A semi empirical model of vertically aligned carbon nanofiber for field emission devices for circuit application

Abstract

The field emission from carbon thin films, nanotubes and nanofibers has received a great deal of attention because of its potential application in flat panel displays and other nanoelectronic devices. Recently, a concept for maskless Digital Electrostatically Focused E-Beam Array DirectWrite Lithography (DEAL) using a Vertically Aligned Carbon Nanofiber (VACNF) array has been developed at Oak Ridge National Laboratory (ORNL), USA [1]. This concept incorporates a digitally addressable field emission array (DAFEA) integrated into a logic and control circuit realized in standard bulk CMOS process. In order to simulate and predict the system behavior, a compact circuit model for the VACNF field emission devices is required. A physics based model for the field emission triode (FET) was previously shown [2] and an empirical model for carbon nanotube field effect transistor logic has been demonstrated [3]. There is no carbon nanofiber circuit model which can be applied in a CAD tool in order to simulate the DEAL system. This paper presents a compact model for the static and the transient electrical behavior of a VACNF field emitter devices. The VACNF has a very high aspect (height to radius) ratio [4]. As a result the work function at the tip is reduced and this can be described by Fowler-Nordheim (FN) theory [5]. The FN theory predicts the current out of the field emission devices as a function of the applied voltage and is given by: