Investigations On Digital Circuits Using Nano Quantum Dot Cellular Automata

Abstract

In the last few decades the exponential scaling in feature size and newlineincrease in processing power have been successfully achieved by newlineconventional lithographybased VLSI technology However this trend newlinefaces serious challenges due to fundamental physical limits of CMOS newlinetechnology such as ultrathin gate oxides short channel effects doping newlinefluctuations and increasingly difficult and expensive lithography at nanoscale newlineregimes It is projected that the scaling process of CMOS technology will end newlineby the channel length of 7 nm There has been extensive research in recent newlineyears at nanoscale to supersede conventional CMOS technology It is newlineanticipated that these technologies can achieve a density of 10 devicescm2 newlineand operate at TH frequencies newlineNanotechnology provides new possibilities for computing due to newlinethe unique properties that arise at such reduced feature sizes Among these newlinenew devices Quantumdot Cellular Automata QCA relies on new physical newlinephenomena such as Coulombic interactions and innovative techniques that newlineradically depart from a CMOSbased model The QCA not only gives a newlinesolution at nanoscale but it also offers a new method of computation and newlineinformation transformation Consider the processing features of CMOS newlinesystems some circuits ie logic gates perform computation while others newlineie wires are used for signaldata transfer and communication In contrast newlinecomputation and communication occurs simultaneously in QCA newlineThe fundamental QCA logic primitives are the three input majority newlinegate wire and inverter Each of these can be considered as a separate QCA newlinelocally interconnected structure where QCA digital architectures are newlinecombination of these cellular automata structures The existing QCA circuit newlinedesigns are based on only majority gate reduction technique Further reducing newlinethe area as well as complexity the cell minimization techniques are used in newlinethis thesis This thesis presents the design and QCA implementation of Digital newlineCircuits The digital circuits are Logic Gates Combinational Logic Circuits newlineCLC and Sequential Logic Circuit