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1 Jul 2002

Volume 92, Issue 1, pp. 1-646

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Electrical activation of high concentrations of N+ and P+ ions implanted into 4H–SiC

M. Laube, F. Schmid, G. Pensl, G. Wagner, M. Linnarsson, and M. Maier

J. Appl. Phys. 92, 549 (2002); http://dx.doi.org/10.1063/1.1479462 (6 pages) | Cited 35 times

Online Publication Date: 19 June 2002

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Comparative Hall effect investigations are conducted on N- and P-implanted as well as on (N+P)-coimplanted 4H–SiC epilayers. Box profiles with three different mean concentrations ranging from 2.5×1018 to 3×1020 cm−3 to a depth of 0.8 μm are implanted at 500 °C into the (0001)-face of the initially p-type (Al-doped) epilayers. Postimplantation anneals at 1700 °C for 30 min are conducted to electrically activate the implanted N+ and P+ ions. Our systematic Hall effect investigations demonstrate that there is a critical donor concentration of (2–5)×1019 cm−3. Below this value, N- and P-donors result in comparable sheet resistances. The critical concentration represents an upper limit for electrically active N donors, while P donors can be activated at concentrations above 1020 cm−3. This high concentration of electrically active P donors is responsible for the observed low sheet resistance of 35 Ω/□, which is about one order of magnitude lower than the minimum sheet resistance achieved by N implantation. © 2002 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
61.72.up Other materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

RF voltage modulations and the coupled bunch instabilities

M. H. Wang and S. Y. Lee

J. Appl. Phys. 92, 555 (2002); http://dx.doi.org/10.1063/1.1482426 (9 pages) | Cited 4 times

Online Publication Date: 19 June 2002

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The effects of rf cavity voltage modulation on longitudinal beam dynamics were studied experimentally at Taiwan Light Source by using a streak camera system that measured the attractor amplitude of the beam bunch. Theoretical description of rf voltage modulation that includes the effect of nonzero synchronous phase has been developed. The characteristics of the quadrupole parametric resonance in the single bunch and multibunch modes were studied and compared with theory. The formation of beamlets in the bucket helps to damp the coherent coupled bunch oscillation driven by parasitic modes of the rf cavity. This beam manipulation technique can be employed to alleviate stability problems associated with high brightness electron storage rings. © 2002 American Institute of Physics.
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29.27.Bd Beam dynamics; collective effects and instabilities
29.27.Eg Beam handling; beam transport
29.20.db Storage rings and colliders
07.77.Ka Charged-particle beam sources and detectors
41.75.Fr Electron and positron beams
41.85.Ct Particle beam shaping, beam splitting

Ablative generation of surface acoustic waves in aluminum using ultraviolet laser pulses

J. P. Gospodyn, A. Sardarli, A. M. Brodnikovski, and R. Fedosejevs

J. Appl. Phys. 92, 564 (2002); http://dx.doi.org/10.1063/1.1479472 (8 pages) | Cited 2 times

Online Publication Date: 19 June 2002

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Surface acoustic wave generation using ablative excitation with ultraviolet laser pulses is studied experimentally in order to quantify the magnitude of response. The acoustic waves are interferometrically measured on the surface of polished aluminum samples at distances of 5–40 mm from the excitation spot. Amplitudes of the surface acoustic waves are measured as a function of laser energy (1–60 mJ) and distance from the excitation spot yielding peak-to-peak displacements of 1–40 nm. The results are compared to theoretical calculations using the Green’s function for a step impulse response. The impulse required to match the measured results is compared to the expected impulse based on plasma pressure scaling in the ablative regime and the experimentally measured response is found to agree within a factor of 2 with the theoretical predicted impulse. © 2002 American Institute of Physics.
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43.35.Pt Surface waves in solids and liquids
79.20.Ds Laser-beam impact phenomena
68.35.Iv Acoustical properties

Structural and magnetic phase transformation in metastable Fe–Cr alloys induced by ion irradiation

E. Wieser, H. Reuther, F. Prokert, A. Gorbunov, A. Tselev, W. Pompe, A. A. Levin, D. C. Meyer, and P. Paufler

J. Appl. Phys. 92, 572 (2002); http://dx.doi.org/10.1063/1.1484234 (6 pages) | Cited 21 times

Online Publication Date: 19 June 2002

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Unusual metastable paramagnetic phases have been observed in Fe–Cr thin films (thickness about 40 nm) fabricated by pulsed laser deposition. In the present article, x-ray diffraction and Mössbauer spectroscopy have been applied to follow the structural and magnetic phase transformation in these alloys induced by ion irradiation with a projected range positioned in the center of the films. It has been found that the critical dose for the transformation to the more stable body-centered cubic (bcc) structure depends on the initial phase of the film and the ion mass. The initial body-centered tetragonal phase, which forms in the alloys with low Cr content (∼30 at. %), can be completely transformed to the bcc phase already by a dose of 5×1015 Cr/cm2, whereas the primitive orthorhombic phase of roughly equiatomic Fe–Cr alloys is about four times more resistant against ion bombardment. A five times higher Ne ion dose is required to induce the same transformation as by the Cr bombardment. The observed effects are discussed in view of radiation damage caused by the different ions and the grade of affinity of the initial phase to the bcc one. © 2002 American Institute of Physics.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
61.82.Bg Metals and alloys
75.20.En Metals and alloys
64.70.K- Solid-solid transitions
61.80.Jh Ion radiation effects
76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Strain field and scattered intensity profiling with energy dispersive x-ray scattering

M. Croft, I. Zakharchenko, Z. Zhong, Y. Gurlak, J. Hastings, J. Hu, R. Holtz, M. DaSilva, and T. Tsakalakos

J. Appl. Phys. 92, 578 (2002); http://dx.doi.org/10.1063/1.1483373 (9 pages) | Cited 10 times

Online Publication Date: 19 June 2002

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Two powerful synchrotron x-ray scattering techniques for residual strain depth-profiling and tomography-like scatter-intensity profiling of materials are presented. The techniques utilize energy dispersive x-ray scattering, from a fixed microvolume, with microscanning of the specimen being used to profile its interior. The tomography-like profiles exploit scattering-cross-section variations, and can be contrast enhanced by separately monitoring scattering from different crystal structures. The strain profiling technique is shown to finely chronicle the internal strain variation over several mm of steel. Detailed strain profiling for a cantilever spring demonstrates the interplay of residual and external stresses in elastic/plastic deformation. Since surface compression, by shot peening, is a classic method to fortify against fatigue failure, the strain profile for a shot-peened, surface-toughened material is determined and discussed in terms of a simple elastic–plastic stress/strain model. Finally the lattice strains in a WC/Co coated steel composite material are discussed. © 2002 American Institute of Physics.
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82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
81.40.Lm Deformation, plasticity, and creep
78.70.Ck X-ray scattering
61.05.cf X-ray scattering (including small-angle scattering)
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Microcrystalline silicon thin films studied by atomic force microscopy with electrical current detection

B. Rezek, J. Stuchlík, A. Fejfar, and J. Kočka

J. Appl. Phys. 92, 587 (2002); http://dx.doi.org/10.1063/1.1486032 (7 pages) | Cited 30 times

Online Publication Date: 19 June 2002

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Hydrogenated microcrystalline silicon (μc-Si:H) layers with thickness from 100 to 540 nm were prepared in situ by plasma enhanced chemical vapor deposition. The growth of μc-Si:H on various substrates [NiCr, device quality, and laser annealed amorphous silicon (a-Si:H)] was studied in ultrahigh vacuum by atomic force microscope using a conductive cantilever which enabled simultaneous measurement of morphology and local current with lateral resolution below 5 nm. The effect of barriers, voltage, and time on contrast in local current map is discussed in detail. Coexistent amorphous and microcrystalline regions are clearly identified due to their different conductivity. Laser annealing of the a-Si:H substrate significantly increases the crystalline fraction at the same layer thickness. Grains as small as 10–30 nm separated by less conductive grain boundaries were revealed in microcrystalline regions. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Cy Elemental semiconductors
73.61.Cw Elemental semiconductors
68.37.Ps Atomic force microscopy (AFM)
72.80.Cw Elemental semiconductors
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.25.+i Surface conductivity and carrier phenomena
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.Mm Grain and twin boundaries
61.82.Fk Semiconductors

Ignition phenomena in combustion synthesis: An experimental methodology

M. Monagheddu, N. Bertolino, P. Giuliani, C. Zanotti, and U. Anselmi Tamburini

J. Appl. Phys. 92, 594 (2002); http://dx.doi.org/10.1063/1.1486254 (6 pages) | Cited 15 times

Online Publication Date: 19 June 2002

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An experimental methodology is presented to investigate the ignition in combustion synthesis. The aim of this work is to study the ignition phenomena, separating the initiation from the propagation process. The reactions were activated by a CO2 laser with a power range from 20 to 60 W. The experimental configuration was set to avoid the sample heat losses. All the experiments were performed in thermal explosion mode. The studied system was Ni–Al at three compositions (Ni:Al=3:1, Ni:Al=1:1 and Ni:Al=1:3). The results indicate that the ignition temperature is not affected by the laser power applied, but it is characteristic for each composition. A theoretical approach, aimed to the ignition energy calculation, supports the experiments. The calculated ignition energy, for the investigated powder mixtures, is equal to 17±0.5 kJ/molat, independent of stoichiometric ratio and of used heating ramps. A mechanistic interpretation of the ignition is attempted to compare experimental results and numerical simulations. © 2002 American Institute of Physics.
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81.05.Cy Elemental semiconductors
42.62.-b Laser applications
81.05.Bx Metals, semimetals, and alloys

An analytical approach to the determination of surface temperature history from subsurface data

J. Fivez and J. Thoen

J. Appl. Phys. 92, 600 (2002); http://dx.doi.org/10.1063/1.1486058 (5 pages) | Cited 1 time

Online Publication Date: 19 June 2002

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In this article we address the problem of the reconstruction of surface temperature history of a semi-infinite solid from subsurface temperature wave data at one instant. This problem proves particularly interesting in relation to the geothermal history and the detection of climatic changes using borehole data. In particular we present exact analytical results valuable for this important inverse problem. We show how this provides us with a straightforward method which eliminates the need of foreknowledge typical of the current numerical approaches. © 2002 American Institute of Physics.
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07.20.Dt Thermometers

Bulk photothermal model for laser ablation of polymers by nanosecond and subpicosecond pulses

N. Bityurin and A. Malyshev

J. Appl. Phys. 92, 605 (2002); http://dx.doi.org/10.1063/1.1486040 (9 pages) | Cited 13 times

Online Publication Date: 19 June 2002

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The main feature of polymeric materials is the hierarchy of bonds between molecular groups. This feature is explicitly taken into account in a model of photothermal laser ablation of polymers derived in the present work. According to this model the reason for laser ablation is a photothermal bond-breaking reaction within the bulk of material originated from laser heating. In order to address the movement of the interface between gaseous and condensed phases, we change the Stefan-like boundary condition considered previously for the Frenkel–Wilson one. In the latter case the activation energy for elimination of a short enough polymer chain from the surface is proportional to the sum of the energies of weak bonds connecting this chain with the surface. We compare predictions of this model with the previously derived Stefan-like bulk model and with the surface photothermal evaporation model with respect to kinetics and dynamics of laser ablation by both nanosecond and subpicosecond pulses, including ablation by two subpicosecond pulses. This consideration suggests experimental evidence that allows one to distinguish between surface and bulk photothermal ablation mechanisms. The parameters used in numerical calculation correspond to the KrF excimer laser ablation of polyimide. The results of the theoretical modeling are compared with the existing data on kinetics of nanosecond laser ablation as well as with findings of time-resolved UV subpicosecond laser ablation experiments. © 2002 American Institute of Physics.
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52.38.Mf Laser ablation
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
79.20.Ds Laser-beam impact phenomena
78.47.-p Spectroscopy of solid state dynamics

Intermixing-promoted scaling of Ge/Si(100) island sizes

M. De Seta, G. Capellini, F. Evangelisti, and C. Spinella

J. Appl. Phys. 92, 614 (2002); http://dx.doi.org/10.1063/1.1483370 (6 pages) | Cited 36 times

Online Publication Date: 19 June 2002

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The shape evolution and the effect of deposition temperature on size and composition of chemical vapor deposition grown Ge/Si(100) islands have been investigated in the deposition temperature range 450–850 °C. It is found that the increase of the growth temperature above 600 °C entails a strong island enlargement due to an increased Si/Ge intermixing. The crystallographic structure of the islands was investigated by transmission electron microscopy. The analysis of the resulting Moiré pattern reveals that the island lattice deformation decreases with increasing island size and that the effective mismatch ϵ between the silicon substrate and the epilayer decreases with increasing deposition temperature. The island nucleation size, the mean size of coherent islands and the critical size for the insertion of misfit dislocations have been found to scale as ϵ−2, ϵ−2, and ϵ−1, respectively. The agreement of our experimental scaling results with the predictions of theoretical calculation performed for homogeneous heterostructures suggests that, although the Si distribution inside the islands is not homogeneous, the island growth is driven by the mean effective strain. © 2002 American Institute of Physics.
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68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Fx Diffusion; interface formation
68.37.Lp Transmission electron microscopy (TEM)

Effect of plasma and thermal annealing on optical and electronic properties of SnO2 substrates used for a-Si solar cells

Steven S. Hegedus

J. Appl. Phys. 92, 620 (2002); http://dx.doi.org/10.1063/1.1481192 (7 pages) | Cited 4 times

Online Publication Date: 19 June 2002

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The sensitivity to various types of annealing treatments of three commercially available textured SnO2 substrate materials was investigated using optical transmission and Hall effect measurements. The treatments included H2 plasma and annealing in H2/Ar, Ar, or air from 100 to 400 °C. With both types of H2 treatments, the mobility of the SnO2 having the lowest carrier density (<2×1020 cm−3) doubles from ∼30 to ∼60 cm2/V s while the mobilities of SnO2 materials having a higher carrier density were unaffected. There was no significant change in carrier density with either treatment for any SnO2. The visible transmission degrades significantly with H2 plasma at 200 °C but it is unaffected by H2/Ar annealing up to 400 °C. A 20 nm layer of sputtered ZnO is sufficient to protect the SnO2 from plasma-induced damage while still allowing the factor of 2 improvement in SnO2 mobility. The resistivity of bare SnO2 can be decreased by a factor of 2 without any loss of transmission using H2/Ar or Ar annealing at 400 °C without a protective ZnO layer. The changes were stable over 2 years of storage in air. Results are consistent with thermal desorption of oxygen from grain boundaries in a reducing ambient. An optimum SnO2 product for superstrate a-Si solar module fabrication should be deposited with a low carrier density, <2×1020 cm−3, then annealed in H2/Ar or Ar at 300–400 °C to increase the mobility without increasing the absorption losses. © 2002 American Institute of Physics.
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81.05.Hd Other semiconductors
81.65.-b Surface treatments
61.72.Cc Kinetics of defect formation and annealing
73.61.Le Other inorganic semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
78.66.Li Other semiconductors
52.77.-j Plasma applications
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.Mm Grain and twin boundaries
68.43.Vx Thermal desorption
84.60.Jt Photoelectric conversion
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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