Eu Jin Tan

Surface functionalization of BaTiO3 nanoparticles and improved electrical properties of BaTiO3/polyvinylidene fluoride composite

Surface functionalization of BaTiO3 nanoparticles with dopamine was carried out using a reflux method to strongly bind dopamine on the BaTiO3 nanoparticle surface and improve its compatibility with the polyvinylidene fluoride (PVDF) polymer matrix. Fourier transform infrared spectra confirm the successful surface functionalization of BaTiO3 nanoparticles after immobilization with dopamine. Electrical properties of the resultant nanocomposite show that the dielectric constant can be enhanced up to 56.8 with low dielectric loss.

Dopant induced hollow BaTiO3 nanostructures for application in high performance capacitors

In this work, large-scale single crystalline Nd-doped BaTiO3 hollow nanoparticles have been synthesized via a simple hydrothermal method without the assistance of a surfactant or high temperature sintering. With unique hollow structures, the nanoparticles not only exhibit excellent compatibility with poly(vinylidene fluoride) (PVDF), but significantly enhanced the dielectric properties of the nanocomposites. We demonstrated that the dielectric constant of the nanocomposite reached up to 480.3 with dielectric loss of 0.6 at 102 Hz. Design and optimization of the synthesis method have been achieved through a systematic study of the effect of reaction conditions on the size and morphology evolution of the hollow nanoparticles. The formation of hollow nanostructures is proposed to follow a Kirkendall induced hollowing mechanism which is governed by the differences in diffusion rates of dopant ions, water molecules and core ions during the synthesis reaction.

Green aqueous modification of fluoropolymers for energy storage applications

Fluoropolymers are of prime interest as solution processable materials for electronic applications such as embedded capacitors, multilayer capacitors, and high-energy-density capacitors. Herein, for the first time, we investigated an environmentally friendly green aqueous modification of fluoropolymers, poly(vinylidene fluoride) (PVDF) for energy storage applications. The PVDF polymer was modified in aqueous medium by using bioinspired protein dopamine without any harmful toxic chemicals. Dopamine functionalization onto pre-irradiated PVDF polymer powder was carried out using a simple reflux method to strongly bind dopamine onto the PVDF surface. The resulting dopamine modified PVDF films exhibited excellent dielectric properties, when compared with the pristine PVDF polymer. The dielectric constant can be enhanced up to 32 with fairly low dielectric loss as compared to pristine PVDF. Furthermore, the modified films were found to have good flexibility; they could be curled as easily as pristine PVDF films. Since this method avoids the use of toxic chemicals, it may allow the application of modified PVDF not only for energy storage applications but also for other applications such as in biocompatible materials.

Polystyrene grafted polyvinylidenefluoride copolymers with high capacitive performance

Electroactive materials are of great interest for high performance capacitive behavior due to their relaxed ferroelectric properties. In this work, we studied the dielectric properties of poly(vinylidene fluoride) (PVDF) grafted with polystyrene (PS) by electron beam radiation induced free radical graft copolymerization reaction in solution. The dielectric constant of polystyrene grafted PVDF copolymers reaches about 90 at 100 Hz at room temperature representing more than seven times increment compared with the pristine PVDF matrix. The dielectric loss of 0.005 at 1 KHz can be achieved. Correlation of the dielectric properties with the graft copolymerization reaction mechanism was discussed. This route represents one of the most effective techniques to synthesize potential graft copolymers with desirable dielectric properties in a wide frequency range for energy storage applications.

Pyramidal structural defects in erbium silicide thin films

Pyramidal structural defects, 5–8μm wide, have been discovered in thin films of epitaxial ErSi2−x formed by annealing thin Er films on Si(001) substrates at temperatures of 500–800°C. The formation of these defects is not due to oxidation. We propose that they form as a result of the separation of the silicide film from the substrate and its buckling in order to relieve the compressive, biaxial epitaxial stresses. Silicon can then diffuse through the silicide or along the interface to fully or partially fill the void between the buckled erbium disilicide film and the substrate.

Demonstration of Schottky Barrier NMOS Transistors With Erbium Silicided Source/Drain and Silicon Nanowire Channel

We have fabricated silicon nanowire N-MOSFETs using erbium disilicide (ErSi2-x) in a Schottky source/drain back-gated architecture. Although the subthreshold swing (~180 mV/dec) and drain-induced barrier lowering (~500 mV/V) are high due thick BOX as gate oxide, the fabricated Schottky transistors show acceptable drive current ~900 muA/mum and high Ion/Ioff ratio (~105). This is attributed to the improved carrier injection as a result of low Schottky barrier height (Phib) of ErSi2-x/n - Si(~0.3 eV) and the nanometer-sized (~8 nm) Schottky junction. The carrier transport is found to be dominated by the metal-semiconductor interface instead of the channel body speculated from the channel length independent behavior of the devices. Furthermore, the transistors exhibit ambipolar characteristics, which are modeled using thermionic/thermionic-field emission for positive and thermionic-field emission for negative gate biases.

Nickel-Silicided Schottky Junction CMOS Transistors With Gate-All-Around Nanowire Channels

We demonstrate high-performance Schottky CMOS transistors with NiSi source/drain and gate-all-around (GAA) silicon nanowire (~5 nm) channels. The transistors exhibit good I on/I off characteristics, along with fully controlled shortchannel effects revealed by low drain-induced barrier lowering (~10 mV/V) and near-ideal subthreshold swing (~60 mV/dec). Although the N-MOSFET required dopant segregation to suppress the ambipolar behavior, excellent P-MOSFET characteristics could be achieved without the use of barrier modification techniques. We attribute this to the Schottky barrier thinning in a nanosized metal-semiconductor junction and superior gate electrostatic control in a GAA nanowire architecture.

Improved electrical performance of erbium silicide Schottky diodes formed by Pre-RTA amorphization of Si

Erbium silicide Schottky diodes formed on Si(001) substrate using rapid thermal annealing method show degraded Schottky-barrier height /spl phi//sub Beff/ and ideality factor n due to the presence of silicide-induced microstructural defects which are likely sources of trap states. A method to improve the /spl phi//sub Beff/ and n of the diodes utilizing in situ Ar plasma cleaning to induce a light amorphization of the Si(001) substrate is proposed. Even though the diodes formed in this way are less textured and have a poorer interface, they are free of silicide-induced microstructural defects, leading to an overall improvement in current transport and conduction properties which can be modeled using inhomogenous Schottky contact model.

Textured Ni(Pt) germanosilicide formation on a condensed Si1-xGex/Si substrate

cInstitute of Microelectronics, Singapore 117685 A study of Ni and NiPt germanosilicidation on a condensed Si1�xGex/Si substrate was performed. The partial relaxation of the condensed SiGe layer resulted in an improvement in the morphological stability of the germanosilicide through the alleviation of compressive stress. Pt alloying to the Ni film resulted in highly textured NiPt germanosilicide grains, particularly in the 002 orientation, due to the reduction in the interfacial energy caused by the presence of Pt alloy. Pt atoms diffuse slowly and result in a variation in lattice parameters in the NiPtSiGe grain as a function of depth. Nevertheless, Pt alloying has increased the morphological stability of the NiPtSiGe film.

Erbium silicided schottky source/drain silicon nanowire N-metal–oxide–semiconductor field-effect transistors

Schottky source/drain (S/D) N-metal–oxide–semiconductor-field-effect transistor (MOSFET) have been fabricated using a simplified top down process with silicon nanowires (SiNW) as the channel body and ErSi2-x as the metal silicide S/D. Despite the use of a thick buried oxide (BOX) layer as the gate dielectric, the devices show good electrical characteristics with high Ion/Ioff ratio of ~105, high drive current of ~900 µA/µm, which are significantly higher than those previously reported Schottky S/D MOSFETs without barrier-modified junctions. The effect of physical characteristics such as metal-silicided junction depth, number of SiNW channels, and metal–semiconductor junction size were investigated and found to have a direct effect on the electrical performance of the devices. Current transport as a function of Schottky barrier height (Φbeff) modulation was also studied.