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12 Sep 2005

Volume 87, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 113902 (2005); http://dx.doi.org/10.1063/1.2045549 (3 pages)

M. Laroussi and X. Lu
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Scalability of phononic crystal heterostructures

R. Ramprasad and N. Shi

Appl. Phys. Lett. 87, 111101 (2005); http://dx.doi.org/10.1063/1.2043242 (3 pages) | Cited 7 times

Online Publication Date: 7 September 2005

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Phononic (or acoustic) band structure calculations have been performed for a nanoscale HfO2–ZrO2 multilayer stack using first-principles methods at the atomistic level and by solving the acoustic wave equation at the continuum level, as a first step toward determining the length scales when conventional continuum acoustic band-gap treatments become inadequate. Transverse acoustic waves are the focus of this study. The material parameters that continuum acoustic band gap methods require, such as the mass density and transverse wave velocity of the components of the acoustic crystal (i.e., for HfO2 and ZrO2), were determined using separate phonon calculations of the corresponding bulk materials. Comparison of the phononic band structure for a nanoscale HfO2–ZrO2 multilayer stack calculated using first-principles and continuum methods indicates the need for careful treatments of wave propagation properties at these length scales.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Surface-mode microcavity

Sanshui Xiao and Min Qiu

Appl. Phys. Lett. 87, 111102 (2005); http://dx.doi.org/10.1063/1.2043243 (3 pages) | Cited 9 times

Online Publication Date: 7 September 2005

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Optical microcavities based on zero-group-velocity surface modes in photonic crystals are studied. It is shown that high quality factors can be easily obtained for such microcavities in photonic crystal slabs. With increasing of the cavity length, the quality factor is gradually enhanced and the resonant frequency converges to that of the zero-group-velocity surface mode in the photonic crystal. The number of the resonant modes with high quality factors is mainly determined by the number of surface modes with zero-group velocity.
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42.70.Qs Photonic bandgap materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Broadband infrared emission from Er–Tm:Al2O3 thin films

Zhisong Xiao, R. Serna, C. N. Afonso, and I. Vickridge

Appl. Phys. Lett. 87, 111103 (2005); http://dx.doi.org/10.1063/1.2040005 (3 pages) | Cited 19 times

Online Publication Date: 7 September 2005

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Thin films of amorphous aluminum oxide (Al2O3) co-doped with Er3+ and Tm3+ have been synthesized by alternate pulsed laser deposition. When pumped at 794 nm a broad emission band over 1400–1700 nm is observed. Two peaks related to the 1540 nm band from Er3+ and to the 1640 nm band from Tm3+ are clearly distinguished. The photoluminescence intensity ratio of the 1640–1540 nm emissions has been controlled by modifying the Tm concentration. A spectrum with a fairly flat profile and a full width at half maximum of 230 nm is obtained for an Er concentration of 7.2×1019 cm−3 and a [Tm]/[Er] concentration ratio of 3. It is found that the Er3+ to Tm3+ energy transfer processes play an important role in the definition of the luminescent response. The large width of the emission band and the excellent optical and thermomechanical properties of the Er–Tm co-doped Al2O3 signal this system as a potential candidate for the development of broadband integrated optical amplifiers.
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78.55.Qr Amorphous materials; glasses and other disordered solids
78.66.Nk Insulators
42.70.Hj Laser materials

Tunable surface plasmons in coupled metallo-dielectric multiple layers for light-emission efficiency enhancement

Roberto Paiella

Appl. Phys. Lett. 87, 111104 (2005); http://dx.doi.org/10.1063/1.2045560 (3 pages) | Cited 30 times

Online Publication Date: 7 September 2005

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The coupling of spontaneously emitted photons to surface plasmons in metal films is a promising technique to increase the efficiency of light-emitting devices. Here we propose and theoretically investigate the use of metallo-dielectric multiple layers to engineer the surface-plasmon density of states, so as to introduce tunable resonances in the emission efficiency through the anticrossing of modes localized on neighboring interfaces. To illustrate, large enhancements in the radiative recombination rate at tunable wavelengths are predicted for a GaN-based light-emitting device, using a Ag/Si3N4/Au/Si3N4 structure with different combinations of the layers thicknesses.
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78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
77.55.-g Dielectric thin films
85.60.Jb Light-emitting devices

1.55 μm GaInNAs resonant-cavity-enhanced photodetector grown on GaAs

Q. Han, X. H. Yang, Z. C. Niu, H. Q. Ni, Y. Q. Xu, S. Y. Zhang, Y. Du, L. H. Peng, H. Zhao, C. Z. Tong, R. H. Wu, and Q. M. Wang

Appl. Phys. Lett. 87, 111105 (2005); http://dx.doi.org/10.1063/1.2048828 (3 pages) | Cited 11 times

Online Publication Date: 8 September 2005

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We report the design, growth, fabrication, and characterization of a GaAs-based resonant-cavity-enhanced (RCE) GaInNAs photodetector operating at 1.55 μm. The structure of the device was designed using a transfer-matrix method (TMM). By optimizing the molecular-beam epitaxy growth conditions, six GaInNAs quantum wells were used as the absorption layers. Twenty-five (25)- and 9-pair GaAs/AlAs-distributed Bragg reflectors were grown as the bottom and top mirrors. At 1.55 μm, a quantum efficiency of 33% with a full width at half maximum of 10 nm was obtained. The dark current density was 3×10−7 A/cm2 at a bias of 0 V and 4.3×10−5 A/cm2 at a reverse bias of 5 V. The primary time response measurement shows that the device has a rise time of less than 800 ps.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.30.De Semiconductor-device characterization, design, and modeling
42.79.Bh Lenses, prisms and mirrors
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Midinfrared intersubband absorption in lattice-matched AlInN/GaN multiple quantum wells

S. Nicolay, J.-F. Carlin, E. Feltin, R. Butté, M. Mosca, N. Grandjean, M. Ilegems, M. Tchernycheva, L. Nevou, and F. H. Julien

Appl. Phys. Lett. 87, 111106 (2005); http://dx.doi.org/10.1063/1.2045559 (3 pages) | Cited 35 times

Online Publication Date: 9 September 2005

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We report the observation of midinfrared intersubband (ISB) absorption in nearly lattice-matched AlInN/GaN multiple-quantum-wells. A clear absorption peak is observed around 3 μm involving transitions from the conduction band ground state to the first excited state. In addition to ISB absorption, photoluminescence experiments were carried out on lattice- matched AlInN/GaN single quantum wells in order to determine the spontaneous polarization discontinuity between GaN and Al0.82In0.18N compounds. The experimental value is in good agreement with theoretical predictions. Our results demonstrate that the AlInN/GaN system is very promising to achieve crack-free and low dislocation density structures dedicated to intersubband devices in the 2–4 μm wavelength range.
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78.66.Fd III-V semiconductors
78.67.De Quantum wells
73.21.Fg Quantum wells
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Highly efficient wide-angle transmission into uniform rod-type photonic crystals

T. P. White, C. Martijn de Sterke, R. C. McPhedran, and L. C. Botten

Appl. Phys. Lett. 87, 111107 (2005); http://dx.doi.org/10.1063/1.2048823 (3 pages) | Cited 11 times

Online Publication Date: 9 September 2005

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We report on very high coupling efficiencies into rod-type photonic crystal (PC) slabs with unmodified interfaces. Three-dimensional finite difference time domain simulations show that reflected powers of less than 1.5% can be achieved for incident angles from 0° to more than 25°. We use this property to design a beam combiner exhibiting both high efficiency coupling and self-collimation. The results could be applied to the design of efficient superprisms and other dispersion-based PC devices.
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42.70.Qs Photonic bandgap materials
42.15.Eq Optical system design
42.79.Gn Optical waveguides and couplers
42.79.Ag Apertures, collimators
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Current instability and plasma waves generation in ungated two-dimensional electron layers

Michel Dyakonov and Michael S. Shur

Appl. Phys. Lett. 87, 111501 (2005); http://dx.doi.org/10.1063/1.2042547 (3 pages) | Cited 27 times

Online Publication Date: 9 September 2005

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We predict instability of the steady state with a direct current for an ungated two-dimensional (2D) electron layer. This instability caused by the current flow is similar to the “shallow water” instability in the gated 2D electron gas [see M. Dyakonov and M. S. Shur, Phys. Rev. Lett. 71, 2465 (1993) ]. The mathematics of the problem correspond to “deep water” solutions for plasma waves. Just like in the “shallow water” case, this instability occurs when the boundary conditions correspond to zero ac voltage at the source and zero ac current at the drain. Such boundary conditions can be realized using either an external circuit or a depleted region at the drain. For the same device dimensions and electron mobility, the plasma wave generated in an ungated 2D device has a much higher frequency and, as a consequence, a much higher resonance quality factor, which makes the ungated devices promising for applications in resonant terahertz detectors.
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72.30.+q High-frequency effects; plasma effects
73.63.-b Electronic transport in nanoscale materials and structures
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.20.Fr Low-field transport and mobility; piezoresistance

Approach to optimize conversion efficiency of discharge-pumped plasma extreme ultraviolet sources

Majid Masnavi, Mitsuo Nakajima, Akira Sasaki, Eiki Hotta, and Kazuhiko Horioka

Appl. Phys. Lett. 87, 111502 (2005); http://dx.doi.org/10.1063/1.2048824 (3 pages) | Cited 5 times

Online Publication Date: 9 September 2005

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The possibility of enhancing the conversion efficiency of a capillary-discharged xenon plasma via a current step is theoretically demonstrated using a simplified model. The current step is shown to exert a significant effect on the plasma dynamics in capillary discharge extreme ultraviolet sources. In particular, the pinching phase can be maintained at a quasi-steady-state by the current control, which prolongs the emission period of radiating plasma.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.-s Electric discharges
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
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Thermally driven non-contact atomic force microscopy

Anil Gannepalli, Abu Sebastian, Jason Cleveland, and Murti Salapaka

Appl. Phys. Lett. 87, 111901 (2005); http://dx.doi.org/10.1063/1.2037197 (3 pages) | Cited 14 times

Online Publication Date: 6 September 2005

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In this letter a thermally driven frequency modulated atomic force microscopy (FM-AFM) technique is developed. Thermal fluctuations of the cantilever are employed to estimate the cantilever’s equivalent resonant frequency. The corresponding cantilever oscillations are the smallest possible at a given temperature. Related experiments that establish the feasibility of thermally driven FM-AFM in ambient room conditions have achieved tip-sample separations less than 2 nm with long term separation stability (>30 min). Employing this method a narrowband 250 Hz modulation of the tip-sample separation was detected with a vertical resolution of 0.25 Å in a 0.4 Hz bandwidth. The corresponding estimated force sensitivity is 7 fN. In all experiments the cantilever tip was maintained in the attractive regime of the tip-sample interactions. This demonstrates a thermally driven non-contact mode operation of AFM. It also provides a limits of performance study of small amplitude FM-AFM methods.
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07.79.Lh Atomic force microscopes

Properties of W–Ge–N as a diffusion barrier material for Cu

S. Rawal, D. P. Norton, T. J. Anderson, and L. McElwee-White

Appl. Phys. Lett. 87, 111902 (2005); http://dx.doi.org/10.1063/1.2042534 (3 pages) | Cited 19 times

Online Publication Date: 6 September 2005

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The properties of W–Ge–N thin films are reported, focusing on issues relevant to their use as diffusion barriers for Cu metallization on silicon. The amorphous W–Ge–N thin films were deposited on thermally grown SiO2/Si using reactive sputter deposition. This was followed by in situ deposition of Cu films. Annealing studies for W–Ge–N were then carried out in a vacuum to investigate Cu diffusion and barrier film crystallization. X-ray diffraction was used to assess the crystallinity of the films upon annealing. The results show that W–Ge–N has a recrystallization temperature that is higher that that for WNx. Auger electron spectroscopy was used to measure the depth profile of Cu diffusion through the barrier layer. Little or no Cu diffusion was detected for a relatively high annealing temperature. The W–Ge–N films were conductive, although the resistivity is somewhat higher than that for WNx. The results suggest that W–Ge–N may be an attractive diffusion barrier material for Si or SiGe devices.
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68.35.Fx Diffusion; interface formation
85.40.Ls Metallization, contacts, interconnects; device isolation
81.40.Gh Other heat and thermomechanical treatments
64.70.K- Solid-solid transitions
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
79.20.Fv Electron impact: Auger emission

Formation of InAs wetting layers studied by cross-sectional scanning tunneling microscopy

P. Offermans, P. M. Koenraad, R. Nötzel, J. H. Wolter, and K. Pierz

Appl. Phys. Lett. 87, 111903 (2005); http://dx.doi.org/10.1063/1.2042543 (3 pages) | Cited 31 times

Online Publication Date: 6 September 2005

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We show that the composition of (segregated) InAs wetting layers (WLs) can be determined by either direct counting of the indium atoms or by analysis of the outward displacement of the cleaved surface as measured by cross-sectional scanning tunneling microscopy. We use this approach to study the effects of the deposited amount of indium, the InAs growth rate, and the host material on the formation of the WLs. We conclude that the formation of (segregated) WLs is a delicate interplay between surface migration, strain-driven segregation, and the dissolution of quantum dots during overgrowth.
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81.05.Ea III-V semiconductors
68.47.Fg Semiconductor surfaces
68.55.A- Nucleation and growth
68.55.Nq Composition and phase identification
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
64.75.-g Phase equilibria
68.35.Dv Composition, segregation; defects and impurities

A candidate LiBH4 for hydrogen storage: Crystal structures and reaction mechanisms of intermediate phases

Jeung Ku Kang, Se Yun Kim, Young Soo Han, Richard P. Muller, and William A. Goddard

Appl. Phys. Lett. 87, 111904 (2005); http://dx.doi.org/10.1063/1.2042632 (3 pages) | Cited 27 times

Online Publication Date: 6 September 2005

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First-principles calculation and x-ray diffraction simulation methods have been used to explore crystal structures and reaction mechanisms of the intermediate phases involved in dehydriding of LiBH4. LiBH4 was found to dehydride via two sequential steps: first dehydriding through LiBH, followed by the dehydriding of LiBH through LiB. The first step, which releases 13.1 wt. % hydrogen, was calculated to have an activation barrier of 2.33 eV per formula unit and was endothermic by 1.28 eV per formula unit, while the second step was endothermic by 0.23 eV per formula unit. On the other hand, if LiBH4 and LiBH each donated one electron, possibly to the catalyst doped on their surfaces, it was found that the barrier for the first step was reduced to 1.50 eV. This implies that the development of the catalyst to induce charge migration from the bulk to the surface is essential to make LiBH4 usable as a hydrogen storage material in a moderate temperature range, which is also important to stabilize the low-temperature structure of Pnma (no. 62) LiBH on dehydrogenation. Consequently, the high 13.1 wt. % hydrogen available from the dehydriding of LiBH4 and LiBH and their phase stability on Pnma when specific catalysts were used suggest that LiBH4 has good potential to be developed as the hydrogen storage medium capable of releasing the Department of Energy target of 6.5 wt. % for a hydrogen fuel cell car in a moderate temperature range.
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84.60.-h Direct energy conversion and storage
61.66.Fn Inorganic compounds
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Annealing behavior of hydrogen-plasma-induced n-type HgCdTe

Keedong Yang, Yong Soo Lee, and Hee Chul Lee

Appl. Phys. Lett. 87, 111905 (2005); http://dx.doi.org/10.1063/1.2043239 (3 pages)

Online Publication Date: 7 September 2005

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In this letter, the effect of annealing in plasma-induced-type converted HgCdTe was observed. The Hg deficient annealing process reconverts the type converted n-HgCdTe into p-type. The activation energy of the process was determined to be 0.99eV regardless to the gas species used for the type conversion process. However, the absorption edge moved toward short-wave direction for hydrogen-plasma-treated sample. The absorption edge shift was observed even after the annealing process, which means the passivation and junction formation are separate phenomena.
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61.72.Cc Kinetics of defect formation and annealing
78.66.Hf II-VI semiconductors
81.65.Rv Passivation
52.77.-j Plasma applications

Crystal structure and phase transformation in Ni53Mn25Ga22 shape memory alloy from 20 K to 473 K

D. Y. Cong, P. Zetterström, Y. D. Wang, R. Delaplane, R. Lin Peng, X. Zhao, and L. Zuo

Appl. Phys. Lett. 87, 111906 (2005); http://dx.doi.org/10.1063/1.2043250 (3 pages) | Cited 18 times

Online Publication Date: 7 September 2005

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The crystal structures, magnetic structures, and phase transformation of the off-stoichiometric Ni53Mn25Ga22 were studied by neutron powder diffraction at different temperatures. It is shown that Ni53Mn25Ga22 has a tetragonal I4/mmm structure from 20 K to 403 K. An abrupt jump in unit-cell volume around room temperature, corresponding to an endothermic peak in the differential scanning calorimetry curve, was observed. This indicates a pretransformation in the martensitic phase of Ni53Mn25Ga22, which is completely different from the phase transformation in the stoichiometric Ni2MnGa. The sequence of structural transformation in Ni53Mn25Ga22 is closely related to its intrinsic temperature-dependent magnetic structure.
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64.70.K- Solid-solid transitions
81.30.Kf Martensitic transformations
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.66.Bi Elemental solids
61.66.Dk Alloys
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Mismatch strain as a driving force for the annealing-induced formation of In–N bonds in (In,Ga)(As,N)

M. Ramsteiner, G. Mussler, P. Kleinert, and K. H. Ploog

Appl. Phys. Lett. 87, 111907 (2005); http://dx.doi.org/10.1063/1.2043251 (3 pages) | Cited 5 times

Online Publication Date: 8 September 2005

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The mismatch strain and local bonding of N atoms in epitaxial (In,Ga)(As,N) layers has been studied by Raman spectroscopy in connection with cluster-Bethe-lattice calculations. The frequency of GaAs-like phonons is found to be applicable for a characterizion of the average strain in the epilayers by using a consistent approximation for the composition dependences. The analysis of N-related vibrational modes reveals that the preferential formation of In-N bonds during thermal annealing is driven not only by the local strain distribution, but correlates also with the average mismatch strain in (In,Ga)(As,N) via strain inhomogeneities on a longer length scale.
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68.60.Bs Mechanical and acoustical properties
78.30.Fs III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

InGaN/GaN multi-quantum-well structures on (111)-oriented bonded silicon-on-insulator substrates

L. S. Wang, S. Tripathy, S. J. Chua, and K. Y. Zang

Appl. Phys. Lett. 87, 111908 (2005); http://dx.doi.org/10.1063/1.2045562 (3 pages) | Cited 6 times

Online Publication Date: 8 September 2005

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We report growth of InGaN/GaN multiple quantum wells (MQWs) on (111)-oriented bonded silicon-on-insulator (SOI) substrates by metalorganic chemical vapor deposition (MOCVD). Prior to MOCVD growth of MQWs, about a 1.2 μm thick GaN layer was deposited on SOI substrate with a high-temperature transitional buffer layer. The growth conditions were tuned to realize blue-green emission peaks centered around 420–495 nm from such MQWs on SOI. X-ray diffraction, atomic force microscopy, scanning electronic microscopy, and photoluminescence techniques were used to characterize these MQWs. Such an approach to realize multicolor light-emitting layers on SOI substrates is suitable for the integration of InGaN/GaN-based optoelectronic structures on SOI-based micro-optoelectromechanical systems and sensors.
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68.65.Fg Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors
78.67.De Quantum wells

Chiral optical absorption bands in [ ]CdGa2(1−x)In2xS4 semiconducting compound

N. V. Joshi and Jorge Luengo

Appl. Phys. Lett. 87, 111909 (2005); http://dx.doi.org/10.1063/1.2048826 (3 pages) | Cited 3 times

Online Publication Date: 8 September 2005

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Spectroscopic investigation of chiral absorption bands in [ ]CdGa2(1−x)In2xS4 has been carried out at 55 K. The origin of these bands is attributed to both the complex structure of the midgap defect states created by inhomogeneity in as-grown samples and the presence of ordered vacancies at cadmium sites. The appearance of chiral bands are associated with dangling bonds in ordered vacancies which help to bring the component of the magnetic dipole moment parallel to the electric dipole moment. The cause for rotation of electric vector of the field is also discussed.
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78.40.Fy Semiconductors
78.30.Hv Other nonmetallic inorganics
71.55.Ht Other nonmetals
71.20.Nr Semiconductor compounds
75.30.Cr Saturation moments and magnetic susceptibilities
61.72.J- Point defects and defect clusters

Silicon layer transfer using plasma hydrogenation

Peng Chen, S. S. Lau, Paul K. Chu, K. Henttinen, T. Suni, I. Suni, N. David Theodore, T. L. Alford, J. W. Mayer, Lin Shao, and M. Nastasi

Appl. Phys. Lett. 87, 111910 (2005); http://dx.doi.org/10.1063/1.2048811 (3 pages) | Cited 4 times

Online Publication Date: 8 September 2005

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In this work, we demonstrate a novel approach for the transfer of Si layers onto handle wafers, induced by plasma hydrogenation. In the conventional ion-cut process, hydrogen ion implantation is used to initiate layer delamination at a desired depth, which leads to ion damage in the transferred layer. In this study, we investigated the use of plasma hydrogenation to achieve high-quality layer transfer. To place hydrogen atoms introduced during plasma hydrogenation at a specific depth, a uniform trapping layer for H atoms must be prepared in the substrate before hydrogenation. The hydrogenated Si wafer was then bonded to another Si wafer coated with a thermal oxide, followed by thermal annealing to induce Si layer transfer. Cross-section transmission electron microscopy showed that the transferred Si layer was relatively free of lattice damage. The H trapping during plasma hydrogenation, and the subsequent layer delamination mechanism, are discussed. These results show direct evidence of the feasibility of using plasma hydrogenation to transfer relatively defect-free Si layers.
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61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
52.77.Dq Plasma-based ion implantation and deposition

Ultrasound propagation in the micropores of track membranes

T. E. Gómez Álvarez-Arenas, B. González, P. Yu. Apel, O. L. Orelovitch, and A. V. Mitrofanov

Appl. Phys. Lett. 87, 111911 (2005); http://dx.doi.org/10.1063/1.2045542 (3 pages) | Cited 2 times

Online Publication Date: 9 September 2005

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Air-coupled and high-frequency ultrasonic spectroscopy is used to study ultrasound transmission through track membranes (TMs). Observed behavior, anomalous compared to that observed for other membranes, suggests independent ultrasound propagation through the pores. This is proved experimentally by studying frequency dependence of some acoustical parameters and by closing the pore aperture at the TM surface. This changes boundary conditions so that such wave is inhibited. Ultrasound propagation in such small pores opens up a new way to investigate gas behavior under rarefied conditions and provides a new technique to characterize TMs.
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62.65.+k Acoustical properties of solids
61.43.Gt Powders, porous materials
68.55.-a Thin film structure and morphology

Morphological instability of elastic thin films–effect of electromechanical interaction

Fuqian Yang and Wei Song

Appl. Phys. Lett. 87, 111912 (2005); http://dx.doi.org/10.1063/1.2045544 (3 pages) | Cited 8 times

Online Publication Date: 9 September 2005

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We examine surface evolution of a stressed elastic conducting thin film in an electric field. A dispersion relation describing morphological evolution of the film is derived by using the theory of linear perturbation. The growth behavior of surface perturbations depends on surface energy, elastic energy, electric energy and electromechanical interaction. Under certain conditions, electric field can suppress surface instability. For surface perturbations of large spatial wavelength, the critical frequency is inversely proportional to the square root of the surface energy of the thin film.
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68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.35.Md Surface thermodynamics, surface energies

Raman spectroscopy of strain in subwavelength microelectronic devices

Emiliano Bonera, Marco Fanciulli, and Marcello Mariani

Appl. Phys. Lett. 87, 111913 (2005); http://dx.doi.org/10.1063/1.2045545 (3 pages) | Cited 10 times

Online Publication Date: 9 September 2005

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The use of Raman spectroscopy to determine strain in microelectronic devices is intrinsically limited by optical diffraction. The critical issue is not the limited spatial resolution itself, but rather the averaging of inhomogeneously strained regions reducing the sensitivity significantly. To eliminate this effect, we took advantage of the near-field properties of an illuminated subwavelength periodic structure. As it is possible to restrict the investigated volume to the transistor channel only, the sensitivity increases significantly. The technique is advantaged by a very small pitch of the devices, and therefore can be also used in the future technological nodes.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.30.Pq Bipolar transistors

General relationship between contact stiffness, contact depth, and mechanical properties for indentation in linear viscoelastic solids using axisymmetric indenters of arbitrary profiles

Yang-Tse Cheng and Che-Min Cheng

Appl. Phys. Lett. 87, 111914 (2005); http://dx.doi.org/10.1063/1.2048820 (3 pages) | Cited 14 times

Online Publication Date: 9 September 2005

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We derive a relationship between the initial unloading slope, contact depth, and the instantaneous relaxation modulus for indentation in linear viscoelastic solids by a rigid indenter with an arbitrary axisymmetric smooth profile. Although the same expression is well known for indentation in elastic and in elastic-plastic solids, we show that it is also true for indentation in linear viscoelastic solids, provided that the unloading rate is sufficiently fast. Furthermore, the same expression holds true for both fast loading and unloading. These results should provide a sound basis for using the relationship for determining properties of viscoelastic solids using indentation techniques.
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46.55.+d Tribology and mechanical contacts
46.35.+z Viscoelasticity, plasticity, viscoplasticity
46.50.+a Fracture mechanics, fatigue and cracks

Effect of pore interconnection on Cu-diffusion-induced failures in porous spin-on low-k dielectrics

Sang-Soo Hwang, Hee-Chan Lee, Hyun Wook Ro, Do Yeung Yoon, and Young-Chang Joo

Appl. Phys. Lett. 87, 111915 (2005); http://dx.doi.org/10.1063/1.2048822 (3 pages) | Cited 2 times

Online Publication Date: 9 September 2005

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The porosity dependence of electric reliability in the spin-on low-k dielectric with the same matrix but with various porosities was examined using time-dependent dielectric breakdown and capacitance voltage measurements. Abrupt changes in the time to dielectric breakdown and a flatband voltage shift were observed when the porosity of low-k dielectrics was between 20% and 30%. Such a characteristic agrees with the positronium annihilation lifetime spectroscopy data, which indicates that the interconnectivity of the pores abruptly increased in those materials with a porosity between 20% and 30%, and it causes an increase in Cu-diffusion-induced failures.
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77.22.Jp Dielectric breakdown and space-charge effects
78.70.Bj Positron annihilation
66.30.J- Diffusion of impurities
61.43.Gt Powders, porous materials
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A mechanism for hole generation by octahedral B6 clusters in silicon

Kengo Ohmori, Noboru Esashi, Masakazu Takao, Daisuke Sato, and Yoshinori Hayafuji

Appl. Phys. Lett. 87, 112101 (2005); http://dx.doi.org/10.1063/1.2035880 (3 pages) | Cited 3 times

Online Publication Date: 6 September 2005

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The electronic structure and x-ray photoelectron spectra of silicon with octahedral B6 clusters are investigated using first-principles calculations. It is found that the B6 clusters act as double acceptors in silicon and that the simulated chemical shift of the B 1s orbital signals of the B6 clusters in x-ray photoelectron spectra coincides with the chemical shift of B 1s experimentally observed in as-implanted silicon at an extremely high dose of boron. These results reveal that the B6 clusters are the origin of hole carriers. We propose a mechanism of hole generation and a model of B6 cluster formation at implantation-induced divacancy sites.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
79.60.Bm Clean metal, semiconductor, and insulator surfaces
71.15.-m Methods of electronic structure calculations
71.20.Mq Elemental semiconductors
72.80.Cw Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
61.72.uf Ge and Si
61.72.J- Point defects and defect clusters
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