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1 Jan 2007

Volume 101, Issue 1, Articles (01xxxx)

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Elastic properties of a‐C:N:H films

Chengbing Wang, Shengrong Yang, Hongxuan Li, and Junyan Zhang

J. Appl. Phys. 101, 013501 (2007); http://dx.doi.org/10.1063/1.2402477 (6 pages) | Cited 11 times

Online Publication Date: 2 January 2007

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Dual dc-rf plasma system has been used to deposit hydrogenated carbon nitride (CNx:H) films that exhibit high elastic recovery (75%). Transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra and Raman spectra were subsequently used to study the microstructure and bonding of the resultant films. The structure of the films from TEM is seen to consist of many particles embedded in an amorphous carbon matrix, and the films can be described as graphitelike or onionlike with interplanar distances of ≈ 1.15, 1.95, and 3.5 Å, as obtained from selected area electron diffraction (SAED). FTIR shows that nitrogen promotes the formation of sp2 C=C/C=N aromatic rings in the films. Raman spectra shows two apparent peaks at about 700 and 1200 cm−1 in addition to the G and D peaks. Only by adding two extra peaks at approximately 1230 and 1470 cm−1 can we deconvolute the Raman spectra of CNx:H in the region of 1000–2000 cm−1. Combining TEM and SAED, we attribute the three peaks at about 700, 1200, and 1470 cm−1 to fullerene or onion structure. However, the elastic recovery is relatively lower than elastic hydrogenated free carbon nitride films. We think that this is due to the fact that hydrogen is mainly incorporated to sp3 carbon and suppresses cross-linking three-dimensional (3D) network growth.
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68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
68.37.Lp Transmission electron microscopy (TEM)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Characterization of interdiffusion around miscibility gap of lattice matched InGaAs/InP quantum wells by high resolution x-ray diffraction

F. Bollet and W. P. Gillin

J. Appl. Phys. 101, 013502 (2007); http://dx.doi.org/10.1063/1.2404784 (7 pages)

Online Publication Date: 3 January 2007

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A methodology to characterize of thermally interdiffused heterostructures by high resolution x-ray diffraction is presented. The technique provides detailed information on the strains and compositions generated throughout the interdiffusion process in a 10 nm lattice matched InGaAs/InP sample annealed at 800 °C. It shows that the diffusion process is complex and subject to the influence of the miscibility gap in the quaternary InGaAsP system. The technique also appears to provide a route to mapping the binodal isotherms of the InGaAsP miscibility gap.
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68.65.Fg Quantum wells
66.30.Ny Chemical interdiffusion; diffusion barriers
61.72.Cc Kinetics of defect formation and annealing

Study of dependence of molecular orientation and optical properties of zinc phthalocyanine grown under two different pressure conditions

J. Sindu Louis, D. Lehmann, M. Friedrich, and D. R. T. Zahn

J. Appl. Phys. 101, 013503 (2007); http://dx.doi.org/10.1063/1.2403845 (7 pages) | Cited 7 times

Online Publication Date: 4 January 2007

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Zinc phthalocyanine (ZnPc) thin films were prepared by organic molecular beam deposition on Si (111) covered with a thin native oxide layer under two different pressure conditions. The samples are characterized by infrared spectroscopy and ellipsometry measurements aiming at the determination of dielectric functions and average molecular orientation in the ZnPc films. A two order of magnitude increase in the pressure during growth increases the average molecular tilt angle with respect to the substrate surface from ∼ 19° to ∼ 61° implying a change of crystal phase as well. Likewise sizeable differences are observed in the anisotropic dielectric functions of the ZnPc thin films in the infrared as well as in the visible and ultraviolet spectral ranges.
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78.66.Qn Polymers; organic compounds
68.55.-a Thin film structure and morphology
78.30.Hv Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Me Organic compounds and polymers

Contactless electroreflectance of GaInNAsSb/GaAs single quantum wells with indium content of 8%–32%

R. Kudrawiec, H. B. Yuen, M. Motyka, M. Gladysiewicz, J. Misiewicz, S. R. Bank, H. P. Bae, M. A. Wistey, and James S. Harris

J. Appl. Phys. 101, 013504 (2007); http://dx.doi.org/10.1063/1.2382721 (9 pages) | Cited 12 times

Online Publication Date: 4 January 2007

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Interband transitions in GaInNAsSb/GaAs single quantum wells (SQWs) with nominally identical nitrogen and antimony concentrations (2.5% N and 7% Sb) and varying indium concentrations (from 8% to 32%) have been investigated by contactless electroreflectance (CER). CER features related to optical transitions between the ground and excited states have been clearly observed. Energies of the QW transitions extracted from CER measurements have been matched with those obtained from theoretical calculations performed within the effective mass approximation for various conduction-band offsets (QC) and various electron effective masses. It has been found that the QC increases from 40% to 80% with the rise of the indium content from 8% to 32% and the electron effective mass is close to 0.09m0. The results show that the band gap discontinuity in GaInNAsSb/GaAs SQWs can be broadly tuned with a change in the indium concentration.
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73.21.Fg Quantum wells
78.20.Jq Electro-optical effects
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Influence of working pressure on properties of titanium oxide thin films at room temperature

Z. W. Zhao and B. K. Tay

J. Appl. Phys. 101, 013505 (2007); http://dx.doi.org/10.1063/1.2403837 (5 pages)

Online Publication Date: 4 January 2007

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Titanium oxide thin films were deposited by off-plane filtered cathodic vacuum arc (FCVA) at room temperature as a function of working pressure. The deposition rate decreases with working pressure. The deposited films are amorphous with low residual stress (less than 0.5 GPa) and smooth surface. The film transmittance increases with the increase of working pressure, while the refractive index and extinction coefficient both decrease. Similar behaviors of film properties (e.g., deposition rate and optical properties) are also found in other metal oxides by FCVA, such as zirconium oxide and aluminium oxide. Common features observed in various metal oxides are explained by a model based on ion-gas interactions. The feasibility of these metal oxide thin films as optical coatings is also discussed.
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78.66.Nk Insulators
61.43.Er Other amorphous solids
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.60.Bs Mechanical and acoustical properties
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Experimental investigation of liquid spall in laser shock-loaded tin

T. de Rességuier, L. Signor, A. Dragon, M. Boustie, G. Roy, and F. Llorca

J. Appl. Phys. 101, 013506 (2007); http://dx.doi.org/10.1063/1.2400800 (7 pages) | Cited 14 times

Online Publication Date: 4 January 2007

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When a metal is shocked above its melting pressure or melted on release, the tensile stresses generated upon reflection of the compressive pulse from a free surface are induced into a liquid state. Instead of the well-known spallation process observed in solid targets, cavitation is expected in the melted material, and liquid fragments are ejected from the free surface. Their size, velocity, and temperature distributions are issues of increasing interest, as well as their impact on other nearby materials, but data are limited on the subject. Here, we present an experimental study performed on tin samples subjected to high pressure laser shocks (ranging from about 50 to 200 GPa) of short duration ( ∼ 5 ns). The results include post-test observations of the ejecta recovered after impact on a polycarbonate shield and time-resolved measurements of the free surface velocity through the shield. For shock pressures below some 80 GPa, the velocity profiles are compared to the predictions of one-dimensional simulations involving a multiphase equation of state. For higher loading pressures, the emergence of the shock at the free surface produces a rapid loss of reflectivity so the particle velocity cannot be determined. In all cases, solidified fragments of tin are recovered on the shield. Their sizes, their shapes, and the induced damage depend significantly on shock pressure, and are indicative of a very wide range of ejection velocities. The data provide a basis for a phenomenological description of the process.
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61.82.Bg Metals and alloys
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
62.50.-p High-pressure effects in solids and liquids
79.20.Ds Laser-beam impact phenomena
81.40.Vw Pressure treatment
81.30.Fb Solidification
64.70.D- Solid-liquid transitions
78.20.-e Optical properties of bulk materials and thin films
78.47.-p Spectroscopy of solid state dynamics

Contactless electroreflectance of InAs/In0.53Ga0.23Al0.24As quantum dashes grown on InP substrate: Analysis of the wetting layer transition

R. Kudrawiec, M. Motyka, J. Misiewicz, A. Somers, R. Schwertberger, J. P. Reithmaier, A. Forchel, A. Sauerwald, T. Kümmell, and G. Bacher

J. Appl. Phys. 101, 013507 (2007); http://dx.doi.org/10.1063/1.2405233 (5 pages) | Cited 4 times

Online Publication Date: 9 January 2007

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Contactless electroreflectance (CER) spectroscopy has been applied to study optical transitions in InAs/In0.53Ga0.23Al0.24As quantum dashes (QDashes) grown on an InP substrate by molecular beam epitaxy. CER resonances related to optical transitions in all relevant parts of the structure, i.e., InAs coverage, In0.53Ga0.23Al0.24As barriers, and the cap layer, have been clearly observed at room temperature. The signal, which is associated with light absorption in the InAs coverage, has been carefully analyzed, and the optical transitions in the wetting layer (WL) quantum well (QW) and QDashes have been identified in CER spectra. It has been shown that measurements of WL transitions and analysis of their energies allow us to determine the band gap discontinuity for the QDash/QDash-barrier interface. It has been found that the conduction band offset for the InAs/In0.53Ga0.23Al0.24As interface is close to ∼ 70%. Moreover, it has been observed that the intensity of the WL transition varies with the cap layer which was used to terminate the QDash structure. The conditions for the observation of WL transitions are discussed in this work.
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78.67.Hc Quantum dots
73.21.La Quantum dots

Tilt and dislocations in epitaxial laterally overgrown GaAs layers

Z. R. Zytkiewicz, J. Z. Domagala, D. Dobosz, L. Dobaczewski, A. Rocher, C. Clement, and J. Crestou

J. Appl. Phys. 101, 013508 (2007); http://dx.doi.org/10.1063/1.2405234 (5 pages) | Cited 6 times

Online Publication Date: 9 January 2007

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Transmission electron microscopy (TEM) and high-resolution x-ray diffraction were used to study the crystalline quality of GaAs layers grown by liquid phase epitaxial lateral overgrowth (ELO) on SiO2-masked (001) GaAs substrates. A low-angle grain boundary with a well-organized set of dislocations accommodating the misorientation of tilted ELO wings was found at the coalescence front of ELO layers. Similar behavior is often reported for GaN on sapphire ELO structures. Unlike the GaN case, however, no dislocations were found above edges of the mask, which is explained by the much smaller wing tilt angle in our case. The geometry of the dislocation network and analysis of thickness fringes on TEM images were used to measure misorientation of merging ELO wings. The values obtained are in good agreement with those determined by x-ray diffraction.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Mm Grain and twin boundaries
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

(20−23) ZnO thin films grown by pulsed laser deposition on CeO2-buffered r-sapphire substrate

J.-R. Duclère, B. Doggett, M. O. Henry, E. McGlynn, R. T. Rajendra Kumar, J.-P. Mosnier, A. Perrin, and M. Guilloux-Viry

J. Appl. Phys. 101, 013509 (2007); http://dx.doi.org/10.1063/1.2404782 (7 pages) | Cited 10 times

Online Publication Date: 10 January 2007

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Composite ZnO/CeO2 thin films were grown epitaxially on r-sapphire substrates using the pulsed laser deposition technique. Their crystalline properties were established using x-ray diffraction and showed the ZnO (wurtzite structure) and CeO2 (fluorite structure) layers to be highly textured with the (20−23) and (100) orientations, respectively. ϕ-scan measurements were also carried out and the (20−23)ZnO‖(100CeO2), [1−210]ZnO‖〈011〉 CeO2 epitaxial relations established. The rocking curve profiles indicated that the ZnO films grew as four crystallographically equivalent domains. Series of rocking curve and χ−scan measurements at varying ϕ angles, respectively, were used to investigate the domain structure. These showed that the normal to the (20−23) plane in each domain is tilted away from the substrate normal towards one of the four equivalent CeO2 ⟨111⟩ directions by ∼ 1.60. Atomic force microscopy measurements showed that the ZnO/CeO2 composite film has a granular microstructure with a rough surface (typical root mean square roughness of 7.9 nm). Low temperature photoluminescence spectra showed an intense near-band-edge emission at a photon energy of 3.361 eV, with a full width at half maximum of 1.8 meV, testifying to the good optical quality of the ZnO material. The optical transmission of the ZnO/CeO2 composite film was measured in the 200–1000 nm spectral domain; it was completely opaque to UV radiation and became transparent with a sharp transition above 380 nm. Secondary ion mass spectrometry measurements were used for depth profiling of the ZnO/CeO2 composite structure. The corresponding data suggest that the CeO2 buffer layer acts as an efficient barrier against the diffusion of aluminum from the sapphire substrate into the ZnO layer.
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68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors

Effects of surface stresses on contact problems at nanoscale

G. F. Wang and X. Q. Feng

J. Appl. Phys. 101, 013510 (2007); http://dx.doi.org/10.1063/1.2405127 (6 pages) | Cited 17 times

Online Publication Date: 10 January 2007

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Based on the surface elasticity theory, we examined the effects of surface stresses on nanosized contact problems. The Fourier integral transform method is adopted to derive the general solution for the contact problem under pressure. As two examples, the deformations induced, respectively, by a uniform distributed pressure and a concentrated force are analyzed in detail. The results indicate some interesting characteristics in contact mechanics, which are distinctly different from those in classical elasticity theory. Both the contact normal stress and the deformation gradient on the deformed surface vary smoothly across the loading boundary as a result of surface stress. In addition, the indent depth and the maximum normal contact stress depend strongly on the surface stress for nanoindentation.
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68.35.Gy Mechanical properties; surface strains
46.55.+d Tribology and mechanical contacts
46.50.+a Fracture mechanics, fatigue and cracks

Prediction of MAX phases, VN+1SiCN (N = 1,2), from first-principles theory

C. M. Fang, R. Ahuja, and O. Eriksson

J. Appl. Phys. 101, 013511 (2007); http://dx.doi.org/10.1063/1.2405721 (3 pages) | Cited 3 times

Online Publication Date: 10 January 2007

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We have investigated the phase stability of two MAX phases, V3SiC2 and V2SiC, by means of first-principles total-energy calculations within the generalized-gradient approximation and the projector-augmented wave method. The theoretical bulk modulus of V3SiC2 is 219 GPa, which is ∼ 17% larger than that of Ti3SiC2 (187 GPa). The total-energy calculations show that V2SiC is stable with a formation energy of about 0.27 eV̸f.u. and that V3SiC2 is metastable (only 0.02 eV̸f.u. is required to stabilize this phase from its competing phases). We suggest that both these two MAX compounds should be possible to synthesize as stable (or metastable) phases using, e.g., thin-film deposition.
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71.15.Nc Total energy and cohesive energy calculations
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

In-plane order of liquid crystal molecules adsorbed on photoaligned polyimide films: Coverage dependence in submonolayer range

Kiyoaki Usami, Kenji Sakamoto, Yoichi Uehara, and Sukekatsu Ushioda

J. Appl. Phys. 101, 013512 (2007); http://dx.doi.org/10.1063/1.2405723 (5 pages) | Cited 1 time

Online Publication Date: 10 January 2007

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We have examined the in-plane orientation of liquid crystal (LC) molecules adsorbed on polyimide films as a function of coverage over a submonolayer range. In this study we used 12‐nm-thick photoaligned films of polyimide containing azobenzene in the backbone structure (Azo-PI). The in-plane molecular order of the LC layer and the Azo-PI film was determined from the polarization angle dependence of infrared absorption. Even at ∼ 0.2 ML (monolayer) the orientational distribution of the LC molecules was anisotropic with an in-plane order parameter almost equal to that of the Azo-PI backbone structure in the underlying film. The in-plane order parameter of the LC molecules was constant up to 1 ML. This result indicates that the orientation of the LC molecules directly adsorbed on the polyimide film is determined by the interaction between the polyimide and LC molecules. The interaction among the LC molecules in the first monolayer was found to be negligibly weak compared with that between the polyimide and LC molecules.
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61.30.-v Liquid crystals
68.43.Mn Adsorption kinetics
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
78.30.Jw Organic compounds, polymers

Effects of Al doping on the electromigration performance of damascene Cu interconnects

Shinji Yokogawa and Hideaki Tsuchiya

J. Appl. Phys. 101, 013513 (2007); http://dx.doi.org/10.1063/1.2405739 (6 pages) | Cited 10 times

Online Publication Date: 10 January 2007

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We report the effects of Al doping on electromigration in damascene Cu interconnects. Al doping was performed by thermal diffusion from a CuAl seed layer positioned underneath the Cu interconnects. To investigate the dependencies of the Al concentration, the seed CuAl layer thickness was increased from 40 to 90 nm on a planar surface. The effects of Al doping on the incubation time, drift velocity, and critical product of electromigration were investigated. The drift velocity of Cu mass transport in CuAl alloys decreases with an increase in the concentration of Al atoms. The observed critical product of electromigration is 1500 A/cm, and it is independent of the Al concentration. The measured activation energies of the normalized drift velocities for CuAl seed layer thicknesses of 40, 60, and 90 nm are 1.2, 1.4, and 1.5 eV, respectively. The Al concentrations at Cu/SiCN interface, grain boundary, Ta/Cu interface, and bulk were investigated along the length of a line by the electron microprobe technique. The time dependent Al concentration at the Cu/SiCN interface near the cathode end of the line is observed. These characteristics indicate that the doped Al affects the electromigration-induced Cu diffusion and does not affect the driving force.
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66.30.Qa Electromigration
61.72.up Other materials
85.40.Ls Metallization, contacts, interconnects; device isolation

Effect of Al addition on the microstructure and electronic structure of HfO2 film

X. F. Wang, Quan Li, R. F. Egerton, P. F. Lee, J. Y. Dai, Z. F. Hou, and X. G. Gong

J. Appl. Phys. 101, 013514 (2007); http://dx.doi.org/10.1063/1.2405741 (5 pages) | Cited 3 times

Online Publication Date: 10 January 2007

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We have investigated the microstructures and electronic structures of a series of hafnium aluminate (HfAlO) films with Al concentration ranging from 0% to 100%. When the films evolve from pure HfO2 to pure Al2O3 by increasing the aluminum content, we find changes in their radial distribution functions, which disclose the short-range order of the materials, despite the amorphous nature of all films. The HfAlO films (with Al/Hf ratio ranging from 0.25 to 5.8) appear to be a single glassy phase of Hf, Al, and O, instead of simple mixtures of HfO2 and Al2O3. The Hf (Al)–O, Hf (Al)–Al, and Hf–Hf bonds are observed to be insensitive to the amount of Al in the film, except when the Al concentration is large (Al/Hf ∼ 5.8), in which case the bonding is similar to that in pure Al2O3. Although the local symmetry of Hf in amorphous HfO2 is suggested by the electron energy-loss spectrum taken at an oxygen K edge, it is largely disrupted when Al is introduced. The valence electron energy-loss spectroscopy reveals three distinct evolving features as the Al content increases, which we discuss in terms of the electronic structure of HfO2.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
71.23.-k Electronic structure of disordered solids
79.20.Uv Electron energy loss spectroscopy

Very high-cycle fatigue failure in micron-scale polycrystalline silicon films: Effects of environment and surface oxide thickness

D. H. Alsem, R. Timmerman, B. L. Boyce, E. A. Stach, J. Th. M. De Hosson, and R. O. Ritchie

J. Appl. Phys. 101, 013515 (2007); http://dx.doi.org/10.1063/1.2403841 (9 pages) | Cited 18 times

Online Publication Date: 11 January 2007

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Fatigue failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle fatigue behavior of these films (up to 1012 cycles), there is still an on-going debate on the precise mechanisms involved. We show here that for devices fabricated in the multiuser microelectromechanical system process (MUMPs) foundry and Sandia Ultra-planar, Multi-level MEMS Technology (SUMMiT V™) process and tested under equi-tension/compression loading at ∼ 40 kHz in different environments, stress-lifetime data exhibit similar trends in fatigue behavior in ambient room air, shorter lifetimes in higher relative humidity environments, and no fatigue failure at all in high vacuum. The transmission electron microscopy of the surface oxides in the test samples shows a four- to sixfold thickening of the surface oxide at stress concentrations after fatigue failure, but no thickening after overload fracture in air or after fatigue cycling in vacuo. We find that such oxide thickening and premature fatigue failure (in air) occur in devices with initial oxide thicknesses of ∼ 4 nm (SUMMiT V™) as well as in devices with much thicker initial oxides ∼ 20 nm (MUMPs). Such results are interpreted and explained by a reaction-layer fatigue mechanism. Specifically, moisture-assisted subcritical cracking within a cyclic stress-assisted thickened oxide layer occurs until the crack reaches a critical size to cause catastrophic failure of the entire device. The entirety of the evidence presented here strongly indicates that the reaction-layer fatigue mechanism is the governing mechanism for fatigue failure in micron-scale polycrystalline silicon thin films.
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68.60.Bs Mechanical and acoustical properties
07.10.Cm Micromechanical devices and systems
68.37.Lp Transmission electron microscopy (TEM)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Tunable negative refraction based on the Pockels effect in two-dimensional photonic crystals composed of electro-optic crystals

Jian Li, Ming-Hui Lu, Liang Feng, Xiao-Ping Liu, and Yan-Feng Chen

J. Appl. Phys. 101, 013516 (2007); http://dx.doi.org/10.1063/1.2401281 (5 pages) | Cited 10 times

Online Publication Date: 11 January 2007

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A two-dimensional square lattice photonic crystal composed of ferroelectric cylinder rods in air background is proposed to realize tunable negative refraction by applying electric field. Based on the Pockels effect, refractive indices of rods can be changed linearly along with applied electric field, and then photonic band structure and equifrequency surface can be modified. The refractive angle could vary from negative to positive depending on intensity of electric field at a certain incident angle. The feasibility of the photonic crystal operating in visible region at the frequency of 476.5 THz was presented, which might have potential applications in photoelectronic devices.
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42.70.Qs Photonic bandgap materials
78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.80.-e Ferroelectricity and antiferroelectricity

Strain nonuniformity in GaAs heteroepitaxial films on Si(001) studied by x-ray diffraction

Artem Shalimov, Jadwiga Bąk-Misiuk, Vladimir M. Kaganer, Maria Calamiotou, and Alexandros Georgakilas

J. Appl. Phys. 101, 013517 (2007); http://dx.doi.org/10.1063/1.2407260 (6 pages) | Cited 4 times

Online Publication Date: 11 January 2007

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High-resolution x-ray diffraction measurements are used to fully characterize the strain state of relaxed highly mismatched GaAs films, grown on vicinal Si (001) substrates by molecular beam epitaxy. The nonuniformity of the misfit dislocation network at the GaAs/Si (001) interface is studied by analyzing the profiles of x-ray diffraction peaks and the reciprocal space maps for different reflections. The detailed analysis of the peak positions shows a dependence of the relaxation on the crystallographic direction, with the relaxation being larger in the direction perpendicular to the α-dislocation lines. Based on analytical expressions for the full width at half maximum in the longitudinal and transverse sections, an advanced version of the Williamson-Hall plot [ Acta Metall. 1, 22 (1953) ] is proposed that takes into account the geometry of dislocation distribution and the scattering geometry. We show that this type of analysis can reveal both the type and density of misfit dislocations. The measured peak widths are attributed to random uncorrelated 60°-type misfit dislocations with density much smaller than the total dislocation density required for lattice-mismatch relaxation. The major part of the GaAs/Si lattice mismatch is accommodated by periodic arrays of edge-type perfect dislocations that do not cause nonuniform strain in the film. The applied theoretical and experimental analysis is easily applicable on other zinc blende highly lattice-mismatched systems.
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68.60.Bs Mechanical and acoustical properties
68.35.Dv Composition, segregation; defects and impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Ge1−ySny/Si(100) composite substrates for growth of InxGa1−xAs and GaAs1−xSbx alloys

Radek Roucka, John Tolle, Brandon Forrest, John Kouvetakis, Vijay R. D’Costa, and José Menéndez

J. Appl. Phys. 101, 013518 (2007); http://dx.doi.org/10.1063/1.2407274 (7 pages) | Cited 5 times

Online Publication Date: 11 January 2007

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We describe unique methodologies for integration of InxGa1−xAs and GaAs1−xSbx semiconductor alloys with Si involving an innovative buffer layer approach based on lattice-engineered Ge1−ySny alloys. These are grown strain-free on Si(100) via formation of Lomer edge dislocations and exhibit a continuous selection of lattice parameters higher than that of Ge. This allows close lattice matching with the InxGa1−xAs and GaAs1−xSbx compounds, thereby providing a manifestly different approach to the integration of mismatched III-V semiconductors with silicon. A series of compositions across the entire alloy range were grown for both systems using metal organic chemical vapor deposition at low temperatures between 500–550 °C. The materials displayed high quality morphological, structural, and optical properties as evidenced by Rutherford backscattering spectroscopy, ion channeling, cross sectional transmission electron microscopy, atomic force microscopy, and photoluminescence characterizations. High resolution x-ray diffraction measurements indicated that the films grow with much less strain than those grown on conventional substrates.
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68.55.-a Thin film structure and morphology
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.37.Lp Transmission electron microscopy (TEM)

Influence of initial surface reconstruction on nitridation of Al2O3 (0001) using low pressure ammonia

B. Agnarsson, M. Göthelid, S. Olafsson, H. P. Gislason, and U. O. Karlsson

J. Appl. Phys. 101, 013519 (2007); http://dx.doi.org/10.1063/1.2384807 (7 pages) | Cited 3 times

Online Publication Date: 11 January 2007

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The purpose of this study is to investigate the effect of initial surface reconstruction on the nitridation process of Al2O3 (0001). This was done by exposing differently reconstructed sapphire substrates at different temperatures to low pressure ammonia (NH3). Structural and chemical analysis were carried out using low-electron energy diffraction and x-ray photoelectron spectroscopy. The experiments revealed that using low pressure ammonia (PNH3<1×10−5 Torr), no nitridation takes place on (1×1) unreconstructed surfaces. However, when the unreconstructed surface starts to change to a (math×math)R±9° reconstructed surface, with increasing substrate temperature, the nitridation becomes successful. When using the initially reconstructed surface, the nitridation is successful even from the lowest temperature used. These results suggest that the initial surface reconstruction has a major effect on the nitridation process. This kinetic behavior has not been reported before, with most nitridation studies mainly focusing on the effect of surface temperature on the resulting surface morphology, rather than the actual kinetics of the process itself.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Interpolation of quaternary III-V alloy parameters with surface bowing estimations

T. Mei

J. Appl. Phys. 101, 013520 (2007); http://dx.doi.org/10.1063/1.2404791 (6 pages) | Cited 1 time

Online Publication Date: 11 January 2007

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We present the weighted-sum expression of quaternary parameter estimations via balancing surface bowing estimation errors. Expressions have been derived for both quaternary alloys AxByCzD and AxB1−xCyD1−y and applied to the band gaps of AlGaInAs, AlGaInP, InAsPSb, GaInAsP, and GaInAsSb. Approximation can be improved by fitting known data of quaternary alloys and maximum deviations are less than 20 meV with respect to the lattice-matched polynomial expressions.
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81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
68.47.Fg Semiconductor surfaces

Attachment loss of micromechanical and nanomechanical resonators in the limits of thick and thin support structures

John A. Judge, Douglas M. Photiadis, Joseph F. Vignola, Brian H. Houston, and Jacek Jarzynski

J. Appl. Phys. 101, 013521 (2007); http://dx.doi.org/10.1063/1.2401271 (11 pages) | Cited 14 times

Online Publication Date: 11 January 2007

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Analytical expressions are provided for the energy loss from vibrating mechanical resonators into their support structures for two limiting cases: supports that can be treated as plates, and supports that act as semi-infinite elastic media, with effectively infinite thickness. The former case is applicable to many microscale resonators, while the latter is appropriate for nanoscale devices. General formulations are given, applicable to a wide range of resonator geometries. These formulations are then applied to two geometries commonly used in microelectromechanical systems and nanelectromechanical systems applications: cantilevered beams and doubly fixed beams. Experimental data are presented to validate the finite-thickness support theory, and the predictions of the theory are also compared to data from existing literature for a microscale rectangular paddle oscillator.
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07.10.Cm Micromechanical devices and systems

Relaxed graded SiGe donor substrates incorporating hydrogen-gettering and buried etch stop layers for strained silicon layer transfer applications

David M. Isaacson, Arthur J. Pitera, and Eugene A. Fitzgerald

J. Appl. Phys. 101, 013522 (2007); http://dx.doi.org/10.1063/1.2405237 (9 pages) | Cited 3 times

Online Publication Date: 12 January 2007

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We report on the use of buried, tensilely strained Si (i.e., ε-Si) layers for improving the fabrication of strained silicon-on-insulator (SSOI) substrate via the hydrogen-induced layer exfoliation process. Previous work involving tensile ε-Si0.4Ge0.6 layers in relaxed Ge/∇x(Si1−xGex)/Si demonstrated significant hydrogen gettering via the formation of strain-relieving platelets within the tensile ε-Si0.4Ge0.6 layers, leading to an overall increase in layer transfer efficiency for germanium-on-insulator substrate fabrication. The use of buried ε-Si layers in relaxed Si1−xGex for SSOI fabrication, however, exhibits more complex exfoliation behavior that is dependent on a combination of both the degree of tensile strain as well the amount of damage present in the adjacent Si1−xGex alloy. It was determined that a tensile strain level of approximately 1.6% in Si (corresponding to a Si0.6Ge0.4-based donor structure) was needed to overcome the intrinsic gettering potential of implantation damage in the adjacent Si0.6Ge0.4 layers to result in enhanced layer exfoliation. The primary mechanism responsible for improving layer exfoliation was found to be the formation of strain-relieving {100}-type platelets in the 1.6% strained-Si epilayer. Lastly, a Si0.6Ge0.4-based donor structure which incorporated ε-Si layers as transfer, hydrogen gettering, and etch stop layers was demonstrated. Such a structure may prove useful for the reuse of a significant portion of the original SSOI donor structure.
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61.72.Yx Interaction between different crystal defects; gettering effect
81.65.Tx Gettering
68.60.Bs Mechanical and acoustical properties

Accuracy limits and window corrections for photon Doppler velocimetry

B. J. Jensen, D. B. Holtkamp, P. A. Rigg, and D. H. Dolan

J. Appl. Phys. 101, 013523 (2007); http://dx.doi.org/10.1063/1.2407290 (10 pages) | Cited 16 times

Online Publication Date: 12 January 2007

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Symmetric, plate-impact experiments were performed to validate photon Doppler velocimetry (PDV) with established shock wave diagnostics. Impact velocity measurements using shorting pins demonstrated that the velocity accuracy of PDV can be 0.1% or better. Shock velocities and refractive indices were also measured with PDV (at 1550 nm) and velocity interferometer system for any reflector (VISAR) (at 532 nm) to obtain window corrections for single crystal LiF (100), c-cut sapphire, and z-cut quartz. Time-dependent, free-surface velocity histories for shocked LiF(100) provide a direct comparison between PDV and VISAR diagnostics and illustrate the benefits and shortcomings of the new diagnostic. Further implications of these results are presented.
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06.30.Gv Velocity, acceleration, and rotation
43.28.Mw Shock and blast waves, sonic boom

Modeling the optical constants of Cu2In4Se7 and CuGa3Se5 crystals

M. León, R. Serna, S. Levcenko, A. Nateprov, A. Nicorici, J. M. Merino, and E. Arushanov

J. Appl. Phys. 101, 013524 (2007); http://dx.doi.org/10.1063/1.2409608 (4 pages) | Cited 7 times

Online Publication Date: 12 January 2007

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Spectral dependence of the pseudodielectric function ε(E) = ε1(E)+iε2(E) as well as of the complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity of Cu2In4Se7 and CuGa3Se5 ordered vacancy compound crystals are modeled in the 0.8–4.4 eV photon energy range using a modification of Adachi’s model [ T. Kawashima et al. J. Appl. Phys. 84, 5202 (1998) ] for optical properties of semiconductors. Model parameters are determined using the acceptance-probability-controlled simulated annealing method. Excellent agreement with experimental data is obtained; the relative errors for the real ε1 and for imaginary ε2 part of the dielectric function are equal to 0.9%–1.5% and 3.2%–4.1% for the studied compounds.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
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