Friction mechanism of zinc oxide films prepared by atomic layer deposition

Abstract

5Friction and wear can make the normal operation of zinc oxide (ZnO) films in many devices impracticable. In this paper, the friction mechanism of ZnO films was studied. The ZnO films were prepared by atomic layer deposition (ALD) on a Si (111) substrate, and the crystal structure of the films was controlled by adjusting the substrate temperature. The surface morphology, microstructure and composition of the ZnO films were studied by a scanning probe microscopy (SPM), a 10 transmissionelectron microscopy (TEM) and an Auger electron microscopy (AES), respectively. The friction coefficient of the ZnO films was measured by a ball-on-disk tester. The results show that the ZnO film deposited at 300 °C has lager crystal size than that deposited at 150 °C. In addition, the 300 °C deposited ZnO film consists of mainly (002)-textured nanocrystal, while the 150 °C deposited ZnO film consists of other orientational nanocrystal, such as (100) and (101)-textured nanocrystals. The friction 15 coefficient of the ZnO films is ~0.1, much smaller than 0.6 of the Si (111) substrate. Low friction coefficient is attributed to plastic deformation induced nanocrystal structure to amorphous structure transformation. The 150 °C deposited ZnO film has smaller crystal size than the 300 °C deposited ZnO film, and thus deformation more easily and the friction coefficient is smaller. 20 65 sliding tester. In order to make clear the mechanism of the improved tribological property of ZnO films, site selective TEM samples were prepared inside the wear track. ExperimentalThis journal is

Influence of Oxygen Vacancies on the Frictional Properties of Nanocrystalline Zinc Oxide Thin Films in Ambient Conditions

“…Furthermore, because the wettability conversion of the ZnO surface is reversible by alternation of UV exposure and dark storage, we also find that the velocitydependent frictional behavior on ZnO of each wettability state is reproduced. The observed friction phenomena on our PLD ZnO surface should also be found on those prepared by other methods such as atomic layer deposition, 28 magnetron sputter deposition, 30 and sol−gel method, 31 or ZnO films prepared using nanomaterials such as nanorods, 41 due to the inevitable presence of defects and surface roughness. Thus, it is in general possible to control the frictional behavior of ZnO surface via PCE.…”

“…Furthermore, water molecules have been found to dissociatively absorb on the sites of oxygen vacancies, resulting in surface hydroxylation and water adsorption on the ZnO surface. − Such dissociative adsorption of water has been experimentally observed on both oxygen-terminated , and zinc-terminated ZnO surface in ultrahigh vacuum (UHV) conditions. Although the frictional properties of ZnO surface have been investigated in the last decades by either the ball-on-flat tribometer ,− or atomic force microscopy (AFM), − how the presence of oxygen vacancies influences the frictional properties of ZnO surface in ambient has not been systematically explored.…”

Tri-system integration in metal-oxide nanocomposites via in-situ solution-processed method for ultrathin flexible transparent electrodes

“…3e, where r is the spreading radius, σ is the surface energy and μ f is the friction coefficient 51 . In this analysis, μ f is chosen as 0.1 as an intrinsic material property of the surface and σ varies inversely as the size of ZnO NP decreases 52,53 . Coherently, the collapsed lines of Fig.…”