Effective Interfacial Bubble Elimination in 2D Heterostructures via Atomic Force Microscope

Two-dimensional (2D) heterostructures hold significant promise in electronics and photonics. However, bubbles that spontaneously form at the interface between two crystals often degrade the performance of electronic devices. Atomic force microscopy (AFM) offers a direct method for bubble removal in contact mode, but the efficiency of this method varies widely across different substrates, and the removal mechanism is unclear. In this study, we use a nanospherical AFM tip to remove bubbles at the interface between monolayer MoS2 and three crystals, including hexagonal boron nitride (hBN), silicon dioxide (SiO2), and etched SiO2 substrates. The average bubble elimination ratios are 90.0, 80.7, and 14.4% for hBN, SiO2, and etched SiO2, respectively. This substrate-dependent difference is related to the interfacial adhesion energy rather than the surface roughness of the substrate. Given the similar aspect ratio of bubbles, the yield of bubble elimination is inversely proportional to the adhesion energy, which can be used to predict the efficiency of bubble elimination using an AFM tip and provides valuable guidance for the fabrication of 2D heterostructures with clean interfaces.