Polymorphs And Electronic Processes In The Crystalline And Thin Films Of Pentacene

Organic semiconductor based on pentacene or other aromatic hydrocarbon molecules have recently attracted an enormous interest regarding their use for molecular electronics. A pentacene filed effect transistor showing a temperature-independent high-mobility has been fabricated. Despite the devoted efforts in device applications, however, there are many open questions concerning even rather basis properties of pentacene, in particular its crystal structure and its electronic properties. The conventional view is that in molecular crystals of aromatic molecules like pentacene hole transport is dominant and that the valence band width is of order 100 meV, much smaller than the experimental 500meV estimate for the conducting charge transfer salt TTYF-TCNQ.We study pentacene, a molecular semiconductor, with a relatively high mobility. Single crystals and thin films of this material were grown using physical vapour transport in a horizontal glass tube. We analyze the growth about pentacene thin film by combining the thermodynamic with the dynamic of molecular, and notice that there are some morphologies in the crystal structure and the thin film structure of our single crystals. In this thesis we conclude that there exist even four crystal structures of pentacene. This brings up two important questions. Firstly, why do four crystal structures of pentacene exist? Secondly, what are the differences in conduction between the different crystal structures? For the answers to both questions it is necessary to study in the intermolecular interactions.Start from the crystal structure, herringbone arrangement in cell unit, changement of molecule length and displacement between molecules of pentacene we obtain the reason on polymorphs in the thin film pentacene. Pentacene crystallizes in layered structures. The molecules form a...