Egberts, PhilipMacdonald, Malcolm Geoffrey2025-03-062025-03-062025-03-05Macdonald, M. G. (2025). The influence of substrate surface roughness parameters on the frictional and adhesive properties of graphene monolayers (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.https://hdl.handle.net/1880/1208292D lubricating materials, such as graphene, are becoming more prevalent in micro and nanoscale technology. As this technology continues to advance and become smaller, it is likewise becoming important to understand the material properties of graphene at the micro and nano scale. As a solid lubricant, graphene is deposited onto surfaces to reduce friction between parts that rub together. Therefore, it is important to understand how substrate surface parameters, such as roughness, influence the frictional and adhesive properties of graphene. This thesis investigates load-dependent friction analysis and phase change analysis experiments usingAFM on graphene, which was deposited onto silicon oxide wafers. There were four different combinations of scratched and heated silicon oxide wafers with graphene monolayers mechanically exfoliated onto them. Load-dependent friction analysis revealed that samples that had negative skewness were shown to reverse the effect that heat had on the graphene silicon substrate. A model to explain this behaviour is proposed wherein graphene on a heated substrate will conform to the shape of a valley caused by scratching the silicon substrate. As an AFM tip slides into the valley, more contact between the tip and graphene occurs, which potentially allows for more puckering between the graphene and the tip as the tip emerges from the valley. This potential puckering decreases the conformity between the graphene and the silicon. Additionally, scratched samples were shown to increase the chances that graphene monolayers would fold. Tapping mode experiments investigating substrate surface adhesion found that increased substrate surface roughness was correlated with an increase in phase change. This is thought to be caused by graphene poorly conforming to unheated samples—which will result in higher phase changes—and conforming well to heated samples—which will result in lower phase changes. Heating the samples was shown to decrease the phase change and the variance of the phase change. At higher roughness’, the phase change of heated samples would also increase. This is thought to be because there may be many regions of suspended graphene between the peaks of highly rough surfaces, which result in a greater phase change measurement.enUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.TribologyGrapheneFrictionLubricationAdhesionContact Mode AFMRoughnessSkewnessKurtosisTapping Mode AFMEngineeringEngineering--Mechanicalmaster thesis