Twist angle homogeneity in twisted bilayer graphene devices studied with STM

Theoretic models that describe magic-angle twisted bilayer graphene strongly depend on how homogeneous the twist angle is. Furthermore, (in)homogeneity is suggested to be the cause for differences between similar devices fabricated by different research groups. It is thus of high importance to characterize the (in)homogeneity experimentally, on the local scale. We use scanning tunneling microscopy to explore non-encapsulated twisted bilayer graphene devices with different nominal twist angles. In this talk, I will introduce a new method to quantitatively describe the local (in)homogeneity present in these devices, potentially on different length scales.