THE EFFECT OF SPIN COATING’S SPEED ON GRAPHENE-OXIDE’S LAYER TOPOGRAPHY AND QCM VISCOELASTICITY

Abstract

Spin coating speed controls the deposition process, affecting the formation of the layer’s topography of graphene oxide and the viscoelastic properties of quartz crystal microbalance (QCM). In this work, the graphene oxide was deposited on the QCM surface by spin coating method with speeds ranging from 500 to 800 rpm. The layer’s surface topography was subsequently measured and analyzed using a roughness multiparameter, which included the area average (Sa), area roughness deviation (Sq), localized surface roughness (Sz), surface skewness (Ssk), and surface kurtosis (Sku). The Sa, Sq, and Sz, which were decreased as the spinning speed increased. The measurements indicated that the graphene oxide layer deposited at 500 rpm had a rough and clumpy texture, while at a high speed of 800 rpm, the layer had a much smoother texture. A detailed analysis using the Sku and Ssk parameters revealed that the clumpy texture in the 500 rpm sample contains tapered sharp graphene oxide structures and a small amount of porosity. On the other hand, the sharp structures were significantly reduced, and porosity was dominant in the sample deposited at high speeds of 700 rpm and 800 rpm. The effect of the spinning speed and the topography on the viscoelasticity was studied using an impedance analyzer. The impedance of the layer deposited at 500 rpm was relatively higher than that at 800 rpm. The frequency shift was also relatively significant for the sample deposited at low speed and was reduced at higher speed. The impedance analysis demonstrated that the layer’s viscosity is affected by its mass, roughness, texture, and porosity.