NER: Molecular Diode and Molecular Nonvolatile Memory

Louisiana State University, Baton Rouge LA

Investigators

Abstract

PROPOSAL NO.: 0102765 PRINCIPAL INVESTIGATOR: Choi, Jaewu INSTITUTION NAME: Louisiana State University & Agricultural and Mechanical College TITLE: NER: Molecular Diode and Molecular Nonvolatile Memory The proposed research program addresses the challenges and opportunities available with molecular diode and molecular nonvolatile memory. The proposed molecular diode and molecular nonvolatile memory can be achieved with carbon nanotubes functionality and heterostructure of carbon nanotubes with a ferroelectric linear polymer. The carbon nanotube, itself, has many functional properties, such as quasi-one dimensionality, metal-semiconductor, mechanical stiffness, capillarity, high aspect ratio, large surface area, and chemical stability. In application of these carbon nanotubes to the electronic devices, one serious obstacle is handling the chiarlity, which plays an important role in determining the metallic-semiconducting behavior of the carbon nanotubes. The proposed research program allows us to overcome these difficulties by utilizing the carbon nanotubes as a backbone for a diode and a sensor for a nonvolatile memory. First of all, the proposed molecular diode consists of the differentially doped single carbon nanotube. This is based on our own research work on the electronic structure study of the modified carbon nanotubes by ion-bombardments, alkali metal doping, and atomic and molecular gas adsorption. These recent studies show that the density of states near Fermi level, work function, and band gap of the carbon nanotubes can be tunable. Therefore, it does not require any junction of two carbon nanotubes with different chirality to make a molecular diode, which has been suggested in a theoretical calculation by growth of a single carbon nanotube with different chiraity. To make a diode from a single carbon nanotube in this proposed research program, the half of the tube will be doped with p-type acceptor (like oxygen or fluorine) and the other half will be doped with n-type donors (alkali metals) using screening doping. Secondly, the proposed molecular nonvolatile memory is a heterostructure of a carbon nanotube and a ferroelectric linear polymer with a permanent dipole moment. The carbon nanotube has been studied as a gas sensor and a gas-storage. Adsorption of gas on carbon nanotube induces the conductivity change and band gap opening. In this proposed carbon nanotube-ferroelectric polymer heterostructure, we are going to detect the conductivity change of the carbon nanotube due to the electric dipole reorientation of the ferrolectric polymer by applying the normal TTL (transistor-tansistor logic) voltage. Therefore, the carbon nanotube-ferroelectric polymer heterostructure is the combination of the sensor and information storage. The interface between the carbon nanotube and the ferroelectric polymer, PVDF, of the proposed heterostructure systems is changed from the hydrogen or fluorine rich to the hydrogen and fluorine mixture across the conformational switching from all trans to gauch-trans-gauch bar with variation of temperature or applied voltage (a gate voltage). This is the working principle of the proposed molecular nonvolatile memory. Through this proposed program on molecular diode and molecular nonvolatile memory, graduate and undergraduate students will be involved and trained in the cutting- edge research area (an emerging area of nanoscale science and technology, in special molecular electronics) of science and technology with advanced synchrotron and microfabrication facilities.