Biomedical subjects

David P Nackashi

Publications and source records attributed to David P Nackashi.

3 recordsLinked to original sources

PubMed2006

Controlled modulation of conductance in silicon devices by molecular monolayers.

We have controllably modulated the drain current (I(D)) and threshold voltage (V(T)) in pseudo metal-oxide-semiconductor field-effect transistors (MOSFETs) by grafting a monolayer of molecules atop oxide-free H-passivated silicon surfaces. An electronically controlled series of molecules, from strong pi-electron donors to strong pi-electron acceptors, was covalently attached onto the channel region of the transistors. The device conductance was thus systematically tuned in accordance with the electron-donating ability of the grafted molecules, which is attributed to the charge transfer between the device channel and the molecules. This surface grafting protocol might serve as a useful method for controlling electronic characteristics in small silicon devices at future technology nodes.

Journal Article↗

PubMed2004

Clustering effects on discontinuous gold film NanoCells.

Reproducible negative differential resistance (NDR)-like switching behavior is observed in NanoCells. This behavior is attributed to the formation of filaments and clusters between the discontinuous gold films. Control experiments are performed by self-assembly of insulating molecules between the gold islands and conducting molecules on these islands. Additional control experiments are performed by removing the filaments and clusters between islands using a piranha bath. The results are consistent with theoretical predictions and extend the domain of molecular electronics based in organic molecules to include nanosized clusters as active units. This facilitates a scenario where synthetically accessible organic molecules, with defined characteristics, can be adjusted by metallic nanoclusters as an in situ fine-tuning element, able to compensate for the lack of addressing in the nanosize regime.

Electric Impedance↗

PubMed2003

NanoCell electronic memories.

NanoCells are disordered arrays of metallic islands that are interlinked with molecules between micrometer-sized metallic input/output leads. In the past, simulations had been conducted showing that the NanoCells may function as both memory and logic devices that are programmable postfabrication. Reported here is the first assembly of a NanoCell with disordered arrays of molecules and Au islands. The assembled NanoCells exhibit reproducible switching behavior and two types of memory effects at room temperature. The switch-type memory is characteristic of a destructive read, while the conductivity-type memory features a nondestructive read. Both types of memory effects are stable for more than a week at room temperature, and bit level ratios (0:1) of the conductivity-type memory have been observed to be as high as 10(4):1 and reaching 10(6):1 upon ozone treatment, which likely destroys extraneous leakage pathways. Both molecular electronic and nanofilamentary metal switching mechanisms have been considered, though the evidence points more strongly toward the latter. The approach here demonstrates the efficacy of a disordered nanoscale array for high-yielding switching and memory while mitigating the arduous task of nanoscale patterning.

Journal Article↗