In Vacuo Fabrication and Electronic Structure Characterization of Atomic Layer Deposition Thin Films

Improvement of novel electronic devices is possible by tailor-designing the electronic structure at device interfaces. Common problems observed at interfaces are related to unwanted band alignment caused by the chemical diversity of interface partners, influencing device performance negatively. One way to address this problem is by introducing ultra-thin interfacial dipole layers, steering the band alignment in a desired direction. The requirements are strict in terms of thickness, conformity and low density of defects, making sophisticated deposition techniques necessary. Atomic layer deposition (ALD) with its Ångstrom-precise thickness control can fulfill those requirements. The work presented here encompasses the implementation of an ALD reactor into an UHV photoemission characterization system to enable in-situ experimentation while avoiding ambient contamination. With this setup, the study of the electronic structure of two prototypical heterojunction systems – Ru(Ox)|Au and In2O3|TiO2 is presented with a focus on interface dipole modulation and growth behavior. In addition, this work presents a proof-of-concept integration of a nanoparticle injector system into the ALD reactor. The implementation of the ALD reactor was demonstrated successfully. The study of the Ru(Ox)|Au and In2O3|TiO2 heterojunctions yielded insight into the interface dipole formation depending on ALD parameters, substrate conformation and preparation method. It was further shown that micro-plasma nanoparticle synthesis can be adapted to high vacuum environments. This established a direct path to the application of surface sensitive vacuum based techniques for the characterization of such nanoparticles and experiments with co-deposited ALD structures