Evaluation of mechanical characteristics of the plate-type polymer hyperfine pit pattern by the nanoindentation process

Abstract

It’s important to measure quantitative properties about the thermal-nano behavior of polymers in order to produce high quality components using the nanoimprint lithography process. Nanoscale indentation can be used to make the cells for molecular electronics, drug delivery, slots for integration into nanodevices and defects for tailoring both the structure and properties. In this study, the formability of polymethylmetacrylate (PMMA) and polycarbonate (PC) were characterized. Thermo-mechanical properties during formation at a high temperature. Polymers become softer at elevated temperature due to heating. In this case it is particularly important to study the high temperature-induced mechanical properties of the polymer. Nanoindentation was used to measure the thermo-mechanical properties of both PMMA and PC. The polymer was heated with the heating stage on a NanoXP. For a CSM (Continuous Stiffness Method) mode test, the heating temperature was 110°C, 120°C, 130°C, 140°C and 150°C for the PMMA, and 140°C, 150°C, 160°C, 170°C and 180°C for the PC. The maximum indentation depth for this test was 2000 nm. For the basic mode test, the heating temperature was 90°C and 110°C for the PMMA, and 140°C and 160°C for the PC. The maximum loads for this test were 10 mN, 20 mN and 40 mN. An indented pattern was also observed by using AFM. The pile-up phenomenon was mitigated due to the indentation at elevated temperature but the sink-in phenomenon occurred in this instance. When patterning at a high temperature, one should consider the variation in the indentation profile and depth after unloading when designing a structure. It was thought that the mechanical properties decrease when the working temperature increases because PMMA and PC are thermoplastics which soften or melt by heating. Further research in this area is required about the molecular weight and molecular movement at elevated temperature when the free volume of molecules increases.