Ion energy analysis of a bipolar HiPIMS discharge using a retarding field energy analyser



Walk, F, Valizadeh, R and Bradley, JW
(2022) Ion energy analysis of a bipolar HiPIMS discharge using a retarding field energy analyser. PLASMA SOURCES SCIENCE & TECHNOLOGY, 31 (6). 065002-065002.

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Abstract

<jats:title>Abstract</jats:title> <jats:p>The time evolution of the positive ion energy distribution functions (IEDF’s) at the substrate position in an asymmetric bipolar high-power impulse magnetron sputtering (HiPIMS) system was determined using a gridded energy analyser. This was done for a range of operating conditions, namely the positive voltage <jats:italic>U</jats:italic> <jats:sub>rev</jats:sub> and ‘on-time’ negative pulse duration <jats:italic>τ</jats:italic> <jats:sub>neg</jats:sub>. The magnetron sputtering discharge was equipped with a Nb target. Based on the knowledge of the IEDF’s, the bombarding ion flux density Γ<jats:sub>i</jats:sub> and energy flux density <jats:italic>Q</jats:italic> <jats:sub>i</jats:sub> to a grounded surface were calculated. Time-resolved IEDF measurements showed that ions with energies approaching the equivalent of the positive pulse voltage <jats:italic>U</jats:italic> <jats:sub>rev</jats:sub> were generated as the reverse positive voltage phase developed. On time-average, we observed that increasing the set <jats:italic>U</jats:italic> <jats:sub>rev</jats:sub> value (from 0 to 100 V), resulted in a marginal decrease in the ion flux density Γ<jats:sub>i</jats:sub> to the analyser. However, this is accompanied by a five-fold increase in the ion energy flux density <jats:italic>Q</jats:italic> <jats:sub>i</jats:sub> compared to the unipolar, <jats:italic>U</jats:italic> <jats:sub>rev</jats:sub> = 0 V case. Reducing the negative HiPIMS pulse duration <jats:italic>τ</jats:italic> <jats:sub>neg</jats:sub> (from 130 to 40 <jats:italic>μ</jats:italic>s) at a constant discharge power leads to a modest increase in Γ<jats:sub>i</jats:sub>, but a four-fold increase in <jats:italic>Q</jats:italic> <jats:sub>i</jats:sub>. The results reveal the benefit of the bipolar HiPIMS technique, in which it is possible to control and enhance the power density of ions bombarding a grounded (or fixed bias) substrate, for potentially better tailoring of thin film properties.</jats:p>

Item Type: Article
Uncontrolled Keywords: bipolar pulsing, HiPIMS, ion energy analyser, ion energy distribution function, RFEA
Divisions: Faculty of Science and Engineering > School of Electrical Engineering, Electronics and Computer Science
Depositing User: Symplectic Admin
Date Deposited: 23 Jun 2022 08:37
Last Modified: 18 Jan 2023 20:57
DOI: 10.1088/1361-6595/ac6a0d
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3157032