bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Bio-Stable and Biodegradable Composites for Tissue Replacement and Tissue Regeneration
Authors: Wang Min
Published: June 2019

Bone is the substantial unit of human skeletal system, which supports the body and its movement. At the ultra-structure level, the bone matrix is a composite material consisting of bone mineral particles, which are mainly substituted, calcium-deficient hydroxyapatite, and collagen, which is a natural polymer. Bone serves as the template for developing bone replacement materials. Research on biomaterials analogous to bone was started in the early 1980s by incorporating bioactive particles into biocompatible polymers so as to produce bone substitutes. Over the last two decades, a variety of bioactive polymer matrix composites have been developed for tissue substitution and tissue regeneration. The bioactive phases in these composites are normally one of the calcium phosphates, especially synthetic hydroxyapatite (HA, Ca10(PO4)6(OH)2) which closely resembles bone apatite and exhibits osteoconductivity. If enhanced bioactivity is required, bioceramics having higher bioactivity such as Bioglass® and A-W glass-ceramic can be used as the bioactive phase in the composites. For tissue replacement, bio-stable polymers such as polyethylene (PE) and polysulfone (PSU) are used as the matrix polymer. For tissue regeneration, natural, biodegradable polymers such as polyhydroxybutyrate (PHB) and chitin are used as matrices. Furthermore, mechanical as well as biological performance of a particular composite can be controlled by varying the amount of the bioactive phase in the composite, thus meeting specific clinical requirements. For bioactive ceramic-polymer composites, major influencing factors such as shape, size and size distribution of bioactive particles, mechanical properties and volume percentage of the bioactive phase, properties of the matrix polymer, distribution of bioactive particles in the matrix and the particle-matrix interfacial state should be controlled in order to obtain materials of desirable properties. Various techniques are used to evaluate the composites.
The Investigation on Preparation & Physicochemical Process of Nanosized Hydroxyapatite Powder
Authors: Song Yunjing , Wen Shulin , Li Musen
Published: June 2019

The investigations of the preparation and physicochemical process of the HA nanostructured powder with high performance have been performed at present study. The HA preparation starts from the ethanol solution of calcium nitrate tetra-hydrate and phosphorous pentoxide as raw materials. The characterization of the effects of reacting temperatures on preparation, the crystalline degrees (some amorphous HA formed at certain condition) of the reacting products are carried out in the meanwhile. The physicochemical processes and the conditions for different reactions stages of the HA preparation have been traced and characterized by the TG-DTA (thermogravimetric and differential thermal analysis), the FTIR (Fourier-transformed infrared spectroscopy) and other methods. The investigations of the chemical reactions for the HA preparation show that the synthesis of HA is completely finished at the temperature of 500°for hours. The grain sizes and shapes of the HA reacting products are observed and characterized by the TEM and the XRD. The results show that the mean diameters of these product grains are as fine as 30-40nm at the temperature of 500°C. The XRD pattern of the present HA powders sintered at 500°C for 2h coincided very well with the JCPDS standards showing its superior purity and therefore, with really high performance for later applications.
Magnetic Material Arrangement In Apis MelliferaAbdomens
Authors: Esquivel Darci M. S. , Wajnberg Eliane , Cernicchiaro Geraldo R. , Acosta-Avalos Daniel , Garcia B.E.
Published: June 2019

Honeybees are the most studied insects in the magnetic orientation research field. Experiments on the magnetic remanence of honeybees have shown the presence of magnetite nanoparticles, aligned transversely to the body axis on the anterodorsal abdomen horizontal plane. These results support the hypothesis of ferromagnetic sensors for the magnetoreception mechanism. An Electron Paramagnetic Resonance (EPR) study identified isolated magnetite nanoparticles and aggregates of these particles with a low temperature transition (52 K – 91 K). Hysteresis curves of Apis mellifera abdomens organized parallel and perpendicular to the applied magnetic field were obtained from 5K to 310K. At low temperatures, the hysteresis curves indicate a preferential orientation of the magnetic easy axis parallel to the body axis. The saturation (Js) and remanent (Jr) magnetizations, coercive field (Hc) and initial susceptibility (Ψ) were obtained. Results were interpreted based on the presence of magnetite nanoparticles with 50 K and 120 K mean blocking temperatures.
Thermal Properties of Mineralized and Non Mineralized Type I Collagen in Bone
Authors: Lozano L. F. , Peña-Rico M. A. , Jang-Cho H. , Heredia A. , Villarreal E. , Ocotlán-Flores J. , Gomez-Cortes A. L. , Aranda-Manteca F. J. , Orozco E. , Bucio L.
Published: June 2019

The research about the structural stability of bone, as a composite material, compromises a complete understanding of the interaction between the mineral and organic phases. The thermal stability of human bone and type I collagen extracted from human bone by different methods was studied in order to understand the interactions between the mineral and organic phases when is affected by a degradation/combustion process. The experimental techniques employed were calorimetry and infrared spectroscopy (FTIR) techniques. The extracted type I collagens result to have a bigger thermal stability with a Tmax at 500 and 530 Celsius degrees compared with the collagen present in bone with Tmax at 350 Celsius degrees. The enthalpy value for the complete degradation/combustion process were similar for all the samples, being 8.4 +- 0.11 kJ/g for recent bones diminishing with the antiquity, while for extracted collagens were 8.9 +- 0.07 and 7.9 +-1.01 kJ/g. These findings demonstrate that the stability loss of type I collagen is due to its interactions with the mineral phase, namely carbonate hydroxyapatite. This cause a change in the molecular properties of the collagen during mineralization, specifically in its cross-links and other chemical interactions, which have a global effect over the fibers elasticity, but gaining tensile strength in bone as a whole tissue. We are applying this characterization to analyze the diagenetic process of bones with archaeological interest in order to identify how the environmental factors affect the molecular structure of type I collagen. In bone samples that proceed from an specific region with the same environmental conditions, the enthalpy value per unit mass was found to diminish exponentially with respect to the bone antiquity.
Self-Assembly of Hydrogels From Elastin-Mimetic Block Copolymers
Authors: Wright Elizabeth R. , McMillan R. Andrew , Cooper Alan , Apkarian Robert P. , Conticello Vincent P.
Published: June 2019

Triblock copolymers have traditionally been synthesized with conventional organic components. However, triblock copolymers could be synthesized by the incorporation of two incompatible protein-based polymers. The polypeptides would differ in their hydrophobicity and confer unique physiochemical properties to the resultant materials. One protein-based polymer, based on a sequence of native elastin, that has been utilized in the synthesis of biomaterials is poly (Valine-Proline-Glycine-ValineGlycine) or poly(VPGVG) [1]. This polypeptide has been shown to have an inverse temperature transition that can be adjusted by non-conservative amino acid substitutions in the fourth position [2]. By combining polypeptide blocks with different inverse temperature transition values due to hydrophobicity differences, we expect to produce amphiphilic polypeptides capable of self-assembly into hydrogels. Our research examines the design, synthesis and characterization of elastin-mimetic block copolymers as functional biomaterials. The methods that are used for the characterization include variable temperature 1D and 2D High-Resolution-NMR, cryo-High Resolutions Scanning Electron Microscopy and Differential Scanning Calorimetry.
Antimicrobial Coatings Obtained in an Atmospheric Pressure Dielectric Barrier Glow Discharge
Authors: Paulussen Sabine , Vangeneugden Dirk , Goossens Olivier , Dekempeneer Erik
Published: June 2019

This paper addresses the development of plasma polymer coatings that should prevent bacteria from adhering to medical devices, implants, textile fibers, packaging materials, etc. The two main parameters affecting bacterial colonization onto surfaces are the surface energy and the surface roughness. Both parameters can be adjusted by the deposition of a thin plasma polymer coating in an atmospheric pressure dielectric barrier glow discharge. According to SEM, FTIR, SPM, XPS and contact angle measurements, smooth, hydrophilic plasma polymer coatings were obtained under specific plasma conditions starting from 2-hydroxyethyl methacrylate (HEMA) and ethyl diazoacetate (EDA).
Calcium Carbonate Reinforced Natural Polymer Composite For Bone Grafts
Authors: Kalita Samar J. , Bose Susmita , Hosick Howard L. , Martinez Steve A. , Bandyopadhyay Amit
Published: June 2019

Challenges in tissue engineering have always-motivated scientists and engineers to develop new biomaterials that can restore the structural features and physiological functions of natural tissues. A novel ceramic-polymer composite was processed with bio-active ceramics dispersed in a natural bio-active polymer for bone graft applications. A commercially available caster bean extract polymer (CBP) was used. It is a natural polymer extracted from the oily caster beans of the dicotyledonous class. During processing of these composites, in situ random interconnected porosity was generated similar to natural bone. Hg-porosimetry results of these composites show that most of the pores are between 50 to 150 microns. Compression tests were performed on cylindrical samples to determine the mechanical properties. Average compression modulus was calculated as 173 MPa, while the average failure strength was 6.7 MPa. Cytotoxicity and cell proliferation studies were conducted with modified human osteoblast cell-line (OPC-1) to show that these composites are biocompatible. Composites showed good cell attachment with a continuous increase in cell growth for at least up to two weeks.
Synthesis and Characterization of Electrostatical Self-Assembly CdSe/Polymer Nanocomposite Films
Authors: Zhang Liangmin , Zhang Fajian , Claus R. O.
Published: June 2019

Using a novel electrostatic self-assembly (ESA) method to incorporate CdSe quantum dots into polymer we have successfully synthesized ultrathin films. This method allows the molecular-level thickness control and layer-by-layer formation of multilayer thin and thick films using alternative anionic and cationic molecular solution dipping. From ellipsometric measurements, we obtained that the thickness of per bilayer is around 3.7 nm. UV-vis absorption spectra versus the number of bilayers have also been obtained using an Hitachi 2001 spectrometer. The size of CdSe quantum dots has been measured using transmission electron microscopy before the CdSe quantum dots are incorporated and confirmed using atomic force microscopy after the formation of the film, respectively. Both measurements indicate that the diameter of the CdSe quantum dots is 2-3 nm. Xray photoelectron spectroscopy indicates that the concentration of the CdSe quantum dots in the film is 2.14%.
Spectral Analysis of Frictional Forces in ILD CMP
Authors: Philipossian Ara , Rosales-Yeomans Daniel , Charns Leslie , Rogers Chris , Doy Toshiroh , Kinoshita Masaharu
Published: June 2019

Spectral analysis of real-time friction data obtained during ILD CMP is used to elucidate the tribology of the process in terms of stick-slip phenomena. Fourier transform analysis is employed to quantify the total amount of mechanical interaction in the pad-slurry-wafer interface as a function of various IC-1000 pad surface textures, PL-4217 fumed silica concentrations, relative pad-wafer velocities and applied wafer pressures. A new parameter termed the ‘Interfacial Interaction Index’ (γ) is defined and determined empirically by integrating the amplitude of the force spectra over a wide range of frequencies. Values of γ extracted from individual force spectra are in qualitative agreement with the tribological information obtained in previous studies using Stribeck curve analysis. This new method is remarkable since it has the potential to eliminate having to perform a multitude of experiments needed for constructing and interpreting Stribeck curves. For a given tribological mechanism, analysis of the spectra for various types of pad textures indicates significant differences between the K-Grooved pad and other types of pads. A qualitative model relating the observed spectra to pad storage modulus is presented as a potential explanation for the above observation.
In Situ Temperature Measurement During Oxide Chemical Mechanical Planarization
Authors: Cornely Jesse , Rogers Chris , Manno Vincent , Philipossian Ara
Published: June 2019

This paper presents temperature and friction force data at the pad-slurry-wafer interface during real time CMP polishing with in situ pad conditioning. Experiments are performed on a 1:2 scale laboratory tabletop rotary polisher with variable pad speed and wafer down force control. Dual emission laser induced fluorescence (DELIF) techniques are used to optically measure the temperature directly beneath the wafer during polishing using a two camera imaging system. An infrared camera and a thermocouple are alternately used to measure bow wave temperatures. Optically transparent BK-7 glass wafers with either concave (wafer edges sloping toward the pad) or convex (wafer edges sloping away from the pad) curvature were used. When concave wafers are polished, the bow wave temperatures are 3°C to 5°C higher than the corresponding value for convex wafers. Similarly, slurry temperatures under the concave wafers are 5°C to 6°C higher than the value for convex wafers (±0.5°C). The friction force per unit area is typically 2 kPa to 3 kPa higher for concave wafers. Temperatures beneath the wafer are as high as 12°C above the ambient temperature for a concave wafer at a high applied wafer pressure (41.4 kPa) or linear velocity (0.93 m/sec). Bow wave temperatures reach as high as 9°C above ambient at a linear velocity of 0.93 m/sec. The lowest temperatures, within 1°C of ambient at the bow wave and 5°C above ambient under the wafer, were found with convex wafers at low applied wafer pressures (20.7 kPa). Linear velocity has little effect on the slurry temperature while polishing convex wafers. Increasing slurry abrasive concentration causes an increase in temperature, despite a decrease in friction force. A correlation, with an R-squared value greater than 0.96, exists between the bow wave temperature and the temperature beneath the wafer. This correlation holds at constant linear velocities across wafer shapes, applied wafer pressures, and slurry concentrations.
A Novel CMP Process on Fixed Abrasive Pads for the Manufacturing of Highly Planar Thick Film SOI Substrates
Authors: Kulawski Martin , Henttinen Kimmo , Suni Ilkka , Weimar Frauke , Mäkinen Jari
Published: June 2019

A new approach using Fixed Abrasive (FA) pads has been undertaken to overcome the problem of non-uniform thick film Silicon-on-Insulator (SOI) wafers after CMP polishing. The theoretical models indicating the advantages of the 2-body system of the fixed abrasive configuration vs. the conventional 3-body system of slurry based polishing have been convincingly demonstrated in practise upon experiments in a wide range of parameters. As a result it is possible to maintain or improve the flatness of wafers after back grinding, while simultaneously removing the sub-surface damage. A surface quality of prime wafers can be reached on the device layer. Capacitive thickness measurement scans and atomic force microscopy (AFM) monitoring confirm the results. A detailed comparison with conventional processing has been carried out to clarify the advantages on bulk silicon wafers. Decoration etching is used to analyse the wafer surface quality in terms of oxide induced stacking faults (OISF). As a result an alternative processing method is proposed for manufacturing thick film SOI substrates with improved uniformity.
Transferwear During Cu CMP
Authors: Liang H. , Xu G. Helen , Martin J.M. , Mongne Th. Le
Published: June 2019

We conducted fundamental investigation of interfacial interactions between copper and polyurethane surfaces. Using in situ surface analysis techniques we were able to evaluate effects of water molecules on both materials surfaces during rubbing. Evidence of transferring elements between copper and urethane surfaces due to friction was found. Further investigation on pad wear indicated that transfer wear was taking a major role during copper CMP and mixed wear modes dominated pad wear.
Transient Electrochemical Measurements During Copper Chemical Mechanical Polishing
Authors: Lee Seung-Mahn , Choi Wonseop , Craciun Valentin , Singh Rajiv K.
Published: June 2019

Chronoamperometry was used to investigate the reaction/passivation kinetics and thickness of the chemically modified surface layer on the copper during chemical mechanical polishing (CMP). The result showed that the reaction/passivation kinetics and the thickness of the chemically modified surface layer are strongly dependent on the chemistry of CMP slurry in the chemical aspect of CMP and play critical keys in the selection of the chemistry and its concentration. BTA and H2O2 enhanced the passivation kinetics, resulting in thinner layer on the copper surface. In addition, the reaction kinetics increased as pH decreased.
The Effects of Particle Adhesion in Chemical Mechanical Polishing
Authors: Lu Zhenyu , Babu S.V. , Matijević Egon
Published: June 2019

The properties of abrasive particles, and their interactions with surface films to be polished, play a key role in chemical mechanical polishing (CMP). This study applies the packed column technique for the investigation of the adhesion phenomena at the particle/film interface as a function of different slurry chemistries relevant to polishing processes. Well-defined dispersions, including uniform spherical silica and silica cores coated with nanosized ceria, as well as calcined alumina were used to represent slurry abrasives, and copper or glass beads to simulate wafers or discs. It was shown that the pH and slurry flow rate had significant effects on particle attachment and removal. The results of deposition of silica particles on copper beads in the presence of various concentrations of H2O2 and of detachment from copper beads of alumina particles, loaded at different pH values, had strong correlations to the polish rates of the metal.
The Development of a Direct-Polish Process for STI CMP
Authors: Martin Antonella , Spinolo Giulia , Morin Sonia , Bacchetta Maurizio , Frigerio Francesca , Bonner Benjamin A. , McKeever Peter , Tremolada Maurizio , Iyer Anand
Published: June 2019

The development of a direct polish process for STI CMP on 200mm wafers using highselectivity slurry (HSS) has been achieved for production of 0.13μm technology microelectronic devices. The new process has improved on-wafer performance compared to standard STI CMP processes. The step height range across the wafer was decreased by 84%, planarity Cpk values (silicon nitride thickness and step-height uniformity) were increased by >25%, leakage current statistics were superior, and the cost of ownership was lowered by 78%. Cross-sectional SEMs both after direct polish CMP and after removal of the silicon nitride show improved planarity.
Dispersion Number Studies in ChemicalMechanical Planarization
Authors: Philipossian Ara , Mitchell Erin
Published: June 2019

This study explores aspects of the fluid dynamics of CMP processes. The residence time distribution of slurry under the wafer is experimentally determined and used to calculate the Dispersion Number (Δ) of the fluid in the wafer-pad region based on a dispersion model for non-ideal reactors. Furthermore, lubrication theory is used to explain flow behaviors at various operating conditions. Results indicate that at low wafer pressure and high relative pad-wafer velocity, the slurry exhibits nearly ideal plug flow behavior. As pressure increases and velocity decreases, flow begins to deviate from ideality and the slurry becomes increasingly more mixed beneath the wafer. These phenomena are confirmed to be the result of variable slurry film thicknesses between the pad and the wafer, as measured by changes in the coefficient of friction (COF) in the pad-wafer interface.
Slurry Development For Cu/Ultra Low k CMP
Authors: Li Hugh , VanHaneham Matt , Quanci John
Published: June 2019

Conventional CMP for Cu/Ultra-low k (k<2.4) integration faces significant technical challenges [1-2]. The majority of ULK materials are made porous to reduce the dielectric constant, while trading off on the mechanical strength [3-6]. With diminished hardness, elasticity and adhesion, the CMP process has to be “kinder and gentler”: lower down force, lower relative velocity, softer pad, and slurry with lower abrasive content [1,7]. In a word, the mechanical portion of the planarization process would be greatly reduced. To maintain the same performance, one has to rely on the chemical reactions to make Cu/ULK CMP a viable process.
Effect of Tool Kinematics, Brush Pressure and Cleaning Fluid pH on Coefficient of Friction and Tribology of post-CMP PVA Brush Scrubbing Processes
Authors: Philipossian Ara , Mustapha Lateef
Published: June 2019

Real-time coefficient of friction (COF) analysis is used to determine the extent of normal and shear forces during post-CMP PVA brush scrubbing and identify the tribology of the process. Fluid pH and applied pressure have pronounced effects on process tribology and the magnitude of COF. In cases where brush rotation is the only kinematic attribute of the system, low pH results in ‘mixed lubrication’ where increasing brush velocity causes a dramatic reduction in COF in accordance with classical tribological arguments. At lower pressures the tribological mechanism shifts to ‘hydrodynamic lubrication’ with significantly lower values of COF. Regardless of pressure, increasing the pH to 7 and 10.7 causes the tribology to remain in ‘hydrodynamic lubrication’ and results in even lower values of COF. Trends are explained qualitatively by considering the effect of pH on the solubility and gellation characteristics of silica in the silica-water system. Stribeck curves fail to shed light on the tribology of the system when complex ranges of tool kinematics (i.e. wafer rotation and brush oscillation superimposed on brush rotation) are employed. The results are counter-intuitive since they indicate nearly an order of magnitude increase in COF with increasing brush velocity. Nevertheless, results demonstrate the utility of having complex ranges of motion in PVA brush scrubbing such that very low or very high values of COF can be realized by simply increasing the rotational velocity of the brush while maintaining a constant wafer rotation and brush oscillation.
Selectivity Studies On Tantalum Barrier Layer In Copper CMP
Authors: Vijayakumar Arun , Du Tianbao , Sundaram Kalpathy B. , Desai Vimal
Published: June 2019

Copper metallization in sub-0.18 μm semiconductor devices is achieved by combining the dual damascence techniques followed by chemical mechanical planarization (CMP). Tantalum and its nitride have been identified as the diffusion barrier layer for copper metallization. However, the wide differences in properties between copper and tantalum layers result in selectivity problems during CMP process. The aim of this work is to obtain a better understanding on the slurry selectivity for copper and tantalum and to develop slurries with best selectivity performance. In this work, the effect of several chemical parameters (abrasive type, oxidizer type, concentration, pH etc.) was studied through static and dynamic tests using advanced electrochemical techniques and surface analysis techniques. The surface layers of the statically etched copper and tantalum discs were investigated using X-ray photoelectron spectroscopy (XPS) and surface planarity was studied using atomic force microscopy (AFM). Polishing rates results show that alumina-based slurry polished copper very well whereas tantalum removal rate was low. However, for the silica-based slurry the tantalum shows much higher removal rate than copper and better surface planarity was obtained.
Comparison of Glycine and Citric Acid as Complexing Agents in Copper Chemical-Mechanical Polishing Slurries
Authors: Gorantla Venkata , Babu S.V.
Published: June 2019

Two complexing agents, glycine and citric acid, in hydrogen peroxide based slurries for planarizing copper have been compared. Copper dissolution and polish rates and in situ electrochemical experimental results at various slurry pH values and hydroxyl radical concentrations at pH=8.4 are presented. It was observed that the pH of the slurry has a strong influence on copper dissolution and polish rates. While high copper removal rates were observed with citric acid-peroxide solutions at low pH values, glycineperoxide system yielded high Cu removal rates at alkaline pH values. Copper dissolution rates in both the systems at pH 4 and 8 were consistent with the electrochemical measurements. The concentration of hydroxyl radicals generated in citric acid-peroxide system was less than that of those generated in glycine peroxide system at pH=8.4 indicating low copper removal rates at alkaline conditions in the former system.
In-situ electrical and spectroscopical techniques for the study of degradation mechanisms and life time prediction of organic based electronic material systems
Authors: Manca Jean , Goris Ludwig , Kesters Els , Lutsen Laurence , Martens Tom , Haenen Ken , Nesladek Milos , Sanna Ornella , Vanderzande Dirk , D'Haen Jan , Schepper Luc De
Published: June 2019

In order to tailor the synthesis of new robust organic materials for electronic applications and to guarantee the required life time for the emerging commercial plastic electronic applications it is of key importance to understand the underlying degradation mechanisms. Since plastic electronics is a rather young technology introducing new material systems, its reliability is characterized by new failure and degradation mechanisms, a relatively high amount of early failures and multi-modal failure distributions. To understand the mechanism responsible for a given failure or degradation mode, it is essential to study it separately, through appropriate test structures and test techniques. Powerful techniques for this purpose are a.o. analytical techniques (SEM, TEM, SPM,…), in-situ electrical measurement techniques and spectroscopical techniques (in-situ FTIR, in-situ UV-Vis, PDS). The benefits of these in-situ techniques in the reliability study of organic based electronics will be illustrated in this contribution.
Low Temperature Poly-Si on Flexible Polymer Substrates for Active Matrix Displays and Other Applications
Authors: Young Nigel D. , Trainor Michael J. , Yoon Soo-Young , McCulloch David J. , Wilks Richard W. , Pearson Andrew , Godfrey Sandra , Green Peter W. , Roosendaal Sander , Hallworth Elizabeth
Published: June 2019

A variety of polymer materials including polyimide (PI), polyarylate (PAR), polynorbonene (PNB) and polyethersulphone (PES) have been studied for use as substrates in the formation of active matrix displays based upon polycrystalline silicon (poly-Si) thin film transistors (TFTs). A process used to fabricate transflective mobile phone displays at 250°C on such substrates is described in detail. The NMOS TFTs show a mobility of 100cm2/Vs, and a threshold voltage of 3.9V; the PMOS devices have a mobility of 52cm2/Vs, and a threshold voltage of -6V. Issues relating to performance of these devices, yield of the arrays, and manufacturability are discussed.
Flexible monocrystalline Si films for thin film devices from transfer processes
Authors: Berge Christopher , Wagner Thomas A. , Brendle Willi , Craff-Castillo Cecilia , Schubert Markus B. , Werner Jürgen H.
Published: June 2019

Transfer of monocrystalline silicon films to arbitrary foreign substrates is a promising way for the fabrication of high quality silicon films on foreign substrates, demonstrated by solar cell efficiencies on glass as high as 16.6 % in the past. Transfer technologies also enable the use of flexible substrates. This paper investigates the mechanical stability of the separation layer for two different morphologies. First measurements on the minimum bending radius of unsupported silicon films are presented that allow us to estimate minimum curvatures for flexible monocrystalline devices. Finally, we report the first flexible monocrystalline thin film silicon solar cell of 4 cm2 with an independently confirmed efficiency of 14.6 %.
Organic Electronics for Large Area Electronic Devices
Authors: Chason Marc
Published: June 2019

With market opportunities continuing to drive electronic products to smaller size, significant research efforts continue to shrink semiconductor devices in accordance with Moore's Law. However, a new set of market opportunities is emerging for which the significant driver is not semiconductor complexity, but rather lower product cost arising from the novel integration of technologies making use of organic and flexible substrates. These new technologies present opportunities for research into new materials and fabrication processes. These new research opportunities extend from embedding passive devices, microfluidics, and polymeric optical waveguides in printed wiring boards, to organic transistors. This paper will discuss these new technologies and present some of the market forces driving these efforts.
Amoled Tft Pixel Circuitry for Flexible Displays on Metal Foils
Authors: Troccoli Matias , Afentakis Themis , Hatalis Miltiadis K. , Voutsas Apostolos T. , Adachi Masahiro , Hartzell John W.
Published: June 2019

Active matrix organic light emitting diode displays based on thin, flexible metal foil substrates offer a novel approach to fabricate light, flexible and rugged displays. Metal foils allows devices to be fabricated at higher process temperatures yielding better device characteristics than plastic substrates. Furthermore, the conductive nature of such substrates enables more efficient use of pixel area through the use of a global power electrode. We are implementing Active Matrix Organic Light Emitting Diode (AMOLED) displays on flexible stainless steel substrate using 2 TFT and 4 TFT pixel circuit topologies with two different layout realizations that exploit the conductive properties of the substrate.
Oled Matrix-Displays
Authors: Metzdorf Dirk , Becker Eike , Dobbertin Thomas , Hartmann Soeren , Heithecker Dirk , Johannes Hans-Hermann , Kammoun Anis , Krautwald Henning , Riedl Thomas , Schildknecht Christian , Schneider Daniel , Kowalsky Wolfgang
Published: June 2019

The field of organic light emitting diodes (OLEDs) has matured considerably within recent years and first products are commercially available. After a brief review of the improvement of individual OLEDs we will focus on research topics for the preparation of passive matrix (PMOLED), active matrix (AMOLED) and full color displays. To date, the properties of organic matrix displays basically meet consumer product requirements. Anyhow an industrial cheap fabrication technology for reliable displays is not established yet. To meet the industrial demands for device fabrication a new horizontal in-line vacuum system for a massproduction compatible device manufacturing was installed. For material saving large area coatings the system accommodates up to 7” × 13” substrates. Different PMOLED-Displays based on vacuum deposited organic compounds have been prepared by various fabrication techniques. We demonstrate a 2 inch organic display with 24 × 32 single pixels and 0.9 × 0.9 mm2 pitch whereby cathode texture was achieved using photoresist barriers featuring a distinct undercut. Due to the inherent limitations of multiplexing and in order to satisfy the need for large area, high resolution displays the basic concepts for an active matrix addressing scheme are dealt with. In this regard transparent and electrically inverted top-side emitting diodes (IOLEDs) will be demonstrated. The latter are advantageous for the incorporation of powerful nchannel thin film transistors in the AMOLED driver backplanes. An all-organic smart pixel device comprising a single Pentacene based organic field effect transistor (OFET) and a conventional OLED was successfully prepared. Furthermore a new flash-sublimation technique for the spatially selective deposition of small organic molecules will be presented. We prepared OLEDs comprising flash-deposited Tris-(-8-hydroxyquinoline) aluminium (Alq3) and Alq3 doped with DCM2 which demonstrate the suitability of this technique for preparation of fullcolor displays based on small organic molecules.
Degradation in a Methyl-phenyl Co-Polymeric Polysilane for LED Applications
Authors: Sharma Asha , Deepak  , Katiyar Monica , Kumar Satyendra , Chandrasekhar V. , Saxena A. K. , Ranjan A. , Tiwari R. K.
Published: June 2019

The optical degradation of polysilane copolymer has been studied in spin cast thin films and solutions using light source of 325 nm wavelength. The room temperature photoluminescence (PL) spectrum of these films show a sharp emission at 368 nm when excited with a source of 325 nm. However, the PL intensity deteriorates with time upon light exposure. Further the causes of this degradation have been examined by characterizing the material for its transmission behaviour and changes occurring in molecular weight as analysed by GPC data.
Evolution of Nanocrystalline Silicon Layers Deposited at 150°C for Thin Film Transistor Channels
Authors: Cheng I-Chun , Allen Steven , Wagner Sigurd
Published: June 2019

Thin film transistors of nanocrystalline silicon (nc-Si:H) are made in the staggered topgate, bottom-source/drain geometry. To achieve both high carrier mobility and low off current, the nc-Si:H channel material must be kept thin but comprise a contiguous 10-nm thick crystalline layer at its top. We study this electrically most interesting top layer of the nc-Si:H channel film by AFM and SEM. Introducing an nc-Si:H seed layer underneath the TFT promotes the structural evolution of the nc-Si:H channel layer and raises the electron field effect mobility up to 40 cm2V-1s-1.
Fabricaton Ofactive Devices and Logic Gates on Fibers
Authors: Choi YongWoo , Kymissis Ioannis , Wang Annie , Akinwande Akintunde I.
Published: June 2019

Textiles are a suitable substrate for large area, flexible and wearable electronics because of their excellent flexibility, mechanical properties and low cost manufacturability. The ability to fabricate active devices on fiber is a key step for achieving large area and flexible electronic structures. We fabricated transistors and inverters with a-Si film and pentacene film on Kapton film and cut them into fibers. The a-Si TFT showed a threshold voltage of 8.5 V and on/off ratio of 103 at a drain voltage of 10 V. These are similar to the characteristics of a TFT fabricated on a glass substrate at the same time. The maximum gain of the inverter with an enhancement n-type load was 6.45 at a drain voltage of 10 V. The pentacene OTFT showed a threshold voltage of -8 V and on/off ratio of 103 at a drain voltage of -30 V. The inverter with a depletion p-type load showed a voltage inversion but the inversion occurred at the wrong voltage. The antifuse was successfully programmed with a voltage pulse and also a current pulse. The resistance decreased from 10 GΩ to 2 kΩ after the programming.
Optimization of 75°C amorphous silicon nitride for TFTs on plastics
Authors: McArthur Christian , Meitine Mark , Sazonov Andrei
Published: June 2019

Amorphous silicon nitride (a-SiNx) is widely used as the gate dielectric and passivation layer in a-Si:H based electronics. For devices on plastic substrates deposited at low temperature, the a-SiNx quality seems to determine the device performance. This paper investigates the effects of hydrogen dilution, helium dilution, ammonia-silane gas flow ratio, and RF power on the properties of PECVD silicon nitrides deposited in large-area parallel-plate reactors at substrate temperatures of 75°C. The chemical composition and bonding of the SiNx:H films was studied using FTIR spectroscopy. The physical properties were investigated, and the density, growth rate, and compressive stress of the films were determined. The electrical properties such as leakage current, breakdown, stability, trap density, and dielectric constant of the films were characterized by I-V and C-V measurements of metal-insulator semiconductor (MIS) structures. Analysis of Variance (ANOVA) was performed on the results, and the deposition conditions for the optimal film properties were determined. The optimum film had SiNx:H stoichiometry of x=1.56 with hydrogen concentrations of 17 at.%, and exhibited compressive stress of -220 MPa. The film displayed good stability under electrical stress with ohmic leakage of Rleak ∼1016 Ωcm. Strong relationships between the film properties and deposition conditions were observed, and are discussed within the paper. A-Si:H bottom gate TFTs were fabricated using the optimized nitrides for gate dielectrics and passivation layers, and the influence of a-SiNx on TFT performance is discussed.
Efficient Near Infrared Si/Ge Quantum Dot Photo-Detector Based on a Heterojunction Bipolar Transistor
Authors: Elfving Anders , Larsson Mats , Holtz Per-Olof , Hansson Göran V. , Ni Wei-Xin
Published: June 2019

Ge dots embedded in Si offer the possibility of Si-based light detection at 1.3-1.55 μm. In this communication, we report a very efficient photo-detector based on a Si/SiGe heterojunction bipolar transistor structure with 10 Ge dot layers (8 ML Ge each) incorporated in the basecollector junction. The device structures were grown using low-temperature molecular beam epitaxy, and fabricated for both normal and edge incidence with no electrical contact to the base. The processed Ge-dot transistor detectors revealed a rather low dark current density, 0.01 mA/cm2 at -2 V. Photoconductivity measurements were performed at room temperature. At 1.31 μm, responsivity values of 50 mA/W at normal incidence have been directly measured at Vce = -4 V, without involving any rescaling factor due to light coupling. This value is a ∼250-fold increase compared to a reference p-i-n diode with the same dot layer structure, due to the current amplification function of the transistor. For a rib waveguide device, a very high responsivity value of about 470 mA/W (Vce = -4V) has been obtained at 1.31 μm. Measurements were also performed at 1.55 μm, and the photo-response of the waveguide phototransistor was 25 mA/W, which is again a large improvement compared with the reference waveguide photodiode (∼1 mA/W). Moreover, time-resolved photoconductivity measurements have been carried out. The results have indicated that the device frequency performance is primarily limited by the emitterbase junction capacitance.
Pump-Probe Measurements Using Silicon Nanocrystal Waveguides
Authors: Smith Nathanael , Lederer Max J. , Samoc Marek , Luther-Davies Barry , Elliman Robert G.
Published: June 2019

Optical pump-probe measurements were performed on planar slab waveguides containing silicon nanocrystals in an attempt to measure optical gain from photo-excited silicon nanocrystals. Two experiments were performed, one with a continuous-wave probe beam and a pulsed pump beam, giving a time resolution of approximately 25 ns, and the other with a pulsed pump and probe beam, giving a time resolution of approximately 10 ps. In both cases the intensity of the probe beam was found to be attenuated by the pump beam, with the attenuation increasing monotonically with increasing pump power. Time-resolved measurements using the first experimental arrangement showed that the probe signal recovered its initial intensity on a time scale of 45-70 μs, a value comparable to the exciton lifetime in Si nanocrystals. These data are shown to be consistent with an induced absorption process such as confined carrier absorption. No evidence for optical gain was observed.
Photoluminescence from Silicon Nanocrystals Formed by Pulsed-Laser Deposition
Authors: Chen X. Y. , Lu Y. F. , Wu Y. H. , Cho B. J. , Song W. D. , Hu H.
Published: June 2019

Si nanocrystals (NCs) consisting of small crystals from 1 to 20 nm were formed by pulsedlaser deposition (PLD) in inert Ar gas and reactive O2 gas. The oxygen content of the Si NCs increases with increasing O2 ambient pressure and nearly SiO2 stoichiometry is obtained when O2 pressure is higher than 100 mTorr. The optical absorption of the Si NCs shows an indirect band transition. Broad PL spectra are observed from Si NCs. The peak position and intensity of the PL band at 1.8–2.1 eV are dependent on excitation laser intensity, while intensity changes and blue shifts are observed after oxidation and annealing. The PL band at 2.55 eV displays vibronic structures with periodic spacing of 97 ± 9 meV, while no peak shift is found before and after oxidation and annealing. The as-deposited Si NCs show a polycrystal structure and crystallinity improves after annealing. Combined with the PL of Si NCs obtained by crumbling electrochemical-etched porous Si layer, the results give strong evidence that the PL band at 1.8–2.1 eV is due to the quantum confinement effect (QCE) in Si NC core while the PL band at 2.55 eV is related to the localized surface states at SiOx/Si interface.
Two - Color Mid-Infrared Spectroscopy of Isoelectronic Centers in Silicon
Authors: Vinh N.Q. , Gregorkiewicz T.
Published: June 2019

One of the open questions in semiconductor physics is the origin of the small splittings of the excited states of bound excitons in silicon. A free electron laser as a tunable source of the mid-infrared radiation (MIR) can be used to investigate such splittings of the excited states of optical centers created by transition metal dopants in silicon. In the current study, the photoluminescence from silver and copper doped silicon is investigated by two color spectroscopy in the visible and the MIR. It is shown the PL due recombination of exciton bound to Ag and Cu is quenched upon application of the MIR beam. The time-resolved photoluminescence measurements and the quenching effects of these bands are presented. By scanning the wavelength of the free-electron laser ionization spectra of relevant traps involved in photoluminescence are obtained. The formation and dissociation of the bound excitons, and the small splittings of the effective-mass excited states are discussed. The applied experimental method allows correlation of DLTS data on trapping centers to specific channels of radiative recombination. It can be applied for spectroscopic analysis in materials science of semicondutors.
Preparation and Microstructure of Au (Ru)-SiO2 Micro/Nano-particles
Authors: Ma Xicheng , Cai Yuanhua , Ao Qing , Lun Ning , Li Shitong , Li Fengzhao , Wen Shulin , Dou Fan , Zhu Hongwei
Published: June 2019

In this presentation, we described a study on preparation and microstructure of Au (Ru) nano-particles embedded in SiO2 matrices, which were prepared as advanced display materials by using Sol-gel method. Both microstructure and composition of these micro/nano-particles composites were characterized by HRTEM (high resolution transmission electron microscope), EMP (electron microprobe) and nano-probe EDS (energy dispersive X-ray spectroscopy). Experimental results showed that the products have multi-levels in structure like nebulae. The aggregation of Au/Ru nano-particles can be extremely diminished by using SiO2 micro-particles as matrices. Distortions of the atomic lattices of Au and Ru nano-crystallites were often observed in the surface of these nano-particles. Moreover, nano-EDS measurements revealed that Au and Ru nano-particles are always separately embedded in SiO2 matrices, no alloy of them is observed.
Epitaxial Si1-xGex Films and Superlattice Structures Grown by CVD for Infrared Photodetectors
Authors: Maddiona L. , Coffa S. , Lorenti S. , Bongiorno C.
Published: June 2019

Integration of photodetectors with high responsitivity in the near infrared (1.3-1.55 μm) on standard Si electronic circuits is important for a variety of applications in the field of on-chip, local area and long haul optical communications. In this work we report on a detailed structural and optical characterization of epitaxial Si1-xGex films and Si1-xGex /Si multilayers grown by chemical vapor deposition on (100) Si wafers. Cross-sectional transmission electron microscopy analyses show that metastable strained Si1-xGex films of few nanometer with x>40% can be deposited at low growth temperature and pressure. Absorption measurements on these films demonstrate the extension of the photo-response to 1.55 μm. Using these films as active layers Schottky integrated photodetectors have been fabricated.
Tunneling Conductivity in Thermally Oxidized Porous Silicon
Authors: Yarkin Dmitrii G. , Balagurov Leonid A. , Orlov Andrei F. , Zvyagin Igor P.
Published: June 2019

Metal/PS/c-Si structures with porous silicon (PS) layers of 55-75% porosity were fabricated on moderately doped p- and n-type c-Si substrates and were thermally oxidized at 400-960°C. The effect of oxidation on the photoluminescence and the transport of charge carriers in these structures were studied. We demonstrated that trap-filled space charge limited current (SCLC) is the dominant transport mechanism at large forward bias. The analysis of the current – voltage characteristics in the SCLC region allowed us to determine the oxidation dependence of the effective thickness of the trap-rich tissue isthmuses, in which space charge is mostly accumulated. The exponential dependence of the ohmic conductance on the thickness of SiOX tissue is explained by tunneling of carriers through potential barriers formed by the tissue surrounding silicon crystallites.
The Nd-nanocluster Coupling Strength and its Effect in Excitation/de-excitation of Nd3+Luminescence in Nd-doped Silicon-rich Silicon Oxide
Authors: Seo Se-Young , Shin Jung H.
Published: June 2019

The Nd-nanocluster Si (nc-Si) coupling strength and its effect in excitation/de-excitation of Nd3+luminescence in Nd-doped silicon-rich silicon oxide (SRSO) is investigated. Nd-doped SRSO thin films, which consist of nc-Si embedded inside a SiO2matrix, were prepared by electron-cyclotron-resonance plasma enhanced chemical vapor deposition (ECR-PECVD) of SiH4and O2with co-sputtering of Nd and subsequent anneal at 950 °C. Efficient Nd3+luminescence with moderate temperature quenching is observed. Based on the temperature dependence of Nd3+luminescence lifetime, a coupling strength between nc-Si and Nd that is strong enough to result in efficient excitation of Nd3+via quantum confined excitons while weak enough to result in a small back-transfer rate is identified as the key to Nd3+luminescence.