Direct Observation of Defects and Increased Ion Permeability of a Membrane Induced by Structurally Disordered Cu/Zn-Superoxide Dismutase Aggregates

Interactions between protein aggregates and a cellular membrane have been strongly implicated in many protein conformational diseases. However, such interactions for the case of Cu/Zn superoxide dismutase (SOD1) protein, which is related to fatal neurodegenerative disorder amyotrophic lateral sclerosis (ALS), have not been explored yet. For the first time, we report the direct observation of defect formation and increased ion permeability of a membrane induced by SOD1 aggregates using a supported lipid bilayer and membrane patches of human embryonic kidney cells as model membranes. We observed that aggregated SOD1 significantly induced the formation of defects within lipid membranes and caused the perturbation of membrane permeability, based on surface plasmon resonance spectroscopy, atomic force microscopy and electrophysiology. In the case of apo SOD1 with an unfolded structure, we found that it bound to the lipid membrane surface and slightly perturbed membrane permeability, compared to other folded proteins (holo SOD1 and bovine serum albumin). The changes in membrane integrity and permeability were found to be strongly dependent on the type of proteins and the amount of aggregates present. We expect that the findings presented herein will advance our understanding of the pathway by which structurally disordered SOD1 aggregates exert toxicity in vivo

Cobalt titanium nitride amorphous metal alloys by atomic layer deposition

The formation of thin amorphous cobalt titanium nitride (CoTiN) layers was investigated using a supercycle method of atomic layer deposition (ALD). The stoichiometry of the resultant ALD CoTiN films was controlled by changing the ratio of Co and TiN thicknesses. X-ray diffraction analysis and transmission electron microscopy observations showed that the microstructure of the ALD Co and TiN was transformed from polycrystalline to amorphous CoTiN. The stoichiometry of the CoTiN layer was affected by the growth characteristics of ALD Co and TiN on each surface. The results revealed that ALD TiN undergoes nucleation incubation on the ALD Co surface, whereas ALD Co does not undergo nucleation incubation on the ALD TiN surface. The properties of the amorphous CoTiN layers were evaluated by diffusion experiments and mechanical tests. Because of the lack of grain boundaries, the CoTiN efficiently blocks the diffusion of Cu at elevated temperatures and exhibits higher hardness compared with ALD Co. (c) 2017 Elsevier B.V. All rights reserved

Comparative study on atomic layer deposition of HfO(2)via substitution of ligand structure with cyclopentadiene

With the scaling down of complementary metal-oxide semiconductors (CMOS), atomic layer deposition of high-quality HfO2 has emerged as a key technology for ultrathin and high-k gate dielectrics. Recently, heteroleptic ligand structures have been introduced to complement the limitations of existing homoleptic precursors. Among the heteroleptic precursors, partial substitution with cyclopentadiene (Cp)-based ligands has been employed for controlling the volatility and thermal stability of precursors. In this study, we investigated the effects of the Cp ligand on the high-k properties of ALD HfO2 by comparing Hf(N(CH3)(2))(4) and CpHf(N(CH3)(2))(3) through theoretical and experimental methods. We theoretically predicted the changes in precursor behavior on the surface due to the Cp ligand, such as the high activation energy for the final chemisorption and the steric hindrance caused by the bulky Cp ligand. Additionally, we experimentally found that these changes affect not only the growth rate of ALD HfO2 but also the film properties. The Cp ligand on the surface sterically hinders the reaction of the nearby OH group with precursor molecules, retaining the residual OH content in the films. Consequently, the high OH content in the films degrades the film density and leakage current of ALD HfO2 as a high-k film

Surface-Localized Sealing of Porous Ultralow‑<i>k</i> Dielectric Films with Ultrathin (<2 nm) Polymer Coating

Semiconductor integrated circuit chip industries have been striving to introduce porous ultralow-<i>k</i> (ULK) dielectrics into the multilevel interconnection process in order to improve their chip operation speed by reducing capacitance along the signal path. To date, however, highly porous ULK dielectrics (porosity >40%, dielectric constant (<i>k</i>) <2.4) have not been successfully adopted in real devices because the porous nature causes many serious problems, including noncontinuous barrier deposition, penetration of the barrier metal, and reliability issues. Here, a method that allows porous ULK dielectrics to be successfully used with a multilevel interconnection scheme is presented. The surface of the porous ULK dielectric film (<i>k</i> = 2.0, porosity ∼47%) could be completely sealed by a thin (<2 nm) polymer deposited by a multistep initiated chemical vapor deposition (iCVD) process. Using the iCVD process, a thin pore-sealing layer was localized only to the surface of the porous ULK dielectric film, which could minimize the increase of <i>k</i>; the final effective <i>k</i> was less than 2.2, and the penetration of metal barrier precursors into the dielectric film was completely blocked. The pore-sealed ULK dielectric film also exhibited excellent long-term reliability comparable to a dense low-<i>k</i> dielectric film