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Methods for Determining the Effective Order of Absorption in Radical Multiphoton Photoresists: A Critical Analysis
Author(s) -
Liaros Nikolaos,
Fourkas John T.
Publication year - 2021
Publication title -
laser and photonics reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.778
H-Index - 116
eISSN - 1863-8899
pISSN - 1863-8880
DOI - 10.1002/lpor.202000203
Subject(s) - photoresist , reciprocity (cultural anthropology) , absorption (acoustics) , materials science , computer science , optics , nanotechnology , physics , layer (electronics) , composite material , psychology , social psychology
The accurate determination of the effective order of absorption (EOA) for multiphoton absorption polymerization in radical photoresists is critical for the development and characterization of new materials with improved sensitivity and/or resolution. However, reliable measurement of the EOA is a challenging problem. The accuracy of four techniques that have been developed to address this issue is analyzed in terms of the known kinetics of the radical polymerization of polyfunctional monomers. It is demonstrated that methods that are based upon full reciprocity, i.e., the concept that the chemical response of the photoresist depends on the exposure dose, but not on the period over which this dose is delivered, only enable reliable determination of the EOA under a highly constrained set of circumstances. Methods that depend on limited reciprocity, i.e., the concept that the chemical response of the photoresist is the same when the total exposure window is constant, even if the details of the exposure within that window are varied, can enable accurate determination of the EOA over a considerably broader range of operating conditions. This prediction is verified experimentally. The analysis presented here provides guidance for future experiments and a basis for clearer interpretation of previously published results.