Fundamentals on Bionanotechnologies - Bionanoelectronics: Bioinquiring and Bioinspired Devices - page 24

Fig. 1.19 The principle of
atomic beam lithography

atom beam

light mask

resist

substrate

SUBMICRON
TECHNOLOGY

NANOTECHNOLOGY ATOM TECHNOLOGY

EB

atom lithography

FIB

EUV

optical nanoimprint

1000 100 10 1 0.1

feature size (nm)

Fig. 1.20 The performances of the main lithographical techniques

is generated via the antinodes and nodes of the light beam. The incoming atoms pass
through the mask and are deposited on a resist, which is subsequently developed.
The performances of various nanolithography techniques are illustrated in
Fig. 1.20 . There are several recent reviews dealing with nanolithography and its
ultimate limits, which indicate also the strategies to be adopted when a certain
device with certain features must be fabricated ( Pease and Chou 2008 ; Saavedra
et al. 2010 ).
The bottom-up approach to nanotechnologies is best represented by the self-
assembly techniques. The self-assembly process stands for spontaneous organi-
zation of several components, such as molecules or nanoparticles, into a desired
pattern. The organization process involves chemical, physical, or biochemical
interactions, such as electrostatic and surface forces, or chemical hydrophilic and
hydrophobic interactions. All these processes are extremely selective and have low
defect rates, the resulted structures possessing a high quality ( Huie 2003 ). Some
basic self-assembly techniques are explained below.
The Langmuir-Blodgett (LB) technique is a well-known self-assembly method
for thin film fabrication in which the pattern results by growing one monolayer
at a time. A monolayer of a required material, originally adsorbed at a gas-liquid
interface, is placed on the substrate on which the self-assembly structure will form.
For instance, a monolayer of a fatty acid or, in general, a surfactant, is first spread