Plasma polymerization of silicon-containing monomers

Plasma depositions of ultra thin films from seven silicon-containing liquid monomers were investigated using a continuos wave (CW) plasma source. The deposition rate of plasma polymerized films were determined using a quartz crystal microbalance (QCM) technique while the film composition were determined spectroscopiclly using primarily X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared method (FT-IR). The wettability of the plasma-polymerized films was also investigated by measuring the contact angles of water on the film surfaces. It was observed that the C=C absorption band was not present in these films. This observation is consistent with selective polymerization through the double bond. Oxygen was present in all samples investigated and this may be attributed to the quenching of radicals in the film by reactions with oxygen when exposed to atmosphere

Ab initio Derivation of Low-Energy Model for κ\kappa-ET Type Organic Conductors

We derive effective Hubbard-type Hamiltonians of $\kappa$-(ET)$_2X$, using an {\em ab initio} downfolding technique, for the first time for organic conductors. They contain dispersions of the highest occupied Wannier-type molecular orbitals with the nearest neighbor transfer $t$$\sim$0.067 eV for a metal $X$=Cu(NCS)$_2$ and 0.055 eV for a Mott insulator $X$=Cu$_2$(CN)$_3$, as well as screened Coulomb interactions. It shows unexpected differences from the conventional extended H\"uckel results, especially much stronger onsite interaction $U$$\sim$0.8 eV ($U/t$$\sim$12-15) than the H\"uckel estimates ($U/t$$\sim$7-8) as well as an appreciable longer-ranged interaction. Reexamination on physics of this family of materials is required from this realistic basis.Comment: 5 pages, 2 figures, and 1 tabl

Mott Transition and Phase Diagram of κ\kappa-(BEDT-TTF)2Cu(NCS)2 Studied by Two-Dimensional Model Derived from Ab initio Method

We present an ab initio analysis for the ground-state properties of a correlated organic compound $\kappa$-(BEDT-TTF)2Cu(NCS)2. First, we derive an effective two-dimensional low-energy model from first principles, having short-ranged transfers and short-ranged Coulomb and exchange interactions. Then, we perform many-variable variational Monte Carlo calculations for this model and draw a ground-state phase diagram as functions of scaling parameters for the onsite and off-site interactions. The phase diagram consists of three phases; a paramagnetic metallic phase, an antiferromagnetic (Mott) insulating phase, and a charge-ordered insulating phase. In the phase diagram, the parameters for the real compound are close to the first-order Mott transition, being consistent with experiments. We show that the off-site Coulomb and exchange interactions affect the phase boundary; (i) they appreciably stabilize the metallic state against the Mott insulating phase and (ii) enhance charge fluctuations in a wide parameter region in the metallic phase. We observe arc-like structure in Fermi surface around the region where the charge fluctuations are enhanced. Possible relevance of the charge fluctuations to the experimentally observed dielectric anomaly in the $\kappa$-BEDT-TTF family compounds is also pointed out.Comment: 15 pages, 11 figures (minor revision, to appear in JPSJ