M. Pendharkar
Stanford University,
United States
Keywords: 2D materials, graphene, moire superlattice
Summary:
Moire superlattices formed in dissimilar or twisted 2D materials (a.k.a. twistronics) have been central to the observation of novel physics in recent years - unconventional superconductivity, orbital ferromagnetism, ferroelectricity, to name a few. A change as small as a hundredth of a degree in interlayer twist angle can lead to a measurable change in the moire wavelength and samples where twist angle varies dramatically every few hundred nanometers are common. Yet, techniques to rapidly and reliably image moire superlattices in twisted Van der Waals (VdW) materials remain scarce. In this talk, I will introduce an AFM based technique we termed Torsional Force Microscopy (TFM), which relies on dynamic friction at the tip-sample interface to reveal moire superlattices. TFM operates in air, at room temperature without the need for any complex sample preparation and was also found to image atomic lattices of graphene and hBN as well as reveal sub-surface moires. TFM enables determination of precise structural information of VdW heterostructures is expected to enable their predictable stacking.