For full details see MethodsX paper: Fabricating Ordered 2-D Nano-Structured Arrays Using Nanosphere Lithography
- cleaning: Si wafer or glass should be cleaned using a modified piranha cleaning process, specifically, H2O2: NH4OH: H2O = 1: 1: 5, 1' x 1' wafer soaked into the solution mixture and heated to 110 C for about 1 hour. Then the wafers rinsed in DI water and dried in N2 flow. Stored in DI water before use, note that it can't be stored in DI water for more than a week, cleaned it again if a week elapsed from last cleaning
- beads deposition: the beads solution should be first ultrasonic for 30 minutes, be sure to put the suspension at the center of the ultrasonic bath (or other position gives the strong vibration, based on your observation). Move to clean room to use the spinner for beads deposition. The recipe for monolayer on silicon or glass:1' x 1' wafer placed at the center of the spinner wafer holder, set the speed = 8000rpm, accel = 800rpm, time = 2min. drop 200ul beads suspension onto the wafer, wait for 20 seconds before start spinning. watch the wafer while spinning, you should see the diffraction pattern changes. after spinning, take the wafer off and stored in a sample box, make sure they are not scratching each other
- Ag deposition - see: Perkin-Elmer RF Sputtering System-6 Inch protocol: MOST
- Beads removal, use a plastic tape to remove the beads after deposition, you should do at least 3 times at the same area where you want to remove the beads, until there's no diffraction pattern seen from the tape or wafer.