NANOSCALE DEVICES: APPLICATIONS AND MODELING - Bio-Inspired and Nanoscale Integrated Computing - page 37

Figure 2.1. 3D view of a section of a single-walled carbon nanotube.
could also be rather brittle. A nanotube is, on the other hand, one of the natural,
stable forms of its material. For example, a carbon nanotube is an allotrope of
carbon, the same way graphite and diamond are. A nanotube surface does not
have dangling bonds and all atoms are in a perfect crystalline structure,
contributing to the stability of the overall system. A carbon nanotube is, in
fact, a giant molecule. For a detailed study of carbon nanotubes the reader is
referred to [7].
2.3. WORKING AT THE NANOSCALE
Nanofabrication, at least so far, has been heavily reliant on the processes used to
fabricate microelectronic circuits or micro electro mechanical systems (MEMS).
In fact, many of the processes used for nanodevice fabrication are simply
microfabrication processes. In most cases, the term ''nanofabrication'' only
implies that we are using them to make nanodevices. For a detailed study of
microfabrication and MEMS techniques references [8, 9] can be used. A typical
nanodevice fabrication process involves several microfabrication steps, with
the addition of one or two new steps to the process. Let us consider a device
consisting of a nanotube attached to two metal electrodes lying on an insulating
surface (Fig. 2.2). The fabrication of this device starts with thermal oxidation of
silicon to create a thin dielectric layer on a silicon wafer. Then lithography and
metal deposition are used to create the contact electrodes. Another lithography
step helps pattern catalyst islands that will later be used to grow carbon
nanotubes. So far everything is standard microfabrication. The last step, i.e.,
the growth of the nanotube, can be done using chemical vapor deposition (CVD)
[10]. Although CVD has long been around for various fabrication purposes,