Investigation of RF and DC plasma jet system during deposition of highly oriented ZnO thin films

RF and DC plasma jet sputtering systems were investigated as sources for deposition of ZnO thin films. Deposited zone films have a strong orientation of hexagonal crystallites with the ‘c’ axis perpendicular to the substrate surface. Temperature of the substrate did not exceed 150 °C during the deposition. Langmuir probe measurement performed at the substrate revealed two groups of electrons with different temperatures in the DC plasma jet. A single group of electrons was found in the RF plasma jet system. Electron concentration in the RF jet was found to be about neRF≈5×109–1010 cm−3 with temperature TeRF≈2.5–3.5 eV. In the DC plasma jet, concentration of cold electrons was usually nec≈109 cm−3 with temperature Tec≈0.5 eV and concentration of hot electrons was neh≈108 cm−3 with temperature Teh≈2–3.5 eV. Photographs also confirmed that the plasma density is higher in the position of the substrate in the RF jet than in the DC jet. Other obtained macroscopic parameters as plasma potential and floating potential relative to the grounded reactor are presented.