Wetting and Adhesion Behavior of Undulated a-C:H Film Deposited on Nano-Scale Copper Dot

Abstract

This paper investigated the wetting and adhesion property of undulated a-C:H surfaces with surface morphology controlled for a reduced real area of contact. The nano-undulated a-C:H films were prepared by radio frequency plasma enhanced chemical vapor deposition (r.f. PECVD) using nanoscale Cu dots surface on a Si (100) substrate. FE-SEM, AFM analysis showed that the after repeat deposition and plasma induced damage with Ar ions, the surface was nanoscale undulated. This phenomenon changed the surface morphology of a-C:H surface. Raman spectra of film with changed morphology revealed that the plasma induced damage with Ar ions significantly suppressed the graphitization of a-C:H structure. Also, it was observed that while the untreated flat a-C:H surfaces had wetting angle starting ranged from 72° and adhesion force of 332.79 nN. Had wetting angle the undulated a-C:H surfaces, which resemble the surface morphology of a cylindrical shape, increased up to 103.6° and adhesion force decreased down to 11 nN. The measurements agree with Hertz and JKR models. The surface undulation was affected mainly by several factors: the surface morphology affinity to cylindrical shape, reduction of the real area of contact and air pockets trapped in cylindrical double asperities of the surface.