Depositionsmechanismen, Struktur und mechanische Eigenschaften laserdeponierter Poly(methyl methacrylat)-Filme

Abstract

In the recent years Pulsed Laser Deposition (PLD) was established as a versatile technique to deposit thin films of different materials. The deposition of organic materials is made difficult by the possible destruction of the material.Laser deposited films from poly(methyl methacrylate) (PMMA) show a characteristic two component structure, consisting of a smooth highly cross-linked component and droplets consisting of polymer with a molecular mass reduced to 8 kg/mol. As responsible mechanism the so-called incubation could be identified. By photochemical changes it reduces the chain length and leads to droplet formation.To minimize the mechanism of incubation, the absorption in the target was raised in different ways. Mechanically mixed and RAFT-polymerized targets with higher absorption were utilized to show that the surface morphology can be improved. Less chemical decomposition of the material during deposition could be reached by building a Matrix Assisted Pulsed Laser Evaporation (MAPLE) setup.For the investigation of the mechanical properties of the laser deposited films a new in-situ mechanical spectroscopy technique was developed, the Plasma Plume eXcited Reed (PPXR). This is a vibrating reed, which is excited to vibration by the moment of the PLD-plasma plume.PPXR-measurements on pulsed laser deposited PMMA-films show that a the complex elastic modulus can be measured in dependence of the temperature. By comparison with other spectroscopy techniques it could be shown that the mechanical spectroscopy on PMMA is dominated by the α-relaxation. From measurements performed on films deposited at higher substrate temperatures conclusions about the mechanism of film formation and the deposited products could be drawn.