Ionized particle transport in reactive HiPIMS discharge: correlation between the energy distribution functions of neutral and ionized atoms

TL;DR

This study explores the transport and energy distribution of neutral and ionized titanium atoms in reactive HiPIMS discharges, revealing how nitrogen addition influences ion populations and their physical origins.

Contribution

It provides a detailed analysis of ion energy distribution functions and their correlation with neutral atom transport, highlighting the effects of nitrogen on ion populations in reactive HiPIMS.

Findings

Ion energy distributions reveal four distinct ion populations.

Adding nitrogen significantly reduces ion signals and affects ion populations.

High-energy ions (>4 eV) originate from specific physical processes.

Abstract

We investigated the transport titanium ions produced in a reactive high-power impulse magnetron sputtering (HiPIMS) device used for TiN coating deposition. Time-resolved mass spectrometry measurements of ionized sputtered atoms correlated to time-resolved tuneable diode-laser induced fluorescence (TR-TDLIF) measurements of neutral sputtered atoms were used to understand transport features. Based on ion energy distributions of Ti$^+$, we identified four populations of ions and explore their physical origins. The signals of all ion populations decrease strongly when only 1% N$_2$ is added to the Ar/N$_2$ gas mixture. Time resolved mass spectrometry confirms the result reported in previous work: the fast target poisoning when nitrogen is added in HiPIMS discharges. Based on the measured energy distribution functions of Ti$^{++}$, N$^+$, N$_2^+$, and Ar$^+$, we discuss the production of these ions in HiPIMS discharges. The temperature of thermalized sputtered neutral atoms determined by previous TR-TDLIF measurements evidences the physical origin of an ion population with energies lower than 4 eV. According to discharge pressure, cathode voltage, and ion type, we also discuss the physical origins of high-energy ions (>4 eV).