  In the past couple of decades, colloidal inorganic nanocrystals and, more
specifically, semiconductor quantum dots have emerged as crucial materials for
the development of nanoscience and nanotechnology, with applications in very
diverse areas such as optoelectronics and biotechnology. Films made of
inorganic NCs deposited on a substrate can be patterned by e-beam lithography,
altering the structure of their capping ligands and thus allowing exposed areas
to remain on the substrate while non-exposed areas are redispersed in a
solvent, as in a standard lift-off process. This methodology can be described
as a direct lithography process, since the exposure is performed directly on
the material of interest, in contrast with conventional lithography which uses
a polymeric resist as a mask for subsequent material deposition or etching. A
few reports from the late 1990 and early 2000 used such direct lithography to
fabricate electrical wires from metallic NCs. However, the poor conductivity
obtained through this process hindered the widespread use of the technique. In
the early 2010, the same method was used to define fluorescent patterns on QD
films, allowing for further applications in biosensing. For the past 2 ,3
years, direct lithography on NC films with e-beams and X rays has gone through
an important development as it has been demonstrated that it can tune further
transformations on the NCs, leading to more complex patternings and opening a
whole new set of possible applications.
