bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress and Defect Generation in Si Epitaxy
Authors: Wang Tien , Carlson Douglas 
Published: April 2011

ABSTRACTA quasi-static model is proposed to describe wafer deformation due to stress build up in the Si epitaxy process. The analysis takes into account temporal stress variations as the wafer sags into the dish-shaped pocket of the susceptor at a deposition temperature above 1100 °C. It is shown that the magnitude of the negative bending moment at the wafer supporting edge decreases over time. As a result, the maximum deflection at the wafer center and the tensile stress at the wafer supporting edge also decrease over time. The generation of slip defects near the wafer edge as the wafer responds the thermal, gravitational and contact stress is explored. A new test methodology is developed to track the time-varying wafer deflection. It allows for the measurement of quality of the susceptor and its fitness for use in the reactor system.
Evaluation on Stress and Optical Property of Thin Films Used in Optical MEMS Device
Authors: Sun Lianchao , Hou Ping 
Published: April 2011

ABSTRACTControl of the film stress and optical property has long been considered as an issue in the tunable optical MEMS (Micro-Electro-Mechanical Systems) devices. In this paper, the atmospheric evolution of Titanium Dioxide (TiO2) and Silicon Dioxide (SiO2) thin films for the optical MEMS devices were studied. These films were prepared by ion-assisted e-beam evaporation. It is found that as-deposited SiO2 films exhibit compressive stress; whereas, it is tensile in the TiO2 films under present processing conditions. When annealed at 150 °C, both SiO2 and TiO2 films show slight changes in stress with annealing time. However, increasing the anneal temperature to 250°C caused an apparent change of film stresses with time, in which SiO2 film turns into less compressive and TiO2 film appears to be more tensile. The optical properties after annealing were also investigated by measuring the thickness and the refractive index changes using the spectroscopic ellipsometry technique. At both experimental temperatures, the film thickness increases slightly and the refractive index at 1550 nm decreases a little at the initial annealing stage for SiO2 films. For TiO2 films, it is found that the refractive index increases after annealing at 250°C. This might be caused by the TiO2 film densification process during amorphous-to-crystalline phase transformation. Because most of the significant film evolutions occur during the initial 12 hours of annealing, a practical way of stabilizing the film properties in a MEMS device is to pre-anneal the as-deposited thin films.
Investigation of mechanical properties of mesoporous methyl-substituted SiO2 thin films (Methylsilesquioxane materials).
Authors: Verdier M. , Montagnat M. , Maîtrejean S. , Passemard G. 
Published: April 2011

ABSTRACTIn ULSI circuit, interlayer thin film with low dielectric constant shall be used in order to reduce the interconnection RC delay. One promising material is methylsilesquioxane (MSQ) deposited by spin coating with controlled porosity. High porosity combined with matrix weakness result in low mechanical properties that could be detrimental to circuit reliability.The aim of this study is to investigate the deformation behavior of mesoporous MSQ thin films by nanoindentation and by AFM analysis of residual indents. At first, proper measurement conditions were explored by modulating the film thickness from 100 nm up to 600nm for a fixed film density: the very low elastic modulus of the material on stiff substrate requires great care in the raw data analysis. Next, the density of these mesoporous films has been adjusted and the response to indentation is compared with dense bulk fused silica. AFM investigations lead to the sequence of fracture processes and to the sensitivity to hydrostatic pressure on the deformation of these materials.
Stress and texture in sputter deposited Cr films
Authors: Grachev S. Yu. , Kamminga J.-D. , Janssen G. C. A. M. 
Published: April 2011

ABSTRACTIntrinsic stress in coatings is often responsible for its performance. We studied tensile stress in sputter deposited chromium films as a function of film thickness and Ar pressure during deposition. We correlate the stress evolution to the grain growth in the polycrystalline films. Both grain growth and stress evolution obey the same power law dependence on thickness. We conclude that the tensile stress is generated at the grain boundaries. The power law exponent did not depend on pressure of Ar and remained 0.36. However, texture and microstructure in the layers changed when pressure was increased from 2×10-2 to 6×10-2 mbar. Texture switched from 110 to 111 fiber type. Grooves and sharp star-like grains were observed at higher pressure. We explain changes in terms of suppressed shadowing and less surface diffusion.
Effect of Dielectric Materials on Stress-Induced Damage Modes in Damascene Cu Lines
Authors: Paik Jong-Min , Park Hyun , Park Ki-Chul , Joo Young-Chang 
Published: April 2011

ABSTRACTVarious low-k materials are being pursued as dielectric materials for future interconnects. However, poor thermo-mechanical properties of low-k materials cause tremendous reliability concerns, thus the proper materials for integration with Cu are not suggested yet. In this study, the line width and spacing dependence of damascene Cu lines embedded by TEOS and low-k materials (CORAL) was analyzed using x-ray diffraction. Generally, the hydrostatic stress of Cu/TEOS was greater than that of Cu/CORAL, while the opposite for von-Mises stress. Using a three-dimensional finite analysis (FEA), the effect of low-k materials on the stress and its distribution in via-line structures of dual damascene Cu interconnects was studied. In the case of Cu/TEOS, the hydrostatic stress was concentrated at the via and on the top of the lines, where it was suspected that the void would nucleate. On the other hand, in the via-line structures integrated with organic low-k materials, large von-Mises stress was maintained in the via. Therefore, the deformation of via, rather than voiding, may be the main failure mode in the interconnects with low-k materials.
Stretchable conductors: thin gold films on silicone elastomer
Authors: Lacour Stéphanie P. , Wagner Sigurd , Suo Z. 
Published: April 2011

ABSTRACTThin stripes of gold deposited onto elastomeric substrates can be stretched reversibly by more than 20 % while remaining electrically conducting. We are developing such stripes to serve as electrical interconnects on stretchable electronic skins. The gold layers are 25-nm to 500-nm thick. We observe two different film morphologies: the stripe is either buckled and continuous, or flat and contains micrometer-long cracks. Stretchability is correlated with the thickness and initial topography of the gold layer. Stripes thicker than 100-nm fail electrically at tensile strain of ∼ 1 %, while thinner stripes remain conducting up to much larger strain. Upon stretching the buckled stripes flatten and break into islands of 1 to 100 micrometers on a side, while the initially microcracked stripes retain their micrometer scale structure. The electrical resistance of the buckled stripes is the lowest but the micro-textured stripes can be stretched more.
Effects of the substrate on the determination of hardness of thin films by the nanoscratch and nanoindentation techniques: A comparative study for the cases of soft film on hard substrate and hard film on soft substrate.
Authors: Tayebi Noureddine , Polycarpou Andreas A. , Conry Thomas F. 
Published: April 2011

ABSTRACTHardness values of Au/Fused Quartz and SiO2/Al systems, which correspond to the cases of soft film on hard substrate and hard film on soft substrate, were measured using both the nanoindentation and nanoscratch techniques. The effect of substrate interaction on the measurement of hardness using the nanoscratch technique is found to be much less pronounced compared to that of the nanoindentation technique. Such reduction in substrate effect is attributed to the features used in the nanoscratch analysis: (a) direct imaging of residual profile allows for the effect of pile-up/sink-in to be considered, (b) lower normal loads applied as compared to the nanoindentation, (c) effect of elastic recovery of the plastically deformed surfaces is included in the nanoscratch analysis, whereas the nanoindentation analysis is based solely on the load-displacement data. Moreover, experiments with residual scratch depths as shallow as 3 nm are used to estimate hardness of thin films; a promising indication for the use of such technique in the measurements of ultra-thin films.
Cracking and Phase Transformation in Silicon During Nanoindentation
Authors: Jang Jae-il , Wen Songqing , Lance M. J. , Anderson I. M. , Pharr G. M. 
Published: April 2011

ABSTRACTNanoindentation experiments were performed on single crystals of (100) Si using a series of triangular pyramidal indenters with centerline-to-face angles in the range 35.3° to 85.0°. The influences of the indenter geometry on cracking and phase transformation during indentation were systematically studied. Although reducing the indenter angle reduces the threshold load for cracking and increases the crack lengths, c, at a given indention load, P, the frequently observed relation between P and c3/2 is maintained for all of the indenters over a wide range of load. Features in the nanoindentation load-displacement curves in conjunction with Raman spectroscopy of the crystalline and amorphous phases in and around the contact impression show that the indenter geometry also plays a role in the phase transformation behavior. Results are discussed in relation to prevailing ideas about indentation cracking and phase transformation in silicon.
Effects of Process Parameters on the Adhesion of Copper Film on Polyethylene Tetrephthalate(Pet) Substrate Prepared by ECRMOCVD Coupled with a Periodic DC Bias
Authors: Hyun Jin , Jeon Bup Ju , Byun Dongjin , Lee Joong Kee 
Published: April 2011

ABSTRACTCharacteristics of Cu/C:H films on the PET substrate prepared by ECR-MOCVD coupled with a DC bias under Cu(hfac)2-Ar-H2 was investigated with special attention to process parameters. Our results showed that the Cu/C:H film has strongly adhere with the polymer substrate by chemical bonding and exhibited wide range of electrical conductivity that could be controlled by process parameters. The increase in H2/Ar ratio, microwave power and negative DC bias voltage brought on the higher pulling strength between Cu/C:H films and PET substrate. The effects of surface pretreatments of polymer substrate on pulling strength were insignificant in the range of our experimental range.
Adhesion Strength of Polymer Coatings studied by Laser Induced Delamination
Authors: Fedorov A. , van Veen A. , van Tijum R. , de Hosson J. Th. M. 
Published: April 2011

ABSTRACTLaser Induced Delamination is a novel technique aimed at quantification of adhesion of thin polymer films to a metal substrate. In this technique a high power IR pulsed laser beam (maximum 500 mJ in 5 ns) is used to create the primary delaminated area in the form of a blister. The blister is formed due to heating of the metal substrate and because of partial evaporation of the polymer material adjacent to the interface. By varying the power of the laser pulse the gas pressure inside the blister is increased until further delamination takes place. This critical pressure is related to the strength of adhesion of the polymer to the substrate. The shape of the blister (radius and height) is controlled with a stylus profiler and with an optical confocal microscope.In the present work 30 μm thick PET films on steel substrate were studied. From the shape of the obtained blisters the strength of adhesion of the polymer is estimated. Various models describing blister formation and growth are discussed.
An Atomistic View of Interface-Mediated Dislocation Plasticity in Thin Metal Films
Authors: Ege E. S. , Shen Y.-L. 
Published: April 2011

ABSTRACTAtomistic simulations using molecular statics are carried out to study dislocation plasticity in thin metal films attached to stiff substrates. The analysis utilizes a sample two-dimensional crystal, with an embedded initial point defect used for triggering dislocation activities in a controlled manner. The existence of an interface between the film and the substrate is shown to delay plastic yielding and lead to film strengthening. The capability of atoms to slide along the interface plays a crucial role in determining the macroscopic stress-strain response and the microscopic dislocation activities. Within the modeling framework we examine the quantitative interfacial sliding behavior and the resulting dislocation-interface interactions and their consequences.
Electrical and Photonic Functions in Transparent Oxide Semiconductors: Utilization of Built-in Nanostructure
Authors: Hosono Hideo 
Published: April 2011

AbstractWe review distinct photonic/electronic properties onginating from built-in nano-structures in transparent oxide based matenals, emphasizing potential of nanostructures hidden in crystal structure. Matenals focused are oxychalcogenides LaCuOCh (Ch=chalcogen ion) and homologous oxides InGaO3(ZnO)m(m=integer) having naturally formed multi-quantum well structures. Novel functions and devices ansing from the built-in nanostructure are: (1) modulation doping of positive holes and room temperature stable exciton in LaCuOCh, (2) high performance transparent field-effect transistor fabncated in InGaO3(ZnO)5 epitaxial thin films, and (3) conversion of insulator to persistent electronic conductor by carner doping in 12CaO 7A12O3 (C12A7).
Surface Electronic Structure of Nitric-oxide-treated Indium Tin Oxide
Authors: Jianqiao Hu , Jisheng Pan , Zhu Furong , Hao Gong 
Published: April 2011

ABSTRACTThe surface electronic properties of the nitric oxide (NO) treated indium tin oxide (ITO) are examined in-situ by a four-point probe and X-ray photoelectron spectroscopy (XPS). The XPS N1s peak emerged at a high binding energy of 404 eV indicating that NO is reactive with ITO. NO adsorption induces an increase of film sheet resistance, arising from an oxygen rich layer near the ITO surface region, with approximately 2.5 nm thick. This implies that the interaction of NO with ITO is occurred around surface region. Valence band maximum measured for NO-absorbed ITO was shifted to the low binding energy side. This is related to the upward surface band bending.
Emission of Rare Earth Ions Incorporated into Metal Oxide Thin Films and Fibres
Authors: Sildos Ilmo , Lange Sven , Tätte Tanel , Kiisk Valter , Kirm M. , Aarik J. 
Published: April 2011

ABSTRACTPhotoluminescence (PL) of undoped and Sm-doped TiO2, ZrO2and HfO2thin films and fibers was investigated at temperatures ranging from 6 to 300 K. The thin films were grown by the atomic layer deposition (ALD) technique and doped by using the ion implantation method. The fibers were prepared by using the sol-gel method whereas anin-situdoping was used to obtain the required concentration of Sm3+ions in the films. In undoped as well as doped materials, PL was efficiently excited via band-to-band transitions. The emission of undoped materials was attributed to the radiative recombination of self-trapped excitons (STE). In doped materials, intense emission of Sm3+was recorded. It is proposed, that there exists a concurrence between the radiative recombination of bound excitonic states and the energy transfer to Sm3+ions, particularly at lower temperatures.
Correlations Between Conditions of Synthesis, Phase Composition and Luminescent Properties of Eu - Polytantalate
Authors: Vasilyev Vladimir , Drehman Alvin , Bouthillette Lionel 
Published: April 2011

ABSTRACTCorrelations between synthesis conditions, phase composition, and spectral properties of the sintered ceramic, thin films and single crystals of EuTa7O19 phosphors have been studied using x-ray diffractometry and temperature dependent photoluminescence (PL) spectroscopy at temperatures between 18 K and 650 K. From the PL spectra of Eu3+, one can obtain information about the area of homogeneity of phases, their temperature transformations, and changes in the bonding character in the neighborhood of the luminescent ion. As a result, this information helps to optimize the synthesis parameters for luminescent materials.
Study of ZnTe:Cu/Metal Interfaces in CdS/CdTe Phovoltaic Solar Cells
Authors: Gessert T. A. , Perkins C. L. , Asher S. E. , Duda A. , Young M. R. 
Published: April 2011

ABSTRACTThe present model for current transport at the CdTe/p-ZnTe:Cu/metal back contact assumes that the CdTe and ZnTe valence bands align, while current transport at a highly doped ZnTe and a metal interface proceeds by tunneling. To test part of this model, we have investigated the electrical and material properties of CdS/CdTe devices where the outer metal is either Ti or Ni. Our results show that differences in device series resistance are not linked simply to metal/ZnTe:Cu interfacial contact resistance, but that metallization-induced diffusion remains a more likely cause of significant performance distinctions.
The Organic/Inorganic Interface in Micro and Nano Composite Materials
Authors: Tang Zhexiong , Wan Hui , Clark Robert , Yang Sze C. 
Published: April 2011

ABSTRACTWe report the synthesis of new inorganic/organic composite particles with a core/shell structure. The core component is an inorganic oxide (e.g. TiO2, CeO2 or MoO3), and the shell component is a double-strand polyaniline. Three methods for material synthesis were examined. The electrochemical properties of one type of the composite particles show electronic interaction between the organic conducting polymer shell and its inorganic core. The double-strand polyaniline in the composite shows better pH stability of the conductive form than that of the corresponding single-strand polyaniline in a similar core/shell composite.
High Current Injection to a UV-LED grown on a Bulk AlN Substrate
Authors: Nishida Toshio , Ban Tomoyuki , Saito Hisao , Makimoto Toshiki 
Published: April 2011

ABSTRACTWe applied a bulk AlN substrate to an AlGaN-based ultraviolet light emitting diode (UV-LED) and found that this combination enables high injection current, which shows the LED's potential for large ultraviolet flux extraction. Heat dissipation is an important issue for LEDs. Bulk AlN substrate has high thermal conductivity, a wurtzite crystal symmetry the same as that of nitride emitters, and transparency in the ultraviolet wavelength range. An UV-LED grown on a bulk AlN substrate shows output power linearity up to high injection current up to 300 mA, whereas a similar device grown on an AlN-template formed on a sapphire substrate only shows linearity up to an injection current of about 150 mA. It also showed very stable emission peak wavelength. For example, the emission peak shift is less than 2 nm in spite of the large injection current of 200 mA. Both findings are attributed to the heat dissipation afforded by the high thermal conductivity of the bulk AlN. This LED still suffers from internal absorption loss caused by the residual color centers in the AlN at present. However, further improvement of bulk AlN substrates will lead to high flux and highly efficient ultraviolet sources.
Growth and Characterization of AlN and GaN Thin Films Deposited on Si(111) Substrates Containing a Very Thin Al Layer
Authors: Reitmeier Zachary J. , Davis Robert F. 
Published: April 2011

ABSTRACTAlN films and GaN films with AlN buffer layers were deposited via metalorganic vapor phase epitaxy on Si(111) substrates previously exposed to trimethylaluminum for increasing times. Atomic force microscopy (AFM) was used to determine the influence of Al pre-flow time on the nucleation and surface morphology of the AlN and GaN films. When preceded by a 10 second Al pre-flow, AlN films feature an increased and more uniform nucleation density as compared to films deposited without Al pre-flows. Ten second Al pre-flows were also found to result in a reduction of the RMS roughness for 100 nm thick AlN films from 3.6 nm to 1.0 nm. AFM of 0.5 μm thick GaN films deposited on AlN buffers with varying pre-flow times showed reduced roughness and decreased pit density when using Al pre-flows of 10 or 20 seconds. High resolution x-ray diffraction of the GaN films showed a reduction in the average full-width halfmaximum (FWHM) of the GaN (00.2) reflection from 1076 arcsec to 914 arcsec when the AlN buffer layer was initiated with a 10 second Al pre-flow. Increasing the pre-flow time to 20 seconds and 30 seconds resulted in average (00.2) FWHM values of 925 arcsec and 928 arcsec, respectively. Similar behavior of the peak widths was observed for the (30.2) and (10.3) reflections when the pre-flow times were varied from 0 to 30 seconds.
MBE Grown AlN Films on SiC for Piezoelectric MEMS Sensors
Authors: Doppalapudi Dharanipal , Mlcak Richard , Chan Jeffrey , Tuller Harry , Bhattacharya Anirban , Moustakas Theodore 
Published: April 2011

AbstractMiniaturized piezoelectric sensors based on Microelectromechanical Systems (MEMS) offer the advantages of reduced size, reduced power consumption, increased sensitivity coupled with the ability to form compact multi-sensor arrays. Fabrication of such sensors from single crystal materials further insure more highly reproducible and stable devices with improved performance. In this paper, we describe the integration of MBE grown AlN films onto photoelectrochemically machined SiC microcantilevers and membranes. AlN exhibits excellent piezoelectric properties, including an electromechanical coupling coefficient of 0.088 and a high in-plane acoustic velocity (∼5700m/sec) as well as excellent thermal-mechanical compatibility with SiC. The fabrication of AlN-SiC-based microresonators and flexural plate wave devices, and their application to chemical, biological and fluid sensing, are reported.
N-rich GaNAs with High As Content Grown by Metalorganic Vapor Phase Epitaxy
Authors: Kimura Akitaka , Tang H. F. , Paulson C. A. , Kuech T. F. 
Published: April 2011

ABSTRACTGaN1-yAsy epitaxial alloys on the N-rich side with high As content were grown by metalorganic vapor phase epitaxy. They had specular surfaces and the single-phase epitaxial nature was confirmed by X-ray diffraction. The As incorporation increased through both a decrease in the growth temperature and V/III ratio. These trends were similar to that found in other III-V alloy systems which exhibit a large miscibility gap and the anion incorporation was considered to have been limited kinetically under the conditions of the low V/III ratio. The range of achieved As content was extended up to y=0.067, which is a composition well within the miscibility gap. The As-content dependence of the band gap energy was determined by optical absorption measurements and large bowing parameter of 16.8 ± 0.9 eV was determined.
Curvature and strain in thick HVPE-GaN for quasi-substrate applications
Authors: Roder Claudia , Böttcher Tim , Paskova Tanya , Monemar Bo , Hommel Detlef 
Published: April 2011

ABSTRACTUncracked HVPE-GaN layers of different thicknesses were investigated using high resolution x-ray diffraction at variable temperatures. The absolute lattice parameters as well as the wafer curvature were measured simultaneously at different temperatures. All samples were found to be under biaxial tension at growth temperature. At room temperature the GaN film is under biaxial compression while the substrate is tensile strained. A simulation of the stress and curvature of the heterostructures was performed for different thicknesses of the films and substrates and a good agreement was found with the experimentally determined values.