Interfacial strength and surface damage characteristics of atomically-thin h-BN, MoS2, and graphene
Bien Cuong Tran Khac, Frank W. DelRio, Koo-hyun Chung
Surface damage characteristics of single- and multi-layer hexagonal boron nitride (h-BN), molybdenum disulfide (MoS2) and graphene films were systematically investigated via atomic force microscopy (AFM)-based progressive-force and constant-force scratch tests and Raman spectroscopy. The film-to-substrate interfacial strengths of these atomically-thin films were assessed based on their critical forces (i.e., normal force where the atomically-thin film was delaminated from the underlying substrate) as determined from progressive-force scratch tests. The evolution of surface damage with respect to normal force was further investigated using constant-force tests. The results showed that single-layer h-BN, MoS2, and graphene strongly adhere to the SiO2 substrate, which significantly improves its tribological performance. Moreover, defect formation induced by scratch testing was found to affect the topography and friction force differently prior to the failure, which points to distinct surface damage characteristics. Interestingly, the residual strains at scratched areas suggest the scratch test-induced in-plane compressive strains were dominant over tensile strains, thereby leading to buckling in front of the scratching tip and eventually failure at sufficient strains. These trends represent the general failure mechanisms of atomically-thin materials due to a scratch test. As the number of layers increased, the tribological performance of atomically-thin h-BN, MoS2, and graphene were found to significantly improve due to an increase in the interfacial strengths and a decrease in the surface damage and friction force. In all, the findings on the distinctive surface damage characteristics and general failure mechanisms are useful for the design of reliable nanoscale protective and solid-lubricant coating layers based on these materials.
Tran Khac, B.
, DelRio, F.
and Chung, K.
Interfacial strength and surface damage characteristics of atomically-thin h-BN, MoS2, and graphene, ACS Applied Materials and Interfaces, [online], https://doi.org/10.1021/acsami.8b00001, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=924911
(Accessed December 2, 2023)