title: Accurate dosimetry in scanning transmission X-ray microscopes via the cross-linking threshold dose of poly(methyl methacrylate).
abstract: The sensitivity of various polymers to radiation damage by soft X-rays has been measured previously with scanning transmission X-ray microscopes. However, the critical dose values reported by different groups for the same material differ by more than 100%. Possible sources of this variability are investigated here for poly(methyl methacrylate) (PMMA) using controlled exposure to monochromatic soft X-rays at 300 eV. Radiation sensitivity, judged by several different criteria, was evaluated as a function of dose rate, pre-exposure thermal treatments and X-ray polarization. Both the measured critical dose and the dose required to initiate negative mode (cross-linking) were observed to depend only on dose, not the other factors explored. A method of determining detector efficiency from the dose required to initiate negative mode in PMMA is outlined. This method was applied to many of the soft X-ray STXMs presently operating to derive the efficiencies of their transmitted X-ray detectors in the C 1s absorption-edge region.
authors.affiliation: Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada. leontoaf@mcmaster.ca
authors.forename: Adam F G
authors.initials: AF
authors.lastname: Leontowich
authors.forename: Adam P
authors.initials: AP
authors.lastname: Hitchcock
authors.forename: Tolek
authors.initials: T
authors.lastname: Tyliszczak
authors.forename: Markus
authors.initials: M
authors.lastname: Weigand
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Chithra
authors.initials: C
authors.lastname: Karunakaran