| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | J. Leon Shohet, University of Wisconsin-Madison |
| Authors: | F. Choudhury, University of Wisconsin-Madison G. Sabat, University of Wisconsin-Madison M. Sussman, University of Wisconsin-Madison Y. Nishi, Stanford University J.L. Shohet, University of Wisconsin-Madison |
| Correspondent: | Click to Email |
A high concentration of free-radicals is present in many processing plasmas, which affects the processing conditions and the properties of materials exposed to the plasma. Determining the types and concentrations of such free radicals is critical in order to determine their effects on the materials being processed. Current methods for detecting free radicals in a plasma require multiple expensive and bulky instruments, complex setups and often, modifications to the plasma reactor. This work presents a simple technique that detects reactive-oxygen radicals incident on a surface from a plasma. The measurements are made using a fluorophore dye (Alexa 488) that selectively reacts with oxygen radicals. It is commonly used in biological and cellular systems for assay labeling in liquids. Using fluorometric analysis, it was found that the fluorophore reacts with oxygen radicals incident from the plasma which is indicated by degradation of its fluorescence. The results show that the fluorescence degrades for about 60 seconds and reaches a constant fluorescence value after which little degradation is observed for longer exposure times. As plasma power was increased, the quenching of the fluorescence significantly increased as expected, because the radicals have higher energies as microwave power was increased. Although they are commonly used in liquid form, the dye can also be immobilized on a surface using an appropriate volatile solvent. Both immobilized and liquid fluorophores were used and the results indicate that both states function effectively under vacuum conditions. The immobilized dye can be ‘painted’ on a surface and the radical density incident on the surface can be inferred from fluorometric analysis. The immobilized technique can be very useful for many plasma applications - especially when used under vacuum since it prevents the dye from evaporating.
This work has been supported by the Semiconductor Research Corporation under Contract No. 2012-KJ-2359 and the National Science Foundation under Grant No. CBET-1066231.