Biography
Biography: Kavita Garg
Abstract
Porphyrins are highly conjugated, intense colored and the core of key biomolecules “hemoglobin and chlorophyllâ€. Biological systems use porphyrins and metalloporphyrins as catalysts, small molecule transporters, electrical conduits and energy transducers in photosynthesis, hence are an obvious class of molecules to investigate for molecular electronic functions. As a class of molecule, they are robust; possess distinctive reversible oxidation and reduction chemistry. As synthetic porphyrin chemistry is well developed and molecular orbital models accurately predict the electronic consequences of appending organic substituents and binding metal ions. Electronic properties of porphyrins can be tuned by chelation of a metal ion and substitution on the macrocycle that potentiates their use as wires, switches, transistors, junctions, and photodiodes. There are two notable early examples of supramolecular devices based on porphyrins, one as photo-gated ion conductors and another as memory device. Here, we have demonstrated molecular resonance tunneling diode and molecular rectifier based on porphyrin molecules. Resonance tunneling diode is constructed on a σ−π−σ molecular architecture, with a ‘quantum well (a Ï€ conjugated molecule “Porphyrinâ€)’ surrounded by tunnel barriers (σ alkyl chains), electro-grafted on H-terminated Si. These devices exhibited reversible, stable (up to 8 h of voltage scanning) and room temperature NDR (Negative Differential Resistance) effects. Molecular rectifier with donor-spacer-acceptor (D-s-A) structure, electro-grafted on H-terminated Si behaves as a diode. These devices showed RR (Rectification Ratio) up to 107 in reverse bias as a result of alignment of the LUMO levels of the molecules with the Fermi-levels of the electrodes.