Metal-molecule-silicon (MMSi) devices have been fabricated, electrically characterized, and analyzed. Molecular layers were grafted to n and p+ silicon by electrochemical reduction of para-substituted aryl-diazonium salts and characterized using standard surface analysis techniques; MMSi devices were then fabricated using traditional silicon (Si) processing methods combined with this surface modification. The measured current-voltage characteristics were strongly dependent on both substrate type and molecular head group. The device behavior was analyzed using a qualitative model considering semiconductor depletion effects and molecular dipole moments and frontier orbital energies.

This letter describes a technique for realizing a gold ͑Au͒ surface with roughness at the atomic scale using techniques compatible with integrated device fabrication. The Au layer is electron-beam evaporated on a self-assembled monolayer of ͑3-Mercaptopropyl͒ trimethoxysilane on an oxidized silicon substrate and shows a root-mean-square surface roughness of ϳ2 Å over a 1 m 2 area. The physical stability of the Au film toward commonly used chemicals and processes for photolithography and self-assembly, and its suitability for formation of well-ordered organic monolayers indicate that the films are well suited as substrates for future device fabrication in molecular electronics or other devices involving self-assembled monolayers.

In-situ infrared spectroscopy of metallized aromatic molecular monolayers directly bound to silicon has been performed. Monolayers of two nitro-containing species were characterized before metallization using transmission mode and following metallization using a p-polarized backside reflection technique. The vibrational signature of the molecular layer is not significantly altered after vapor-depositing gold using a soft evaporation technique; however, standard gold evaporation completely destroys the molecular signature. The time evolution of vibrational peaks associated with the molecular layer and surface silicon oxide species shows that the molecular layer is stable, but the silicon oxide evolves over time within the junction.

In order to understand information processing in neural circuits, it is necessary to detect both electrical and chemical signaling with high spatial and temporal resolution. Although the primary currency of neural information processing is electrical, many of the downstream effects of the electrical signals on the circuits that generate them are dependent on activity-dependent increases in intracellular calcium concentration. It is therefore of great utility to be able to record electrical signals in neural circuits at multiple sites while at the same time detecting optical signals from reporters of intracellular calcium levels. We describe here a microfluidic multi-electrode array (MMEA) capable of high-resolution extracellular recording from brain slices that is optically compatible with calcium imaging at single cell resolution. We show the application of the MMEA device to record waves of spontaneous activity in developing cortical slices and to perform multi-site extracellular recordings during simultaneous calcium imaging of activity. The MMEA has the unique capability to simultaneously allow focal electrical and chemical stimuli at different locations of the surface of a brain slice.

Molecular electronics has drawn significant attention for nanoelectronic and sensing applications. A hybrid technology where molecular devices are integrated with traditional semiconductor microelectronics is a particularly promising approach for these applications. Key challenges in this area include developing devices in which the molecular integrity is preserved, developing in situ characterization techniques to probe the molecules within the completed devices, and determining the physical processes that influence carrier transport. In this study, we present the first experimental report of inelastic electron tunneling spectroscopy of integrated metal-molecule-silicon devices with molecules assembled directly to silicon contacts. The results provide direct experimental confirmation that the chemical integrity of the monolayer is preserved and that the molecules play a direct role in electronic conduction through the devices. Spectra obtained under varying measurement conditions show differences related to the silicon electrode, which can provide valuable information about the physics influencing carrier transport in these molecule/Si hybrid devices.

We report a metalization technique for electrically addressing templated vertical single-walled carbon nanotubes (SWNTs) using in situ palladium (Pd) nanowires. SWNTs are synthesized from an embedded catalyst in a modified porous anodic alumina (PAA) template. Pd is electrodeposited into the template to form nanowires that grow from an underlying conductive layer beneath the PAA and extend to the initiation sites of the SWNTs within each pore. In this way, individual vertical channels of SWNTs are created, each with a vertical Pd nanowire back contact. Further Pd deposition results in annular Pd nanoclusters that form on portions of SWNTs extending onto the PAA surface. Two-terminal electrical characteristics produce linear I-V relationships, indicating ohmic contact in the devices.

AuNP/PDMS nanocomposites have been synthesized in the form of gels, foams, and films with distinctive structure and morphology. A simple in situ process in aqueous medium for the formation of such composite materials is described. The nanoparticles are held firmly within the PDMS while still being chemically accessible to substances soluble in PDMS. We demonstrate the utility of this property for water purification applications such as removing aromatic solvents and sulfur‐containing contaminants from water. The contaminants can be freed from the composite with a simple thermal treatment, allowing the material to be reused. We also demonstrate chemically selective uptake and release of a fluorescent dye by the nanocomposite as a drug delivery model system.magnified image

Design and fabrication of electronic biosensors based on field-effect-transistor (FET) devices require understanding of interactions between semiconductor surfaces and organic biomolecules. From this perspective, we review practical considerations for electronic biosensors with emphasis on molecular passivation effects on FET device characteristics upon immobilization of organic molecules and an electrostatic model for FET-based biosensors.