Nanotechnology:
A Brief Overview
 |
| AZOBENZENE POLYMERS | |
|
In the Barrett Research Group, we study azobenzene chromophores. Among azobenzene's many unusual optical properties is the ability for low molecular weight azobenzene polymers to spontaneously form surface relief patterns in response to light intensity and polarization gradients.(1) Essentially, the isomerization of the azo chromophore causes a mechanical deformation of the film surface, with accompanying long-distance migration of bulk material (over distances of 100s of nm to a few microns). In the prototypical experiment, a laser is interfered with itself to generate a sinusoidally-varying light interference pattern, which causes a corresponding sinusoidal deformation of the polymer film surface.
Although the deformation of the surface is still limited by the diffraction of light (hence spatial periodicities no lower than ~250nm), this system has many interesting features. Firstly, the system is an organic polymer, which (unlike the inorganic crystals and metals of conventional lithography) can be manipulated in interesting ways (such as the compression of elastomeric masks, thereby reducing spatial periodicities mechanically). Secondly, the inscription is mask-less, since the surface relief pattern can be created using interference of free-space laser beams. Alternately, the all-optical patterning can be thought of as producing the fourier transform of any object half the pump beam is reflected off of (making it essentially holography). Thirdly, since the polymer is moved, not destructively ablated, the inscription is reversible. Essentially, the same layer of polymer can be used for subsequent patterning steps (with erasure back to a flat film between steps, if desired), in sharp contrast to conventional resists in lithography. Can these unique features be exploited to circumvent the diffraction limit of light, giving rise to a new form of nano-lithography? Good question. I'm looking into it.
|
|
| REFERENCES | |
|
|
|
|
|
|