Joong-Sik Kim

Physical characterization of emulsion intercalated polyaniline-clay nanocomposite

Using emulsion polymerization method, polyaniline (PAN)‐Na a ‐montmorillonite (MMT) clay nanocomposites were synthesized. Dodecylbenzenesulfonic acid (DBSA) was used as an emulsifier and dopant during emulsion polymerization. The X-ray diAraction patterns showed that PAN‐DBSA was intercalated between clay layers in the order of nanoscale. The room temperature (RT) dc conductivities of nanocomposites were 1‐10 ˇ3 S=cm depending on the molar ratio of dopants used. Temperature dependence of dc conductivity for the nanocomposites followed a quasi-one-dimensional (1D) variable range hopping (VRH) model. From temperature dependence of electron paramagnetic resonance experiments, magnetic properties and the density of states of the systems were obtained. The doping level of the nanocomposites was deduced from the results of X-ray photoelectron spectroscopy experiments. From the comparison of physical properties between PAN with clay and PAN without clay, the eAects of dopant and the layer of clay on charge transport and structure are discussed. ” 2001 Elsevier Science B.V. All rights reserved.

Polypyrrole-montmorillonite nanocomposites synthesized by emulsion polymerization

The structural, electrical, magnetic, and thermal properties were investigated for the nanocomposites of polypyrrole (PPy) and inorganic clay (Na+-montmorillonite) prepared by emulsion polymerization. Dodecylbenzenesulfonic acid (DBSA) was used as emulsifier (surfactant) and dopant. The X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images showed that the conducting PPy was intercalated into the clay layers in nanoscale (<10 A). The dc conductivity (σdc) of PPy–DBSA with clay was ∼6 S/cm, while that of PPy–DBSA without clay was ∼20 S/cm at room temperature (RT). Temperature dependence of σdc of both samples followed the three dimensional variable range hopping (VRH) model. From the g-value and the temperature dependence of EPR linewidth, paramagnetic signals were strongly affected by the partially negatively charged clay layers. The thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) showed that the clay induced the thermal stability of the systems.

Two-Dimensional Quantum Mechanical Modeling for Multiple-Channel FinFET

In this paper, we report our preliminary study on the 2D quantum-mechanical modeling of multiple-channel FET through solving the coupled Poisson-Schrodinger equations for a multiple-channel FET structure in a self-consistent manner. Our simulation revealed that the drain current driving capability as well as the transconductance for multiple-channel FETs was tremendously improved when compared to FinFETs. The simulation results also revealed that the short-channel effects are more effectively suppressed with comparison to the conventional FinFETs

Quantum mechanical device modeling: FinFET having an isolated n+/p+ gate region strapped with poly-silicon.

In this paper, we present our numerical study on FinFET having an isolated n+/p+ gate region strapped with metal and poly-silicon structure. Our theoretical work is based on 2-D quantum-mechanical simulator with a self-consistent solution of Poisson-Schrödinger equation. Our numerical simulation revealed that the threshold voltage (VT) is controlled within -0.1 approximately +0.2 V with varying the doping concentration of the n+ and p+ polysilicon gate region from 1.0 x 10(17) to 1.0 x 10(18) cm(-3). We also confirmed that the better VT tolerance of the FinFET on the variation of the fin thickness can be expected over the conventional FinFET structure. For instance, the VT of the FinFET under this work exhibited 0.02 V tolerance with respect to the variation of the fin thickness change of 5 nm (from 30 to 35 nm) while the traditional FinFET demonstrates the tolerance of 0.12 V for the same variation of the fin thickness.

Kinetic monte carlo modeling of boron diffusion in strained silicon

We discuss the boron diffusion in a biaxial tensile-strained {001} Si and SiGe layer using the kinetic Monte Carlo (KMC) method. We created strain in silicon by adding a germanium mole fraction to the silicon in order to perform a theoretical analysis. The generation of strain in silicon influences the diffusivity as well as the penetration profile during the implantation. The strain energy of the charged defects was calculated from ab initio calculation whereas the diffusivity of boron was extracted from the Arrhenius formula. Hereby, the influence of the germanium content on the dopant diffusivity was estimated. Our KMC study revealed that the diffusion of the B atoms was retarded with increasing germanium mole fraction in the strained silicon layer. Furthermore, we derived the functional dependence of the in-plane strain as well as the out-of-plane strain on the germanium mole fraction, which is based on the distribution of equivalent stress along the Si/SiGe interface.

Atomistic modelling for boron diffusion in strained silicon substrate

We discuss the issue of boron diffusion in biaxial tensile strained {001} Si and SiGe layer with kinetic Monte Carlo (KMC) method. We created strain in silicon by artificially adding a germanium mole fraction to the silicon in order to perform a theoretical analysis. The strain energy of the charged defects was calculated from ab initio calculation whereas the diffusivity of boron was extracted from the Arrhenius formula. Hereby, the influence of the germanium content on the diffusivity of the impurity atom was estimated. Our KMC study revealed that the diffusion of the boron atoms was retarded with increasing germanium mole fraction in the strained silicon layer. Furthermore, we derived the functional dependence of the in-plane strain as well as the out-of-plane strain as a function of the germanium mole fraction, which is based on the distribution of equivalent stress along the Si/SiGe interface.

Device Optimization of Multiple-Channel Field Effect Transistor with Two Dimensional Poisson–Schrödinger Solver

In this paper, we report our numerical study of the optimization of the short-channel performance of a multiple-channel field effect transistor (FET), wherein the center gate is placed at the center of a fin to form multiple channels. The distinctive features of a multiple-channel FET are carefully investigated using our simulator, solving the coupled Poisson–Schrodinger equations in a self-consistent manner. To analyze the short-channel effects of a multiple-channel FET, device characteristics including subthreshold swing, threshold voltage roll-off, and drain-induced barrier lowering were investigated.

Device optimization of multiple-channel FET with 2D Poisson-Schrodinger solver

Recently, a double-gate (DG) structure has attracted a great deal of attention for its potential as a technology driver for sub-40nm MOSFET. In this paper, we report our quantum-mechanical investigation on mulitple-channel FET in an effort to optimize the device structure.