Effect of the local morphology in the field emission properties of conducting polymer surfaces

• Published in: Journal of physics. Condensed matter Vol. 25; no. 28; pp. 285106 - 9
• Main Authors: de Assis, T A, Benito, R M, Losada, J C, Andrade, R F S, Miranda, J G V, de Souza, Nara C, de Castilho, C M C, de B Mota, F, Borondo, F
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 17.07.2013; Institute of Physics
• Subjects: Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Current density; Density; Dirichlet problem; Electric potential; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Field emission; Field emission, ionization, evaporation, and desorption; Local current; Physics; Roughness; Conducting polymers; Fowler-Nordheim theory; Atomic force microscopy; Laplace equations; Electric field effects; Roughness; Rough surfaces; Microstructure; Electron field emission; Polyanilines
• ISSN: 0953-8984; 1361-648X; 1361-648X
• DOI: 10.1088/0953-8984/25/28/285106

In this work, we present systematic theoretical evidence of a relationship between the point local roughness exponent (PLRE) (which quantifies the heterogeneity of an irregular surface) and the cold field emission properties (indicated by the local current density and the macroscopic current density) of real polyaniline (PANI) surfaces, considered nowadays as very good candidates in the design of field emission devices. The latter are obtained from atomic force microscopy data. The electric field and potential are calculated in a region bounded by the rough PANI surface and a distant plane, both boundaries held at distinct potential values. We numerically solve Laplace's equation subject to appropriate Dirichlet's condition. Our results show that local roughness reveals the presence of specific sharp emitting spots with a smooth geometry, which are the main ones responsible (but not the only) for the emission efficiency of such surfaces for larger deposition times. Moreover, we have found, with a proper choice of a scale interval encompassing the experimentally measurable average grain length, a highly structured dependence of local current density on PLRE, considering different ticks of PANI surfaces.