Dense yttrium oxyfluoride (YOF) coating was successfully deposited by suspension plasma spraying (SPS) with coaxial feeding. After deposition for 6 min at a plasma power of 105 kW, the thickness of the YOF coating was 55 ± 3.2 µm with a porosity of 0.15% ± 0.01% and the coating rate was ~9.2 µm/min. The crystalline structure of trigonal YOF was confirmed by X-ray diffractometry (XRD). The etching behavior of the YOF coating was studied using inductively coupled CHF₃/Ar plasma in comparison with those of the Al₂O₃ bulk and Y₂O₃ coating. Crater-like erosion sites and cavities were formed on the whole surface of the Al₂O₃ bulk and Y₂O₃ coating. In contrast, the surface of the YOF coating showed no noticeable difference before and after exposure to the CHF₃/Ar plasma. Such high resistance of the YOF coating to fluorocarbon plasma comes from the strongly fluorinated layer on the surface. The fluorination on the surface of materials was confirmed by X-ray photoelectron spectrum analysis (XPS). Depth profiles of the compositions of Al₂O₃, Y₂O₃, and YOF samples by XPS revealed that the fluorination layer of the YOF coating was much thicker than those of Al₂O₃ and Y₂O₃. These results indicate that if the inner wall of the semiconductor process chamber is coated by YOF using SPS, the generation of contamination particles would be minimized during the fluorocarbon plasma etching process.

We measured the size distribution of positively and negatively charged nanoparticles generated abundantly in the gas phase during the syntheses of ZnO nanowires by a carbothermal reduction process using a differential mobility analyzer. Under the conditions where these charged nanoparticles were not generated, no nanowires could be grown. The evolution of ZnO nanostructures on the substrate was studied with in-situ measurements of the size distribution of charged nanoparticles with varying reactor temperature and oxygen flow rate. The results suggest that the electrostatic energy arising from charged nanoparticles would play a critical role in the growth of ZnO nanowires.