Long-term stabilization of nanoparticle production in a gas aggregation source using a full-face erosion magnetron

Long-term operation of magnetron-sputtering-based gas aggregation sources is often limited by poor target utilization and time-dependent evolution of the erosion zone, which affect the stability of nanoparticle production. In this work, a simple full-face erosion (FFE) magnetron with an eccentrically rotating magnetic circuit was developed and systematically investigated for gas-phase nanoparticle synthesis. The influence of magnetic-circuit eccentricity on erosion-track evolution and target utilization was analyzed using a semi-empirical erosion model based on experimentally measured sputtering profiles. The model predictions were compared with experimentally obtained erosion patterns during long-term sputtering of Cu targets. Furthermore, the temporal evolution of nanoparticle deposition rate and nanoparticle size distribution was investigated for both static and rotating magnetic-circuit configurations using quartz crystal microbalance measurements and scanning electron microscopy. The rotating magnetic-circuit configuration enabled nearly constant nanoparticle deposition rates over extended operating times and increased the effective target lifetime by more than a factor of four compared to a conventional static magnetron assembly. Although gradual nanoparticle size evolution was observed during prolonged operation, the size drift remained substantially lower than in the static configuration within the typical operational lifetime of a target used in a conventional magnetron. The results demonstrate that eccentric rotation of the magnetic circuit significantly modifies erosion-zone evolution and provides an effective approach for improving the long-term stability of nanoparticle production in magnetron-sputtering-based gas aggregation sources.