exposed areas between the spheres or the surface in these exposed areas
can be etched by using ion beams. The pattern produced can be manipulated in several ways. For example, chemical deposition can be done at
different angles, or heating the packed array of nanospheres at different
temperatures can cause it to deform in desired ways. It is also possible to
create multiple layers of sphere arrays where the upper layers can act as a
mask for the lower layers, leaving a complex three-dimensional structure.
It is worth noting that the resolution is dependent on the size of the
nanospheres used in the mask. By using sufficiently small spheres, one can
achieve resolutions below 100 nm.
This technique has the benefit of being simple and inexpensive compared
to other nanolithographic techniques. Nanosphere lithography can also
produce structures that are difficult or impossible to create with other
nanolithographic techniques. Unfortunately, it is difficult to produce a
flawless surface with the method; errors occur as the result of difficult-toavoid disorder in the nanosphere mask, which may lead to small differences between masks that are formed in similar conditions. Furthermore,
the space between features and their size cannot be changed independently, as both are directly determined by the size of the nanospheres
used. The number of structures that can be created by this method is also
limited because structures created by nanosphere lithography must be
based on the unoccupied interstices of a packed sphere array. For
example, it is unlikely that a field of square nanosphere pillars could be
produced by a mask of patterned spheres.
10.6.4 Patterning using AFM
In addition to being used as an imaging tool, an AFM can be used to
manipulate surfaces on a very small scale. In standard use, the AFM
images a surface in three dimensions by measuring the deflection of a
small, very sharp tip as it moves along a surface. For patterning, however,
the tip can be used to interact with a surface and alter it in order to
produce very small structures.
Some nanolithographic techniques that employ AFM may be termed
“destructive”—they etch or otherwise damage a surface to create the
intended surface structures. The tip can be used to break apart surfaces
on a very small scale or to move very small objects around on a surface.
The AFM tip can also be modified to irreversibly alter the surface in
various ways. For example, a catalyst can be added to the tip to initiate
reactions. Another common method for surface alteration is the initiation
PATTERNING 417
can be etched by using ion beams. The pattern produced can be manipulated in several ways. For example, chemical deposition can be done at
different angles, or heating the packed array of nanospheres at different
temperatures can cause it to deform in desired ways. It is also possible to
create multiple layers of sphere arrays where the upper layers can act as a
mask for the lower layers, leaving a complex three-dimensional structure.
It is worth noting that the resolution is dependent on the size of the
nanospheres used in the mask. By using sufficiently small spheres, one can
achieve resolutions below 100 nm.
This technique has the benefit of being simple and inexpensive compared
to other nanolithographic techniques. Nanosphere lithography can also
produce structures that are difficult or impossible to create with other
nanolithographic techniques. Unfortunately, it is difficult to produce a
flawless surface with the method; errors occur as the result of difficult-toavoid disorder in the nanosphere mask, which may lead to small differences between masks that are formed in similar conditions. Furthermore,
the space between features and their size cannot be changed independently, as both are directly determined by the size of the nanospheres
used. The number of structures that can be created by this method is also
limited because structures created by nanosphere lithography must be
based on the unoccupied interstices of a packed sphere array. For
example, it is unlikely that a field of square nanosphere pillars could be
produced by a mask of patterned spheres.
10.6.4 Patterning using AFM
In addition to being used as an imaging tool, an AFM can be used to
manipulate surfaces on a very small scale. In standard use, the AFM
images a surface in three dimensions by measuring the deflection of a
small, very sharp tip as it moves along a surface. For patterning, however,
the tip can be used to interact with a surface and alter it in order to
produce very small structures.
Some nanolithographic techniques that employ AFM may be termed
“destructive”—they etch or otherwise damage a surface to create the
intended surface structures. The tip can be used to break apart surfaces
on a very small scale or to move very small objects around on a surface.
The AFM tip can also be modified to irreversibly alter the surface in
various ways. For example, a catalyst can be added to the tip to initiate
reactions. Another common method for surface alteration is the initiation
PATTERNING 417