Negative ion formation by field ionization on a polymer layer grown by field polymerization of tetracyanoethylene

• Published in: Applied surface science 1993-04, Vol.67 (1), p.128-133
• Main Authors: Röllgen, F.W., Schmidt, U., Schmitz, R., Theiss, A.
• Format: Article
• Language: English
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(93)90304-T

The growth of a polymer layer on the surface of a cathode tip has been observed for tetracyanoethylene (TCNE) and benzoquinones under conditions of negative ion formation by field ionization (NFI). Studies of the ion emission from the polymer layers by field ion microscopy showed the formation of negative ions at field strengths significantly below the onset of electron emission and revealed a decisive role of the polymer in lowering the field strength for NFI. This role of the polymer layer is discussed for TCNE and attributed to a loose structure of the TCNE layer with a large capacity for adsorption and absorption of molecules from the gas phase. A new mechanism of NFI is derived which explains the observed ion and electron emission phenomena. In this mechanism NFI is achieved by charge transfer reactions between absorbed molecules in the bulk and adsorbed molecules on the surface of the layer.