Tetracene Crystals Surface Versus Bulk Transport

Tetracene Crystals Surface Versus Bulk Transport 

This section will begin with a particular focus on the surface versus the bulk transport in the case of tetracene single crystals. Single crystal FETs with PPX 

In combination with contact metals such as Ag or Au, tetracene exhibits hole transport only, because of the matching between the metal workfrinction and the tetracene HOCO highest occupied crystal orbital). The hole mobility can be independently estimated from the saturation of the output curve 

Alternatively, chemical inhomogeneities and degradation have to be considered. It is well established, that local chemical impurities might act as electrically active trap states in a wide-band gap organic semiconducting host and reduce the effective mobility in the crystal [15, 49]. To judge on possible variation in the impurity concentration at the crystal surface and in the bulk it is necessary to carry out depth dependent chemical analyses, which we accomplished by repeated GC (see Section 25.2.2). 

It is important to stress certain aspects at this point. Firstly, although oxidation products are expected to behave preferentially as electron traps due to their higher electron affinity, the distortion of the surrounding crystal lattice due to steric constraints might also influence the transport of holes [18,19]. 

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Tetracene Crystals Surface Versus Bulk Transport... 

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