DEPOSITION OF ORGANIC THIN FILMS USING ENERGY TUNABLE MOLECULAR BEAMS ON SILICON DIOXIDE AND OCTADECYLTRICHLOROSILANE MODIFIED SILICON DIOXIDE
Mack, Jared Lynn
Organic semiconductors, in particular organic thin-film transistors (OTFTs), have been gaining recognition and spurring development in the electronics world now for more than a decade. The use of organic semiconductors is playing an ever increasing role in today?s industrial research in an effort to fill niches in technology left behind by traditional semiconductors such as silicon. The vast majority of research leading this outreach has been limited to the capabilities of thermally evaporated deposition techniques. A more advanced approach to investigating the underlying growth mechanics of organic semiconductors employs the use of a tunable molecular beam. Through controlling the expansive parameters of a molecular gas, a supersonic beam for molecular deposition can be created with strict control over the incident kinetic energy. This supersonic beam technique was employed to study the growth characteristics of pentacene and how they pertain to the electrical properties of an organic semiconducting device. At a constant growth rate, films were deposited at three incident kinetic energies (1.5 eV, 2.7 eV, 4.5 eV, and 6.7 eV) and analyzed using ellipsometry and atomic force microscopy. Growth characteristics of the film (roughening exponent ?, growth exponent ?, and the correlation length) were then extracted. Finally, surface modification of the dielectric with the self-assembled monolayer (SAM) octadecyltrichlorosilane (OTS) was used to influence the nucleation and growth parameters of the pentacene film. These parameters were studied as a function of the incident kinetic energy and electrical properties that resulted.