Date: 22 December 2010

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Nickel enhanced amorphous Si crystallization and silicidation on polyimide were studied during multipulse excimer laser annealing (ELA) from submelting to melting conditions. A ∼ 8 nm thick Ni film was deposited on a 100 nm thick α-Si layer at ∼ 70 °C in order to promote partial nickel diffusion into silicon. In the submelting regime, Ni atoms distributed during deposition in α-Si and the thermal gradient due to the presence of the plastic substrate were crucial to induce low fluence ( ≥ 0.08 J/cm2) Si crystallization to a depth which is strictly related to the starting Ni profile. Αmorphous-Si crystallization is not expected on pure Si at those low fluences. Additional pulses at higher fluences do not modify the double poly-Si/α-Si structure until melting conditions are reached. At a threshold of ∼ 0.2 J/cm2, melting was induced simultaneously in the polycrystalline layer as well as in the residual α-Si due to a thermal gradient of ∼ 200 °C. Further increasing the laser fluence causes the poly-Si layer to be progressively melted to a depth which is proportional to the energy density used. As a consequence of the complete Si melting, columnar poly-Si grains are formed above 0.3 J/cm2. For all fluences, a continuous NiSi2 layer is formed at the surface which fills the large Si grain boundaries, with the beneficial effect of flattening the poly-Si surface. The results would open the perspective of integrating Ni-silicide layers as metallic contacts on Si during α-Si-crystallization by ELA on plastic substrate.
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64.70.kg Semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
61.72.Mm Grain and twin boundaries
66.30.-h Diffusion in solids
81.65.-b Surface treatments

Water sprints uphill on glass

A. Y. Vorobyev and Chunlei Guo

J. Appl. Phys. 108, 123512 (2010); http://dx.doi.org/10.1063/1.3511431 (4 pages) | Cited 7 times

Online Publication Date: 23 December 2010

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As a material, glass has been widely used in traditional fluidic devices and more recently in micro- and nanofluidic devices, and its wetting properties are crucially important in these applications. In this work, by using a high-intensity femtosecond laser structuring technique, we create a unique surface pattern on glass that transfer a regular glass surface to superwicking. As a result, water defies the gravity and sprints vertically uphill along the structured glass surface at an unprecedented velocity of 3.8 cm/sec. Our study shows that the dynamics of this fast self-propelled water flow follows a square root of time dependence.
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47.85.Np Fluidics
68.08.Bc Wetting
47.55.nd Spreading films
47.61.-k Micro- and nano- scale flow phenomena

Effect of low energy ion irradiation on CdTe crystals: Luminescence enhancement

J. Olvera, O. Martínez, M. Avella, J. L. Plaza, S. de Dios, and E. Diéguez

J. Appl. Phys. 108, 123513 (2010); http://dx.doi.org/10.1063/1.3452386 (5 pages) | Cited 1 time

Online Publication Date: 23 December 2010

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In this work we show that low energy ion sputtering is a very efficient technique as a cleaning process for CdTe substrates. We demonstrate, by using several techniques like grazing-angle x-ray diffraction, cathodoluminescence, microluminescence, and micro-Raman spectroscopy that the luminescent properties of CdTe substrates can be very much increased when CdTe surfaces are irradiated with low energy Argon ions. We postulate that this enhancement is mainly due to the removal of surface damage induced by the cutting and polishing processes. The formation of a low density of nonluminescent aggregates after the sputtering process has also been observed.
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81.65.Ps Polishing, grinding, surface finishing
61.82.-d Radiation effects on specific materials
68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
78.60.Hk Cathodoluminescence, ionoluminescence
61.80.Jh Ion radiation effects

Magnetic thermodynamics of fcc Ni from first-principles partition function approach

Shun-Li Shang, James E. Saal, Zhi-Gang Mei, Yi Wang, and Zi-Kui Liu

J. Appl. Phys. 108, 123514 (2010); http://dx.doi.org/10.1063/1.3524480 (6 pages) | Cited 8 times

Online Publication Date: 23 December 2010

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Exploration of longstanding issues in magnetic materials, for example the nature of Curie/Néel temperature and the Schottky anomaly of heat capacity, appeals to reliable models at finite temperatures. Based on first-principles calculations and partition function approach with the microstates being the collinear magnetic configurations, the magnetic thermodynamics of fcc Ni, including the heat capacity and the pressure-dependent Curie temperature, is predicted well and compared with the results from experiments and mean-field approach. As demonstrated in fcc Ni, it is found that the magnetic thermodynamics containing anomalies stems from the magnetic configurational entropy caused by the competition of various magnetic states.
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75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
65.40.Ba Heat capacity

Phonon wave-packet simulations of Ar/Kr interfaces for thermal rectification

N. A. Roberts and D. G. Walker

J. Appl. Phys. 108, 123515 (2010); http://dx.doi.org/10.1063/1.3517159 (7 pages) | Cited 6 times

Online Publication Date: 23 December 2010

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The frequency and direction dependence of transmission coefficients at interfaces was investigated theoretically. The interfaces are formed by having two Lennard-Jones materials differing in mass and interatomic potential equally divided at the center of an fcc lattice system. A single frequency wave-packet is generated at one end of the system and allowed to propagate through the system until all interactions with the interface are complete. The transmission coefficient is then calculated by comparing the energy of the packet that is transmitted with the original wave-packet. Results show a difference in transmission when the wave-packet originates from opposite sides.
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73.40.Ei Rectification
68.35.Ja Surface and interface dynamics and vibrations

Correlation between primary phases and atomic clusters in a Zr-based metallic glass

X. J. Liu, G. L. Chen, and C. T. Liu

J. Appl. Phys. 108, 123516 (2010); http://dx.doi.org/10.1063/1.3525985 (5 pages) | Cited 4 times

Online Publication Date: 23 December 2010

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Atomic clusters exiting in the Zr65Ti10Ni25 metallic glass and primary phases generated during crystallization were studied by x-ray scattering and high-resolution transmission microscopy. An intrinsic correlation between the atomic clusters and the primary phases has been revealed. It is found that there are topological icosahedral short-range orders (ISROs) in the as-cast sample in addition to fcc-Zr2Ni-type chemical SROs. These topological ISRO and fcc-Zr2Ni-type chemical SRO can simultaneously quasicrystallize/crystallize into the corresponding nanoscaled icosahedral quasicrystalline phase (I-phase) and fcc-Zr2Ni crystal as primary products during crystallization. The synchronic precipitation of these two metastable phases can be understood in terms of their structural similarity between the fcc-Zr2Ni and I-phase in local atomic configuration. In comparison with fcc-Zr2Ni crystal, the I-phase has a smaller size and lower volume fraction due to its lower growth rate attributed to its more complex composition and higher structural symmetry. The competitive growth between these two phases results in the development of nanostructured materials in this alloy after annealing.
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81.16.-c Methods of micro- and nanofabrication and processing
64.70.K- Solid-solid transitions
78.70.Ck X-ray scattering
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.46.Bc Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)

Ge instability and the growth of Ge epitaxial layers in nanochannels on patterned Si (001) substrates

G. Wang, E. Rosseel, R. Loo, P. Favia, H. Bender, M. Caymax, M. M. Heyns, and W. Vandervorst

J. Appl. Phys. 108, 123517 (2010); http://dx.doi.org/10.1063/1.3525982 (8 pages) | Cited 2 times

Online Publication Date: 28 December 2010

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We report the Ge thermal instability against surface diffusion in extremely narrow channels isolated by SiO2 and demonstrate the selective growth of strain-relaxed Ge epitaxial layers in channels as narrow as 10 nm on patterned Si (001) substrates by a combination of low temperature growth and selective recrystallization using Ge melt and regrowth during a millisecond laser anneal. Filling narrow channels at high growth temperatures is prohibited by Ge outdiffusion due to the high Ge chemical potential in such narrow channels. The Ge thermal instability depends on the channel width and a critical channel width of 50 nm is extracted from our calculation and experimental results. The Ge surface diffusion rate is dominated by the surface diffusion activation energy barrier that is significantly enhanced by the adsorbed surface hydrides. At a low temperature below 450 °C, a hydride-terminated surface is maintained which increases the Ge surface diffusion barrier and retards the outdiffusion of the Ge adatoms, providing excellent channel filling. The resulting low crystalline quality can be restored with a millisecond laser melt and regrowth.
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81.16.Rf Micro- and nanoscale pattern formation
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
61.72.Cc Kinetics of defect formation and annealing
85.40.Hp Lithography, masks and pattern transfer

The persistent luminescence and up conversion photostimulated luminescence properties of nondoped Mg2SnO4 material

Jiachi Zhang, Minghui Yu, Qingsong Qin, Hongliang Zhou, Meijiao Zhou, Xuhui Xu, and Yuhua Wang

J. Appl. Phys. 108, 123518 (2010); http://dx.doi.org/10.1063/1.3524280 (7 pages) | Cited 11 times

Online Publication Date: 28 December 2010

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The nondoped Mg2SnO4 material with inverse spinel structure was synthesized by solid state reaction. This phosphor showed a broad green emission band covering 470–550 nm under 291 nm excitation, which was due to the recombination of F centers with holes. Stimulated by 980 nm infrared laser, the green photostimulated luminescence was first observed in a nondoped oxide. After ultraviolet irradiation, the green persistent luminescence of Mg2SnO4 could be seen in darkness for about 5 h. The decay curves revealed that the long persistent luminescence was governed by tunneling mechanism and it proved the presence of different trap clusters in Mg2SnO4. These trap clusters (such as [SnMg••–Oi″], [SnMg••–2e′], and [SnMg••–e″]) induced the trap levels with different depths in band gap and corresponded to the three components (at 110, 168, and 213 °C) of the thermoluminescence glow curve of Mg2SnO4. These trap levels with different depths were proved to be not independent. It revealed that the shallow traps (110 °C) and part of the deep traps (168 and 213 °C) were involved in the persistent luminescence. Meanwhile, all the shallow and deep traps were responsible for the photostimulated luminescence. Accordingly, the photoluminescence, persistent, and photostimulated luminescence mechanisms of the nondoped Mg2SnO4 material were first proposed.
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78.55.Hx Other solid inorganic materials
78.45.+h Stimulated emission
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Ht Other nonmetals
78.60.Kn Thermoluminescence
61.72.jn Color centers

Study of composition dependent structural, optical, and magnetic properties of Cu-doped Zn1−xCdxS nanoparticles

Amit Kumar Chawla, Sonal Singhal, Sandeep Nagar, Hari Om Gupta, and Ramesh Chandra

J. Appl. Phys. 108, 123519 (2010); http://dx.doi.org/10.1063/1.3524516 (7 pages) | Cited 4 times

Online Publication Date: 28 December 2010

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Cu-doped Zn1−xCdxS nanoparticles were synthesized by coprecipitation technique in ice bath at 280 K. The band gap energy of Zn1−xCdxS:Cu nanoparticles can be tuned to a lower energy by increasing the Cd content, indicating the formation of the alloyed nanoparticles. The alloy structure is further supported by the systematic shifting of characteristic x-ray diffraction peaks to lower angles with increase in Cd content. Systematic copper doping induces a red shift in the energy band gap of Zn0.9Cd0.1S:Cu nanoparticles with increase in copper concentration. Cu-doped Zn0.9Cd0.1S nanoparticles were found to have ferromagnetic nature at 5 K whereas undoped particles were found to be diamagnetic. Green luminescence further proves proper doping of Cu into the ZnCdS matrix. It is believed that the green luminescence originates from the recombination between the shallow donor level (sulfur vacancy) and the t2 level of Cu2+. This method provides an inexpensive and simple procedure to produce ternary ZnCdS:Cu nanoparticles with tunable optical properties via changing Cd and/or Cu concentrations.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.55.Et II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
75.50.Dd Nonmetallic ferromagnetic materials
61.72.uj III-V and II-VI semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization

Determining phonon deformation potentials of hexagonal GaN with stress modulation

Jun-Yong Lu, Zhi-Jia Wang, Dong-Mei Deng, Yong Wang, Kevin Jing Chen, Kei-May Lau, and Tong-Yi Zhang

J. Appl. Phys. 108, 123520 (2010); http://dx.doi.org/10.1063/1.3524548 (5 pages) | Cited 5 times

Online Publication Date: 28 December 2010

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In this work, phonon deformation potentials for E2H and A1(LO) phonons of epitaxial hexagonal GaN thin films grown by metalorganic chemical vapor deposition on Si (111) substrate were precisely determined with a stress modulation method, which was achieved via coin-shaped patterning of an originally flat film. By changing the size of patterned coin-shaped islands, the original biaxial stress in the flat film was reduced to different levels at the island centers, which was analyzed by finite element calculations. The proposed stress modulation method allows one to carry out a large number of Raman scattering tests, thereby leading to reliable results. With this method, the Raman biaxial pressure coefficients of E2H and A1(LO) phonons of GaN were determined to be 4.47 cm−1/GPa and 2.76 cm−1/GPa, respectively.
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78.30.Fs III-V and II-VI semiconductors
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.55.ag Semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Interfacial reactions in Ru metal-electrode/HfSiON gate stack structures studied by synchrotron-radiation photoelectron spectroscopy

H. Kamada, S. Toyoda, T. Tanimura, H. Kumigashira, M. Oshima, G. L. Liu, Z. Liu, and T. Sukegawa

J. Appl. Phys. 108, 123521 (2010); http://dx.doi.org/10.1063/1.3525584 (4 pages)

Online Publication Date: 28 December 2010

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We have investigated the thermal stability and interfacial reactions of a Ru/HfSiON gate stack structure, annealed in a nitrogen ambient, using synchrotron-radiation photoelectron spectroscopy. We find that in HfSiON films with Ru metal, competition between catalyst-induced oxidation and oxygen or SiO desorption arises upon high-temperature annealing, unlike in the same films without Ru. The desorption reaction during high-temperature annealing at 1050 °C could be caused by the decomposition of an unstable Si oxide component, formed by catalytic oxidation at the interface between the HfSiON layer and the Si substrate after annealing below 850 °C.
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79.60.Jv Interfaces; heterostructures; nanostructures
68.43.Nr Desorption kinetics
81.40.Gh Other heat and thermomechanical treatments
82.45.-h Electrochemistry and electrophoresis
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Inclined dislocation arrays in AlGaN/AlGaN quantum well structures emitting at 290 nm

T. Y. Chang, M. A. Moram, C. McAleese, M. J. Kappers, and C. J. Humphreys

J. Appl. Phys. 108, 123522 (2010); http://dx.doi.org/10.1063/1.3525622 (5 pages) | Cited 2 times

Online Publication Date: 28 December 2010

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We report on the structural and optical properties of deep ultraviolet emitting AlGaN/AlGaN multiple quantum wells (MQWs) grown on (0001) sapphire by metal-organic vapor phase epitaxy using two different buffer layer structures, one containing a thin (1 μm) AlN layer combined with a GaN interlayer and the other a thick (4 μm) AlN layer. Transmission electron microscopy analysis of both structures showed inclined arrays of dislocations running through the AlGaN layers at an angle of ∼ 30°, originating at bunched steps at the AlN surface and terminating at bunched steps at the surface of the MQW structure. In all layers, these inclined dislocation arrays are surrounded by AlGaN with a relatively higher Ga content, consistent with plan-view cathodoluminescence maps in which the bunched surface steps are associated with longer emission wavelengths. The structure with the 4 μm-thick AlN buffer layer had a dislocation density lower by a factor of 2 (at (1.7±0.1)×109 cm−2) compared to the structure with the 1 μm thick AlN buffer layer, despite the presence of the inclined dislocation arrays.
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68.65.Fg Quantum wells
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.67.De Quantum wells
78.60.Hk Cathodoluminescence, ionoluminescence

Improving Er3+ 1.53 μm luminescence by CeF3 nanocrystallization in aluminosilicate glass

Yunlong Yu, Zhifa Shan, Daqin Chen, Ping Huang, Hang Lin, and Yuansheng Wang

J. Appl. Phys. 108, 123523 (2010); http://dx.doi.org/10.1063/1.3525589 (5 pages) | Cited 4 times

Online Publication Date: 29 December 2010

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In order to develop promising materials for the Er3+-doped fiber amplifier, transparent glass ceramics containing hexagonal CeF3 nanocrystals were prepared by melt-quenching and subsequent heating. The obvious Stark splitting in the absorption and emission spectra, the intensification of the 1.53 μm emission, and the prolongation of the Er3+:4I13/2 decay lifetime demonstrated the partition of Er3+ ions into the CeF3 nanocrystals. Evidently, the efficient cross-relaxation between Ce3+ and Er3+, i.e., Er3+:4I11/2+Ce3+:2F5/2→Er3+:4I13/2Ce3+:2F7/2 led to the quenching of the upconversion and the enhancing of the desired Er3+ 1.53 μm emission. Based on the emission and absorption spectra, it was further calculated that the glass ceramic possesses broad bandwidth as that of the ZBLAN glass, and large emission cross-section close to the silicate glass, for the 1.53 μm emission.
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81.05.Pj Glass-based composites, vitroceramics
81.16.Be Chemical synthesis methods
61.72.up Other materials
61.43.Fs Glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.Gh Other heat and thermomechanical treatments

X-ray photoelectron spectroscopy analysis of TlInGaAsN semiconductor system and their annealing-induced structural changes

Kang Min Kim, Woo-Byoung Kim, Daivasigamani Krishnamurthy, Manabu Ishimaru, Hikaru Kobayashi, Shigehiko Hasegawa, and Hajime Asahi

J. Appl. Phys. 108, 123524 (2010); http://dx.doi.org/10.1063/1.3525979 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2010

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TlInGaAsN thin films grown by gas-source molecular-beam epitaxy were investigated by x-ray photoelectron spectroscopy (XPS) to analyze the Tl incorporation and to study the annealing-induced transformation of the atomic configurations. XPS analysis revealed that the Tl composition in the grown TlInGaAsN is around 1.5% and that the dominant atomic configuration of the TlInGaAsN changes from the In–As and Ga–N bonds to the In–N and Ga–As bonds by 700 °C rapid thermal annealing. High-resolution x-ray diffraction and reciprocal space mapping measurements showed that no significant out-diffusion of the elements occurs in the TlInGaAsN/TlGaAsN quantum wells (QWs) even after the same annealing. It is concluded that the blueshift in the photoluminescence peak for the TlInGaAsN/TlGaAsN QWs after annealing is attributed to the transformation of the atomic configuration in TlInGaAsN.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
64.70.K- Solid-solid transitions

Influence of krypton atoms on the structure of hydrogenated amorphous carbon deposited by plasma enhanced chemical vapor deposition

M. H. Oliveira, Jr., G. A. Viana, M. M. de Lima, Jr., A. Cros, A. Cantarero, and F. C. Marques

J. Appl. Phys. 108, 123525 (2010); http://dx.doi.org/10.1063/1.3526000 (8 pages) | Cited 1 time

Online Publication Date: 30 December 2010

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Hydrogenated amorphous carbon (a-C:H) films were prepared by plasma enhanced chemical vapor deposition using methane (CH4) plus krypton (Kr) mixed atmosphere. The depositions were performed as function of the bias voltage and krypton partial pressure. The goal of this work was to study the influence of krypton gas on the physical properties of a-C:H films deposited on the cathode electrode. Krypton concentration up to 1.6 at. %, determined by Rutherford Back-Scattering, was obtained at high Kr partial pressure and bias of −120 V. The structure of the films was analyzed by means of optical transmission spectroscopy, multi-wavelength Raman scattering and Fourier Transform Infrared spectroscopy. It was verified that the structure of the films remains unchanged up to a concentration of Kr of about 1.0 at. %. A slight graphitization of the films occurs for higher concentration. The observed variation in the film structure, optical band gap, stress, and hydrogen concentration were associated mainly with the subplantation process of hydrocarbons radicals, rather than the krypton ion energy.
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68.60.Wm Other nonelectronic physical properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Hv Other nonmetallic inorganics

Magnetic-field-induced recovery strain in polycrystalline Ni–Mn–Ga foam

Markus Chmielus, Cassie Witherspoon, Robert C. Wimpory, Andreas Paulke, André Hilger, Xuexi Zhang, David C. Dunand, and Peter Müllner

J. Appl. Phys. 108, 123526 (2010); http://dx.doi.org/10.1063/1.3524503 (7 pages) | Cited 3 times

Online Publication Date: 30 December 2010

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Recently, we have shown that a polycrystalline Ni–Mn–Ga magnetic shape-memory alloy, when containing two populations of pore sizes, shows very high magnetic-field-induced strain of up to 8.7%. Here, this double-porosity sample is imaged by x-ray microtomography, showing a homogenous distribution of both pore populations. The orientation of six large grains—four with 10M and two with 14M structure—is identified with neutron diffraction. In situ magnetomechanical experiments with a rotating magnetic field demonstrate that strain incompatibilities between misoriented grains are effectively screened by the pores which also stop the propagation of microcracks. During uniaxial compression performed with an orthogonal magnetic bias field, a strain as high as 1% is recovered on unloading by twinning, which is much larger than the elastic value of <0.1% measured without field. At the same time, repeated loading and unloading results in a reduction in the yield stress, which is a training effect similar to that in single crystals.
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81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
61.72.Mm Grain and twin boundaries
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mt Cracks
back to top Electronic Structure and Transport

Deuterium-induced passivation of boron acceptors in polycrystalline diamond

N. Habka, E. Chikoidze, F. Jomard, Y. Dumont, J. Chevallier, J. Barjon, C. Mer, and P. Bergonzo

J. Appl. Phys. 108, 123701 (2010); http://dx.doi.org/10.1063/1.3518608 (5 pages) | Cited 2 times

Online Publication Date: 17 December 2010

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In monocrystalline boron-doped diamond (BDD), the diffusion of deuterium induces an electrical passivation of acceptors by the formation of (B,D) complexes. However, device applications based on this process are presently limited by the small size of available monocrystalline substrates. In this work, we show that the grain size of polycrystalline diamond is a key parameter in order to achieve efficient deuterium diffusion by trapping on boron atoms. As a result, we present the first clear evidences of the electrical passivation of boron acceptors in the case of polycrystalline diamond layers with an average grain size of 50 μm. We show that, for a boron concentration of 2×1019 cm−3, the room temperature hole mobility increases from 70 to 120 cm2 V−1 s−1 after deuteration. More surprisingly, the compensation ratio keeps the same order of magnitude which suggests a passivation effect on both acceptors and donors.
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81.05.ug Diamond
81.65.Rv Passivation
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
68.35.Fx Diffusion; interface formation

High efficiency semimetal/semiconductor nanocomposite thermoelectric materials

J. M. O. Zide, J.-H. Bahk, R. Singh, M. Zebarjadi, G. Zeng, H. Lu, J. P. Feser, D. Xu, S. L. Singer, Z. X. Bian, A. Majumdar, J. E. Bowers, A. Shakouri, and A. C. Gossard

J. Appl. Phys. 108, 123702 (2010); http://dx.doi.org/10.1063/1.3514145 (5 pages) | Cited 24 times

Online Publication Date: 20 December 2010

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Rare-earth impurities in III–V semiconductors are known to self-assemble into semimetallic nanoparticles which have been shown to reduce lattice thermal conductivity without harming electronic properties. Here, we show that adjusting the band alignment between ErAs and In0.53Ga0.47−XAlXAs allows energy-dependent scattering of carriers that can be used to increase thermoelectric power factor. Films of various Al concentrations were grown by molecular beam epitaxy, and thermoelectric properties were characterized. We observe concurrent increases in electrical conductivity and Seebeck coefficient with increasing temperatures, demonstrating energy-dependent scattering. We report the first simultaneous power factor enhancement and thermal conductivity reduction in a nanoparticle-based system, resulting in a high figure of merit, ZT = 1.33 at 800 K.
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73.63.Bd Nanocrystalline materials
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.20.Pa Thermoelectric and thermomagnetic effects
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Approach to the physical origin of breakdown in silicon solar cells by optical spectroscopy

Paul Gundel, Wolfram Kwapil, Martin C. Schubert, Holger Seifert, and Wilhelm Warta

J. Appl. Phys. 108, 123703 (2010); http://dx.doi.org/10.1063/1.3517086 (5 pages) | Cited 3 times

Online Publication Date: 20 December 2010

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The electrical breakdown of silicon solar cells at low reverse currents has recently gained increased attention. In this study we investigate the physical properties of prebreakdown sites with high resolution spectroscopy techniques. These techniques comprise the measurement of the electroluminescence under reverse voltage, microphotoluminescence spectroscopy, and micro-Raman spectroscopy. The measurements show very high levels of stress at the prebreakdown sites, an increase in the breakdown size with applied reverse bias and redshift in the breakdown electroluminescence spectrum with increasing onset voltage. The results are tentatively explained by a lower bandgap energy at the breakdown sites, which could be caused by stress.
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88.40.jj Silicon solar cells

Size effects on the Hall constant in thin gold films

Ricardo Henriquez, Simon Oyarzun, Marcos Flores, Marco Antonio Suarez, Luis Moraga, German Kremer, Claudio A. Gonzalez-Fuentes, Marcelo Robles, and Raul C. Munoz

J. Appl. Phys. 108, 123704 (2010); http://dx.doi.org/10.1063/1.3525704 (6 pages) | Cited 4 times

Online Publication Date: 21 December 2010

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We report the Hall constant RH, drift mobility μD, and Hall mobility μH measured at 4 K in thin gold films deposited on mica substrates, where the dominant electron scattering mechanism is electron-surface scattering. RH increases with increasing film thickness and decreases with increasing magnetic field. For high magnetic fields B ≥ 6 T, RH turns out to be approximately independent of magnetic field, and its value is close to that of the free electron model. We use the high magnetic field values of RH to determine film thickness. This nondestructive method leads to a determination of film thickness that agrees to within 10% with the thickness measured by other techniques. The theoretical predictions, based upon the theory of Fuchs–Sondheimer and the theory of Calecki, are at variance with experimental observations.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.aj Insulators

Excess carbon in silicon carbide

X. Shen, M. P. Oxley, Y. Puzyrev, B. R. Tuttle, G. Duscher, and S. T. Pantelides

J. Appl. Phys. 108, 123705 (2010); http://dx.doi.org/10.1063/1.3517142 (5 pages) | Cited 7 times

Online Publication Date: 21 December 2010

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The application of SiC in electronic devices is currently hindered by low carrier mobility at the SiC/SiO2 interfaces. Recently, it was reported that 4H–SiC/SiO2 interfaces might have a transition layer on the SiC substrate side with C/Si ratio as high as 1.2, suggesting that carbon is injected into the SiC substrate during oxidation or other processing steps. We report finite-temperature quantum molecular dynamics simulations that explore the behavior of excess carbon in SiC. For SiC with 20% excess carbon, we find that, over short time ( ∼ 24 ps), carbon atoms bond to each other and form various complexes, while the silicon lattice is largely unperturbed. These results, however, suggest that at macroscopic times scale, C segregation is likely to occur; therefore a transition layer with 20% extra carbon would not be stable. For a dilute distribution of excess carbon, we explore the pairing of carbon interstitials and show that the formation of dicarbon interstitial cluster is kinetically very favorable, which suggests that isolated carbon clusters may exist inside SiC substrate.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
72.20.Ee Mobility edges; hopping transport
71.20.Nr Semiconductor compounds
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
61.72.jj Interstitials
61.46.Bc Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)
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