Functional organic thin films
Organic thin films are used in many technological and engineering applications nowadays. They find use as coatings, sensors, detectors, as matrix materials in nanocomposites, as self-assembled monolayers for surface functionalization, as low-k dielectrics in integrated circuits and in advanced organic electronic applications like organic light emitting diodes, organic field effect transistors and organic photovoltaics (esp. organic solar cells) and many other applications. OLED displays are now commonly implemented in portable multimedia products like mp3-players. And just recently, self-cleaning ultrahydrophobic and ultrahydrophilic surfaces found first applications. Organic thin films can exhibit a large variety of mechanical, electronical and chemical properties depending on their composition and structure. The applications mentioned above use very different properties of these organic thin films. For example, in magnetic nanocomposites for high frequency applications the electric insulating properties of Teflon thin films are used to reduce losses due to eddy currents, while electronic applications utilize very different properties, like a low dielectric number in low-k dielectrics or semiconduction in organic electronics. This work shows how different properties of even the same organic thin film can be used to create different functionalities that alter the macroscopic properties of the coated materials. Due to the huge variety of organic thin films it is impossible to describe their properties and functionalities comprehensively within the framework of a PhD thesis. In order to address the topic, examples from various fields of actual research in materials science were chosen, including organic semiconductors, dielectrics, barrier layers and hydrophobic materials. For organic semiconductors, diffusion of noble metal atoms is examined and correlated with the changes in the electronic properties of the interface between metal contact and the organic semiconductor. Furthermore Teflon-based thin films were tested for their ability to act as capping layer for protection of the organic semiconductor against aging and to control the threshold voltage of organic field effect transistors. Teflon-based thin films were also used to create ultrahydrophobic surfaces and the reflection of water jets on these surfaces was studied for the first time.