TiO2 coating fabrication using gas injection magnetron sputtering technique by independently controlling the gas and power pulses

Abstract

This paper presents the effects of a power pulse delay with regard to a gas pulse generated in the Gas Injection Magnetron Sputtering (GIMS) technique. The GIMS technique is a variant of magnetron sputtering, in which the gas pulses control plasma. During the deposition of a coating, the pressure oscillates between the threshold values, initiating and terminating a discharge. In this work, the power pulse was considered as the second parameter of plasma control over the gas pulse. In our opinion, the state of plasma dynamically changes during the gas pulse period, which was studied using optical emission spectroscopy. The largest population of excited atoms of the sputtering gas was detected in the first stage of the gas pulse, while the highest number of ions was observed in the middle stage and the smallest population of plasma constituents in the end stage. The next step of the study involved examining the structure and phase state of the TiO2 coatings deposited when plasma was generated in various stages of the gas pulse. The structure of the coatings strongly depended on the deposition conditions, such as pressure and plasma content. The coatings were characterized by an amorphous structure that crystallized in rutile form under bombardment by energetic plasma species. The depth of crystallization was influenced by the content of plasma in a particular stage of the gas pulse. During the last stages of the gas pulse, very thick coatings were obtained in the deposition process. Moreover, the coatings exhibited metallic features. In such a condition, it can be expected that there will be no sputtering in reactive gas mixture, and the magnetron might operate in the self-sputtering mode. Thus, this work showed that delaying the power pulse with regard to the gas pulse would help to optimize the features of the deposited coating material.