Francine Ramos Scheffer

Growth of TiO2 nanotube arrays with simultaneous Au nanoparticles impregnation: photocatalysts for hydrogen production

Um novo metodo para a fabricacao de nanotubos (NTs) de TiO 2 organizados e impregnados com nanoparticulas (NPs) de ouro foi desenvolvido, e as propriedades estruturais, morfologicas e opticas dos NTs obtidos foram investigadas. Os arranjos de NTs de TiO 2 foram crescidos pela oxidacao anodica de Ti metalico utilizando solucoes eletroliticas contendo ions fluoreto e NPs de Au. As estruturas resultantes foram caracterizadas por espectrometria de retroespalhamento Rutherford (RBS), difratometria de raios X com incidencia rasante (GIXRD), microscopias eletronicas de transmissao (TEM) e de varredura (SEM) e espectroscopia UV-Vis. Tanto os arranjos de NTs sem Au quanto os impregnados com Au mostraram atividade fotocatalitica boa e estavel na geracao de hidrogenio a partir de misturas agua/metanol. Os nanotubos de TiO 2 contendo Au foram mais ativos na fotogeracao de hidrogenio do que os NTs de TiO 2 sem Au. A novel method for the fabrication of TiO 2 nanotubes (NTs) impregnated with gold nanoparticles (NPs) is reported. TiO 2 NT arrays were grown by anodic oxidation of Ti metal using fluoride electrolytes containing Au NPs. Resulting structures were characterized by Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffractometry (GIXRD), transmission and scanning electron microscopy (SEM and TEM) and UV-Vis spectroscopy. Au-free and Au-impregnated TiO 2 NT arrays showed good and stable photocatalytic activity for hydrogen generation from water/methanol solutions. Au-containing TiO 2 NTs presented higher hydrogen photogeneration activity than Au-free TiO 2 NTs.

Radiation-Sensitive Novel Polymeric Resist Materials: Iterative Synthesis and Their EUV Fragmentation Studies

Polymerization of (4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate (MAPDST), as a key monomer containing the radiation sensitive sulfonium functionality, with various other monomers such as methyl methacrylate (MMA), 4-carboxy styrene (STYCOOH), N-vinyl carbazole (NVK) in different molar ratios via free-radical polymerization method is described. This methodology led to the development of a small chemical library of six different radiation sensitive polymers for lithography applications. Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy identified the reaction products as MAPDST homopolymer and MAPDST-MMA, MAPDST-STYCOOH, MAPDST-NVK copolymers. Molecular weights were obtained from gel permeation chromatography and the decomposition temperature (Td) values were determined using thermogravimetric analysis (TGA). The effect of extreme ultraviolet (EUV) irradiation on a thin poly(MAPDST) film was investigated using monochromatic synchrotron excitation. These new polymeric materials were also exposed to electron-beam lithography (EBL) and extreme ultraviolet lithography (EUVL) to achieve 20-nm line patterns.

Performance evaluation of nonchemically amplified negative tone photoresists for e-beam and EUV lithography

Abstract. Although extreme ultraviolet (EUV) lithography is being considered as one of the most promising next-generation lithography techniques for patterning sub-20 nm features, the development of suitable EUV resists remains one of the main challenges confronting the semiconductor industry. The goal is to achieve sub-20 nm line patterns having low line edge roughness (LER) of <1.8  nm and a sensitivity of 5 to 20  mJ/cm2. The present work demonstrates the lithographic performance of two nonchemically amplified (n-CARs) negative photoresists, MAPDST homopolymer and MAPDST-MMA copolymer, prepared from suitable monomers containing the radiation sensitive sulfonium functionality. Investigations into the effect of several process parameters are reported. These include spinning conditions to obtain film thicknesses <50  nm, baking regimes, exposure conditions, and the resulting surface topographies. The effect of these protocols on sensitivity, contrast, and resolution has been assessed for the optimization of 20 nm features and the corresponding LER/line width roughness. These n-CARs have also been found to possess high etch resistance. The etch durability of MAPDST homopolymer and MAPDST-MMA copolymer (under SF6 plasma chemistry) with respect to the silicon substrate are 7.2∶1 and 8.3∶1, respectively. This methodical investigation will provide guidance in designing new resist materials with improved efficiency for EUVL through polymer microstructure engineering.

Photosensitised Degradation of Organic Dyes by Visible Light Using Riboflavin Adsorbed on the Surface of TiO2 Nanotubes

Visible light-assisted degradation of indigo carmine (IC), methylene blue (MB) and methyl orange (MO) aqueous solutions has been achieved on the surface of TiO2 nanotube (NT) arrays impregnated with riboflavin (RF). Diluted RF water solutions in the presence of RF-TiO2 NTs irradiated with UV light produced O2, CO and CO2 as main gas products. On the contrary, the same solutions irradiated with visible light evolved O2 as a main product. This in situ O2 generation under visible light absorption allows the degradation of the dyes without the necessity to bubble air or oxygen in the reaction system The photocatalytic degradation of MO, MB and IC can be described by a pseudo-first-order kinetic model obtaining ca. 100% degradation of MB, MO and IC in less than 3 h of visible light illumination. The results provided here are highly promising in view of various photocatalytic applications of the prepared RF-TiO2 NTs catalysts by two environmentally friendly compounds in the degradation of pollutants using solar radiation.

Optimization of processing parameters and metrology for novel NCA negative resists for NGL

It is expected that EUV resists must simultaneously pattern 20-nm half-pitch and below, with an LWR of <1.8 nm, and a sensitivity of 5–20 mJ/cm2. In order to make a resist perform optimally, new resist chemistry is required. One such approach being investigated by us is the development of polymeric non-CAR negative photo resists for sub 16 nm technology which is directly sensitive to radiation without utilizing the concept of chemical amplification (CARs). These resist designs are accomplished by homopolymers which are prepared from monomers containing sulfonium groups. We have achieved 20 nm patterns by e-beam lithography using this system. Here we will discuss in detail process parameters such as: spinning conditions for film thicknesses <50 nm and resulting surface topographies, baking regimes, exposure conditions and protocols on sensitivity, contrast, resolution and LER/LWR. Etch resistance data on these thin films will also be provided. Our results are aimed to provide a clear understanding of how these critical steps in the lithographic imaging process will affect extendibility of the non-CAR resist concept to sub 20 nanoscale features. Photodynamics and EUV exposure data will be covered.