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From Insulating to Conducting Polyimides
Published in Andreea Irina Barzic, Neha Kanwar Rawat, A. K. Haghi, Imidic Polymers and Green Polymer Chemistry, 2021
Göknur Dönmez, Ayça Ergün, Merve Okutan, Hüseyin Deligöz
The next mechanisms to be examined are the Schottky (eq 4.8) and Poole-Frenkel (eq 4.9). It pointed out the conformity of either the conduction mechanism to the Schottky or Poole-Frenkel mechanism when lnI–V1/2 graphs is changed linearly.154 These two mechanisms are not likely to be valid at the same time. The Schottky effect is controlled by the properties of the electrode–polymer interface whereas the Poole-Frenkel effect is adjusted by the bulk polymer properties.160 However, it is clear that the conduction is electronic at room temperature in both cases. In order to determine which mechanism is valid, the beta coefficient is calculated first, and then the dielectric constant is estimated from the eq 4.10.154,156J=ART2exp−ϕSkTexpβSE1/2kTJ=ART2exp−ϕPFkTexpβPFE1/2kTβS=q34πε0εrd1/2=βPF2 where J is the current density, AR is the Richardson constant, T is the absolute temperature, ϕ is the barrier height of electrode–polymer interface, k is the Boltzmann constant, E is the electrical field, βS is the Schottky coefficient, βPF is the Poole-Frenkel coefficient, d is the polymeric film thickness, q is the electronic charge, εr is the dielectric constant, and ε0 is the permittivity in vacuum.
Experimental studies of electron affinity and work function from titanium on oxidised diamond (100) surfaces
Published in Functional Diamond, 2022
Fabian Fogarty, Neil A. Fox, Paul W. May
EF-PEEM was also used to extract a map of the work function across a sample surface. As in UPS, photo-emitted electrons were energy filtered using an imaging double-hemisphere energy analyser. For EF-PEEM, images were obtained for successive energies, allowing the work function at different locations to be visualised as a colour-coded map, with an energy resolution of 0.15 eV and a spatial resolution of ∼150 nm. The UV-light source was the same monochromatic He–I lamp used for UPS. Photoelectrons were extracted from the sample by applying a bias of 7–12 kV across the sample-to-extractor-electrode distance of ∼1.8 mm. The work-function values were then corrected for the Schottky effect of 98 meV resulting from the high PEEM extractor field [42], directly producing values of ϕ with an uncertainty of about ±0.15 eV.