Solid state molecular rectifier based on self organized metalloproteins

Recently, great attention has been paid to the possibility of implementing hybrid electronic devices exploiting the self-assembling properties of single molecules. Impressive progress has been done in this field by using organic molecules and macromolecules. However, the use of biomolecules is of great interest because of their larger size (few nanometers) and of their intrinsic functional properties. Here, we show that electron-transfer proteins, such as the blue copper protein azurin (Az), can be used to fabricate biomolecular electronic devices exploiting their intrinsic redox properties, self assembly capability and surface charge distribution. The device implementation follows a bottom-up approach in which the self assembled protein layer interconnects nanoscale electrodes fabricated by electron beam lithography, and leads to efficient rectifying behavior at room temperature.Comment: 13 pages including two figures. Accepted for publication in Advanced Material

A Comparison of TSV Etch Metrology Techniques

International audienceWe use three metrology techniques, vertical scanning interferometry (VSI), confocal chromatic microscopy (CCM), and time domain optical coherence tomography (TD-OCT), for depth measurement of through-silicon vias (TSVs) of various cross sections and depths. The merits of these techniques are discussed and compared. Introduction While sales of semiconductor equipment broke a new record this year, many metrology needs should be addressed to support the development and production of electronic chips based on "More than Moore" scaling. Among these scaling approaches, 3D integration based on TSVs offers superior integration density and reduces interconnect length/latency. Measurements are needed to evaluate the depth uniformity of etched TSVs. Indeed, upon metal filling, geometrical variations of TSVs can affect Cu nails coplanarity and can warp the wafer, resulting in a low stacking yield. Measuring the depth of TSVs is an increasingly challenging task as the diameter of many TSVs has now shrunk to only a few microns

Incipient Anion Intercalation of Highly Oriented Pyrolytic Graphite Close to the Oxygen Evolution Potential: A Combined X-ray Photoemission and Raman Spectroscopy Study

In the present work, we used two different electrochemical (EC) techniques, namely, cyclic voltammetry and normal pulsed voltammetry, applied to a highly oriented pyrolytic graphite (HOPG) electrode for anion intercalation in two different aqueous electrolytes (i.e., perchloric and sulphuric acid). We performed comparative X-ray photoemission (XPS) and Raman spectroscopy studies at various EC potentials. The chemical analysis obtained by XPS and Raman spectroscopy, the latter applied in situ and in real time during the EC processes, indicates that at oxygen evolution potential (i.e., before reaching the well-known intercalation stage potentials), the HOPG intercalation process is already active. These results suggest that the intercalated compound is efficiently obtained before reaching higher potentials, which usually cause a detriment of the graphite crystal

Disclosing the Early Stages of Electrochemical Anion Intercalation in Graphite by a Combined Atomic Force Microscopy/Scanning Tunneling Microscopy Approach

In view of large-scale applications, electrochemical exfoliation of graphite for the production of graphene sheets must follow chemical processes that ensure high quality of the products -wide-size graphene foils, single- or few-layer thickness, and low level of defectivity -in order to guarantee high electrical transport and good mechanical properties. Understanding the exfoliation process of graphite at the atomic scale, that is, the intercalation of graphene layers in the electrolyte solution, is fundamental to really be able to control and optimize such processes. This can be obtained, for instance, by investigation of the exfoliated graphite -the surface of the original crystal left behind in the chemical solution- and by real-time monitoring of graphite surface morphological and structural modifications during the exfoliation process. Here, we monitor graphite surface changes as a function of the electrochemical potential by both electrochemical (EC) atomic force microscopy and EC scanning tunneling microscopy coupled with cyclic voltammetry. Following this strategy, we disclose the surface modifications encountered during the early stages of anion intercalation, for different electrolytes: surface faceting, step erosion, terrace damages, and nanoprotrusions, all affecting the graphite surface and therefore the exfoliation process. Our results represent a key step toward a full investigation of the intercalation process in graphite. Within the current debate on the exfoliation of layered crystals, these data potentially represent important information for investigation of the intercalation process in graphite and, on the other hand, for further optimization of the electrochemical protocol for graphene production