The effect of DC-bias plasma oxygen on the surface chemistry of polystyrene thin film analysis by optical emission spectroscopy

Abstract

Plasma has been known as one method for surface functionalization of apolymer. Surface functionalization of the polymer film as a sensitive material as well as matrix material is essential in a chemical sensor and biosensor. This work shows the effects of oxygen plasma generated using a radio frequency plasma (RF plasma) system to the polystyrene film on top of the Quartz Crystal Microbalance (QCM) sensor. Polystyrene with a molecular weight of 35kD was coated on the QCM sensor surface using a spin coating method. The sensor with the coated film was treated in an oxygen plasma generated using the RF-DC plasma system. A DC bias of high-density RF-DC plasma generator voltage was variated from -150 to -550 V. The RF generator voltage was maintained at 100V. The surface changed of the Polystyrene caused by DC-bias of the oxygen plasma was investigated. The effect of the generated oxygen plasma to the polystyrene surface was analyzed using optical emission spectroscopy method with wavelength range of 200-1100 nm. The emission spectroscopy data showed the existence of CO species besides the acivated oxygen atom (844 nm and 776 nm) and oxygen ion (525 nm, 529 nm, and 654 nm). The FTIR data of the plasma-treated polystyrene film showed the existence of a polar functional group. The transmittance value of the FTIR spectrum after plasma treatment decreased with increasing DC bias. The change relates to the chain scission of the C-C and C-H bond of the polystyrene film.