Mar 10, 2009
Bi-stable memory devices fabricated utilizing hybrid nanocomposites
Researchers in Korea are using an ensemble of quantum dot (QD)/multiwalled carbon nanotube (MWCNT) heterostructures to create switchable and bi-stable nanoscale memory devices. The introduction of MWCNTs provides an effective pathway for carrier transport and capture, and the QDs attached to the surface of the MWCNTs can act as carrier trap regions for the realization of electrical bi-stability.
Even though some work concerning the linking of semiconductor nanocrystals to CNTs has been conducted, very few studies on the facile fabrication method and the physical properties of the CNT/semiconductor heterostructures have been performed. Furthermore, the carrier transport mechanisms for bi-stable memory devices made of the CNT/semiconductor composite heterojunctions, which are important for improving the storage capability of memory devices, have been clarified in this current work.
The group investigated the carrier transport mechanisms of bi-stable memory devices with sidewall conjugations of ZnSe-coated CdSe QDs onto the surface of oxidized MWCNTs by using a simple complexation reaction. Transmission electron microscopy (TEM) measurements were performed to characterize the microstructural properties of the heterojunctions and current-voltage (I-V) data was obtained to evaluate the electrical properties of the bi-stable memory devices fabricated using CdSe/ZnSe QD/MWCNT nanocomposites.
Sidewall conjugation of individual MWCNTs and core-shell CdSe/ZnSe QDs was realized via a complexation reaction, which was clarified by the TEM images. I-V measurements on the Al/CdSe QD:MWCNTs/ITO devices showed that electrical bi-stabilities appeared and that the on/off ratio was dramatically increased due to an improvement in the charge transfer efficiency. Carrier transport mechanisms from the MWCNTs to the CdSe core nanocrytals were described on the basis of the I-V results. The bi-stable memory devices fabricated using QD-MWCNT nanocomposites hold promise for potential applications in next-generation non-volatile memory devices.
About the author
Research professor Fushan Li (Division of Electronics and Computer Engineering, Hanyang University, Korea), graduate student Dong Ick Son (Division of Electronics and Computer Engineering, Hanyang University, Korea), director of National Research Laboratory for Nano Quantum Electronics Laboratory Prof. Tae Whan Kim (Division of Electronics and Computer Engineering, Hanyang University, Korea), graduate student Euidock Ryu (Division of Molecular Science and Technology, Ajou University, Korea) and assistant professor Sang Wook Kim (Division of Molecular Science and Technology, Ajou University, Korea).