The Development of Nanoelectromechanical Structures for GHz Oscillators and Other High Frequency Devices

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

The increasing miniaturization of electronic devices has been the foundation of the electronics revolution. Similar trends ate being seen in the field of actuating devices. where the acronym MicroElectroMechanical Systems is quickly' being replaced at its leading edge by NanoElectroMechanical Systems (NEMS). The ultimate scate for such devices will be the atomic scale. Nanoscale engineered materials will the building blocks of such devices [I]. Among these materials. nanotubes (NTs) provide many of the necessary properties required for NFMS: their geometry, extraordinary mechanical properties [2-6] ( which will allow GI-Iz mechanical resonance), novel electronic properties (metallic, semiconducting) [7-9]. and novel interfacial properties (atomically smooth, low friction)110, llj. We have recently discovered the atomic scale features in both the motion (friction)[1 I] and electrical properties of nanotube contacts [12]. These measured changes in response at the atomic scale in the dynamic electrical contact between NTs allow for a host of novel devices. These include high frequency devices, where the modulated signal depends on the relative velocity of the sliding contact, to atomic scale linear encoders in which the relative movement of a system can be measured to within a unit cell spacing. A necessary technology in the deployment of NT based NEMS will be a batch-fabrication process which includes NT integration. One solution to this problem is through NT growth processes. in which catalyst material is patterned on a substrate to produce desired integrated NI' NEMS. Specifically, growth processes will have to be understood such that NTs of specific crystalline orientation, radius, and length can be grown in-plane within an integrated silicon based device structure. We propose a plan of research that combines both investigations into the basic mechanisms of novel NEMS devices, and growth techniques that make strides toward batch-fabrication of NT NEMS. The specific NEMS devices we have in mind exploit the atomic scale features of the dynamic contact between NT electrical leads, and the mechanical resonance properties of NTs. Ln our view, the idea of position and orientation dependence of electrical contacts is an aspect of NEMS devices that deserves attention. It is a unique property of the nanometer scale and should open up device applications that are unique to NEMS. In a micron scale contact, the transport properties are an average over many relative crystalline orientations of the contacting surfaces as well as defects etc. hi a nanometer scale contact. ncw behavior will be observed due to relative perfection and smoothness of the contacting surfaces [13] and thc ability to tune precisely the relative orientation of contacting atomic lattices. hi this case the atomic structure matters. We propose to create: 1. Voltage to frequency converter. The (M1-lz-GI-Iz) driving signal will be convened to a signal with 1- 1000 times the input frequency depending on the input amplitude 2. Gigahertz frequency mixer: Sum and difference frequencies will be generated from input M1-Iz signals 3. Atomic resolution linear encoder in an integrated. submicron device.