My Research This Semester Has Involved Growing A Water-Stable And Smooth

Aminopropyltriethoxysilane on Gallium Nitride Surfaces

Catherine Cassou, Christina Arisio, and Marya Lieberman

University of Notre Dame

Synthesis of stable monolayers has important applications in the creation of biosensors. APTES (3-aminopropyltriethoxysilane) is a widely used SAM (self-assembled monolayer) and has an amine-terminated carbon chain, to which we hope to attach different crown ethers that will be ion-selective. The stability of the APTES monolayer (grown in a 2% APTES solution for 15 minutes) in aqueous environments was tested by soaking a GaN/APTES on sapphire chip in 18MΩ water. Analysis by both contact angle measurements and AFM imaging revealed that the APTES monolayer had been almost completely removed after 110.5 hours of total soak time. Also tested was the relationship between derivatization time and the roughness of the monolayer as well as its stability in water. Fresh monolayers grown in 2% APTES for 5, 25, 45, and 60 minutes showed that a longer soak time in APTES corresponded to a smoother monolayer. Water stability tests are currently being done on these monolayers.