Speaker
Description
4D Scanning Transmission Electron Microscopy (4D STEM) is a cutting-edge technique that involves scanning an electron beam across a 2D array on a sample. Simultaneously, a detector positioned below the sample records a 2D pattern for each point visited by the electron beam, resulting in a 4D dataset. This method is commonly used in Transmission Electron Microscopy (TEM) for various applications, including virtual imaging, orientation analysis, strain mapping, and differential phase contrast.
Recent advancements in detector technology, particularly in miniaturization and low-energy sensitivity, have made it feasible to apply this technique even in Scanning Electron Microscopes (SEMs). The primary objective of this work is to develop a dedicated 4D STEM detector specifically for SEMs.
The proposed 4D STEM solution relies on a Timepix3 pixelated detector. The Timepix3 detector comprises a matrix of 256 × 256 smart digital pixels (each with a pixel pitch of 55 µm). Within each smart pixel, advanced electronics handle signal processing, including digital registers. Upon detecting an electron, immediate digitization occurs, capturing complex information such as position, energy, and time. This process effectively suppresses unwanted signals, allowing only relevant events to be selected. Consequently, image quality improves significantly, noise is reduced, and resolution and contrast are enhanced in the acquired images.
One of the key advantages of this detector for 4D STEM applications is its data-driven readout. Instead of recording a full image for every probe position, the detector streams data directly from the chip for each detected event. As a result, dwell times can be as short as hundreds of nanoseconds, eliminating the traditional bottleneck associated with image acquisition.
Initial results from the in-situ setup are depicted in Figure 1, where a complete map of 1536 × 1024 points was acquired in just 80 seconds. The full dataset includes individual diffractograms for each point, enabling subsequent virtual diffraction imaging.
