Europhys. Lett, 48 (4), pp. 461-467 (1999)
Polymorphic transformations observed on molecular organic thin films: p-nitrophenyl nitronyl nitroxide radical
J. Fraxedas 1, J. Caro 1, J. Santiso 1, A. Figueras 1
P. Gorostiza 2 and F. Sanz 2
1 Institut de Ciència de Materials de Barcelona (CSIC)
Campus de la UAB, E-08193 Bellaterra, Spain
2 Departament de Química-Física, Universitat de Barcelona
Martí i Franqués 1, E-08028 Barcelona, Spain
(received 10 March 1999; accepted in final form 16 September 1999)
PACS. 81.30Hd - Constant-composition solid-solid
phase transformations: polymorphic,
massive, and order-disorder.
PACS. 68.55 - Thin film structure and morphology.
We report on the experimental observation of the polymorphic transformation from the monoclinic - to the orthorhombic -phase of thin films of the molecular organic radical p-nitrophenyl nitronyl nitroxide (p-NPNN). This solid-solid phase transition to the thermodynamically most stable -phase encompasses clearly differentiated changes in structure and morphology and may be inhibited if the thickness of the films of the initial -phase lies below a certain critical value. In our case, the -phase of p-NPNN (-p-NPNN) has been stabilized as thin film obtained by thermal evaporation in high vacuum (thickness ).
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