APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

9 Apr 2007

Volume 90, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 151106 (2007); http://dx.doi.org/10.1063/1.2722564 (3 pages)

P. Béjot, L. Bonacina, J. Extermann, M. Moret, J. P. Wolf, R. Ackermann, N. Lascoux, R. Salamé, E. Salmon, J. Kasparian, L. Bergé, S. Champeaux, C. Guet, N. Blanchot, O. Bonville, et al.
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Threading dislocations in In-polar InN films and their effects on surface morphology and electrical properties

Xinqiang Wang, Song-Bek Che, Yoshihiro Ishitani, and Akihiko Yoshikawa

Appl. Phys. Lett. 90, 151901 (2007); http://dx.doi.org/10.1063/1.2720717 (3 pages) | Cited 34 times

Online Publication Date: 9 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In-polar InN films with atomically flat surface are grown on Ga-polar GaN templates by molecular beam epitaxy. Densities of threading dislocations with screw and edge components in these films are about 108 and low 1010 cm−2, respectively. It is found that the screw-component threading dislocation is the dominant cause for macroscopic surface defects appearing as growth-spiral hillocks; their densities (their growth temperature dependences) are almost the same (similar) with each other. Further, it is shown that the residual electron concentration in InN is almost the same with the density of dangling bonds at the edge-component threading dislocations.
Show PACS
73.61.Ey III-V semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.47.Fg Semiconductor surfaces
68.55.-a Thin film structure and morphology
71.55.Eq III-V semiconductors

Buckling modes of elastic thin films on elastic substrates

Haixia Mei, Rui Huang, Jun Young Chung, Christopher M. Stafford, and Hong-Hui Yu

Appl. Phys. Lett. 90, 151902 (2007); http://dx.doi.org/10.1063/1.2720759 (3 pages) | Cited 22 times

Online Publication Date: 9 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Two buckling modes have been observed in thin films: buckle delamination and wrinkling. This letter identifies the conditions for selecting the favored buckling modes for elastic films on elastic substrates. Transition from one buckling mode to another is predicted as the stiffness ratio between the substrate and the film or is predicted for variation of the stiffness ratio between the substrate and the film or variation of theinterfacial defect size. The theoretical results are demonstrated experimentally by observing the coexistence of both buckling modes and mode transition in one film-substrate system.
Show PACS
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
68.60.Bs Mechanical and acoustical properties

Optical characterization of CO2-laser-ablated Si-rich SiOx

Gong-Ru Lin, Chun-Jung Lin, and Yia-Chung Chang

Appl. Phys. Lett. 90, 151903 (2007); http://dx.doi.org/10.1063/1.2721141 (3 pages) | Cited 5 times

Online Publication Date: 9 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Anomalous absorption and the corresponding change in the optical band gap of a CO2-laser-ablated Si-rich SiO2 (SiOx) film are studied. The optical band gap energy of as-grown nonstoichiometric SiOx is slightly reduced by increasing Si–Si bonds as compared to quartz. After rapid thermal annealing using a CO2 laser, the dehydrogenation of SiOx film further increases the Si–Si bonding states and redshifts the optical band gap by 1 eV. Laser ablation is initiated at a laser intensity of >7.5 kW/cm2, leaving numerous luminescent centers that are related to neutral oxygen vacancy defects, increasing the absorption coefficient and related optical band gap energy, and reducing the refractive index in partially annealed SiOx.
Show PACS
78.66.-w Optical properties of specific thin films
42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Significant enhancement of Si oxidation rate at low temperatures by atmospheric pressure Ar/O2 plasma

Hiroaki Kakiuchi, Hiromasa Ohmi, Makoto Harada, Heiji Watanabe, and Kiyoshi Yasutake

Appl. Phys. Lett. 90, 151904 (2007); http://dx.doi.org/10.1063/1.2721366 (3 pages) | Cited 6 times

Online Publication Date: 10 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using stable atmospheric pressure plasma, the effect of inert gas (He, Ar, and Kr) mixed with O2 on the oxidation process of Si(001) wafers was investigated. Ar/O2 plasma was shown capable of generating atomic oxygen most efficiently and significantly enhanced the oxidation rate in comparison with He/O2 plasma, while Kr/O2 plasma was not suitable for the low-temperature and high-rate oxidation of Si. As a result, by using Ar/O2 plasma, oxide layers having equivalent quality to that by He/O2 plasma could be formed with a drastically high initial oxidation rate of 28.0 nm/min.
Show PACS
81.65.Mq Oxidation
52.77.-j Plasma applications

Surface-morphology evolution and strain relaxation during heteroepitaxial growth of GaN films without low-temperature nucleation layers

Sanghwa Lee, Hyeokmin Choe, Taegeon Oh, Jai Weon Jean, Boa Shin, Yuri Sohn, Chinkyo Kim, Jaewan Choi, Yong-Tae Moon, and Jeong Soo Lee

Appl. Phys. Lett. 90, 151905 (2007); http://dx.doi.org/10.1063/1.2721401 (3 pages) | Cited 1 time

Online Publication Date: 10 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
With no low-temperature nucleation layers, heteroepitaxial GaN films were grown at 1050 °C on c-plane sapphire substrates by hydride vapor phase epitaxy. Not like for the films grown on low-temperature buffer layers, upon island merging no immediate smoothing of a surface was observed, but through several intermediate stages the surface morphology evolved from three-dimensional islands to terrace-and-step structures. From synchrotron x-ray diffraction measurements, it was revealed that the density of screw-or mixed-type threading dislocations greatly increased when the islands merged, but that of edge-type dislocations did not (edge-type threading dislocations are known to be dominantly formed in the GaN films grown on low-temperature buffer layers). This implies that the evolution of surface morphology sensitively depends on the type of threading dislocations introduced during island merging. Despite the absence of intentional nucleation layers, the strain was found to be fully relaxed even before the nucleated islands began to merge.
Show PACS
81.05.Ea III-V semiconductors
68.60.Bs Mechanical and acoustical properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.A- Nucleation and growth
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Low thermal conductivity of the negative thermal expansion material, HfMo2O8

Catherine A. Kennedy, Mary Anne White, Angus P. Wilkinson, and Tamas Varga

Appl. Phys. Lett. 90, 151906 (2007); http://dx.doi.org/10.1063/1.2721860 (3 pages) | Cited 2 times

Online Publication Date: 10 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The thermal conductivity of the cubic polymorph of hafnium molybdate, HfMo2O8, was determined over the temperature range of 2–400 K. The values of thermal conductivity were low (0.64±0.15 W m−1 K−1 at T = 300 K for a fully dense sample), with a positive temperature coefficient throughout the temperature range examined. Calculations of the theoretical minimum thermal conductivity and the effective phonon mean free path show that the heat-carrying phonons are nearly fully coupled in HfMo2O8, consistent with the rather large magnitude of its Grüneisen parameter. The low-frequency optic modes which lead to negative thermal expansion in HfMo2O8 are likely responsible for the low thermal conductivity.
Show PACS
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
65.40.De Thermal expansion; thermomechanical effects
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Order-disorder phase transformation in ion-irradiated rare earth sesquioxides

M. Tang, J. A. Valdez, K. E. Sickafus, and P. Lu

Appl. Phys. Lett. 90, 151907 (2007); http://dx.doi.org/10.1063/1.2720716 (3 pages) | Cited 2 times

Online Publication Date: 11 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An order-to-disorder (OD) transformation induced by ion irradiation in rare earth (RE) sesquioxides, Dy2O3, Er2O3, and Lu2O3, was studied using grazing incidence x-ray diffraction and transmission electron microscopy. These sesquioxides are characterized by a cubic C-type RE structure known as bixbyite. They were irradiated with heavy Kr++ ions (300 keV) and light Ne+ ions (150 keV) at cryogenic temperature ( ∼ 120 K). In each oxide, following a relatively low ion irradiation dose of ∼ 2.5 displacements per atom, the ordered bixbyite structure was transformed to a disordered, anion-deficient fluorite structure. This OD transformation was found in all three RE sesquioxides (RE = Dy, Er, and Lu) regardless of the ion type used in the irradiation. The authors discuss the irradiation-induced OD transformation process in terms of anion disordering, i.e., destruction of the oxygen order associated with the bixbyite structure.
Show PACS
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
61.80.Jh Ion radiation effects
61.82.Ms Insulators

Influence of silicon doping on vacancies and optical properties of AlxGa1−xN thin films

J. Slotte, F. Tuomisto, K. Saarinen, C. G. Moe, S. Keller, and S. P. DenBaars

Appl. Phys. Lett. 90, 151908 (2007); http://dx.doi.org/10.1063/1.2721132 (3 pages) | Cited 3 times

Online Publication Date: 11 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors have used positron annihilation spectroscopy and photoluminescence measurements to study the influence of silicon doping on vacancy formation in AlGaN:Si structures. The results show a correlation between the Doppler broadening measurements and the intensity from 510 nm photoluminescence transition. The reduction in the W parameter when the [Si]/[Al+Ga] fraction in the gas phase is above 3×10−4 indicates that the positrons annihilate in an environment where less Ga 3d electrons are present, i.e., they are trapped in group-III vacancies. The observation of vacancies at these silicon concentrations coincides with the onset of the photoluminescence transition at 510 nm.
Show PACS
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.72.up Other materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.70.Bj Positron annihilation

Deformation mechanisms of face-centered-cubic metal nanowires with twin boundaries

A. J. Cao, Y. G. Wei, and Scott X. Mao

Appl. Phys. Lett. 90, 151909 (2007); http://dx.doi.org/10.1063/1.2721367 (3 pages) | Cited 38 times

Online Publication Date: 11 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This letter addresses the issue of deformation mechanisms and mechanical tensile behavior of the twinned metal nanowires using atomistic simulations. Free surfaces are always the preferential dislocation nucleation sites in the initial inelastic deformation stage, while with further plastic deformation, twin boundary interfaces will act as sources of dislocations with the assistance of the newly formed defects. The smaller the twin boundary spacing, the higher the yielding stresses of the twinned nanowires. Twin boundaries, which serve both as obstacles to dislocation motion and dislocation sources, can lead to hardening effects and contribute to the tensile ductility. This work illustrates that the mechanical properties of metal nanowires could be controlled by tailoring internal growth twin structures.
Show PACS
62.25.-g Mechanical properties of nanoscale systems
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.Mm Grain and twin boundaries
61.46.-w Structure of nanoscale materials
61.72.Bb Theories and models of crystal defects

Polarity inversion in aluminum nitride thin films under high sputtering power

Morito Akiyama, Toshihiro Kamohara, Naohiro Ueno, Michiru Sakamoto, Kazuhiko Kano, Akihiko Teshigahara, and Nobuaki Kawahara

Appl. Phys. Lett. 90, 151910 (2007); http://dx.doi.org/10.1063/1.2721865 (3 pages) | Cited 6 times

Online Publication Date: 11 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors have investigated the influence of sputtering power on the piezoelectric response of aluminum nitride (AlN) thin films prepared on titanium nitride bottom electrodes. The piezoelectric response strongly depends on the sputtering power. The polar inversion was found by piezoresponse force microscopy. The polarity gradually changes from the N polarity to Al polarity with increasing sputtering power. The piezoelectric response of the films changes from −2.7 to +4.3 pC/N with increasing sputtering power from 100 to 500 W. Furthermore, the polarity inversion from the N polarity to Al polarity is observed by increasing sputtering power during growth.
Show PACS
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.15.Cd Deposition by sputtering
77.65.-j Piezoelectricity and electromechanical effects
81.05.Ea III-V semiconductors

Enhanced red phosphorescence in nanosized CaTiO3:Pr3+ phosphors

Xianmin Zhang, Jiahua Zhang, Zhaogang Nie, Meiyuan Wang, Xinguang Ren, and Xiao-jun Wang

Appl. Phys. Lett. 90, 151911 (2007); http://dx.doi.org/10.1063/1.2722205 (3 pages) | Cited 19 times

Online Publication Date: 11 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The red photoluminescence and phosphorescence originating from 1D2-3H4 transition of Pr3+ in CaTiO3 nanoparticles are studied as a function of Pr3+ concentrations. The nanophosphors exhibit both longer persistence time of 30 min and higher quenching concentration of 0.4 mol % than the bulk (10 min and 0.1 mol %). The initial phosphorescence in the nanophosphor is an order of magnitude stronger than that in the bulk at the corresponding quenching concentrations. Phosphorescence decay patterns and diffused reflectance spectra before and after ultraviolet exposure indicate the existence of more traps contributing to phosphorescence in the nanoparticles.
Show PACS
42.70.-a Optical materials
78.55.Hx Other solid inorganic materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Low-temperature interface engineering for high-quality ZnO epitaxy on Si(111) substrate

X. N. Wang, Y. Wang, Z. X. Mei, J. Dong, Z. Q. Zeng, H. T. Yuan, T. C. Zhang, X. L. Du, J. F. Jia, Q. K. Xue, X. N. Zhang, Z. Zhang, Z. F. Li, and W. Lu

Appl. Phys. Lett. 90, 151912 (2007); http://dx.doi.org/10.1063/1.2722225 (3 pages) | Cited 22 times

Online Publication Date: 11 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
ZnO(0001)/Si(111) interface is engineered by using a three-step technique, involving low-temperature Mg deposition, oxidation, and MgO homoepitaxy. The double heterostructure of MgO(111)/Mg(0001)/Si(111) formed at −10 °C prevents the Si surface from oxidation and serves as an excellent template for single-domain ZnO epitaxy, which is confirmed with in situ reflection high-energy electron diffraction observation and ex situ characterization by transmission electron microscopy, x-ray diffraction, and photoluminescence. The low-temperature interface engineering method can also be applied to control other reactive metal/Si interfaces and obtain high-quality oxide templates accordingly.
Show PACS
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Shear-strain-induced chemical reactivity of layered molecular crystals

Maija M. Kuklja and Sergey N. Rashkeev

Appl. Phys. Lett. 90, 151913 (2007); http://dx.doi.org/10.1063/1.2719031 (3 pages) | Cited 12 times

Online Publication Date: 12 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A density-functional theory study of shear related dissociation of two molecular crystals, diamino-dinitroethylene (FOX-7) and triamino-trinitrobenzine (TATB), is presented. A detailed explanation is proposed for the fact that FOX-7 is more sensitive than TATB while their sensitivities to initiation of chemistry have been expected to be comparable. The authors suggest that shear plays a crucial role in the dissociation of molecules in organic energetic crystals and may be imperative in providing specific recommendations on ways for materials design.
Show PACS
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Raman spectroscopy evidence of strong spin-phonon coupling in epitaxial thin films of the double perovskite La2NiMnO6

M. N. Iliev, H. Guo, and A. Gupta

Appl. Phys. Lett. 90, 151914 (2007); http://dx.doi.org/10.1063/1.2721142 (3 pages) | Cited 32 times

Online Publication Date: 12 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The Raman spectra of epitaxial thin films of La2NiMnO6 on (001)-oriented LaAlO3 substrates have been measured in several exact scattering configurations between 12 and 773 K. The evolution of the spectra with increasing temperature is consistent with a transition from the monoclinic P121/n1 to rhombohedral Rmath structure. The spin-phonon coupling results in significant softening of the phonon mode involving stretching vibrations of the (Ni/Mn)O6 octahedra. The anomalous softening extends above TC = 275 K, indicating the presence of short range ordering up to 400 K.
Show PACS
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Hv Other nonmetallic inorganics
64.70.K- Solid-solid transitions
78.66.Nk Insulators
75.70.Ak Magnetic properties of monolayers and thin films

Magnetic-field-induced fourfold azimuthal angle dependence in the terahertz radiation power of (100) InAs

Elmer Estacio, Hisashi Sumikura, Hidetoshi Murakami, Masahiko Tani, Nobuhiko Sarukura, Masanori Hangyo, Carlito Ponseca, Jr., Romeric Pobre, Reuben Quiroga, and Shingo Ono

Appl. Phys. Lett. 90, 151915 (2007); http://dx.doi.org/10.1063/1.2721385 (3 pages) | Cited 9 times

Online Publication Date: 12 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The azimuthal angle dependence in the terahertz radiation power of (100) InAs under 1 T magnetic field is presented. Results show that although the dominant radiation mechanism is surge current, azimuthal-angle-dependent radiation due to the nonlinear effect is also observed. The twofold symmetry of the p-polarized terahertz radiation power was modified to a fourfold symmetry with the transverse magnetic field. Moreover, results exhibited fourfold symmetry for the s-polarized terahertz power even with no applied field. The anisotropic intervalley scattering of photocarriers is tentatively proposed as the origin of quadrupole response and the fourfold emission symmetry.
Show PACS
78.70.Gq Microwave and radio-frequency interactions
72.40.+w Photoconduction and photovoltaic effects
72.80.Ey III-V and II-VI semiconductors

Subsecond sintering of ice

Denes Szabo and Martin Schneebeli

Appl. Phys. Lett. 90, 151916 (2007); http://dx.doi.org/10.1063/1.2721391 (3 pages) | Cited 9 times

Online Publication Date: 12 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ice grains bond together in less than 1 s. The tensile strength of the resulting bond was measured above −25 °C in the contact time range of 10–1000 ms as a function of temperature and contact load. The bond strength increases nonlinearly with time and with increasing temperature. The results indicate that the most likely mechanism of ice sintering on this time scale is the freezing of the liquidlike layer present on the surface of the ice. A model based on the plastic behavior of ice and the complete freezing of the entire contact patch well describes the observations.
Show PACS
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Short-range order of low-coverage Ti/Al(111): Implications for hydrogen storage in complex metal hydrides

E. Muller, E. Sutter, P. Zahl, C. V. Ciobanu, and P. Sutter

Appl. Phys. Lett. 90, 151917 (2007); http://dx.doi.org/10.1063/1.2722197 (3 pages) | Cited 3 times

Online Publication Date: 12 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using scanning tunneling microscopy and density functional theory, we characterize the population of low-coverage Ti atoms on Al(111) as a model surface system for transition metal doped alanate hydrogen storage compounds, such as NaAlH4. When deposited at room temperature, Ti is kinetically trapped in first-layer substitutional sites, avoids nearest-neighbor locations, and preferentially forms next-nearest-neighbor pairs, similar to a structure that has been predicted to dissociate H2 with no energy barrier. The results on this well-defined system suggest the presence of a large population of Ti-pair complexes that may catalyze the dissociative chemisorption of hydrogen in Ti-doped alanate storage materials.
Show PACS
84.60.-h Direct energy conversion and storage

Epitaxial properties of ZnO thin films on SrTiO3 substrates grown by laser molecular beam epitaxy

X. H. Wei, Y. R. Li, J. Zhu, W. Huang, Y. Zhang, W. B. Luo, and H. Ji

Appl. Phys. Lett. 90, 151918 (2007); http://dx.doi.org/10.1063/1.2719026 (3 pages) | Cited 17 times

Online Publication Date: 13 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Epitaxial ZnO thin films with different orientations have been grown by laser molecular beam epitaxy on (001)-, (011)-, and (111)-orientated SrTiO3 single-crystal substrates. The growth behavior was in situ monitored by reflection high-energy electron diffraction, and the epitaxial orientation relations were reconfirmed by ex situ x-ray diffraction measurements. In the case of ZnO on SrTiO3(001), four orthogonal domains coexisted in the ZnO epilayer, i.e., ZnO(110)‖SrTiO3(001) and ZnO[−111]‖SrTiO3〈100〉. For (011)- and (111)-orientated substrates, single-domain epitaxy with c axial orientation was observed, in which the in-plane relationship was ZnO[110]‖SrTiO3[110] irrespective of the substrate orientations. Additionally, the crystalline quality of ZnO on SrTiO3(111) was better than that of ZnO on SrTiO3(011) because of the same symmetry between the (111) substrates and (001) films. The obtained results can be attributed to the difference of the in-plane crystallographic symmetry. Furthermore, those alignments can be explained by the interface stress between the substrates and the films.
Show PACS
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.62.-b Laser applications
68.35.B- Structure of clean surfaces (and surface reconstruction)

Formation of Cu–Cu interfaces with ideal adhesive strengths via room temperature pressure bonding in ultrahigh vacuum

Rajappa Tadepalli and Carl V. Thompson

Appl. Phys. Lett. 90, 151919 (2007); http://dx.doi.org/10.1063/1.2720297 (3 pages) | Cited 5 times

Online Publication Date: 13 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Low-temperature metal-metal bonding is needed for three-dimensional circuit fabrication and other technologies. Atomic force microscope pull-off measurements were used to characterize the tensile toughness of bonds between Cu layers deposited, pressure bonded, and tested under ultrahigh vacuum (<2×10−10 Torr). Works of adhesion ∼ 3 J/m2 were obtained at room temperature, the ideal value expected for bulklike bonding. The bond toughness was degraded to ∼ 0.1 J/m2 when surfaces were exposed to 10−6 Torr O2 before bonding. Cu layers exposed to O2 must be bonded at 300 °C or above to achieve the same toughness achieved at room temperature with clean surfaces.
Show PACS
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Effects of carbon in MgB2 thin films: Intrinsic or extrinsic

A. Saengdeejing, J. E. Saal, Y. Wang, and Z. K. Liu

Appl. Phys. Lett. 90, 151920 (2007); http://dx.doi.org/10.1063/1.2717569 (3 pages) | Cited 10 times

Online Publication Date: 13 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
First-principles calculations are performed on MgB2, carbon doped MgB2, and MgB2C2. The trend of calculated lattice parameters of MgB2 with increasing carbon content agrees with bulk experiments but not with thin films produced by hybrid physical-chemical vapor deposition. In this work, the authors propose a model to explain this behavior based on the coefficients of thermal expansion of MgB2 and MgB2C2 as predicted from first principles and of graphite from literature. It is concluded that the effect of carbon on the lattice parameters of MgB2 thin films is extrinsic and due to differences of the coefficients of thermal expansion of different phases.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Bt Thermodynamic properties
61.66.Fn Inorganic compounds
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.up Other materials

Method to separate and determine the amount of ejecta produced in a second-shock material-fragmentation event

W. T. Buttler, R. S. Hixson, N. S. P. King, R. T. Olson, P. A. Rigg, M. B. Zellner, N. Routley, and A. Rimmer

Appl. Phys. Lett. 90, 151921 (2007); http://dx.doi.org/10.1063/1.2722676 (3 pages) | Cited 2 times

Online Publication Date: 13 April 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors consider a mathematical method to separate and determine the amount of ejecta produced in a second-shock material-fragmentation process. The technique is theoretical and assumes that a material undergoing a shock release at a vacuum interface ejects particulate material or fragments as the initial shock unloads and reflects at the vacuum-surface interface. In this case it is thought that the reflected shock may reflect again at the source of the shock and return to the vacuum-surface interface and eject another amount of fragments or particulate material.
Show PACS
62.50.-p High-pressure effects in solids and liquids
68.35.Iv Acoustical properties
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close