This paper provides an overview of research developments toward nanometer-scale electronic switching devices for use in building ultra-densely integrated electronic computers. Specifically, two classes of alternatives to the field-effect transistor are considered: 1) quantum-effect and single-electron solid-state devices and 2) molecular electronic devices. A taxonomy of devices in each class is provided, operational principles are described and compared for the various types of devices, and the literature about each is surveyed. This information is presented in nonmathematical terms intended for a general, technically interested readership

Quantum-dot Cellular Automata (QCA) is a nanotechnology which has potential applications in future computers. In this paper, a method for reducing the number of majority gates (a QCA logic primitive) is developed to facilitate the conversion of SOP expressions of three-variable Boolean functions into QCA majority logic. Thirteen standard functions are proposed to represent all three-variable Boolean functions and the simplified majority expressions corresponding to these standard functions are presented. By applying this method, a one-bit QCA adder, with only three majority gates and two inverters, is constructed. We will show that the proposed method is very efficient and fast in deriving the simplified majority expressions in QCA design. Keywords: Quantum-dot Cellular Automata, 3-cube, QCA adder, majority expression. 1.

Microscopes (AFMs) has been under development for a decade, and is now well established as a technique for prototyping nanodevices and for other applications. Until now, the manipulation process for particles with sizes of a few nanometers has been very labor intensive. This severely limits the complexity of the structures that can be built. Particle sizes on the order of 10 nm are comparable to the spatial uncertainties associated with AFM operation, and a user in the loop has been needed to compensate for these uncertainties. This paper addresses thermal drift, which is the major cause of errors for AFMs operated in ambient conditions. It is shown that drift can be estimated efficiently by using Kalman filtering techniques. This approach has firm theoretical foundations and is validated by the experimental results presented in this paper. Manipulation of groups of 15-nm particles is demonstrated under