The key role of the pentacene kinetic energy (Ek) in the early stages of growth on SiOx/Si is demonstrated: islands with smooth borders and increased coalescence differ remarkably from fractal-like thermal growth. Increasing Ek to 6.4 eV, the morphology evolves towards higher density of smaller islands. At higher coverage, coalescence grows with Ek up to a much more uniform, less defected monolayer. The growth, interpreted by the diffusion mediated model, shows the critical nucleus changing from 3 to 2 pentacene for Ek>5-6 eV. Optimal conditions to produce single crystalline films are envisaged.

Plasma based transfer of photoresist (PR) patterns into underlying films and substrates is basic to micro- and nanofabrication but can suffer from excessive surface and line edge roughness in the photoresist and resulting features. The authors have studied the interaction of a set of adamantyl methacrylate-based model polymers with fluorocarbon∕Ar discharges and energetic Ar+ ion beams. Through systematic variation of the polymer structure, the authors were able to clarify the contributions of several critical polymer components on the chemical and morphological modifications in the plasma environment. Etching rates and surface chemical and morphological changes for the model polymers and fully formulated 193 and 248nm photoresists were determined by ellipsometry, atomic force microscopy, time of flight static secondary ion mass spectrometry, and x-ray photoelectron spectroscopy. The polymer structure in the near surface region (∼10nm) of all materials is destroyed within the first seconds of exposure to a fluorocarbon∕Ar plasma. The plasma-induced changes include destruction of polymeric structure in the near surface region and oxygen and hydrogen loss along with fluorination. For the 193nm PR material, the initial densification of the near surface region was followed by the introduction of pronounced surface roughness. This change was not seen for 248nm PR processed under identical conditions. When comparing the responses of different polymer materials, the authors observed a strong dependence of plasma-induced surface chemical and morphological changes on polymer structure. In particular, the adamantane group of 193nm PR showed poor stability under plasma exposure. On the other hand, the plasma-induced changes for polymer resins with or without the low molecular weight chemicals required to make the photoresist system photoactive did not differ significantly. The behavior of the same materials during energetic argon ion beam bombardment was also investigated. No significant differences in etch yield and surface roughness evolution for the different materials were seen in that case.

Plasma-based ashing of photoresist masks after pattern transfer is a common processing step in the fabrication of integrated circuits. In this work we investigated damage mechanisms of nanoporous ultra low k (ULK) materials with different overall porosities due to the ashing process. Oxygen-, nitrogen- and hydrogen-based photoresiststripping using direct and remote plasma processes were examined. Ellipsometry, x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and transmission electron microscopy were utilized to study the damage layer thickness, physical (pore morphology), and chemical modifications of the nanoporous silica thin films after exposure to the O2-, N2- or H2-based ashing processes. As a result of the plasma exposure, carbon groups in nanoporous silica can be removed from the ULK layers which is also accompanied by material densification. We find severe ashing damage of ULK materials after O2-based ashing using both direct and remote discharges. N2 and H2 discharges also damage ultralow k materials for direct plasma ashing processes which are accompanied by low energy ion bombardment of the substrates. The introduction rate and degree of the ULK materials modifications correlates with the overall porosity. We show that the pore interconnectivity is one of the key parameters that determine ashing damage. ULK damage is greatly reduced for remote N2 or H2 discharges, but the resist removal rates are impractically low if the substrate is at room temperature. We show that both acceptable photoresist stripping rates and ULK damage levels can be achieved for remote H2 plasma ashing processes if the substrate temperature is 250°C and higher.

The exploitation of the processes used by microorganisms to digest nutrients for their growth can be a viable method for the formation of a wide range of so called biogenic materials that have unique properties that are not produced by abiotic processes. Here we produced living hybrid materials by giving to unicellular organisms the nutrient to grow. Based on bread fermentation, a bionic composite made of carbon nanotubes (CNTs) and a single-cell fungi, the Saccharomyces cerevisiae yeast extract, was prepared by fermentation of such microorganisms at room temperature. Scanning electron microscopy analysis suggests that the CNTs were internalized by the cell after fermentation bridging the cells. Tensile tests on dried composite films have been rationalized in terms of a CNT cell bridging mechanism where the strongly enhanced strength of the composite is governed by the adhesion energy between the bridging carbon nanotubes and the matrix. The addition of CNTs also significantly improved the electrical conductivity along with a higher photoconductive activity. The proposed process could lead to the development of more complex and interactive structures programmed to self-assemble into specific patterns, such as those on strain or light sensors that could sense damage or convert light stimulus in an electrical signal.

In the rapidly emerging field of layered twodimensional functional materials, black phosphorus, the Pcounterpart of graphene, is a potential candidate for various applications, e.g., nanoscale optoelectronics, rechargeable ion batteries, electrocatalysts, thermoelectrics, solar cells, and sensors. Black phosphorus has shown superior chemical sensing performance; in particular, it is selective for the detection of NO 2 , an environmental toxic gas, for which black phosphorus has highlighted high sensitivity at a ppb level. In this work, by applying a multiscale characterization approach, we demonstrated a stability and functionality improvement of nickel-decorated black phosphorus films for gas sensing prepared by a simple, reproducible, and affordable deposition technique. Furthermore, we studied the electrical behavior of these films once implemented as functional layers in gas sensors by exposing them to different gaseous compounds and under different relative humidity conditions. Finally, the influence on sensing performance of nickel nanoparticle dimensions and concentration correlated to the decoration technique and film thickness was investigated.