Investigation of Porous Zn Growth Mechanism during Zn Reactive Sputter Deposition

Abstract

ArOZn plasma discharges created during DC reactive magnetron sputtering of a Zn target and RF reactive magnetron sputtering of a ceramic ZnO target were investigated and compared by means of the Langmuir probe measurements in order to determine the mechanism of growth of porous Zn lms during DC-mode Zn reactive sputtering. The power supplied to the magnetrons during the sputtering was kept at 125 W and the plasma was characterised as a function of oxygen content in the sputtering gas mixture, ranging from 0 to 60% for two gas pressures related to porous Zn lm deposition, namely 3 mTorr and 5 mTorr. Based on the correlation of plasma properties measurements with scanning electron microscope imaging and X-ray diraction of the lms deposited under selected conditions it was found that the growth of porous, polycrystalline Zn lms was governed by high electron density in the plasma combined with a high electron temperature and an increased energy of the ions impinging on the substrate.

Room temperature sputter deposited catalyst-free nanowires with wurtzite/zinc blende ZnO superstructure and their application in electromechanical nanogenerators on polymer and paper substrates

“…This indicates that no changes take place in the physical sputtering mechanism in this region. As we showed earlier [17], a plasma density greater than 6×10 17 m −3 in reactive Zn sputtering in Ar+O 2 leads to the growth of a porous, nanostructured Zn thin film. In such a high density plasma, the species ejected from the target undergo many collisions on their way to the substrate and do not have enough energy to diffuse along the growing grains, leading to a stick-and-grow mode.…”

“…66 eV (−4%) and U C from 330 V to 283 V (−14%) for 20:4 to 50:10 flows, respectively. As a whole, the values for n e and T e remain in the zone related to nanostructured Zn growth [17]. However, the drop in electron density can be related to the drop in U C similar to the one observed in the transition from nanostructured Zn to columnar ZnO growth [17] and resulting from increasing oxidation of target surface.…”

“…As a whole, the values for n e and T e remain in the zone related to nanostructured Zn growth [17]. However, the drop in electron density can be related to the drop in U C similar to the one observed in the transition from nanostructured Zn to columnar ZnO growth [17] and resulting from increasing oxidation of target surface. In such a case, apart from Zn, also ZnO species are ejected from the target surface during the sputtering process.…”

“…The last aspect worth considering when discussing the morphology of the nanowires is that the total changes in n e and T e are very minute when compared to changes introduced by different Ar:O 2 flow ratios as studied previously [17]. In the referred communication we studied the plasma parameters (n e , T e ) as a function of argon to oxygen ratio changing from 10:1 to 10:15.…”