Spin thin film sensor fabrication

A thin film dissolved oxygen sensor was fabricated by entrapping erythrosin B in a sol-gel matrix95. The silica sol-gel doped with the dye was deposited onto the cleaned glass slides by the spin-coating method. The sensor was linear in the most useful range of dissolved oxygen concentrations, up to 9.1 mg l 1 concentration obtained in air saturated water at 20 °C. 

Interest in the synthesis and processing of mesoporous silica materials has grown extensively since their discovery in 1992, and the exciting potential that these films hold in low-k dielectrics, sensors, nanowire fabrication, catalysis, membrane separations, and many other applications will continue to fuel academic and industrial interest in these films. While there are many new synthesis routes for processing mesoporous silica thin films, spin coating and dip coating remain the most facile methods available. These methods deliver high quality reproducible films that can be used for any of the variety of applications. 

Figure 10.6 Procedure for polymer nanowire fabrication. An aqueous PEDOTtPSS solution was spin-coated on a substrate patterned with a 1.3 ym period grating, then coated with a thin Si02 layer and a PDMS homopolymer brush. A PS-PDMS block-copolymer thin film was then spin-coated and solvent-annealed. The self-assembled block-copolymer patterns were transferred into the underlying PEDOT-.PSS film through a series of reactive ion etching steps employing CF4 and O2 plasmas. (Reprinted with permission from Nano Letters, Nanowire Conductive Polymer Gas Sensor Patterned Using Self-Assembled Block Copolymer Lithography by Y. S. Jung et al., 8, 11. Copyright (2008) American Chemical Society)...

Lin J, Heurich M, Obermeier E (1993) Manufacture and examination of various spin-on glass films with respect to their humidity-sensitive properties. Sens Actuators B 13(14) 104—106 Liu YJ, Shi J, Zhang F, Liang H, Xu J, Lakhtakia A, Fonash SJ, Hueuig TJ (2011) High-speed optical humidity sensors based on chiral sculptured thin films. Sens Actuators B 156 593-598 Mai LH, Hoa PTM, Binh NT, Ha NTT, An DK (2(XX)) Some investigation results of the instability of humidity sensors based on alumina and porous silicon materials. Sens Actuators B 66 63-65 Masuda H, Nishio K, Baba N (1993) Fabrication of a one-dimensional microhole array by anodic oxidation of aluminium. Appl Phys Lett 63 3155-3157... 

Another variation on solution casting is spin coating. This technique borrows from the methods developed by the semiconductor industry to deposit very thin and uniform layers of photoresist onto silicon wafers. This method has been successfully used in the sensor industry to deposit polymer electrolyte membranes onto silicon-based gas sensors [21]. Some main advantages of spin coating are that very thin and reproducible films can be produced, and that an entire array of sensors can be coated simultaneously using batch fabrication methods. In addition, spin coating equipment is readily available fi"om the semiconductor industry. 

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