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15 Sep 2000

Volume 88, Issue 6, pp. 3113-3785

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Relation between the molecular orientations of a very thin liquid crystal layer and an underlying rubbed polyimide film

Naoki Ito, Kenji Sakamoto, Ryuichi Arafune, and Sukekatsu Ushioda

J. Appl. Phys. 88, 3235 (2000); http://dx.doi.org/10.1063/1.1288696 (7 pages) | Cited 12 times

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By polarized infrared absorption spectroscopy, we have determined the relation between the molecular orientation of a rubbed polyimide film and that of a very thin liquid crystal (LC) layer (approximately a monolayer of 8CB molecules) in contact with the polyimide film. The molecular orientation of the rubbed polyimide film was determined by fitting theoretically the incident angle dependence of the infrared absorption for molecular vibrations polarized parallel to the length of the polymer. Approximately a monolayer of 8CB molecules was deposited on a rubbed polyimide film with previously measured molecular orientation. The molecular orientation of this LC layer was also determined by polarized infrared absorption. We found that the LC molecules and the polyimide chains are oriented, on average, along the rubbing direction and tilted up from the surface, and that the molecular order of the LC layer is higher than that of the underlying rubbed polyimide film. © 2000 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
68.15.+e Liquid thin films
78.30.C- Liquids
78.66.Qn Polymers; organic compounds

Influence of impurities on the optical damage of KTiOPO4 crystals

C. Zaldo, J. Carvajal, R. Solé, F. Díaz, D. Bravo, and A. Kling

J. Appl. Phys. 88, 3242 (2000); http://dx.doi.org/10.1063/1.1288014 (7 pages) | Cited 4 times

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Optical damage has been induced in doped c-cut KTiOPO4 (KTP) crystals by low intensity (I0⩽0.1 W/cm2) continuous-wave illumination with ultraviolet (λ=364 nm) light. The presence of two growth sectors with different sensibility to optical damage has been observed and it is related to their different impurity concentrations. Impurities shift the optical absorption edge of KTP to lower energy and make the induced damage more stable at room temperature. The damage saturation depends on the ultraviolet power density and on the impurity concentration. It has also been observed that some impurities (W and others) change their valence due to ultraviolet irradiation. A dynamic model considering the excitation of electrons from donors and their release from traps is proposed. The model allows us to describe the main features of the optical damage and erasure kinetics. © 2000 American Institute of Physics.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Magnetic resonance investigations of defects in Ga14N and Ga15N

M. W. Bayerl, N. M. Reinacher, H. Angerer, O. Ambacher, M. S. Brandt, and M. Stutzmann

J. Appl. Phys. 88, 3249 (2000); http://dx.doi.org/10.1063/1.1289226 (5 pages) | Cited 2 times

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The influence of the nitrogen nuclear spin on the optically detected magnetic resonance and electron spin resonance signatures of the intrinsic shallow donor and a deep defect causing the characteristic yellow luminescence have been studied on wurtzite GaN epitaxial layers grown by plasma induced molecular beam epitaxy with isotopically pure 14N and 15N. In particular, the linewidth of the deep defect signal is observed to be independent of the nitrogen isotope. The missing effect of the different nuclear spin properties of the 14N and 15N isotopes is discussed in view of current microscopic models for the yellow luminescence in GaN. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
76.70.Hb Optically detected magnetic resonance (ODMR)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Si self-interstitial injection from Sb complex formation in Si

J. Fage-Pedersen, P. Gaiduk, J. Lundsgaard Hansen, and A. Nylandsted Larsen

J. Appl. Phys. 88, 3254 (2000); http://dx.doi.org/10.1063/1.1289234 (6 pages) | Cited 12 times

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It has recently been established that Si self-interstitials are generated during annealing of high-concentration Sb layers in Si. In the present work, we make use of samples grown with molecular-beam epitaxy. We monitor, at different times and temperatures, the diffusion enhancement or retardation of deep B or Sb marker layers next to a 1.1×1020 cm−3 Sb box, as well as the formation of Sb precipitates within the box. It is concluded that the interstitials are not associated with precipitate growth, but that they are generated from formation of Sb-vacancy complexes, primarily involving 2 Sb atoms. © 2000 American Institute of Physics.
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61.72.J- Point defects and defect clusters
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
81.05.Cy Elemental semiconductors
64.75.-g Phase equilibria
61.72.Yx Interaction between different crystal defects; gettering effect

Radiotracer identification of a Ta-related deep level in 4H–SiC

J. Grillenberger, N. Achtziger, R. Sielemann, and W. Witthuhn

J. Appl. Phys. 88, 3260 (2000); http://dx.doi.org/10.1063/1.1289484 (6 pages) | Cited 7 times

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To identify tantalum-related deep levels, deep level transient spectroscopy (DLTS) measurements were performed on Ta-implanted n-type 4H–silicon carbide. The DLTS spectra of samples implanted with stable 181Ta exhibit one dominating peak representing a trap energy of about ET=EC−0.67 eV. Due to superimposed signals of intrinsic defects, the exact value depends on the annealing conditions. To achieve a definite assignment of this peak to tantalum, the radioactive isotope 177Ta was recoil implanted into n-type 4H–SiC. DLTS spectra measured subsequently during the nuclear decay of 177Ta to 177Hf reveal a trap with decreasing concentration according to the elemental transmutation. This effect definitely proofs the identification of a Ta-related level at 0.68 eV below the conduction band edge. There is no further DLTS peak of time-dependent height, indicating that there is no deep level of Hf in the part of the band gap investigated. © 2000 American Institute of Physics.
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71.55.Ht Other nonmetals
61.72.up Other materials

Ultrasonic attenuation in Zr41Ti14Cu12.5Ni10−xBe22.5Cx (x=0,1) bulk metallic glasses under high pressure

Wei Hua Wang, R. J. Wang, F. Y. Li, M. X. Pan, Z. C. Qin, D. Q. Zhao, Y. X. Zhuang, and Y. Zhang

J. Appl. Phys. 88, 3266 (2000); http://dx.doi.org/10.1063/1.1289237 (3 pages) | Cited 1 time

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The pressure dependence of ultrasonic attenuation in Zr41Ti14Cu12.5Ni10−xBe22.5Cx (x=0,1) bulk metallic glasses has been studied up to 0.5 GPa by using a pulse echo overlap method. The effect of carbon addition on the attenuation is also investigated. Some unique characteristics of the ultrasonic attenuation are found and compared with those of other glasses. The origin of the anomalous attenuation behavior is discussed. © 2000 American Institute of Physics.
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62.65.+k Acoustical properties of solids
81.05.Kf Glasses (including metallic glasses)
62.50.-p High-pressure effects in solids and liquids

Preparation and transport properties of polycrystalline Bi and Bi–SiO2 nanocomposites

F. Brochin, B. Lenoir, X. Devaux, R. Martin-Lopez, and H. Scherrer

J. Appl. Phys. 88, 3269 (2000); http://dx.doi.org/10.1063/1.1289079 (7 pages) | Cited 11 times

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Bismuth–silica nanocomposites and polycrystalline bismuth were prepared via powder metallurgy in order to study the influence of silica inclusions on the thermoelectric properties of bismuth. Bi–SiO2 powders containing from 0.5 to 15 vol. % of silica and pure Bi powders were produced by an arc-plasma processing. Transmission electron microscopy investigations revealed the presence of a nanometric silica shell around the Bi grains. The powders were cold pressed and sintered close to the melting temperature of bismuth. The bulk microstructures are very different for the bismuth and the Bi–SiO2 nanocomposites because silica, which is primarily dispersed at grain boundaries, inhibits the grain growth during sintering. The electrical resistivity was measured from 5 to 300 K, while the thermoelectric power and the thermal conductivity were measured from 65 to 300 K on both polycrystalline bismuth and Bi–SiO2 samples containing 0.5, 4, and 15 vol. % of silica, respectively. The transport properties are mainly discussed with regard to the microstructures. In spite of a strong reduction of the thermal conductivity for the nanocomposites, the thermoelectric figure of merit is not improved compared to bismuth due to a dominating concurrent increase of the electrical resistivity resulting from a finite-size effect. © 2000 American Institute of Physics.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.80.Tm Composite materials
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Mh Cermets, ceramic and refractory composites
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
72.20.Fr Low-field transport and mobility; piezoresistance

Crystallization kinetics and structural aspects of TeGaSn amorphous alloys

M. Fontana, B. Arcondo, M. T. Clavaguera-Mora, N. Clavaguera, and J. M. Greneche

J. Appl. Phys. 88, 3276 (2000); http://dx.doi.org/10.1063/1.1288691 (9 pages) | Cited 1 time

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Cast and rapidly quenched samples of ternary system GaTeSn in the Te rich corner were studied by means of x-ray diffraction, 119Sn Mössbauer spectrometry at 77 K, and differential scanning calorimetry. The crystallization products, the activation energy, the crystallization enthalpy, and the crystallization and glass temperatures of the amorphous phases are reported. The addition of Sn to GaTe increases the glass forming range of the binary system and the thermal stability of the amorphous phase. In the crystalline samples the divalent Sn atoms are always surrounded by Te in octahedrally coordinated environments. It is observed that the addition of Sn, above a threshold concentration, stabilizes the high temperature phase Ga2Te5 at room temperature. The Mössbauer spectra obtained on amorphous samples indicate two kinds of environments at Sn sites: one ascribed to the octahedral coordination, the other one to Sn surrounded by Te with tetrahedral coordination. The Mössbauer results are related to the calorimetric measurements: the role of Sn to stabilize the amorphous structure is discussed. The first steps of the crystallization of pure Te are modeled assuming homogeneous nucleation followed by three-dimensional interface-controlled growth of the crystal. © 2000 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
65.20.-w Thermal properties of liquids
65.40.gd Entropy
76.80.+y Mössbauer effect; other γ-ray spectroscopy
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Raman spectra of Ge nanocrystals embedded into SiO2

A. V. Kolobov, Y. Maeda, and K. Tanaka

J. Appl. Phys. 88, 3285 (2000); http://dx.doi.org/10.1063/1.1289818 (5 pages) | Cited 9 times

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We start with an analysis of the Raman spectra of Ge nanocrystals obtained in previous studies and demonstrate that in many cases the observed experimental peak attributed to Ge in fact originates from the Si substrate. We further compare various experimental ways to separate the Ge signal from that of the substrate and suggest optimum conditions for such measurements. Finally, we demonstrate that upon the annealing of an amorphous Ge–Si–O film, Ge nanocrystals are formed. The nanocrystals are randomly oriented and Ge–Si mixing takes place only at the interface with the Si substrate. © 2000 American Institute of Physics.
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78.30.Am Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses

The shock Hugoniot of the intermetallic alloy Ti–46.5Al–2Nb–2Cr

Jeremy Millett, George T. (Rusty) Gray, and Neil Bourne

J. Appl. Phys. 88, 3290 (2000); http://dx.doi.org/10.1063/1.1288500 (5 pages) | Cited 16 times

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Plate impact experiments were conducted on a γ-titanium aluminide (TiAl) based ordered intermetallic alloy. Stress measurements were recorded using manganin stress gauges supported on the back of TiAl targets using polymethylmethacrylate windows. The Hugoniot in stress-particle velocity space for this TiAl alloy was deduced using impedance matching techniques. The results in this study are compared to the known Hugoniot data of the common alpha-beta engineering Ti-based alloy Ti-6Al–4V. The results of the current study on the intermetallic alloy TiAl support that TiAl possesses a significantly higher stress for a given particle velocity than the two-phase Ti–6Al–4V alloy. © 2000 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
64.30.-t Equations of state of specific substances

High spatial resolution thermal conductivity and Raman spectroscopy investigation of hydride vapor phase epitaxy grown n-GaN/sapphire(0001): Doping dependence

D. I. Florescu, V. M. Asnin, Fred H. Pollak, R. J. Molnar, and C. E. C. Wood

J. Appl. Phys. 88, 3295 (2000); http://dx.doi.org/10.1063/1.1289072 (6 pages) | Cited 30 times

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We have measured high resolution thermal conductivity (κ) and Raman spectra {E2 mode [high frequency], A1 mode [longitudinal optical (LO)], and high frequency LO-plasmon coupled mode [LPP+]} at 300 K of three series of n-GaN/sapphire (0001) samples fabricated by hydride vapor phase epitaxy (HVPE). The former was determined with a scanning thermal microscope while the latter was obtained using a micro-Raman system, both having a spatial resolution of ≈2–3 μm. For all three sets of samples the thermal conductivity decreased linearly with log n, about a factor of two decrease in κ for every decade increase in n. Also, we found a correlation between film thickness and improved thermal conductivity. Furthermore, κ≈1.95 W/cm K for one of the most lightly doped samples (≈6.9×1016 cm−3), higher than previously reported κ≈1.7–1.8 W/cm K on lateral epitaxial overgrown (LEO) material with n≈(1–2)×1017 cm−3 [V. M. Asnin et al., Appl. Phys. Lett. 75, 1240 (1999)], κ=1.55 W/cm K on LEO samples using a third-harmonic technique [C. Y. Luo et al., Appl. Phys. Lett. 75, 4151 (1999)], and κ≈1.3 W/cm K on a HVPE sample [E. K. Sichel and J. I. Pankove, J. Phys. Chem. Solids 38, 330 (1977)]. The carrier concentration dependence of κ is similar to that of other semiconductors in a comparable temperature range. On a log–log scale the linewidth of the observed E2 Raman mode remained constant up to n≈1×1018 cm−3 and then increased linearly. The carrier concentration obtained from the LPP+ mode is less than the Hall effect determination. This is probably due to the fact that the latter measures n in both the epilayer and GaN/sapphire interfacial region [D. C. Look and R. J. Molnar, Appl. Phys. Lett. 70, 3377 (1997); W. Götz et al., Appl. Phys. Lett. 72, 1214 (1998)] while the Raman signal is primarily from the epilayer. © 2000 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
78.66.Fd III-V semiconductors
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
63.20.kk Phonon interactions with other quasiparticles
78.30.Fs III-V and II-VI semiconductors

Modeling electromigration-induced stress evolution and drift kinetics with a stress-dependent diffusivity

S. A. Chizhik, A. A. Matvienko, A. A. Sidelnikov, and J. Proost

J. Appl. Phys. 88, 3301 (2000); http://dx.doi.org/10.1063/1.1287760 (9 pages) | Cited 3 times

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Clement and Thompson have justified that it is necessary to take into account the stress dependence of atomic mobility when describing stress evolution in a metal conductor caused by electromigration [J. J. Clement and C. V. Thompson, J. Appl. Phys. 78, 900 (1995)]. In the present contribution the role of this dependence is considered in more detail, leading to qualitatively new results concerning stress evolution and drift kinetics. The stationary stress distribution over the length of the elastic zone of the conductor was shown to be nonlinear and asymmetrical at superthreshold conditions, with the zone of compressive stress being more extended than that of tensile stress. This also results in an asymmetrical pattern for plastic deformation, the hillocking zone being more extended than the voiding region at the cathode. The drift rate was shown to achieve its maximum value during the nonstationary stage of stress evolution and then to drop down to its stationary value. The duration of the nonstationary stage of stress evolution is proportional to the conductor length and inversely proportional to the current density. This is essentially different from the result obtained in all previous works. Our model also predicts that for conductors with a length much longer than the critical one, the nonstationary stage of stress evolution corresponds to a quasistationary stage for drift kinetics, during which a constant drift rate is observed. Finally, we will consider the consequences of taking into account the stress dependence of mobility when describing the effects of passivation and thermal stress on drift kinetics. © 2000 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
81.65.Rv Passivation
66.30.Dn Theory of diffusion and ionic conduction in solids

Optical absorption and Hall effect in (220) and (400) oriented polycrystalline silicon films

T. Kamiya, K. Nakahata, T. Sameshima, T. Watanabe, T. Mouri, and I. Shimizu

J. Appl. Phys. 88, 3310 (2000); http://dx.doi.org/10.1063/1.1288170 (6 pages) | Cited 8 times

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Carrier transport properties were investigated for polycrystalline silicon (poly-Si:H:F) films fabricated at 300 °C by 100 MHz plasma enhanced chemical vapor deposition from gaseous mixture of SiF4 and H2. Analysis of free carrier optical absorption (FCA) revealed that 1 μm thick (400) oriented phosphorus-doped poly-Si:H:F films with a carrier concentration of 5×1019 cm−3 had the average electron mobility in crystalline grains at 40 cm2/V s, while the electron mobility of the (220) oriented phosphorus-doped poly-Si:H:F films was only 12 cm2/V s. These results indicated that (400) oriented poly-Si:H:F films had excellent quality crystalline grains. Analyses of the FCA combined with Hall effect current measurements revealed that the electrical conductivity at grain boundaries of top doped films increased as the underlying film thickness increased from 0 to 280 nm for (400) oriented phosphorus-doped/undoped double layered samples, but grain boundaries still acted as large resistive regions limiting the effective conductivity. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.Mm Grain and twin boundaries
73.50.Dn Low-field transport and mobility; piezoresistance
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Theory of feature broadening in direct-write optical lithography

R. Mark Bradley, Andrea Eschmann, and Siu Au Lee

J. Appl. Phys. 88, 3316 (2000); http://dx.doi.org/10.1063/1.1289475 (7 pages) | Cited 7 times

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In direct-write optical lithography (DWOL), an intense, nearly-resonant standing light wave of wavelength λ is used to focus a collimated atomic beam. In this way, a grating structure is deposited on the substrate. We argue that during DWOL adatoms move primarily as a result of collisions with incident atoms. The resulting equation of motion for the film surface describes the way in which the features smooth and broaden as the film thickness increases. We find that as the film thickness grows large, the topography tends to a steady state form with amplitude proportional to λ4. No matter how well focused the incident atomic flux is, in the steady state the surface corrugations have a full-width-at-half-maximum that is greater than 45% of the peak-to-peak distance. © 2000 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)

Anisotropic strain in nitrided austenitic stainless steel

S. Mändl and B. Rauschenbach

J. Appl. Phys. 88, 3323 (2000); http://dx.doi.org/10.1063/1.1289520 (7 pages) | Cited 32 times

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Nitrogen treatment of austenitic stainless steels at temperatures around 300–400 °C leads to the formation of a hard and corrosion resistant phase called expanded austenite. The most puzzling feature of this phase is an anisotropic lattice expansion where the expansion along the (100) is about 20% larger than for the (111) direction. In this report an investigation of the lattice expansion of austenitic stainless steel after nitrogen plasma immersion ion implantation by x-ray diffraction is presented. Pole figure measurements as well as θ/2θ scans at different polar angles were performed. Comparing the data with three different structural models, fcc, tetragonal, and triclinic, it can be concluded that none of them yields good agreement with the data, so that the crystallographic characterization is still open. However, a model for the atomic origin of the observed lattice expansion based on the anisotropic Young’s modulus, which is found for every fcc metal, is presented, showing good agreement with the measured data as well as data taken from the literature. © 2000 American Institute of Physics.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
81.05.Bx Metals, semimetals, and alloys
61.72.up Other materials
81.65.Kn Corrosion protection
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Adhesion of micrometer-sized polymer particles under a scanning electron microscope

Hideki T. Miyazaki, Yasushi Tomizawa, Shigeki Saito, Tomomasa Sato, and Norio Shinya

J. Appl. Phys. 88, 3330 (2000); http://dx.doi.org/10.1063/1.1288006 (11 pages) | Cited 11 times

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Techniques for manipulating micrometer-sized objects and assembling them into a microstructure in a scanning electron microscope (SEM) are important for research related to microscale physics. It has been demonstrated that micro-objects ranging from sub-μm to several 10 μm can be freely manipulated by adhering them to the tip of a probe. However, the present micromanipulation technique in a SEM is still inefficient, because little is known about the adhesion mechanisms of micro-objects in a SEM environment. In this study, the adhesion forces of micrometer-sized polymer particles deposited on a substrate during SEM observation have been directly measured. The adhesion forces between a polyvinyltoluene sphere of 1 μm radius deposited on a Au substrate, and a glass probe with a hemispherical tip with a typical radius of 0.75 μm coated with Au, were found to show various complicated behaviors. An irreversible increase in the adhesion forces initiated by the electron-beam (EB) irradiation, and the dependence of the adhesion on the electron flux and the probe voltage were observed. On the other hand, the dependence on the pressing force and the probe diameter, predicted by a conventional theory, was not confirmed. This observed complicated phenomena were successfully explained using the model based on the formation of an electric double layer at the contact interface by the EB irradiation, and the successive progress of creep deformation. © 2000 American Institute of Physics.
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61.41.+e Polymers, elastomers, and plastics
62.20.Hg Creep
06.60.Sx Positioning and alignment; manipulating, remote handling
07.10.Cm Micromechanical devices and systems
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.35.Gy Mechanical properties; surface strains
81.40.Lm Deformation, plasticity, and creep

Morphological aspects of continuous and modulated epitaxial growth of (GaIn)P

Jiechao Jiang, Andreas K. Schaper, Zeljko Spika, and Wolfgang Stolz

J. Appl. Phys. 88, 3341 (2000); http://dx.doi.org/10.1063/1.1288698 (8 pages) | Cited 3 times

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In contrast to the continuous metalorganic vapor phase epitaxy of (GaIn)P, a modulated growth process yields higher degrees of superlattice ordering along with a more complex domain hierarchy. Using cross-sectional as well as plan view transmission electron microscopy, we have studied the two-dimensional contrast modulation which occurs at a deposition cycle of 1 monolayer (ML) GaP/1 ML InP. The interlocking modulation waves create a columnar domain morphology coexisting with an antiphase domain structure. The lateral size of the domain columns ranges from 25 to 50 nm depending on the misorientation of the GaAs substrate. Dark-field imaging and atomic force microscopy investigations provided clear evidence of stress relief involved in the domain formation. At zero off cut, complementary single ordering variant superdomains are formed in parallel with faceting of the growth front. The 4°–6° B facets appear the energetically more stable growth planes compared to the exact (001) crystallographic plane. © 2000 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.B- Structure of clean surfaces (and surface reconstruction)
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations

Use of necked-down areas to control nucleation site and direction of solidification of polycrystalline silicon using excimer laser crystallization

Akito Hara and Nobuo Sasaki

J. Appl. Phys. 88, 3349 (2000); http://dx.doi.org/10.1063/1.1288502 (5 pages) | Cited 4 times

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We successfully controlled the nucleation site and direction of solidification of polycrystalline silicon films by irradiation with an excimer laser. An amorphous silicon island, including a gradually narrowing region, was formed on a quartz glass substrate. The gradually narrowing region intentionally included a necked-down area. The sidewall and top of the amorphous silicon island were covered by a thick polycrystalline silicon film. A single pulse of excimer laser irradiation from the back through the quartz glass substrate was used to melt the island. This method resulted in lateral growth from the inner region of the island toward the outer region, at the edges of the island. When the width of the necked-down area was twice the distance of the lateral growth, only one nucleus was formed in the necked-down region. Solidification from the nucleus toward the region with the narrower width then occurred in an area 2 μm wide and 3 μm long. This method enabled position-controlled formation of large grains. © 2000 American Institute of Physics.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
42.62.-b Laser applications
64.70.D- Solid-liquid transitions
81.30.Fb Solidification

Crystal morphology and phase purity of diamond crystallites during bias enhanced nucleation and initial growth stages

C. Sun, W. J. Zhang, N. Wang, C. Y. Chan, I. Bello, C. S. Lee, and S. T. Lee

J. Appl. Phys. 88, 3354 (2000); http://dx.doi.org/10.1063/1.1289071 (7 pages) | Cited 16 times

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The crystal morphologies and phase composition of diamond crystallites during bias enhanced nucleation and initial growth stages in microwave plasma chemical vapor deposition were investigated. Diamond nuclei were first formed in the central regions of substrates and then propagated to the sample edges. During the course of bias nucleation, excessive ion bombardment induced secondary nucleation sites on the already formed nuclei. The secondary nucleation deteriorated the overall alignment of the growing crystals. Hence, the elimination of secondary nucleation and homogeneous nucleation over substrates are fundamental requirements for the deposition of large-area uniformly oriented diamond films. Decreasing reactant pressure was found to be effective for improving plasma homogeneity and consequently nucleation uniformity. The results of bias enhanced nucleation within a pressure range from 8 to 20 Torr showed that the lower pressure of reactants enlarged the area of oriented diamond films. However, the optimum bias and duration of nucleation was found to be specific for each pressure. © 2000 American Institute of Physics.
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81.05.ub Fullerenes and related materials
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology

Anisotropic scaling of hard disk surface structures

T. Karabacak, Y.-P. Zhao, T. Liew, G.-C. Wang, and T.-M. Lu

J. Appl. Phys. 88, 3361 (2000); http://dx.doi.org/10.1063/1.1289231 (6 pages) | Cited 4 times

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We present a detailed study of the surface roughness of a computer hard disk using atomic force microscopy and light scattering. The power spectrum density analysis showed that the surface possesses an anisotropic scaling behavior and has both random roughness and periodic roughness components. Quantitative anisotropic correlation length (ξ) and roughness exponent (α) for the directions parallel and perpendicular to the grooves are obtained. A novel in-plane (measurement parallel to the sample surface) light scattering technique is shown to be particularly useful for the analysis of the rough surface parallel to the grooves. © 2000 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Silicon-induced faceting of vicinal GaAs(001)

S. Brennan, G. B. Stephenson, P. H. Fuoss, D. W. Kisker, C. Lavoie, and K. L. Evans-Lutterodt

J. Appl. Phys. 88, 3367 (2000); http://dx.doi.org/10.1063/1.1289482 (10 pages) | Cited 1 time

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This article presents in situ x-ray diffraction studies of the evolution of the morphology of 0.5°-miscut vicinal GaAs(001) surfaces during and following undoped and silicon-doped growth using organometallic vapor-phase epitaxy. Undoped growth leads to ordered monolayer steps. However, growth in the presence of silicon destabilizes this surface morphology and triggers faceting. Coarsening of the facet size proceeds even after the growth has stopped and results in large singular regions of GaAs(001) surface separated by step bunches. Dosing the surface with silicon without growing material does not trigger faceting. Growth of undoped GaAs on faceted surfaces recovers the initial state of ordered monolayer steps. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.uj III-V and II-VI semiconductors

Failure mechanism of Ta diffusion barrier between Cu and Si

Tomi Laurila, Kejun Zeng, Jorma K. Kivilahti, Jyrki Molarius, and Ilkka Suni

J. Appl. Phys. 88, 3377 (2000); http://dx.doi.org/10.1063/1.1288692 (8 pages) | Cited 33 times

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The reaction mechanisms in the Si/Ta/Cu metallization system and their relation to the microstructure of thin films are discussed on the basis of experimental results and the assessment of the ternary Si–Ta–Cu phase diagram at 700 °C. With the help of sheet resistance measurements, Rutherford backscattering spectroscopy, x-ray diffraction, a scanning electron microscope, and a transmission electron microscope, the Ta barrier layer was observed to fail at temperatures above 650 °C due to the formation of TaSi2, the diffusion of Cu through the silicide layer, and the resulting formation of Cu3Si precipitates. However, in order for the TaSi2 phase to form first, the Ta diffusion barrier layer must be thick enough (e.g., 50–100 nm) to prevent Cu diffusion into the Si substrate up to the temperature of TaSi2 formation (∼650 °C). Independent of the Ta layer thickness, Cu3Si was present as large nodules, whereas the TaSi2 existed as a uniform layer. The resulting reaction structure was found to be in local equilibrium on the basis of the assessed Si–Ta–Cu phase diagram at 700 °C, and therefore no further reactions were expected. The role of oxygen was also found to be important in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer. © 2000 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
64.70.-p Specific phase transitions
66.30.Ny Chemical interdiffusion; diffusion barriers
64.75.-g Phase equilibria

Local analysis of the morphological properties of single-wall carbon nanotubes by Fresnel projection microscopy

Vu Thien Binh, P. Vincent, F. Feschet, and J.-M. Bonard

J. Appl. Phys. 88, 3385 (2000); http://dx.doi.org/10.1063/1.1289786 (7 pages) | Cited 10 times

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Direct observations of free-standing single-wall carbon nanotubes (SWNTs), either as individual tubes or bundled in ropes, are performed using a Fresnel projection microscope (FPM). The analysis is done with the support of systematic numerical simulations of Fresnel diffraction images. The images of individual SWNTs are characterized by bright lines, while semitransparency wire fringe patterns are observed for thin ropes. Ropes with a higher number of individual tubes present the conventional Fresnel fringe patterns of an opaque wire. This differentiation in the FPM images between fringe patterns and bright line patterns allows for an easy detection of individual SWNTs. FPM also allows us to detect the presence of localized defects along SWNTs, and, in particular, the characterization of nanotube junctions. Although the exact structure of the junctions cannot be deduced presently from the images they, at least, indicate the presence of strong electric fields associated with the structural connections between the SWNTs. © 2000 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
61.72.-y Defects and impurities in crystals; microstructure

Structural and optical properties of self-assembled InAs/GaAs quantum dots covered by InxGa1−xAs (0⩽x⩽0.3)

H. Y. Liu, X. D. Wang, J. Wu, B. Xu, Y. Q. Wei, W. H. Jiang, D. Ding, X. L. Ye, F. Lin, J. F. Zhang, J. B. Liang, and Z. G. Wang

J. Appl. Phys. 88, 3392 (2000); http://dx.doi.org/10.1063/1.1288225 (4 pages) | Cited 23 times

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Optical and structural investigations of InAs quantum dots (QDs) covered by InxGa1−xAs (0⩽x⩽0.3) overgrowth layer have been systematically reported. The decrease of strain in the growth direction of InAs quantum dots covered by InGaAs layer instead of GaAs is demonstrated by transmission electron microscopy experiments. In addition, the atomic force microscopy measurement shows that the surface of InAs islands with 3-nm-thick In0.2Ga0.8As becomes flatter. However, the InGaAs islands nucleate on the top of quantum dots during the process of InAs islands covered with In0.3Ga0.7As. The significant redshift of the photoluminescence peak energy and reduction of photoluminescence linewidth of InAs quantum dots covered by InGaAs are observed. The energy gap change of InAs QDs covered by InGaAs could be explained in terms of reducing strain, suppressing compositional mixing, and increasing island height. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.55.Cr III-V semiconductors
68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Gy Mechanical properties; surface strains

Photoluminescence from silicon nano-particles synthesized by laser-induced decomposition of silane

S. Botti, R. Coppola, F. Gourbilleau, and R. Rizk

J. Appl. Phys. 88, 3396 (2000); http://dx.doi.org/10.1063/1.1288228 (6 pages) | Cited 22 times

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This work deals with photoluminescence study of silicon nanoparticles produced by CO2-laser-induced decomposition of SiH4 mixed to helium in a controlled atmosphere reactor. By adjusting the pressure of both reactor and precursor gas and its dilution rate in helium, we were able to control, to a certain extent, the silicon growth rate and hence the particle diameter. This latter was determined by both small angle neutron scattering techniques and high resolution transmission electron microscopy observations. Particles with mean diameter ranging between 3 and 10 nm were submitted to photoluminescence and infrared absorption spectroscopy measurements. The photoluminescence spectra revealed two main peaks at about 1.7 and 2.1 eV. The peak position of the former was insensitive to the change of particle size, while its intensity increased after oxidation. The latter showed, however, a slight size dependence but had undergone a drastic decrease after oxidation. These features enabled us to ascribe the red peak (1.7 eV) to some radiative surface defect, while the yellow peak (2.1 eV) appeared consistent with an emission from an oxygen-related defect such as the nonbridging oxygen hole center. © 2000 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.66.Vs Fine-particle systems
71.55.Cn Elemental semiconductors
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Fg Pulsed laser ablation deposition
78.30.Am Elemental semiconductors and insulators
73.20.Hb Impurity and defect levels; energy states of adsorbed species
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