Photolithographic Patterning and Doping of Silica Xerogel Films


This study shows that conventional photolithography can be applied for patterning native or organic dye-doped silica films (about 0.5 micro-m thick) obtained via a base-catalyzed sol-gel process. Photoresist was spin-coated onto high optical quality xerogel films, soft-baked, exposed to UV irradiation through a photomask, and developed with a commercial photoresist developing solution. Etching away of the photoresist-unprotected areas of the silica films was carried out with a dilute HF solution, while the remaining unexposed photoresist was removed with acetone. Interdigitated array patterns with features as small as 0.5 mm show a smooth surface and extremely sharp interfaces. Densification of the films at 550°C for 2 h decreases the film thickness by about 11%, increases the refractive index from 1.420 to 1.456, and allows for well-defined patterning down to length scales of 10 micro-m. Since the densification conditions are incompatible with organic dopants, it is demonstrated that sol-gel films can be doped after pattering (post-doping) by adsorption of cationic dyes from solution. Scanning electron microscopy reveals that the microstructure of patterned sol-gel films is similar to that of bulk monoliths, indicating that the photolithographic procedure is not harmful to the film quality. All patterned films demonstrate highly regular light diffraction patterns.




United States. Air Force. Office of Scientific Research
Petroleum Research Fund

Keywords and Phrases

Methylene blue; Photolithography

Document Type

Article - Journal

Document Version


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