Chemically assembled electronic nanotechnology (CAEN) is a promising technology for constructing circuits with device sizes of only a few nanometers. CAEN takes advantage of chemical synthesis techniques to construct molecular-sized circuit elements such as resistors, transistors, diodes, resonant tunneling diodes (RTDs), and reconfigurable switches. In all cases, the fabricated devices are only a few nanometers in size and exploit quantum mechanical properties to control voltage and current levels across the terminals of the device. This all leads to incredibly low power circuits.
However, CAEN based circuits have a key limitation from a circuit designer's point of view: three-terminal devices, such as transistors, will be practically impossible at the nanoscale. In this paper we present a circuit design and modeling tool, MolSpice, for both logic designers and chemists. MolSpice will allow logic designers to design and simulate circuits based on the molecular devices that are available. It will also allow chemists to experiment with different types of device characteristics, seeing how they interact in real logic circuits.
From the users point of view the core of MolSpice is a graphical based editor which allows the user to create simple circuits based on the most likely architecture, a 2-dimensional grid of nanotube based wires. The designer may drag a device onto any intersection in the grid. MolSpice allows the parameters of the devices to be modified and the logical expression being calculated is automatically updated. The designer may then simulate the circuit at different levels of accuracy. At the highest level of accuracy, MolSpice will automatically generate a SPICE deck and have the circuit simulated by SPICE. MolSpice will automatically generate the proper parasitics in the circuit based on the physical location of the devices and various parameters the user chooses to set. For example, the wire diameters, and conductivity and the dielectric constant are used to add the parasitic resistances and capacitances to the circuit.
Another aspect of MolSpice is the ability to graphically edit the IV curve of a molecular device. This will allow chemists to determine the ways in which to optimize molecular devices.
MolSpice will be available on the Web.
S. C. Goldstein
School of Computer Science, Carnegie Mellon University
5000 Forbes Ave, Pittsburgh, PA 15213 USA
Email: firstname.lastname@example.org http://www.cs.cmu.edu/~seth