Feasibility and strategies for direct atomic force microscopy on standard transmission electron microscopy specimens

Correlative microscopy has gained increasing importance across a range of research disciplines. Combining different microscopy techniques broadens knowledge about a sample by providing more comprehensive insights. In particular, the correlation of atomic force microscopy (AFM) and transmission electron microscopy (TEM) offers a powerful complementary approach for investigating materials, as both surface and subsurface information can be obtained. The fundamental motivation of this study is to establish a direct correlation between measurements obtained from the same specimen region by both methods. Such correlation is not always straightforward, as each technique requires different sample preparation. Consequently, performing AFM measurements on TEM samples inevitably gives rise to several challenges, including, but not limited to, surface distortion and limited accessibility. In this study, we propose a range of AFM measurement strategies tailored to two typical TEM sample types: a 3 nm thin membrane on lacey carbon and a TEM lamella mounted on a lift-out grid. We compare the influence of different cantilever dimensions and AFM modes on image quality, and explore the fabrication of AFM tips positioned at the very front of a cantilever via focused electron beam induced deposition to improve accessibility of regions of interest. With the strategies developed here, we successfully demonstrate the feasibility of AFM measurements on TEM samples without the need for additional sample preparation, enabling direct correlation. The results highlight the practical viability of this combined approach, and expand the scope of correlative microscopy for advanced materials characterization.