RESUMEN
Gas flow sputtering is a sputter deposition method that enables soft and high-rate deposition even for oxides or nitrides at high pressure (in the mbar range). A unipolar pulse generator with adjustable reverse voltage was used to optimize thin film growth by the hollow cathode gas flow sputtering system. In this regard, we describe our laboratory Gas Flow Sputtering (GFS) deposition system, which has been recently assembled at the Technical University of Berlin. Its technical facilities and suitability for various technological tasks are explored. The first experimental efforts are presented by the example of TiOx films on glass substrates obtained at various deposition conditions with forced Argon flow. The influence of pulsing parameters, power, and oxygen gas flow on the plasma generated is studied. The films were characterized by ellipsometry, scanning electron microscopy, x-ray diffraction, and x-ray reflectivity. Optical Emission Spectroscopy (OES) was also used to characterize the remote plasma, and the substrate temperature was measured. The pulsing frequency (f) is a significant factor that provides additional substrate heating by about 100 °C when the plasma regime changes from f = 0 (DC) to 100 kHz. Such a change in frequency provides a significant increase in the OES signals of Ti and Ar neutrals as well as of Ti+ ions. With pulsed operation at high power, the GFS plasma is capable of heating the glass substrate to more than 400 °C within several minutes, which allows for crystalline anatase TiOx film deposition without external heating. For deposition below 200 °C substrate temperature, low power DC operation can be used.
RESUMEN
The crystallisation of sputter-deposited, amorphous In2O3:H films was investigated. The influence of deposition and crystallisation parameters onto crystallinity and electron hall mobility was explored. Significant precipitation of metallic indium was discovered in the crystallised films by electron energy loss spectroscopy. Melting of metallic indium at ~160 °C was suggested to promote primary crystallisation of the amorphous In2O3:H films. The presence of hydroxyl was ascribed to be responsible for the recrystallization and grain growth accompanying the inter-grain In-O-In bounding. Metallic indium was suggested to provide an excess of free electrons in as-deposited In2O3 and In2O3:H films. According to the ultraviolet photoelectron spectroscopy, the work function of In2O3:H increased during crystallisation from 4 eV to 4.4 eV, which corresponds to the oxidation process. Furthermore, transparency simultaneously increased in the infraredspectral region. Water was queried to oxidise metallic indium in UHV at higher temperature as compared to oxygen in ambient air. Secondary ion mass-spectroscopy results revealed that the former process takes place mostly within the top ~50 nm. The optical band gap of In2O3:H increased by about 0.2 eV during annealing, indicating a doping effect. This was considered as a likely intra-grain phenomenon caused by both (In°)Oâ¢â¢ and (OH-)O⢠point defects. The inconsistencies in understanding of In2O3:H crystallisation, which existed in the literature so far, were considered and explained by the multiplicity and disequilibrium of the processes running simultaneously.