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30 Apr 2001

Volume 78, Issue 18, pp. 2617-2804

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Direct observation of a critical length effect in dual-damascene Cu/oxide interconnects

Ennis T. Ogawa, Alexander J. Bierwag, Ki-Don Lee, Hideki Matsuhashi, Patrick R. Justison, Anup N. Ramamurthi, Paul S. Ho, Volker A. Blaschke, David Griffiths, Anne Nelsen, Mark Breen, and Robert H. Havemann

Appl. Phys. Lett. 78, 2652 (2001); http://dx.doi.org/10.1063/1.1365414 (3 pages) | Cited 18 times

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Electromigration results have provided clear evidence of a short or “Blech” length effect in dual- damascene, Cu/oxide, multilinked interconnects. The test structure incorporates a repeated chain of Blech-type line elements and is amenable to failure analysis tools such as focused ion beam imaging. This large interconnect ensemble provides a statistical representation of electromigrationinduced damage in the regime where steady-state interconnect stress is manifest. Statistical analysis yields a critical length of 90 μm for interconnects with line width 0.5 μm at j = 1.0×106 A/cm2 and T = 325 °C. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
66.30.Qa Electromigration
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
85.40.Ls Metallization, contacts, interconnects; device isolation

Photon energy dependence of the sign of the current-induced absorption polarization sensitivity in degenerate semiconductors

B. S. Ryvkin, E. A. Avrutin, and A. C. Walker

Appl. Phys. Lett. 78, 2655 (2001); http://dx.doi.org/10.1063/1.1367290 (3 pages) | Cited 2 times

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We theoretically analyze the effect of current-induced polarization dependence of absorption (fundamental and intersubband) and gain in degenerate semiconductors. The sign of the currentinduced polarization selectivity of absorption is shown to depend on the energy of the initial (or final) state of the transition with respect to the Fermi level and, therefore, on the photon energy. The effect is predicted to be important for understanding and, potentially, engineering polarization properties of devices such as vertical-cavity surface-emitting lasers. © 2001 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
42.55.Px Semiconductor lasers; laser diodes

Characterization of the surface irregularities of cubic GaN using micro-Raman spectroscopy

Ming S. Liu, Steven Prawer, Les A. Bursill, D. J. As, and R. Brenn

Appl. Phys. Lett. 78, 2658 (2001); http://dx.doi.org/10.1063/1.1367303 (3 pages) | Cited 2 times

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The surface irregularities of molecular-beam-epitaxy-grown cubic GaN on GaAs substrates were characterized by micro-Raman spectroscopy. Some surface irregularities are found to be the result of the mixed phases of cubic (zinc-blende) and hexagonal (wurtzite) GaN, while others originate from the alloying of GaN with the GaAs substrate. The polarization scattering of the surface irregularities suggests that misoriented wurtzite GaN clusters sit on or are imbedded in the cubic GaN layer. It is revealed that the crystalline defects created during the growth of cubic GaN induce a growth of hexagonal GaN and, therefore, the surface irregularities consist of a phase mixture of cubic and hexagonal GaN polytypes. © 2001 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Observation of current crowding near fabricated voids in gold lines

R. Yongsunthon, A. Stanishevsky, J. McCoy, and E. D. Williams

Appl. Phys. Lett. 78, 2661 (2001); http://dx.doi.org/10.1063/1.1368190 (3 pages) | Cited 13 times

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The spatial variation of current density in lines with model void defects fabricated using focused-ion beam milling has been imaged using magnetic force microscopy (MFM). At current densities of 3–4×106 A/cm2, an asymmetry in the MFM signal is clearly visible at (1×1) μm2 and (0.5×0.5) μm2 notches at the edge of a 10 μm wide line. Comparison to a simple model calculation suggests that the asymmetry is due to current crowding, with the displaced current 70% localized to within 1μm of the notch. © 2001 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.Qq Microscopic defects (voids, inclusions, etc.)
66.30.Qa Electromigration

Anatase TiO2 thin films grown on lattice-matched LaAlO3 substrate by laser molecular-beam epitaxy

M. Murakami, Y. Matsumoto, K. Nakajima, T. Makino, Y. Segawa, T. Chikyow, P. Ahmet, M. Kawasaki, and H. Koinuma

Appl. Phys. Lett. 78, 2664 (2001); http://dx.doi.org/10.1063/1.1365412 (3 pages) | Cited 58 times

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Epitaxial anatase thin films were fabricated on lattice-matched (−0.2%) LaAlO3 (001) substrates in the layer-by-layer fashion by laser molecular-beam epitaxy. X-ray diffraction and transmission electron microscope show the films to exhibit high crystallinity and atomically defined interfaces. By virtue of the adoption of LaAlO3 substrate, which is transparent to photoexcitation of TiO2, optical band gaps could be determined to be 3.3 eV at room temperature. A photoluminescence band due to recombination of self-trapped excitons was observed at 5 K to give the peak maximum at 2.2 eV. As a result of the high degree of orientation of the epitaxial films, anisotropic optical absorption was clearly observed. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.55.Hx Other solid inorganic materials
78.66.Nk Insulators
68.55.-a Thin film structure and morphology
71.35.Aa Frenkel excitons and self-trapped excitons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Depth profiling of ZnO thin films by cathodoluminescence

H. C. Ong, A. S. K. Li, and G. T. Du

Appl. Phys. Lett. 78, 2667 (2001); http://dx.doi.org/10.1063/1.1368187 (3 pages) | Cited 30 times

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The depth-resolved luminescence of the ZnO epilayer has been studied by using cathodoluminescence (CL) at room temperature. Other than the usual excitonic and deep level emissions, two peaks at 3.13 and 2.57 eV have been observed and are attributed to the defects. The variation of all the emission peaks has been examined as a function of accelerating voltage. The decrease of near-band edge emissions with depth is due to the internal absorption caused by the pronounced band tail. The deep level emission, however, is shown to increase with increasing depth. We have modeled the CL spectra with the consideration of internal absorption and determine the profile of the Urbach parameter, EUrbach, to study the structural imperfection at different depths. A strong dependence between the intensity ratios of the defect emissions to the excitonic emission and the imperfection of material has been found. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Dz II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
71.55.Gs II-VI semiconductors
78.66.Hf II-VI semiconductors
61.72.-y Defects and impurities in crystals; microstructure
71.35.-y Excitons and related phenomena

Robustness of ultrathin aluminum oxide dielectrics on Si(001)

M. Copel, E. Cartier, E. P. Gusev, S. Guha, N. Bojarczuk, and M. Poppeller

Appl. Phys. Lett. 78, 2670 (2001); http://dx.doi.org/10.1063/1.1367902 (3 pages) | Cited 63 times

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The stability of Al2O3 films during thermal processing will help determine their usefulness as an alternative gate dielectric for advanced complementary metal-oxide-semiconductor devices. We used medium energy ion scattering and atomic force microscopy to examine the degradation of ultrathin Al2O3 layers under ultrahigh vacuum annealing and the effects of low-temperature oxidation. No degradation is observed at 900 °C, but voids appear at higher temperatures. Growth of interfacial SiO2 takes place during low-pressure oxidation at 600 °C, which may limit the capacitance of extremely thin structures. © 2001 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.Cc Kinetics of defect formation and annealing
81.65.Mq Oxidation
68.60.Dv Thermal stability; thermal effects
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.72.Qq Microscopic defects (voids, inclusions, etc.)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Young’s modulus measurements and grain boundary sliding in free-standing thin metal films

A. J. Kalkman, A. H. Verbruggen, and G. C. A. M. Janssen

Appl. Phys. Lett. 78, 2673 (2001); http://dx.doi.org/10.1063/1.1367896 (3 pages) | Cited 39 times

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Young’s modulus of free-standing polycrystalline Al, Au, and W films with submicron thickness has been studied using a dynamic bulge-testing technique. For Au and Al films a clear frequency dependence of the modulus is observed at room temperature in the range 1×10−4–0.5 rad/s. The values of the moduli are considerably smaller than the corresponding values of bulk material. The modulus of W films measured under the same conditions does not depend on frequency and is equal to the bulk value. The origin of the behavior found in the Al and Au films is anelastic grain boundary sliding. As a consequence of the relatively small grain size of thin polycrystalline films this phenomenon is observable at room temperature in films with a relatively low melting point. © 2001 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
68.60.Bs Mechanical and acoustical properties

Local environment of rare-earth dopants in silica–titania–alumina glasses: An extended x-ray absorption fine structure study at the K edges of Er and Yb

F. d’Acapito, S. Mobilio, L. Santos, and Rui M. Almeida

Appl. Phys. Lett. 78, 2676 (2001); http://dx.doi.org/10.1063/1.1369417 (3 pages) | Cited 15 times

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We have applied extended x-ray absorption fine structure (EXAFS) spectroscopy to the K edge of rare earths (RE) in a study of the local environments of diluted Er and Yb dopants in silicate glasses, prepared by sol-gel processing. Silica–titania–alumina glasses, doped with RE ions at and above the luminescence quenching concentration were investigated and EXAFS spectra were recorded in a wide k range up to 160 nm−1 not obtainable when working at the LIII edge. No direct RE–RE correlations were found, providing a strong support for previous studies. A model of RE aggregation derived from these observations is also discussed. © 2001 American Institute of Physics.
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61.43.Fs Glasses
78.70.Dm X-ray absorption spectra
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.05.Kf Glasses (including metallic glasses)

Amplified spontaneous emission from a soluble thiophene-based oligomer

M. Anni, G. Gigli, R. Cingolani, M. Zavelani-Rossi, C. Gadermaier, G. Lanzani, G. Barbarella, and L. Favaretto

Appl. Phys. Lett. 78, 2679 (2001); http://dx.doi.org/10.1063/1.1369392 (3 pages) | Cited 15 times

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Optical gain is demonstrated, through pump-probe measurement, in a spin-coated film of a quinquethiophene-S,S-dioxide. The temporal evolution of the gain as a function of the pump intensity shows a progressive shortening of the lifetime as the pump intensity increases. The photoluminescence spectra show line narrowing for excitation intensity higher than 960 μJ cm−2. From these measurements, we conclude that oligothiophene-S,S-dioxides are valuable candidates for thin-film organic light amplifier and lasers. © 2001 American Institute of Physics.
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42.55.Mv Dye lasers
78.45.+h Stimulated emission
78.55.Kz Solid organic materials

Selectivity of nanocavities and dislocations for gettering of Cu and Fe in silicon

B. Stritzker, M. Petravic, J. Wong-Leung, and J. S. Williams

Appl. Phys. Lett. 78, 2682 (2001); http://dx.doi.org/10.1063/1.1363689 (3 pages) | Cited 5 times

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The selectivity of interstitial-based extended defects (loops) and nanocavities for the gettering of Cu and Fe in Si has been studied. Controlled amounts of Cu and Fe were introduced by ion implantation into wafers containing pre-existing nanocavities and/or dislocations. Results show that Cu has a strong preference for gettering to open volume defects, even when high concentrations of interstitial-based loops are present in close proximity. However, the gettering of Fe in samples containing both vacancy- and interstitial-type defects is more complex, with Fe accumulation at all regions in the sample which contain defects, whether they are vacancy- or interstitial-like in character. © 2001 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.82.Fk Semiconductors
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
85.40.Ry Impurity doping, diffusion and ion implantation technology
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Evolution of structure, morphology, and reactivity of hydrogenated amorphous silicon film surfaces grown by molecular-dynamics simulation

Shyam Ramalingam, Saravanapriyan Sriraman, Eray S. Aydil, and Dimitrios Maroudas

Appl. Phys. Lett. 78, 2685 (2001); http://dx.doi.org/10.1063/1.1367298 (3 pages) | Cited 27 times

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The relationship between the structure, H coverage, morphology, and reactivity of plasma deposited hydrogenated amorphous silicon (a-Si:H) film surfaces was investigated using molecular-dynamics simulations. Surfaces of a-Si:H films grown with SiH3 as the sole deposition precursor are found to be remarkably smooth due to a valley-filling mechanism where mobile precursors, such as SiH3 and Si2H6, diffuse and react with dangling bonds in the valleys on the surface. Surface valleys are reactive due to the increased concentration of dangling bonds and decreased H coverage in these regions. The previously speculated physisorbed configuration, where SiH3 is weakly bound to the surface through a H atom, is highly unlikely to be the mobile precursor state. © 2001 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
61.43.Bn Structural modeling: serial-addition models, computer simulation
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Inversion domains in GaN layers grown on (111) silicon by molecular-beam epitaxy

A. M. Sánchez, F. J. Pacheco, S. I. Molina, R. Garcia, P. Ruterana, M. A. Sánchez-García, and E. Calleja

Appl. Phys. Lett. 78, 2688 (2001); http://dx.doi.org/10.1063/1.1368373 (3 pages) | Cited 8 times

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Transmission electron microscopy is used to investigate GaN layers grown on Si(111) substrates by plasma-assisted molecular-beam epitaxy. These layers were grown on top of different AlN buffer layers. Multiple-beam dark-field techniques applied to both cross-sectional and planar-view samples show the presence of inversion domains. These domains grow directly from the interface with the Si(111) substrate. Such observations are related, as in the case of growth on sapphire, to the symmetry difference between wurtzite and diamond. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Edge and screw dislocations as nonradiative centers in InGaN/GaN quantum well luminescence

D. Cherns, S. J. Henley, and F. A. Ponce

Appl. Phys. Lett. 78, 2691 (2001); http://dx.doi.org/10.1063/1.1369610 (3 pages) | Cited 68 times

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Transmission electron microscopy (TEM) and scanning electron microscope cathodoluminescence (CL) have been used to determine the influence of edge and screw dislocations on the light emitting properties of InxGa1−xN quantum wells. TEM is used to locate and identify the nature of dislocations. CL on the same samples is used to determine the spatial variation of the luminescence. A direct correlation of CL maps with TEM has been established, showing that threading edge dislocations act as nonradiative recombination centers with an associated minority carrier diffusion length of 200 nm. Threading dislocations of screw and mixed type were found to be associated with surface pits which were also nonradiative in the quantum well (QW) emission, but owing to the absence of QW growth on the pit facets. The contributions of edge and screw/mixed dislocations to the reduction of the QW emission are quantified, and the wider significance of these results is discussed. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
73.21.Fg Quantum wells
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Lk Linear defects: dislocations, disclinations
68.35.Ct Interface structure and roughness
78.60.Hk Cathodoluminescence, ionoluminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Effect of the density of collision cascades on implantation damage in GaN

S. O. Kucheyev, J. S. Williams, A. I. Titov, G. Li, and C. Jagadish

Appl. Phys. Lett. 78, 2694 (2001); http://dx.doi.org/10.1063/1.1369149 (3 pages) | Cited 12 times

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Damage accumulation in wurtzite GaN films bombarded with 0.5 MeV Bi1 and 1 MeV Bi2 ions (the so-called molecular effect) is studied by Rutherford backscattering/channeling spectrometry. Results show that an increase in the density of collision cascades dramatically enhances the level of implantation-produced lattice disorder in GaN. This effect is attributed to (i) an increase in the defect clustering efficiency with increasing density of ion-beam-generated point defects and/or (ii) to collective nonlinear energy spike processes. Such a strong influence of the density of collision cascades is important to take into account for a correct estimation of implantation-produced lattice disorder in GaN. © 2001 American Institute of Physics.
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61.80.Jh Ion radiation effects
81.05.Ea III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.82.Fk Semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.J- Point defects and defect clusters

Low temperature specific heat of bulk glassy and crystalline Zr41Ti14Cu12.5Ni10Be22.5 alloys

Hai Yang Bai, Jian Lin Luo, Zhao Jia Chen, and Wei Hua Wang

Appl. Phys. Lett. 78, 2697 (2001); http://dx.doi.org/10.1063/1.1369616 (3 pages) | Cited 5 times

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The low temperature specific heat of Zr41Ti14Cu12.5Ni10Be22.5 alloys in glassy and crystalline states has been investigated. The glassy state of the alloy shows much larger specific heat than that of the crystalline state. The density of states at the Fermi level and Debye temperatures, θD of the alloys are determined. It is found that the density of states at the Fermi level for the glassy state is higher than that for crystalline state, the phenomenon is interpreted by localization of electrons in the glassy alloy. A much smaller value of θD in the glassy state indicates marked soften transverse phonons compared to its corresponding crystalline state. © 2001 American Institute of Physics.
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65.40.Ba Heat capacity
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
71.20.Gj Other metals and alloys
71.55.Jv Disordered structures; amorphous and glassy solids
63.90.+t Other topics in lattice dynamics (restricted to new topics in section 63)

Large magneto-optical effect in an oxide diluted magnetic semiconductor Zn1−xCoxO

K. Ando, H. Saito, Zhengwu Jin, T. Fukumura, M. Kawasaki, Y. Matsumoto, and H. Koinuma

Appl. Phys. Lett. 78, 2700 (2001); http://dx.doi.org/10.1063/1.1368375 (3 pages) | Cited 92 times

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Strong magneto-optical effect of Zn1−xCoxO near the optical band gap is reported. Magnetic circular dichroism (MCD) and Faraday rotation of Zn1−xCoxO (x = 0.012 and 0.016) at 5 K are as high as 2°/cm Oe at 3.4 eV, which are about two orders larger than those of ZnO. Absence of strong Co2+ d–d∗ transition near the optical band gap makes Zn1−xCoxO an useful material for short-wavelength magneto-optical applications. Large magneto-optical effects and paramagnetic temperature dependence of MCD show a strong mixing of the sp bands of the host ZnO with Co2+ d orbitals. The polarity of the MCD peak is negative indicating the antiferromagnetic p–d exchange interaction. © 2001 American Institute of Physics.
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78.20.Ls Magneto-optical effects
75.50.Pp Magnetic semiconductors
75.20.Ck Nonmetals
75.50.Ee Antiferromagnetics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
75.30.Et Exchange and superexchange interactions

Anisotropies in magnetron sputtered carbon nitride thin films

Niklas Hellgren, Mats P. Johansson, Esteban Broitman, Lars Hultman, and Jan-Eric Sundgren

Appl. Phys. Lett. 78, 2703 (2001); http://dx.doi.org/10.1063/1.1369388 (3 pages) | Cited 3 times

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Carbon nitride CNx (0 ⩽ x ⩽ 0.35) thin films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges have been studied with respect to microstructure using electron microscopy, and elastic modulus using nanoindentation and surface acoustic wave analyses. For growth temperature of 100 °C, the films were amorphous, and with an isotropic Young’s modulus of ∼ 170–200 GPa essentially unaffected by the nitrogen fraction. The films grown at elevated temperatures (350–550 °C) show anisotropic mechanical properties due to a textured microstructure with standing basal planes, as observed from measuring the Young’s modulus in different directions. The modulus measured in the plane of the film was ∼ 60–80 GPa, while in the vertical direction the modulus increased considerably from ∼ 25 to ∼ 200 GPa as the nitrogen content was increased above ∼ 15 at. %. © 2001 American Institute of Physics.
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81.15.Cd Deposition by sputtering
61.43.Er Other amorphous solids
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Three-dimensional analysis of shape transitions in strained-heteroepitaxial islands

Y. W. Zhang and A. F. Bower

Appl. Phys. Lett. 78, 2706 (2001); http://dx.doi.org/10.1063/1.1354155 (3 pages) | Cited 28 times

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A continuum model of shape transitions in strained heteroepitaxial islands predicts that small islands are hut shaped, while larger islands are domed. The volume of a stable hut can exceed that of a stable dome, however, indicating that the stability of hut-shaped islands plays an important role in shape transition, in addition to energy changes associated with the transition. A hut-shaped island loses stability upon reaching a critical volume, which depends on the anisotropy in surface energy. Impingement between islands reduces the critical volume by nucleating new facets at the base of a hut, which subsequently trigger a shape transition. © 2001 American Institute of Physics.
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68.35.Rh Phase transitions and critical phenomena
68.55.A- Nucleation and growth
68.60.Bs Mechanical and acoustical properties
68.35.Md Surface thermodynamics, surface energies
64.60.Q- Nucleation

Exciton–erbium coupling and the excitation dynamics of Er3+ in erbium-doped silicon-rich silicon oxide

Se-Young Seo and Jung H. Shin

Appl. Phys. Lett. 78, 2709 (2001); http://dx.doi.org/10.1063/1.1369150 (3 pages) | Cited 26 times

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The exciton–erbium coupling and the excitation dynamics of Er3+ in erbium-doped silicon-rich silicon oxide are investigated using time-resolved measurements of Er3+ luminescence. The dependence of the Er3+ luminescence on the pump power and duration indicates that the exciton–erbium coupling is dominant over carrier–exciton coupling. The results further support the idea that the luminescent Er3+ ions are not in the Si nanoclusters but in the interface region surrounding the nanoclusters. © 2001 American Institute of Physics.
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71.35.Cc Intrinsic properties of excitons; optical absorption spectra
71.55.Ht Other nonmetals
78.47.-p Spectroscopy of solid state dynamics
78.55.Hx Other solid inorganic materials

Real-time x-ray microbeam characterization of electromigration effects in Al(Cu) wires

P.-C. Wang, I. C. Noyan, S. K. Kaldor, J. L. Jordan-Sweet, E. G. Liniger, and C.-K. Hu

Appl. Phys. Lett. 78, 2712 (2001); http://dx.doi.org/10.1063/1.1368189 (3 pages) | Cited 14 times

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We report real-time, in situ x-ray microbeam measurements of electromigration-induced Cu redistribution, and the concurrent local stress variation in Al(Cu) wires. The data, which were obtained by combining x-ray microtopography with energy-dispersive fluorescence analysis, encompass both the early and late stages of electromigration as well as the postrelaxation stage at high temperature with the current turned off. We observe that both Cu concentration and stress values show unexpected local variations that may reflect the effect of local configuration such as film–substrate interface integrity or microstructure. © 2001 American Institute of Physics.
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66.30.Qa Electromigration

Ordinary and extraordinary dielectric functions of 4H– and 6H–SiC from 3.5 to 9.0 eV

O. P. A. Lindquist, K. Järrendahl, S. Peters, J. T. Zettler, C. Cobet, N. Esser, D. E. Aspnes, A. Henry, and N. V. Edwards

Appl. Phys. Lett. 78, 2715 (2001); http://dx.doi.org/10.1063/1.1369617 (3 pages) | Cited 8 times

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We report ordinary (ϵ⊥c axis) and extraordinary (ϵ∥c axis) dielectric function data of 4H– and 6H–SiC from 3.5 to 9.0 eV. These data, which were obtained by with spectroscopic ellipsometry, are also compared to recently reported ab initio calculations. Critical point energies were found using real and reciprocal space analysis. © 2001 American Institute of Physics.
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71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors

Electronic structure of oxidized Ni/Au contacts on p-GaN investigated by x-ray absorption spectroscopy

J. C. Jan, K. Asokan, J. W. Chiou, W. F. Pong, P. K. Tseng, M.-H. Tsai, Y. K. Chang, Y. Y. Chen, J. F. Lee, J. S. Wu, H.-J. Lin, C. T. Chen, L. C. Chen, F. R. Chen, and J.-K. Ho

Appl. Phys. Lett. 78, 2718 (2001); http://dx.doi.org/10.1063/1.1370121 (3 pages) | Cited 6 times

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X-ray absorption spectroscopy has been used to investigate the electronic structure of as-deposited and oxidized Ni/Au contacts on p-GaN. The Ni K-, L2,3-, and O K-edges x-ray absorption spectra clearly show the formation of NiO in the annealed contacts. Annealing in air increases Ni-site hole concentration and slightly shortens the nearest-neighbor Ni–O bond length, which enhances p–d hybridization and charge transfer from Ni to O. The observed very low specific contact resistance in the oxidized contacts is found to be due to the enhanced hole concentration at the Ni site. © 2001 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.40.Ns Metal-nonmetal contacts
78.70.Dm X-ray absorption spectra
81.40.Gh Other heat and thermomechanical treatments
68.35.Ct Interface structure and roughness
73.40.Cg Contact resistance, contact potential
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