Construction of miniaturized integrated circuits via traditional methods, such as organometallic chemical vapor deposition (OMCVD) and molecular beam epitaxy (MBE), relies on the ability to grow or etch components within a lithographically defined region. However, the exponential advances in device integration observed over the past several decades in microelectronics may soon end due to fundamental physical and/or economic limitations with lithographic technology. Reductions in device size below 100 nm will become more challenging due to theoretical limits. This prediction has motivated extensive efforts aimed at developing new device concepts and fabrication approaches that may enable integration to go far beyond the limits of conventional microelectronics technology permitting reduced device dimensions and increased circuit density. The construction of devices utilizing these nanomaterials for self-assembled structures may require billions of such “blocks” precisely arranged in an addressable fashion. Bottom-up assembly of well-defined nanoscale building blocks, such as molecules, quantum dots, nanotubes and nanowires, represents a powerful approach to the construction of integrated circuits that could overcome the limits of conventional microelectronics technology while still maintaining some concepts that have proven successful in microelectronics. Furthermore, the development of nanostructures exhibiting new device function could open up additional and potentially unexpected opportunities for nanoelectronic systems.

Metal and semiconductor nanowires have potential applications in nanodevices and as interconnects. While the electrical properties of individual nanowires have been intensely investigated, there are few studies of the electrical properties of organized arrays of nanowires due to the difficulties in placing nanowires into organized structures. Mesoporous thin films and anodic aluminium oxide membranes, however, have been utilized as templates for the synthesis of high-density, ordered arrays of nanowires. Conductive AFM has been utilized as a probe for measuring the conductivity of germanium nanowire arrays within a mesoporous thin film substrate with the pores oriented towards the surface. The conductivity of individual Ge nanowires with diameters of 3 – 4 nm could be measured in some domains. The results also suggested that each nanowire is continuous throughout the length of the substrate demonstrating the reproducibility of nanowire synthesis within the pores. Furthermore, nearly all of the nanowires formed within the AAO membranes are conducting suggesting nearly complete inclusion of nanowires within the matrix. However, there are numerous engineering problems to be resolved before mass production but it appears the preparation of ordered arrays of Ge nanowires within these substrates has promise in the future development of electronic devices.

Another type of device, a nanoelectromechanical system (NEMS), is based on the interplay of mechanical motion and electrical interaction of a flexible nanostructure, such as a nanowire. The nanowire is typically forced into motion by an electric field. While the idea behind the nanorelay may seem simple, it is a rather complex system with a multidimensional parameter space dependent on the van der Waals (vdW), adhesion, elastic, and electrostatic interactions between the nanowire and the electrode as well as the electrical properties (conductance, contact resistance, etc) of the system. Knowledge of these interaction forces, electric properties, and the mechanical strength (elasticity, fatigue, fracture, etc) of these nanowires is important to the proper construction of NEMS.

Traditionally, mechanical devices are considered to be slow. However, utilizing nanoscale structures for mechanical devices could in theory achieve GHz or THz resonance frequencies making NEMS faster than current electronic devices. To date, researchers have focused on using carbon nanotubes as building blocks for the construction of NEMS due to their mechanical strength. However, during carbon nanotube synthesis both metal and semiconducting nanotubes are generated rendering the electrical response of nanodevices based on carbon nanotubes unpredictable. Semiconductor nanowires, such as silicon or germanium, however, offer the distinct advantage over carbon nanotubes in that their sizes and electronic properties can be controlled in a predictable manner during their synthesis. Thus, the electrical response of NEMS based on semiconductor or metallic nanowires should be more predictable than carbon nanotube based devices and have recently been investigated.

It has been known for some time that whiskers can have strengths considerably greater than the bulk crystalline material. This phenomenon has been attributed to a reduction in the defects/length. Therefore, 1-D nanostructures may be expected to have mechanical properties significantly different from bulk materials since the nanostructures may have dimensions smaller than the characteristic length scales associated with various deformation mechanisms. For example, carbon nanotubes have been shown to buckle elastically rather than fracture or plastically deform and nanocrystalline copper displays near-perfect elastoplastic behavior.

Although numerous methods are now available for the preparation of nanomaterials, it is considerably more difficult to measure their electrical and mechanical properties due to the difficulty in manipulating materials on the nanoscale. Scanning probe microscopy (SPM) techniques, such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM), have been powerful tools in manipulating and characterizing the properties of individual nanostructures. However, it is often difficult to view the nanostructures and reveal any structural transformations without the use of transmission electron microscopy (TEM). Combined with the advantages of TEM, TEM-SPM offers a promising approach to the measurement of the mechanical and electrical properties of nanomaterials and the development of NEMS. This in-situ probing technique has been utilized to study the mechanical properties of silicon and germanium nanowires and investigate the force interactions of silicon and germanium nanowires with gold electrodes. Bistable silicon and germanium nanowire-based nanoelectromechanical programmable read-only memory (NEMPROM) devices were demonstrated by TEM-STM. These non-volatile NEMPROM devices have switching potentials as low as 1 V and are highly stable making them ideal candidates for low leakage electronic devices.