Phase formation of photoactive TiO2 thin films by metal plasma immersion ion implantation and deposition

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TiO2 (Eg = 3.2eV) stands out among semiconductors for environmental applications due to its biological and chemical inertness, stability against photocorrosion and chemical corrosion, and cost-effectiveness. A key area of TiO2 photocatalysis is the photodegradation of organic compounds. TiO2 can be produced as powder, crystals, or thin films. While powders are commonly used, thin films created through methods like magnetron sputter deposition, plasma immersion ion implantation, and metal arc deposition are also being explored. Metal Plasma Immersion Ion Implantation and Deposition (MEPIIID) is a novel technique for surface modification. This method utilizes a pulsed regime where accelerated, energetic ions impact the substrate during high voltage pulses, while low-energy hypersonic ions from the cathodic arc generate Ti ions in between pulses. This pulsed mode reduces the total sputter rate of the growing film compared to continuous bombardment with 500-1500 eV ions. Additionally, the backfill of oxygen gas allows for partial transfer of kinetic energy from Ti ions to oxygen molecules, partially ionizing them as they travel from the cathode to the substrate. Neutral oxygen atoms are preferentially adsorbed on the reactive TiO2 surface, contributing to film growth.