The optical absorption spectra of spontaneously electrical solids: the case of nitrous oxide. Issue 3 (19th December 2018)

• Record Type: Journal Article
• Authors: Cassidy, Andrew; James, Rachel L.; Dawes, Anita; Lasne, Jérôme; Field, David
• Is Part Of: Physical chemistry chemical physics. Volume 21:Issue 3(2018)
• Page Start: 1190
• Page End: 1197
• Publication Date: 2018-12-19
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp05746j
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Mud flats, Fejø, Denmark: a 2D representation of defect-free regions in a molecular crystal that can support Wannier–Mott excitons. Abstract : Absorption spectra of films of N2 O, in the range 115–160 nm, are presented for deposition temperatures between 33 K and 64 K. Observed shifts in the absorption energy vs. deposition temperature are analysed in terms of the temperature-dependent spontaneously electrical ('spontelectric') fields present in the films. Using a simple electrostatic theory, we suggest that (i) spectra are associated with Wannier–Mott excitons, (ii) the action of the electric field upon the excitons suffers a blockade at ≤54 K for the C-state and ≤52 K for the D-state of N2 O, (iii) the blockade may be attributed to structural defects, which trap excitons, limiting their size and (iv) films form with defect-free regions containing 324 ± 3, 168 ± 46 and 95 ± 1 molecules of N2 O at 54 K, 52 K and 50 K respectively, yielding an experimental indication of the scale size of regular periodicity associated with Wannier–Mott excitons. Results demonstrate how the spontelectric effect can be used as a tool for exploring the structure of solids and give a graphic image of the structural changes that take place close to the known phase change at 47 K/48 K.