Characterization of molecular scale electronic devices generally involves deposition of a metal top electrode onto an organic film. During the evaporation process, high energetic granules of metals may lead to unwanted reactions between the organic molecules and deposited top electrodes. This can cause, as commonly reported, lasting damage which leaves most junctions either short or open. To overcome this important issue of physical damage to the molecules, we developed a novel technique of interfacing molecules by laying prefabricated metallic electrodes on top of a monolayer of molecules. For the bottom electrode a monolayer of cadmium stearate ((C17H35COO)2Cd) was deposited, using the Langmuir-Blodgett technique, onto platinum (Pt) electrodes which further rested on 200nm of oxide used for isolation. A separate set of Aluminum (Al) electrodes were fabricated on a different oxide free, highly doped substrate and was gently placed on the cadmium stearate monolayer in room ambient. Conduction to the top electrode was accomplished by probing the backside of the highly doped wafer whereas the bottom electrodes were individually addressed. Pressure was applied to ensure firm contact between the molecules and the top electrodes. Preliminary results showed an observed switching voltage of 3.5V. Most of the devices with Al as the top electrodes exhibited a gradual progression from switching on the positive side, closing, and then switching towards the negative side.

Using the recursion-transfer-matrix (RTM) method, which is a powerful method to obtain accurate scattering waves, combined with non-equilibrium Green's function (NEGF) method, we study the transport properties through single molecules sandwiched between electrodes with finite bias voltages. Especially, we investigate the effects of atomic-scale contacts on the I-V characteristics. We find strong nonlinear behaviors appear in the I-V characteristics when the atomic-scale contact at one electrode is not formed well.

We have functionalized single walled carbon nanotubes (SWNTs) using ruthenium centered organometallic supramolecular dendritic complexes. These dendrimers have multiple binding sites with chemically specified chirality. Most importantly, they are mechanically rigid. We have fabricated field effect transistors (FET) using these functionalized SWNTs. Devices were processed with standard optical lithography and high resolution e-beam lithography. We are using FET response of these devices to study charge injection into the nanotubes and the resultant effect on the tube's transport properties. Organometallic based molecular adsorbents onto the nanotubes effect the transistor response. These functionalized tubes change their majority carriers from holes to electrons in these FETs. We believe this is due to charge transfer from the metal center through the ligand and finally onto the nanotube. This results in the potential for optically altering the carrier density, and therefore the transport properties of the nanotubes.

Nanoscale, non-volatile, multi-bit memory devices have been fabricated consisting of carbon nanotube field-effect transistors (CNT-FETs) surrounded by redox active molecules (cobalt porphyrin). Charge was stored in the cobalt center atom of the molecule. Write and erase programming was carried out with back-gate pulses. By varying the back-gate amplitude multi-level memory operation was achieved. Programmed devices were read at zero gate voltage showing distinct logic ON and OFF states at room temperature for several hours. At low temperatures strong increase in retention time was observed and single-electron sensitivity was demonstrated. Charge stability tests show insignificant device change after 105 write and erase cycles.

We present a novel nanotube-on-insulator (NOI) approach to produce high-yield nanotube devices based on aligned single-walled carbon nanotubes. First, we managed to grow aligned nanotube arrays with controlled density on crystalline, insulating sapphire substrates, which bear analogy to industry-adopted silicon-on-insulator substrates. Based on the nanotube arrays, we demonstrated registration-free fabrication of both top-gated and polymer-electrolyte-gated field-effect transistors with minimized parasitic capacitance. In addition, we have successfully developed a way to transfer these aligned nanotube arrays to flexible substrates. Our approach has great potential for high-density, large-scale integrated systems based on carbon nanotubes for both micro- and flexible electronics.