Direct nanopattern of hybrid sol–gel films

We propose a direct nanopatterning process of hybrid sol–gel materials useful for photonics application. A specific organic–inorganic film based on 3-glycidoxypropyltrimethoxysilane with epoxy rings acting as silica network modifier and sensitive to radiation has been developed, with a controlled inorganic crosslinking degree and an almost total absence of organic polymerization. The film has been exposed to electron beam or X-ray synchrotron radiation. Both the interactions induce the polymerization of the organic part of the film generating its hardening after post exposure baking. The exposed material becomes insoluble determining a negative-resist like behaviour: the nanolithographic process results from the dissolution of the un-exposed areas in proper solvents. After its optimization unexpected spatial resolution of the pattern were achieved with structures below 200 nm sized, both with electron beam and X-ray lithography. The real advantages of this approach are that almost all the significant parameters for a photonic device (refractive index, light absorption and emission) can be tailored during the material synthesis and with a single lithographic step the device is ready without any further etching process, undoubtedly simplifying the photonic devices nanofabrication. A demonstration test has been performed doping the film with commercial Rhodamine 6G that after the exposure didn’t degraded its luminescence efficiency.