University of California, Riverside

Department of Electrical and Computer Engineering

Silicon Based Molecular Memory Devices

Silicon Based Molecular Memory Devices
Veena Misra
Department of Electrical Engineering
North Carolina State University, Raleigh, NC

Date: May 10, 2004
Time: 11:10 am
Location: Bourns Hall A265

The field of molecular electronics is gaining interest due to the miniature size of molecules, which may enable memory and logic applications in the nano-scale. Particularly attractive is the hybrid silicon/molecular approach because of its unique nature of combining the molecular electronic elements with existing silicon technology. This approach can also provide a bridge between CMOS-only and future molecular-only technologies. The advantages of molecular-based memory devices include nanoscale size, low voltage operation and multiple-state properties. In this work, redox-active charge-storage molecules are incorporated into silicon structures to generate a class of nano-scale molecular electronic devices.. Application of an oxidizing voltage on these molecules, which exhibit charge states at distinct voltages, causes them to lose electrons and acquire a positive charge (write state). Electrons are transferred back to the molecules from the substrate when a reducing voltage is applied (erase state). In this presentation, the properties of SAMs of redox-active molecules on very thin SiO2 layers will be discussed. The redox potentials, tunneling probability and retention times can be tuned by varying the size of the linker and the oxide thickness. The properties of these monolayers and their dependence on oxide thickness, measurement frequency and amplitude will be discussed. Next, the role of substrate engineering to enhance the properties of molecules will be presented. The use of N+ (or P+) pockets embedded in p-well (or n-well) Si substrates as a means of obtaining multiple states from a two-state molecule will be discussed. We will also report on utilizing N+/P and P+/N diodes to increase the charge-retention times of redox-active monolayers. Both of these strategies illustrate engineering of the silicon component in hybrid silicon-molecular devices. We believe that co-engineering both the silicon and molecular components will enable access to novel device functionalities that may not be possible with silicon or molecular devices alone.


Veena Misra received her B.S. (1991), M.S. (1992) and Ph.D. (1995) degrees from North Carolina State University. After graduation, she joined MOTOROLA's advanced products R&D labs in Austin and worked on integration technologies for the power pc chip for which she received the MOTOROLA high impact technology award. In 1998, she joined as an Assistant Professor of Electrical and Computer Engineering at NCSU. She was promoted to Associate Professor in May, 2003. Her current research activities focus on novel electronic materials for nanoscale CMOS devices, molecular memories integrated with silicon structures, nanostructure fabrication and high performance SiC devices. She is internationally recognized for her work in novel metallic gate electrodes on high-K dielectrics. She has given over 25 invited publications in international conferences on her work on gate electrode work function engineering. She has received the 2001 Presidential Early Career Award for Scientists and Engineers and the NCSU 2002 ALCOA Foundation Engineering Research Achievement Award. Dr. Misra has 3 issued patents and has authored over 80 scientific publications.
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