title: High angular-resolution automated visible-wavelength scanning angle Raman microscopy.
abstract: A scanning angle (SA) Raman microscope with 532-nm excitation is reported for probing chemical content perpendicular to a sample interface. The instrument is fully automated to collect Raman spectra across a range of incident angles from 20.50 to 79.50° with an angular spread of 0.4±0.2° and an angular uncertainty of 0.09°. Instrumental controls drive a rotational stage with a fixed axis of rotation relative to a prism-based sample interface mounted on an inverted microscope stage. Three benefits of SA Raman microscopy using visible wavelengths, compared to near infrared wavelengths are: (i) better surface sensitivity; (ii) increased signal due to the frequency to the fourth power dependence of the Raman signal, and the possibility for resonant enhancement; (iii) the need to scan a reduced angular range to shorten data collection times. These benefits were demonstrated with SA Raman measurements of thin polymer films of polystyrene or a diblock copolymer of polystyrene and poly(3-hexylthiophene-2,5-diyl). Thin film spectra were collected with a signal-to-noise ratio of 30 using a 0.25 s acquisition time.
authors.affiliation: U.S. Department of Energy, Ames Laboratory, Ames, IA 50011, United States; Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, United States.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Lesoine
authors.affiliation: U.S. Department of Energy, Ames Laboratory, Ames, IA 50011, United States; Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, United States.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Bobbitt
authors.affiliation: U.S. Department of Energy, Ames Laboratory, Ames, IA 50011, United States; Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, United States.
authors.forename: Shaobin
authors.initials: S
authors.lastname: Zhu
authors.affiliation: U.S. Department of Energy, Ames Laboratory, Ames, IA 50011, United States; Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, United States.
authors.forename: Ning
authors.initials: N
authors.lastname: Fang
authors.affiliation: U.S. Department of Energy, Ames Laboratory, Ames, IA 50011, United States; Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA 50011, United States. Electronic address: esmith1@iastate.edu.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Smith
keywords: P3HT diblock copolymer; Raman instrumentation; Raman spectroscopy; Thin film measurement; Waveguide