Date: Thursday, Mar 9th
Presenter: Ryan Mansergh, PhD Candidate, OSU Chemistry
Aqueous solution processing offers a sustainable approach to the fabrication of thin films that is eminently scalable. In this work we explore the use of polyoxometalate clusters for aqueous solution deposition of metal oxide thin films. More specifically, we examine tetramethylammonium (TMA) salts of the Lindqvist ions [H2Ta6O19]6- and [H3Nb6O19]5- as thin-film precursors for Ta2O5 and Nb2O5, respectively. We anticipated the large volume change associated with the loss of the TMA countercation would prove detrimental to the quality of the resultant films. Additionally, the structural similarities of the Nb- and Ta-containing Lindqvist species hinted that the precursors might yield films of comparable quality. We studied the reaction pathway of these systems during film formation using temperature-programmed desorption, and assessed film properties using a whole host of thin-film characterization techniques. We find surprising results, including the ability to deposit dense, atomically smooth Ta2O5 films in spite of the bulky TMA countercations,1 and that while [H2Ta6O19]6- and [H3Nb6O19]5- are structurally similar, films derived using these precursors are remarkably different.
Ryan Mansergh is an Innovation Fellow with the Center for Sustainable Materials Chemistry, and a Graduate Research Assistant in the Keszler Group at Oregon State University. Prior to joining OSU and the CSMC, Ryan worked for an energy industry consultancy; he has also been involved with several tech startups. At OSU his research is focused on using polyoxometalates and other solution precursors for the deposition of thin films for advanced electronic and energy applications. The main solution deposition techniques he uses include spin coating for smaller substrates, and aerosol or mist coating for larger substrates. Much of his thin-film characterization work involves X-ray diffraction, X-ray reflectivity, and spectroscopic ellipsometry. He also frequently uses atomic force microscopy, scanning electron microscopy, and transmission electron microscopy for sample imaging.