Piezoelectric ZnO layers

One of the best-known properties of functional oxides is piezoelectricity. Zinc oxide (ZnO) is piezoelectric and a semiconductor with a large direct band gap of about 3.3 eV and an exciton binding energy of about 60 meV, which makes it very interesting for optoelectronic applications. The optimization of its piezoelectric properties represents a particular challenge, since intrinsic defects - e.g. missing oxygen atoms in the otherwise perfect ZnO crystal lattice - generate freely moving charge carriers that shield electric fields, which significantly deteriorates its piezoelectric properties. In this master thesis, thin ZnO layers will be deposited by means of pulsed laser deposition (PLD) on different substrate materials. Using results obtained by X-ray diffraction, optical transmission and electrical measurements, the PLD process parameters will be optimized and suitable substrate materials identified. A close cooperation with the working group magnetism is envisaged, in which the ZnO layers optimized in the course of this master thesis will be used to excite and study spin waves via surface acoustic waves.