AVS 66th International Symposium & Exhibition
    Thin Films Division Monday Sessions
       Session TF+SE-MoA

Paper TF+SE-MoA6
High Density Titanium Oxide and Silicon Oxide Films Deposited by Current-Controlled High Power Impulse Magnetron Sputtering

Monday, October 21, 2019, 3:20 pm, Room A122-123

Session: HiPIMS and Reactive HiPIMS for Novel Thin Films
Presenter: Arutiun P. Ehiasarian, Sheffield Hallam University, UK
Authors: A.P. Ehiasarian, Sheffield Hallam University, UK
P.Eh. Hovsepian, Sheffield Hallam University, UK
D.A. Loch, Sheffield Hallam University, UK
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High density transparent oxide layers on glass can improve the environmental viability of photovoltaics, displays, and low emissivity layers in glazing as well as aid the photocatalytic deactivation of organic contaminants. High Power Impulse Magnetron Sputtering (HIPIMS) produces high density microstructures and high hardness due to the delivery of an ionised metal and dissociated oxygen deposition flux to the substrates.

TiOx and SiOx films were produced in a cluster tool by reactive HIPIMS of a pair of metallic targets in an Ar-Oxygen atmosphere. The HIPIMS process was carried out by controlling the current within the pulse. This resulted in the elimination of stability issues associated with runaway currents for all target poisoning states from metallic to fully poisoned. TiOx was deposited by a fast plasma ignition and a constant current during pulses of up to 200 microseconds. Electron cooling and gas rarefaction were observed sequentially during the initial stages if the pulse. These were followed by a steady increase in metal ion emission at constant power input. SiOx was deposited using a current ramp and shorter pulses of up to 20 microseconds and a bipolar operation. In the transition mode oxygen was emitted mainly from the target whilst in the filly poisoned mode it was detected in the gas phase by time-resolved optical emission spectroscopy. TiOx films deposited without additional heating or substrate biasing had good transparency and a refractive index which increased continuously as the oxygen flow reduced from 45 to 13% reaching a maximum value of 2.55 at a wavelength of 550 nm. The films comprised a mixture of rutile and anatase phase with HIPIMS deposition producing higher fractions of rutile compared to bipolar pulsed DC operation. The HIPIMS films reached higher refractive index of 2.55 compared to 2.47 for bipolar pulsed DC. The hardness of the films and its relation to process conditions are discussed. The morphological density was extremely high as confirmed by a 2 orders of magnitude reduction in corrosion current in potentiodynamic polarisation tests on 304 stainless steel substrates. SiOx microstructural density, refractive index and hardness are discussed.