Growth and Characterization of ZrB2 Thin Films

Abstract: In this thesis, growth of ZrB2 thin films by direct current magnetron sputtering is investigatedusing a high vacuum industrial scale deposition system and an ultra-high vacuum laboratory scalesystem. The films were grown from ZrB2 compound targets at temperatures ranging from ambient (without external heating) to 900 °C and with substrate biases from -20 to -120 V. Short deposition times of typically 100 or 300 s and high growth rates of 80-180 nm/min were emphasized to yield films with thicknesses of 300-400 nm. The films were characterized by thinfilm X-ray diffraction with the techniques θ/2θ and ω scans, pole figure measurements andreciprocal space mapping, scanning and transmission electron microscopy, elastic recoil detection analysis and four point probe measurements. The substrates applied were Si(100), Si(111),4H-SiC(0001) and GaN(0001) epilayers grown on 4H-SiC. The Si(111), 4H-SiC(0001) substrates and GaN(0001) epilayers were chosen given their small lattice mismatches to ZrB2 making them suitable for epitaxial growth.The films deposited in the industrial system were found to be close to stoichiometric with a low degree of contaminants, with O being the most abundant at a level of < 1 at.%. Furthermore, the structure of the films is temperature dependent as films deposited in this system without external heating are fiber textured with a 0001-orientation while the films deposited at 550 °C exhibitrandom orientation. In contrast, epitaxial growth was demonstrated in the laboratory scale system on etched 4H-SiC(0001) and Si(111) deposited at 900 °C following outgassing of the substrates at 300 °C and in-situ heat treatment at the applied growth temperature to remove the native oxides. However, films grown on GaN(0001) were found to be 0001 textured at the applied deposition conditions, which make further studies necessary to enable epitaxial growth on this substrate material. Four point probe measurements on the films deposited in the industrial system show typical resistivity values ranging from ˜95 to 200 μΩcm with a trend to lower values for the films deposited at higher temperatures and at higher substrate bias voltages.