bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thickness Dependences of the Thermoelectric Properties in (001)KCl/PbTe/SnTe/PbTe Heterostructures
Authors: Rogacheva Elena I. , Nashchekina Olga N. , Lyubchenko Svetlana G. , Vekhov Yegor O. , Dresselhaus Mildred S. , Dresselhaus Gene 
Published: April 2011

ABSTRACTThe dependences of the thermoelectric properties of (001)KCl/PbTe/SnTe/PbTe three-layer structures on the SnTe layer thickness (dSnTe = 0.5–6.0 nm) at a fixed thickness of PbTe layers were studied. It was established that the thickness dependences of the Seebeck coefficient, the Hall coefficient, electrical conductivity, charge carrier mobility, and the thermoelectric power factor are distinctly non-monotonic. Two possible reasons for this non-monotonic behavior of the thickness dependences of the thermoelectric properties are considered: the size quantization of the energy spectrum in a SnTe quantum well and / or the formation of edge misfit dislocations at the interfaces after reaching the critical thickness, which corresponds to the transition from a pseudomorphic growth to the introduction of misfit dislocations at the interfaces. It is suggested that the observed effect has a general character and should be taken into account when optimizing thermoelectric properties of superlattices.
Synthesis, Crystal Structure and Thermoelectric Properties of β-K2Bi8Se13 Solid Solutions
Authors: Kyratsi Theodora , Chung Duck Young , Dyck Jeff S. , Uher Ctirad , Lal Sangeeta , Loo Sim , Hogan Tim , Ireland John , Kannewurf Carl R. , Hatzikraniotis Evripides , Paraskevopoulos Konstantinos M. , Kanatzidis Mercouri G. 
Published: April 2011

ABSTRACTSolid solution series of the type K2Bi8-xSbxSe13, K2-xRbxBi8Se13 as well as K2Bi8Se13-xSx were prepared and the distribution of the atoms (Bi/Sb, K/Rb and Se/S) on different crystallographic sites, the band gaps and their thermoelectric properties were studied. The distribution Se/S appears to be more uniform than the distribution of the Sb and Rb atoms in the β-K2Bi8Se13 structure that shows preference in specific sites in the lattice. Band gap is mainly affected by Sb and S substitution. Seebeck coefficient measurements showed n-type character for of all Se/S members. In the Bi/Sb series an enhancement of p-type character was observed. The thermoelectric performance as well as preliminary high temperature measurements suggest the potential of these materials for high temperature applications.
Microstructure – Mechanical Properties Relationship of Laser Interference Irradiated Ni/Al Multi-Film
Authors: Daniel C. , Lasagni A. , Mücklich F. 
Published: April 2011

ABSTRACTDue to the corresponding intermetallic compounds, Ni/Al multi-layered thin film systems are important to protect against the mechanical and chemical impacts on the bulk component. The mechanical properties of these intermetallic compounds, NiAl, can be further improved by combining with other stiff phases. The mechanical properties would be optimized if the lateral surface composite can be made in such a way that the different phases are arranged periodically with a preferred orientation, micro-scaled period and reticulated phase interfaces. Such optimized surface composites have been achieved by laser interference irradiation in a nano-grained structure.In this study, the thin film systems are produced by physical vapor deposition and subsequently irradiated by the interference pattern of two or more coherent laser beams. The corresponding periodical heat treatment has been analyzed by thermal simulation, and thermal simulation results are compared with the experimental results. Further, the phase transitions during laser interference irradiation are calculated. The structural investigations of irradiated films - grain sizes and deformation by TEM, stress and texture by XRD - are compared with the mechanical properties - hardness and Young's modulus by NI-AFM.
Young's Modulus, Poisson's Ratio, and Nanoscale Deformation Fields of MEMS Materials
Authors: Chasiotis I. , Cho S. W. , Friedmann T. A. , Sullivan J. P. 
Published: April 2011

ABSTRACTThe mechanical properties of hydrogen-free tetrahedral amorphous diamond-like carbon have been investigated in connection with its elastic and failure properties. Micro-tension specimens of gage thickness of 1.2–1.8 μm and widths of 10 μm or 50 μm have been fabricated by the Sandia National Laboratories (SNL). The mechanical characterization has been conducted via in situ AFM measurements and Digital Image Correlation (DIC) data strain analysis and the local deformation fields of (a) uniform and (b) internally notched tension specimens with acute notches (K=27) have been experimentally obtained. Young's modulus and Poisson's ratio were measured for the first time directly from such small specimens and averaged 750 GPa and v=0.16 respectively, while the tensile strength was found to be very consistent averaging 7.1 GPa. Stressed material domains with smaller dimensions in the vicinity of micronotches exhibited even higher failure strengths reaching 11.5 GPa with limited data scatter. AFM images of in situ tested specimens have indicated sp3 to sp2 phase transformations on the film surface that was subject to ultra-high tensile stresses (>6 GPa). This is the first time these phase transformations are observed during tensile tests of brittle materials.
Effects of Thickness and Indenter Geometry in Nanoindentation of Nickel Thin Films
Authors: Parakala Padma , Mirshams Reza A. , Nasrazadani Seifollah , Lian Kun 
Published: April 2011

ABSTRACTEffects of thickness and tip geometry on Ni thin films deposited on Cu substrate were studied using nanoindenter. The deformation mechanisms in correlation to hardness measurements were discussed at various loads and depths of penetration. The Berkovich, Cube corner and Conical tips have been used in this study. Initially, the hardness and modulus of elasticity were measured at a depth of 10% of film thickness. The depth of penetration was increased to 20% to observe the depth effects. Analysis of data showed that there is an Indentation Size Effect (ISE) irrespective of indenter tip geometries.
Temperature Dependence of Biaxial Modulus and Thermal Expansion Coefficient of Thin Films Using Wafer Curvature Method
Authors: Capanu M. , Cervin-Lawry A. , Patel A. , Koutsaroff I. , Woo P. , Wu Lynda , Oh J. , Obeng J. , McClelland B. 
Published: April 2011

ABSTRACTThe present work uses wafer curvature (disk) method to measure the temperature variation of the biaxial modulus and the thermal expansion coefficient TEC from 25°C to 205°C. The following thin films were measured: PolySi, low stress LPCVD SixNy and (Ba0.7, Sr0.3)TiO3 (BST). To improve the precision, perfect circular thin wafers were used: 4 inches circular 280μm thick <111>Si and 450μm thick Fused Silica. The measurements were performed using a commercial Tencor FLX2320 Stress Measurement System. The film thickness was measured with Tencor TF1 thin film optical system.
Stress-field in Sputtered Mo Thin Films and Mo/Ni Superlattices: Origin and Evolution after Ion-Irradiation
Authors: Debelle A. , Abadias G. , Michel A. , Jaouen C. , Guérin Ph. , Drouet M. 
Published: April 2011

ABSTRACTIn the present study the ion irradiation technique is used to investigate the origin of the stress-field in Mo layers grown by ion beam sputtering. Strain measurements were performed by X- ray Diffraction (XRD) using the sin2ψ method. The evolution of the sin2ψ plots with ion irradiation shows that the usual assumption of a biaxial stress state is not adequate to determine the true stress-free lattice parameter a0 of the film. A new stress model based on a triaxial state of stress, which includes a hydrostatic component linked to point defects induced volume distortions, is derived to interpret the XRD results. For pure Mo films, the obtained a0 parameter is close to the bulk value, while for Mo sublayers in Mo/Ni superlattices, the a0 value is lower due to intermixing between Ni and Mo. These results demonstrate that ion irradiation is a powerful tool for stress relaxation, which allows to obtain additional information on the respective contribution of chemical effects and growth defects to the a0 value.
Fracture in Thin Oxide Films
Authors: Bahr D. F. , Olson A. L. , Morasch K. R. , Kennedy M. S. , Rodriguez Marek D. , Alamr A. 
Published: April 2011

ABSTRACTIn thin film systems, failure often occurs via fracture mechanisms, with either through thickness cracking or interfacial delamination leading to failure of the device or layer. Measuring the stress at which fracture occurs in these thin film systems requires testing methods amicable to both the small scale of the films as well as the complex relationship between the mechanical properties of the film and the substrate. This paper will cover two oxide film systems, a piezoelectric ceramic (PZT) on platinum and passive oxide films (primarily Cr2O3) on stainless steels. Both will be tested with a bulk method (bulge testing in the case of PZT and circumferentially notched tensile bars for the stainless steel) and then with a nanoindentation method developed for testing fracture for hard coatings on soft substrates. The differences in stresses required for failure between the bulk and the nanoscale tests will be discussed in terms of differences in flaw population.
Measurement of Residual Stress in ZnO Thin Films Deposited on Silicon Wafers by the Indentation Fracture Test
Authors: Zhang Tong-Yi , Huang Bin 
Published: April 2011

ABSTRCT:The indentation fracture test was used to evaluate residual stress in ZnO thin films deposited on silicon wafers. Using the calibrated constants involved in a simple semi-empirical formula, which was developed based on fracture analysis and experimental results, we estimated the residual stress in the ZnO thin films by measuring the indentation-induced crack length as a function of the indentation load.
Fracture patterns in thin films and multilayers
Authors: Volinsky Alex A. , Meyer Dirk C. , Leisegang Tilmann , Paufler Peter 
Published: April 2011

ABSTRACTWhile there are many stress relief mechanisms observed in thin films, excessive residual and externally applied stresses cause film fracture. In the case of tensile stress a network of through-thickness cracks forms in the film. In the case of compressive stress thin film buckling is observed in the form of blisters. Thin film delamination is an inseparable phenomenon of buckling. The buckling delamination blisters can be either circular, straight, or form periodic buckling patterns commonly known as telephone cord delamination morphology.While excessive biaxial residual stress is the key for causing thin film fracture, either in tension, or compression, it is the influence of the external stress that can control the final fracture pattern. In this paper we consider phone cord buckling delamination observed in compressed W/Si and TiWN/GaAs thin film systems, as well as spiral and sinusoidal though-thickness cracks observed in Mo/Si multilayers under 3-point high-temperature bending in tension.
A Membrane Deflection Fracture Experiment to Investigate Fracture Toughness of Freestanding MEMS Materials
Authors: Espinosa H. D. , Peng B. 
Published: April 2011

ABSTRACTThis paper presents a novel Membrane Deflection Fracture Experiment (MDFE) to investigate the fracture toughness of MEMS and other advanced materials in thin film form. It involves the stretching of freestanding thin-film membranes, in a fixed-fixed configuration, containing pre-existing cracks. The fracture behavior of ultrananocrystalline diamond (UNCD), a material developed at Argonne National Laboratory, is investigated to illustrate the methodology. When the fracture initiates from sharp cracks, produced by indentation, the fracture toughness was found to be 4.7 MPa m1/2. When the fracture initiates from blunt notches with radii about 100 nm, machined by focused ion beam (FIB), the mean value of the apparent fracture toughness was found to be 7.2 MPa m1/2. Comparison of these two values, using the model proposed by Drory et al. [9], provides a correction factor of 2/3, which corresponds to a mean value ofρ/2x=1/2.
Stress Relaxation during Isothermal Annealing at Elevated Temperatures in Electroplated Cu Films
Authors: Hwang Soo-Jung , Joo Young-Chang , Koike Junichi 
Published: April 2011

ABSTRACTDeformation mechanisms of electroplated Cu thin films on TaN/SiO2/Si were investigated by performing isothermal annealing above 200 °C. Stress relaxation behavior during isothermal annealing was analyzed by curve fitting using exponential decay equations. During heating, fast relaxation and subsequent slow relaxation processes were observed. In contrast, during cooling, only slow relaxation process was observed. Among possible mechanisms for stress relaxation, diffusion creep was found to be the most plausible mechanism based on the obtained values of the activation energy. It was suggested that the slow relaxation process observed both in the heating and in the cooling processes was attributed to a grain-boundary diffusion creep. On the other hand, the fast relaxation process observed during heating was attributed to a surface-diffusion controlled mechanism. The surface diffusion mechanism was considered to be characteristic to Cu thin films that did not form stable surface oxide.
Thermal Stability and Internal Stress for Strongly (111) Oriented Cu Films
Authors: Takayama Sinji , Oikawa Makato , Himuro Tokuji 
Published: April 2011

ABSTRACTInternal stresses and thermal stability of strongly (111) oriented Cu thin films, which are one of promising interconnect materials in advanced ULSI devices, have been studied comparing with those of non-oriented Cu films. Their internal stresses parallel to a film surface were measured by a conventional X-ray diffraction technique (d-spacing vs. sin2ψ method), while the strain distribution with depth by a grazing incidence X-ray scattering (GIXS) methods. Large stress relaxation in strongly (111) oriented Cu films takes place at 200°C without showing any significant grain growth and formation of thermal defects like hillocks. The residual internal stresses of highly oriented (111) Cu films increase almost linearly throughout the thickness up to the substrates. The feature of stress distribution in film depth does not change on annealing. The changes of the residual stresses at each depth are nearly the same as stresses parallel to film surface measured.
In situ investigation of growth of gold on crystalline TiO2 and amorphous Al2O3 substrates
Authors: Lauter L. , Abermann R. 
Published: April 2011

ABSTRACTThe growth of thin gold films on highly crystalline TiO2 and amorphous Al2O3 substrates and its dependence on substrate temperature was investigated under UHV-conditions by in situ internal stress measurements. Deposition of gold on amorphous Al2O3 at substrate temperatures between 27°C and 300°C shows a stress vs. thickness curve which indicates island growth at first and the formation of a polycrystalline film at higher thickness. A comparable stress vs. thickness curve is found for the growth of gold on the highly crystalline TiO2 substrate at substrate temperatures below 200°C, again indicating island growth. At higher temperatures, however, a new tensile stress feature at low gold coverage is interpreted to indicate the formation of a strained interface layer. This strain in the gold film is eliminated after deposition of a few monolayers most likely through incorporation of dislocations and defects. The growth stress at higher film thickness is indicative of island film growth.
Thickness Dependent Stress Relaxation with the Onset of L10 Ordering in FePt Thin Films
Authors: Wierman K. W. , Platt C. L. , Howard J. K. 
Published: April 2011

ABSTRACTDuring the chemical ordering of the high anisotropy FePt L10 phase a fcc-→fct structural distortion in the unit cell occurs. Monitoring the stress relaxation time dependencies during isothermal annealing cycles may lead to a better understanding of the L10 ordering kinetics thickness dependencies in thin FePt films. During the isothermal portion of the anneal cycle all films showed an exponentially decaying stress relaxation with time to lower compressive stress states for all temperatures and thickness. The stress relaxation rate increased significantly with an increase in Fe51Pt49 film thickness and annealing temperature. Stress relaxation activation energies of 2.21 eV, 2.40 eV, and 2.96 eV for the 50nm, 25nm, and 10nm Fe51Pt49 films, respectively, were extracted. This correlated well with the observed trends in the post annealed film coercivity, increase of the (001) superlattice L10 peak, and the shifting of the (111) peak position, all indicators of L10 chemical ordering transformation.
PROBING STRAIN FIELDS ABOUT THIN FILM STRUCTURES USING X-RAY MICRODIFFRACTION
Authors: Murray C. E. , Noyan I. C. , Mooney P. M. , Lai B. , Cai Z. 
Published: April 2011

ABSTRACTThe transfer of strain between thin film features and the underlying substrate represents an important factor in the performance and reliability of semiconductor devices, particularly as the distances between these structures decrease. In order to characterize the interaction regions produced in the substrate due to strained thin film structures, we employed synchrotron-based x-ray diffraction techniques to map the enhanced diffracted intensity of the single-crystal Si substrate at sub-micron resolution. The dynamic-to-kinematic transition observed in the scattering of x-rays from deformed crystals makes this technique extremely sensitive to the amount of substrate deformation as a function of position. Measurements were conducted on 1 μm thick Ni dots evaporated onto Si (111) substrates and 0.24 μm thick, heteroepitaxially grown SiGe strips of various widths on Si (001). The interaction field resolved by the enhanced Si diffracted intensity in the substrate extended up to 100 times the thickness of these features. Although the boundary of the interaction field varied as a function of feature width, a characteristic curve was generated to describe the decay rate of enhanced Si diffracted intensity when the distance from the feature edge is normalized by a mean interaction distance (MID). The rate of decay of the strain fields predicted by traditional treatments of the mechanical interaction between the thin film and substrate did not correspond to the measured decay rates.
Stress and Strength of free-standing 2-dimensional tetrahedral amorphous carbon bridge arrays
Authors: Chua Daniel H.C. , Tsai T. H. , Milne W. I. , Sheeja D. , Tay B. K. 
Published: April 2011

ABSTRACTThe fabrication of ultrathin (25nm) 2-dimensional free-standing arrays of tetrahedral amorphous Carbon (ta-C) microbridges is reported for the first time. The ta-C films were deposited by a Filtered Cathodic Vacuum Arc (FCVA) deposition system where the sp3 content in the film was measured to be in excess of 90% by high resolution XPS. Continuous arrays of free standing taC bridges whose length/width ratios ranged from 1:1 to 12:1 were successfully fabricated while maintaining the same thickness. Due to the naturally high compressive stress of ta-C films, the buckling of films was perpendicular to the length of the beam. The displacement of curvature obtained was in good agreement with FEM simulation results. Moreover, the curvature or arch of these ultrathin films, coupled with a high Young's modulus (750GPa) and Hardness (60GPa), meant they could withstand a vertical force in excess of 8000μN without breaking.
Dislocation Dynamics in Semiconductor Thin Film-Substrate Systems
Authors: Tan E. H. , Sun L. Z. 
Published: April 2011

ABSTRACTA discrete dislocation dynamics model is developed to establish the equations of motion for three-dimensional interacting dislocation loops in the semiconductor thin film – substrate system. The film is assumed to be an elastic layer and is perfectly bonded with another elastic substrate. Dislocation loops are discretized into segments, each of which is represented by a parametric space curve of specific shape functions and associated degree of freedom. The dislocation stress field is calculated as an essential ingredient in the dislocation dynamics method. Dislocation dynamics and interaction with film surface/interface are simulated.
A Coupled Cellular Automata Representation of Nanoscale Transport Across Semiconductor Interfaces
Authors: Radkowski Peter P. F. , Sands Timothy D. 
Published: April 2011

ABSTRACTThin-film devices pose unique challenges to device simulators. Relaxation approximations to the Boltzmann Transport Equation may be vitiated as the width and length of the thin-film components approach the mean free path lengths of electrons and phonons. Concomitant with these reduced lengths, surface and other interface scattering mechanisms exert greater influences on the transport processes. Consequently, it may not be effective to use transport models that depend upon analytic or other pre-ordained representations of electron, phonon, and photon distribution functions. Finally, thin-film simulations must account for tunneling processes, local defects, nanoscale dopant gradients, nanoscale roughness, and nanoscale variations in local geometries. Consequently, it is desirable to develop a nanoscale simulation technique that (1) can arbitrarily vary material properties in real space while (2) tracking reciprocal space scattering for arbitrary and volatile distributions of electrons, phonons, and photons. The Discrete State Simulation (DSS) forms the backbone of such a simulation. Written with the run-time flexibility of object-oriented code, the Discrete State Simulation (DSS) is a coupled cellular automata (CA) simulator that builds upon the objects and rules of quantum mechanics. The DSS represents global non-equilibrium processes as patterns that emerge through an ensemble of scattering events that are localized at vibronic nodes. The run-time flexibility of the DSS enables dynamic rule construction - computational algorithms that evolve in response to the conditions that are being simulated. The reported DSS effort simulated nanoscale transport processes at dopant-defined junctions by coupling electron-phonon and electron-photon scattering mechanisms. Using electronic band structures, phonon band structures, and deformation potentials analogous to silicon <100> material properties, the DSS generated data depicted the dynamic band bending induced by femtosecond variations in applied electric fields.
Photochemical Bonding of Fluorocarbon and Fused Silica Glass for Ultraviolet Ray Transmitting
Authors: Asano Kenji , Murahara Masataka 
Published: April 2011

ABSTRACTFluorocarbon was photo-chemically combined to a fused silica glass with the silicon oil used as a bonding agent. Balsam, unsaturated polyester resins and UV hardening adhesives have been generally used for joining two optical glasses together. They, however, have a strong absorption band in the UV region. Therefore, a new bonding method was developed for optical materials to allow UV rays to pass through using silicone oil and excimer- lamp. This new method requires the fluorocarbon-polishing pad employed in our PCP (Photo-Chemical Polishing) method in hydrofluoric acid ambience, which is bonded with the silica glass. The silicone oil was put between the fused silica glass and the fluorocarbon (FEP), and an excimer- lamp was irradiated. When the excimer lamplight was irradiated vertically, the silicon oil ((-O-Si(CH3)-O-)n) was photo-dissociated and reacted with the oxygen adsorbed on the silica glass surface to produce a SiO2. On the other hand, the H atoms photo-dissociated from the silicon oil pulled out the F atoms of the FEP. As a result, the FEP and the silica glass were combined. The tensile strength of the sample bonded by the photo-chemical reaction was evaluated. The tensile strength of 5.4 [kgf/cm2] was obtained, whereas that of the non-treatment sample was nil. Moreover, the transmittance of the vitrified silicone oil was measured at the 193 nm of ArF laser wavelength. It increased by 90.6% from 29.2% without the UV photon irradiation. The results showed that the silicon oil changed to silica glass by the excited oxygen, which improved the UV rays under 200nm transmittance.