We focus on the processing-structure relationship of thin films and nanostructures grown by ion-assisted or ionized physical vapor deposition.
These technologies rely on the presence of energetic ions playing a key role in determining the growing film microstructure. Ions can provide
- an amount of energy per material atom which is much larger than the energy provided by any other processes in materials and
- the directionality via momentum transfer resulting in oriented structures.
We explore these properties of the ion-solid interaction at the interface with thin film growth as well as phase separation phenomena, with the aim to achieve substantial control over thin film microstructure and morphology. Examples include the formation of oriented metallic nanocolumns in a carbon matrix or a self-organization process which leads to a periodic compositional nanopattern in composite films.
We cooperate with our partners to explore the fascinating properties of such (multi)functional nanomaterials.
We employ non-destructive ion beam probes to quantitatively determine the changes in composition and depth distribution of the near surface layers induced by thin film growth, thermal or thermochemical treatments. Currently we are aiming at integrating the ion beam probes with conventional laboratory analysis tools in a cluster tool. This combination allows obtaining a comprehensive view on the structural changes after different structure and property evolution stages.
Thin films of metal oxides play crucial roles in a number of contemporary and emerging technologies which require materials combining several functionalities. The present activities covers th investigation of materials for two large groups of applications:
transparent electrodes: thin film photovoltaics, solid state lighting, flat panel display technology
optical thin films: antireflection coatings, interferential filters, etc.
In order to improve the efficiency of thin film solar cells the functionality of transparent electrodes (TE) should be extended well beyond a combination of low electrical resistivity and high optical transmittance. In this case TE material should have:
- high optical transmission also in the near IR spectral range
- defined surface morphology and work function for efficient light trapping and charge collection
- good thermal and chemical stability
- low-cost and low-temperature growth process.
Another set of functionalities is required for optical applications:
- high refractive index and low extinction coefficient
- high homogeneity
- low mechanical stress and high environmental stability.
Our studies aim at achieving the required multifunctionality in films of transparent conducting oxides (TCOs) for applications as TE (In2O3, SnO2 and ZnO) and in transition metal oxides, such as Nb2O5, Ta2O5, and HfO2 for optical applications.
Our goal is to create the scientific knowledge relevant to the sustainable energy management by employing ion-based (nano)material synthesis and analysis approaches. The current activities on oxide films are aimed at:
achieving new combinations of functionalities of metal oxide thin films grown by magnetron sputtering, and
reaching physical limits of the performance of these materials
The activities focus on improving the basic understanding of formation and doping mechanisms of TCOs based on ZnO and In2O3. The present research also includes the investigation of transition metal oxides growth processes in order to control the properties through changes in morphology and structure. A number of in-situ characterization techniques is available to get insight into the relation between the magnetron plasma properties and the physical properties of growing films.