Microwave plasma-assisted reactive HiPIMS of InN films: Plasma environment and material characterisation

This work focuses on the low temperature fabrication process of InN thin films via microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS). The influence of microwave plasma on the HiPIMS discharge process at various nitrogen flows and microwave powers was monitored and characterised through in situ diagnostics, including following HiPIMS I(V,t) curves, optical emission spectroscopy (OES), as well as performing time-resolved Langmuir probe and time-of-flight mass spectroscopy (ToF-MS) measurements. This was followed by the deposition of InN films via standard reactive HiPIMS (reference sample) and MAR-HiPIMS and their characterisation via X-ray diffraction (XRD), reflectometry (XRR), as well as scanning and transmission electron microscopy (SEM, TEM). It was found that the microwave plasma facilitates the dissoci-ation/activation of nitrogen species and supplies seed electrons to the magnetron discharge plasma. Furthermore, the energy of the incoming ions was determined via ToF-MS, and it was possible to identify their plasma origin and temporal behaviour. The produced R-HiPIMS sample was highly metallic, with no nitride phase detected. The MAR-HiPMS film, however, was stoichiometric and exhibited (0002) direction texturing, with an optical bandgap of approx. 1.5 eV, electron concentration of 2.72 x 1020 cm -3 and electron mobility of 7.16 cm2V- 1s- 1 (in the range for polycrystalline InN).

Automated summary

This study focuses on the fabrication of InN thin films at low temperature using microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS). The effects of microwave plasma on the HiPIMS discharge process were investigated through in situ diagnostics. InN films were deposited using both standard reactive HiPIMS and MAR-HiPIMS methods, and their properties were characterized. Results showed that the microwave plasma facilitated the dissociation/activation of nitrogen species and provided seed electrons to the plasma. The MAR-HiPIMS film exhibited stoichiometry, texturing, and desirable electrical properties.