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12 Feb 2001

Volume 78, Issue 7, pp. 853-1016

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Atomic-level study of the robustness of the Si(100)-2×1:H surface following exposure to ambient conditions

M. C. Hersam, N. P. Guisinger, J. W. Lyding, D. S. Thompson, and J. S. Moore

Appl. Phys. Lett. 78, 886 (2001); http://dx.doi.org/10.1063/1.1348322 (3 pages) | Cited 15 times

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The in situ hydrogen-passivated Si(100)-2×1 surface is characterized with x-ray photoelectron spectroscopy (XPS) and ultra-high-vacuum scanning tunneling microscopy (STM) following exposure to ambient conditions. The XPS measurements illustrate the chemical inertness of this surface as the onset of oxidation is not observed for the first 40 h of ambient exposure. After 15 min of contact with atmospheric conditions, the STM images reveal that the Si(100)-2×1:H surface remains atomically pristine. This exceptional stability is of relevance to a wide variety of applications that require ultrapure Si(100) substrates (e.g., microelectronics, semiconductor processing, nanofabrication, etc.). © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Rv Passivation
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Mq Oxidation

Effect of heating ramp rates on transient enhanced diffusion in ion-implanted silicon

G. Mannino, P. A. Stolk, N. E. B. Cowern, W. B. de Boer, A. G. Dirks, F. Roozeboom, J. G. M. van Berkum, P. H. Woerlee, and N. N. Toan

Appl. Phys. Lett. 78, 889 (2001); http://dx.doi.org/10.1063/1.1347397 (3 pages) | Cited 10 times

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Boron marker-layer structures have been used to analyze the heating ramp-rate dependence of transient enhanced dopant diffusion (TED) during rapid thermal annealing of Si implantation damage. The study uses short anneals with heating ramp rates in the range 0.1–350 °C/s, and peak temperatures in the range 900–1100 °C. Increasing the ramp rate is found to reduce the amount of profile broadening caused by TED, as well as reducing the smaller amount of normal “thermal-equilibrium” diffusion which is related to thermal budget. The results show why high ramp rates lead to improved B-implant activation and junction-depth control in Si devices. An Ostwald ripening model of interstitial-cluster evolution describes the detailed trends in the data and predicts further improvements in the case of ultrarapid annealing. © 2001 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
66.30.J- Diffusion of impurities
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.J- Point defects and defect clusters

Critical thickness for transformation of epitaxially stabilized cubic AlN in superlattices

I. W. Kim, Quan Li, L. D. Marks, and S. A. Barnett

Appl. Phys. Lett. 78, 892 (2001); http://dx.doi.org/10.1063/1.1345831 (3 pages) | Cited 31 times

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The epitaxial stabilization and transformation of cubic AlN layers in AlN/VN and AlN/TiN superlattices, grown by reactive sputtering on MgO (001), is described. In AlN/VN, the critical AlN thickness lC for transformation from cubic to hexagonal increased from ≈ 3.0 to >4 nm when the VN superlattice layer thickness was increased from 2.0 to 6.0 nm. The effect of lattice mismatch was observed by comparing AlN/VN (mismatch = 1.46%) and AlN/TiN (mismatch = 3.84%). The lC values were smaller, 2–2.5 nm, for the larger mismatch AlN/TiN system. The dependence of lC on the lattice mismatch and stabilizing layer thickness is discussed based on models of epitaxial stabilization. © 2001 American Institute of Physics.
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68.65.Cd Superlattices
81.07.St Quantum wells
81.15.Cd Deposition by sputtering
64.70.K- Solid-solid transitions
68.37.Lp Transmission electron microscopy (TEM)

Elastic strain relief in nitridated Ga metal buffer layers for epitaxial GaN growth

Yihwan Kim, Noad A. Shapiro, Henning Feick, Robert Armitage, Eicke R. Weber, Yi Yang, and Franco Cerrina

Appl. Phys. Lett. 78, 895 (2001); http://dx.doi.org/10.1063/1.1347016 (3 pages) | Cited 8 times

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Gallium nitride epitaxial layers were grown on sapphire by molecular-beam epitaxy using nitridated gallium metal films as buffer layers. The mechanical properties of the buffer layers were investigated and correlated with their chemical composition as determined by synchrotron radiation photoelectron spectroscopy. Biaxial tension experiments were performed by bending the substrates in a pressure cell designed for simultaneous photoluminescence measurements. The shift of the excitonic luminescence peak was used to determine the stress induced in the main GaN epilayer. The fraction of stress transferred from substrate to main layer was as low as 27% for samples grown on nitridated metal buffer layers, compared to nearly 100% for samples on conventional low-temperature GaN buffer layers. The efficiency of stress relief increased in proportion to the fraction of metallic Ga in the nitridated metal buffer layers. These findings suggest GaN films containing residual metallic Ga may serve as compliant buffer layers for heteroepitaxy. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
68.60.Bs Mechanical and acoustical properties
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology
62.20.F- Deformation and plasticity
79.60.Dp Adsorbed layers and thin films
71.35.-y Excitons and related phenomena

Dispersion and pulse-duration dependence of the nonlinear optical response of Gd2 at C80

Gul Yaglioglu, Robinson Pino, Roger Dorsinville, and J. Z. Liu

Appl. Phys. Lett. 78, 898 (2001); http://dx.doi.org/10.1063/1.1327283 (3 pages) | Cited 3 times

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Single-beam z-scan and transient absorption experiments were carried out between 400 and 1000 nm in Gd2 at C80 thin films and solutions. The third-order nonlinearity was large, negative, and strongly dependent on pulse duration and wavelength. Transient absorption results suggest that the fast nonlinear response is enhanced by two-photon-induced ground-state absorption and excited-state bleaching effects. © 2001 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
78.66.Tr Fullerenes and related materials
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Patterned selective growth of carbon nanotubes and large field emission from vertically well-aligned carbon nanotube field emitter arrays

Jung Inn Sohn, Seonghoon Lee, Yoon-Ho Song, Sung-Yool Choi, Kyoung-Ik Cho, and Kee-Soo Nam

Appl. Phys. Lett. 78, 901 (2001); http://dx.doi.org/10.1063/1.1335846 (3 pages) | Cited 80 times

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We have grown well-aligned carbon nanotube arrays by thermal chemical vapor deposition at 800 °C on Fe nanoparticles deposited by a pulsed laser on a porous Si substrate. We also attain a selective growth of carbon nanotubes on a patterned Fe film on Si substrates in terms of pulsed laser deposition and a liftoff patterning method. Field emission measurement has been made on the carbon nanotube (CNT)-cathode diode device at room temperature and in a vacuum chamber below 10−6 Torr. The distance between the CNT cathode and the anode is 60 μm and is kept through an insulating spacer of polyvinyl film. The measured field emitting area is 4.0×10−5 cm2. Our vertically well-aligned carbon nanotube field emitter arrays on the Si-wafer substrate emit a large current density as high as 80 mA/cm2 at 3 V/μm. The transmission electron microscope image shows that they are multiwalled and bamboolike structures and that the tips of some of the carbon nanotube emitters are open. The open tip structure of our CNTs and their good adhesion via Fe nanoparticles to the Si substrate are part of the reason why we can attain a large field emission current density within a low field. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.De Nanotubes
85.35.Kt Nanotube devices
85.45.Db Field emitters and arrays, cold electron emitters
71.20.Tx Fullerenes and related materials; intercalation compounds
81.05.ub Fullerenes and related materials
85.65.+h Molecular electronic devices
79.70.+q Field emission, ionization, evaporation, and desorption
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.67.Ch Nanotubes
68.35.Np Adhesion

Mechanisms for very long electromigration lifetime in dual-damascene Cu interconnections

C-K. Hu, L. Gignac, S. G. Malhotra, R. Rosenberg, and S. Boettcher

Appl. Phys. Lett. 78, 904 (2001); http://dx.doi.org/10.1063/1.1347400 (3 pages) | Cited 34 times

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Electromigration in 0.27 μm wide Cu damascene interconnections has been investigated. The results show that the electromigration time to failure of Cu interconnections is greatly influenced by the thickness of the metal liner at the contact between the via and underlying line. A remarkably long lifetime was achieved when a 3 nm thick liner (at the via/metal line interface) was used, since the abrupt mass flux divergence at this interface normally seen is greatly diminished. Voids were found in the regions where there was no electric field and on the bamboo Cu grain structure. Void formation is explained by the effect of a vacancy wind. © 2001 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.J- Point defects and defect clusters

Stacking fault effects in pure and n-type doped GaAs

T. M. Schmidt, J. F. Justo, and A. Fazzio

Appl. Phys. Lett. 78, 907 (2001); http://dx.doi.org/10.1063/1.1347005 (3 pages) | Cited 6 times

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Using ab initio total-energy calculations, we investigate the effects of stacking faults on the properties of dopants in pure and n-type doped GaAs. We find that the Si impurity segregates towards a GaAs stacking fault. A Si atom at a Ga site in the stacking fault, in either a neutral or a negative charge state, is energetically favorable as compared to a Si atom at a Ga site in a crystalline environment by as much as 0.2 eV. We also find that a Si impurity in the stacking fault cannot occupy metastable positions, as occurs in the formation of DX centers. Thus, stacking faults can prevent the formation of DX-like centers in GaAs. © 2001 American Institute of Physics.
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71.55.Eq III-V semiconductors
61.72.Nn Stacking faults and other planar or extended defects
71.15.-m Methods of electronic structure calculations
71.15.Nc Total energy and cohesive energy calculations

Energy-dependent anisotropic deformation of colloidal silica particles under MeV Au irradiation

T. van Dillen, A. Polman, W. Fukarek, and A. van Blaaderen

Appl. Phys. Lett. 78, 910 (2001); http://dx.doi.org/10.1063/1.1345827 (3 pages) | Cited 20 times

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Spherical silica colloids with a diameter of 1.0 μm, made by wet chemical synthesis, were irradiated with 2–16 MeV Au ions at fluences in the range (2–11)×1014 cm−2. The irradiation induces an anisotropic plastic deformation turning the spherical colloids into ellipsoidal oblates. After 16 MeV Au irradiation to a fluence of 11×1014 cm−2, a size aspect ratio of 5.0 was achieved. The size polydispersity (∼3%) remains unaffected by the irradiation. The transverse diameter increases exponentially with ion fluence. By performing measurements as a function of ion energy at a fixed fluence, it is concluded that the transverse diameter increases linearly with the average electronic energy loss above a threshold value of ∼0.6 keV/nm. Nonellipsoidal colloids are observed in the case where the projected ion range is smaller than the colloid diameter. The data provide strong support for the thermal spike model of anisotropic deformation. © 2001 American Institute of Physics.
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82.70.Dd Colloids
62.20.F- Deformation and plasticity
61.80.Jh Ion radiation effects
61.82.Ms Insulators

Interaction of vacancies with interstitial oxygen in silicon

R. A. Casali, H. Rücker, and M. Methfessel

Appl. Phys. Lett. 78, 913 (2001); http://dx.doi.org/10.1063/1.1347014 (3 pages) | Cited 14 times

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Based on first-principle total-energy calculations, we show that the majority of vacancies are trapped by interstitial oxygen in silicon wafers with a typical oxygen concentration of about 1018 cm−3. Vacancies and interstitial oxygen form so called A centers with a binding energy of 1.7±0.4 eV. As a consequence, the density of bound vacancies exceeds the equilibrium density of free vacancies by several orders of magnitude and effective vacancy diffusion coefficients in Si are reduced in comparison to the diffusion coefficient of free vacancies. However, we find that trapping of vacancies alone cannot account for the large discrepancies between previously reported diffusion coefficients for vacancies. © 2001 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
71.55.Cn Elemental semiconductors
66.30.J- Diffusion of impurities
61.72.J- Point defects and defect clusters

Strong in-plane birefringence of spatially nanostructured silicon

D. Kovalev, G. Polisski, J. Diener, H. Heckler, N. Künzner, V. Yu. Timoshenko, and F. Koch

Appl. Phys. Lett. 78, 916 (2001); http://dx.doi.org/10.1063/1.1343476 (3 pages) | Cited 52 times

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We report on a strong intrinsic optical anisotropy of Si induced by its dielectric patterning. As a result, an in-plane birefringence for nanostructured (110) Si surfaces is found to be 104 times stronger than that observed in bulk silicon crystals. We found the value of birefringence to be strongly dependent on the dielectric surrounding of the silicon nanoparticles assembling these layers. Beyond numerous potential implications for realization of optical devices and sensors, this gives a favorable route for studying the physics of condensation phenomena in a mesoscopic geometrical scale. © 2001 American Institute of Physics.
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78.20.Fm Birefringence
78.66.Db Elemental semiconductors and insulators
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Kinetics of Si growth from hydride precursors on As-passivated Si(001) surface

E. S. Tok, A. D. Hartell, and J. Zhang

Appl. Phys. Lett. 78, 919 (2001); http://dx.doi.org/10.1063/1.1347396 (3 pages) | Cited 4 times

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The presence of arsenic on a Si(001) surface is known to have a strong effect on the growth rate during epitaxial growth of silicon from hydride precursors. In this letter, the authors describe a study of this effect using the reflection high energy electron diffraction (RHEED) intensity oscillation technique. A number of surface As coverages produced by cycles of arsine adsorption at temperature below 400 °C and hydrogen desorption at 600 °C were considered. The period of the first RHEED intensity oscillation during overgrowth on a partially As-passivated Si(001) surface is found to be proportional to that during homoepitaxy. The constant of proportionality is equal to the inverse of the fraction of the clean Si surface not passivated by As. This experimental finding is explained using a model based on rate equations for surface hydrogen coverage and site exclusion by arsenic. © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.65.Rv Passivation
68.43.Mn Adsorption kinetics

Atomic arrangements and formation mechanisms of the CuPt-type ordered structure in CdxZn1−xTe epilayers grown on GaAs substrates

T. W. Kim, D. U. Lee, D. C. Choo, H. S. Lee, J. Y. Lee, and H. L. Park

Appl. Phys. Lett. 78, 922 (2001); http://dx.doi.org/10.1063/1.1345841 (3 pages) | Cited 12 times

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Selected area electron diffraction pattern (SADP) and transmission electron microscopy (TEM) measurements were carried out to investigate the ordered structure in CdxZn1−xTe epitaxial layers grown on (001) GaAs substrates. The SADP showed to sets of superstructure reflections with symmetrical intensities, and the corresponding high-resolution TEM image showed a doublet periodicity in the contrast of the {111} lattice planes. The results of the SADP and the TEM measurements showed the existence of a CuPt-type ordered structured in the CdxZn1−xTe epitaxial layers. This CuPt-type ordered structure had two different variants with an antiphase boundary existing between the two variants. The formation of a CuPt-type ordered structure in a CdxZn1−xTe epitaxial layer might originate from the minimization of the strain relaxation energy in the reconstructed GaAs (001) surface. A possible atomic arrangement of and a formation mechanism for the CuPt-type ordered structure in the CdxZn1−xTe epitaxial layer are presented based on the TEM results. These results provide important information on the microstructural properties for improving the efficiencies of optoelectronic devices operating in blue-green spectral regions. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
61.50.Ks Crystallographic aspects of phase transformations; pressure effects

Creating process margin in laser thermal processing: Application to formation of titanium silicide

G. Verma, S. Talwar, and J. C. Bravman

Appl. Phys. Lett. 78, 925 (2001); http://dx.doi.org/10.1063/1.1347389 (3 pages) | Cited 1 time

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Recently, we have demonstrated that, due to differential thermal budget, laser silicidation is an attractive alternative for deep submicron metal-oxide field effect transistors. In laser thermal processing, any spatial beam nonuniformities or pulse to pulse energy fluctuations lead to varying Si melt depth and hence variations in the silicide depth. In this letter, we report that amorphization is a possible solution for this problem. We demonstrate that stochiometric titanium disilicide can be fabricated using laser thermal processing. We also show that the depth of the silicide can be defined by amorphization and that process margin can be created in laser thermal processing. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
42.62.Cf Industrial applications
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