Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Top-down approaches for continuous scaling-down of devices and components in semiconductor industries is getting increasingly difficult and expensive, and thus bottom–up strategies, e.g., growth of functional nano-structures using nanowires or nanotubes are being explored rather than patterning and etching. Carbon nanotubes (CNTs) are an interesting option under consideration due to their extraordinary physical and electrical properties that make them suitable for microelectronic applications, such as, semiconductor field-effect-transistors (FET) and capacitors. In recent years, the fabrication of one-dimension (1D) ferroelectric (FE) nanostructures have been investigated as a capacitor for future 3D memories, however several difficulties need to be overcome in particular fabrication and characterization. In this work, the fabrication of ferroelectrics (FE) (e.g., Pb1-xZrxTiO3 (PZT) and BaTiO3 (BT)) multi-walled carbon nanotubes (MWCNTs) composites were synthesised by chemical solution deposition (CSD) method, namely sol gel. Later, the composites were investigated using scanning electron microscope (SEM) equipped with energy dispersive spectroscopy facilities and transmission electron microscopy (TEM) in addition to X Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR), to address the compatibility between FE and CNTs.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Composites of tungsten carbide (WC) and stainless steel (SS) have been produced through an innovative powder coating technique using sputtering. These composites showed remarkable mechanical properties after vacuum sintering, in spite of significant amounts of brittle eta-phase, (M,W)6C. The formation of eta-phase is almost inevitable, because it is thermodynamically favoured for stoichiometric C in the WC-SS system and accelerated in the SS coated WC particles, due to the reduced diffusion distances between WC and SS and the nanocrystalline character of the metallic coating. Surprisingly, the mechanical properties are not seriously affected by the eta-phase. In fact, relatively tough and harder materials have been obtained compared to similar compositions of WC-Co. In order to understand the microscopic reason for the reported mechanical strength, in-depth structural analysis of grain boundaries and interfaces was performed by electron microscopy.

Barium titanate (BT), a typical ferroelectric material with a tetragonal structure bellow TC ≈125 ºC has found widespread applications especially in electronic devices. However, modern electronics demand very small functional structures and, as a consequence nanostructures of ferroeletrics are being considered. However it was observed that there is a critical size for BT nanostructures below which TC decreases, the paraelectric cubic phase is stabilized at room temperature and then ferroelectricity may no longer exist. These observations have stimulated an exponential growth of research aiming to understand the effect of scaling on the ferroelectric properties. In addition some theoretical studies predicted the enhancement of ferroelectricity in anisotropic “cylindrical” shaped nanoparticles. Therefore, the morphology control and fabrication of ferroelectric nanostructures with different size and shapes are of key importance. Within this context, we demonstrated that the control of the morphology of BT nanoparticulates can be achieved by hydrothermal method.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Piezoelectric materials find important applications in micro- and nano-electromechanical systems (MEMS/NEMS). Pb(Zrx,Ti1-x)O3 (PZT) is currently the most widely used composition for such applications but due to environmental concerns over the toxicity of lead, lead free alternative materials are required. K0.5Na0.5NbO3 (KNN) is considered as a potential lead free piezoelectric but the current generation of monolithic ceramics has inferior electromechanical properties as compared to PZT. Consequently, there is great interest in improving the piezoelectric properties of KNN ceramics and various methods such as doping, hot-pressing and texturing are currently being studied. KNN single crystals like lead based single crystals have shown better electromechanical properties as compared to their ceramic counterparts. In addition, the behavior of a ferroelectric is largely dependent on its local domain response to an applied electrical or mechanical loading. Therefore, to understand better the material’s macroscopic properties, it is essential to access local ferroelectric domains behavior which collectively determines the electromechanical performance.

Multiferroics are currently of great interest for applications in microelectronics namely in future data storage and spintronic devices. These materials couple simultaneously ferroelectric and ferromagnetic properties and have potentially different applications resulting from the coupling between their dual order parameters. A true multiferroic material is single phase. However, the known true multiferroic materials possess insufficient coupling between the two phenomena or their magnetoelectric response occurs at temperatures too low to be useful in practical applications. But a tremendous progress in the field of microelectronics can be expected if one is able to design an effective multiferroic material with ideal coupling of the ferromagnetic and ferroelectric properties to suit a particular application. Within this context composite structures are gaining considerable interest and different strategies in terms of materials microstructure have been proposed including horizontal multilayers and vertical heterostructures. In the horizontal multilayer heterostructures, the alternating layers of conventional ferro/ferrimagnetic and ferroelectric phases are grown, while in the vertical heterostructures nanopillars of the ferro/ferrimagnetic phase are embedded in a ferroelectric matrix. The later structures show advantages over the first ones because promote larger interfacial surface area and are intrinsically heteroepitaxial in three dimensions; which is expected to allow a stronger coupling between ferroelectric and ferromagnetic components.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Hydroxyapatite, with a composition that resembles the mineral phase of bone, is often used as a coating of metallic prostheses to improve the adhesion and osseointegration of implants in different parts of the skeleton. Among the available techniques that allow the deposition of this material on metallic substrates, Pulsed Laser Deposition (PLD) is capable of producing high quality and highly biocompatible coatings with excellent final attachment.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

The increasing demand of sources of energy such as oil and natural gas induces at the steel industry a development on low carbon microalloyed steels for pipeline applications in order to achieve excellent mechanical properties of strength and toughness at a reduced cost. To obtain an adequate fine-grained final structure, the strict control of thermomechanical processing and accelerated cooling is crucial. Depending on the thermomechanical processing conditions and chemical composition, pipeline steels can present different microstructures. Several authors have found that the microstructure of acicular ferrite usually provides an optimum combination of mechanical properties. Higher levels of austenite strengthening before cooling promote a refinement of final microstructure but can also restrict the fraction of low temperature transformation products such as acicular ferrite.

Indium sulfide (In2S3) is a promising semiconductor material for window layers in solar cell devices and other optoelectronic applications as it presents a direct band gap around 2.0 eV at room temperature, and large photosensitivity and photoconductivity. The presence of several polymorphic structures depending on the processing parameters is also of interest to tailor the required material properties for different applications. It is currently being investigated for high efficiency solar cell based on CuInS2-In2S3 heterostructures, replacing CdS layers. Few studies have been reported on nanostructured In2S3 grown by several methods.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

An anomaly in the dependence of the kinetics of grain growth on the temperature for strontium titanate (ST) ceramics is reported in this work. It consists of a decrease of the grain size with increasing sintering temperature. Recently, a drop in the grain boundary mobility of ST in the same temperature range was reported. These observations imply an unusual decrease of the grain size with the increase of the sintering temperature, in agreement with our present results. Although the mobility drop was related to structural changes in grain boundaries, the exact mechanism involved is still unknown. The understanding of this anomaly may offer an alternative way of controlling the microstructure and tuning the dielectric response of ST based compositions without the use of dopants. ST is characterized by high dielectric permittivity, high tunability and low dielectric losses, and is thus a particularly interesting material for capacitor or tunable microwave devices. These properties are very dependent on the stoichiometry, structure and microstructure, in which the role of grain boundaries is fundamentally important. Indeed, increasing attention has been paid to grain boundary structures and nonstoichiometry and to its relation with microstructure and electrical properties. Densification proceeds faster with decreasing Sr/Ti ratio (Ti-rich compositions). Sr-rich samples show narrow grain size distributions, while Ti excess favors enlarged grain size distributions and faceting of the grain boundaries.