Direct electron imaging in electron microscopy with monolithic active pixel sensors.

Area of Science:

• * Materials Science and Engineering
• * Physics
• * Imaging Technology

Background:

• * Traditional imaging methods like photographic film and charge-coupled device (CCD) cameras have limitations in dynamic electron microscopy, including insufficient speed, resolution, and radiation hardness.
• * There is a significant need for advanced detectors capable of high-speed, high-resolution imaging with immunity to radiation damage for dynamic electron microscopy.
• * Monolithic Active Pixel Sensors (MAPS) present a promising alternative for overcoming these limitations.

Purpose of the Study:

• * To characterize the performance of monolithic active pixel sensors (MAPS) as detectors in scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
• * To evaluate two versions of the MIMOSA V (MV) chip, a 1M pixel device, for their suitability in dynamic electron microscopy applications.
• * To quantify the impact of electron energy and detector design on image resolution, particularly concerning backscattering effects.

Main Methods:

• * Characterization of two MIMOSA V (MV) chip versions (standard and bottom-thinned) in SEM (few keV to 30 keV) and TEM (40 to 400 keV).
• * Utilized a 1M pixel device with 17 x 17 micrometer pixel size, fabricated in a 0.6 micrometer CMOS process with a thin epitaxial detection layer.
• * Quantified image resolution deterioration caused by backscattering across various electron energies and detector configurations.

Main Results:

• * The tested MAPS demonstrated potential for high-speed, high-resolution imaging in both SEM and TEM environments.
• * The thin epitaxial layer in the MAPS design effectively limited electron beam broadening.
• * Deterioration in image resolution due to backscattering was measured and analyzed for different electron energies and for both standard and bottom-thinned detector versions.

Conclusions:

• * Monolithic Active Pixel Sensors (MAPS) are a viable and effective imaging solution for dynamic electron microscopy, surpassing the capabilities of older technologies.
• * The design of MAPS, particularly the thin epitaxial layer and bottom-thinning, influences their performance and radiation resilience.
• * Understanding and quantifying backscattering effects is crucial for optimizing MAPS performance in high-energy electron microscopy applications.