Electron counting 4D STEM studies of human tooth enamel
Gatan instrument used
The K3® IS camera delivers simultaneous low-dose imaging via real-time electron counting, fast continuous data capture, and a large field of view (FOV). In a 4D STEM experiment, the STEMx® system precisely synchronizes the speed of the scanning probe to the camera frame rate to enable high-speed data acquisition and eliminates the potential for data loss.
Background
Dental enamel is the outer layer component of human teeth that comprises a complex, hierarchically-structured biocomposite. Impairment of an individual’s dental enamel can dramatically affect their quality of life. Therefore, structural details are of high importance in multiple human health contexts. Enamel crystallites nominally contain the mineral apatite, which can be investigated using (scanning) transmission electron microscopy ((S)TEM). Sensitivity of this material to the electron beam is one of the limiting factors for performing such studies. Recently, atomic resolution STEM imaging successfully revealed the coherent atomic structure of crystallites in detail (Figure 1a). However, this required 1) cooling the sample to liquid nitrogen temperature and 2) using significant electron doses of ~6 x 103 e-/Å2 to achieve high signal-to-noise (SNR) images without sample decay. Additionally, 3) a relatively small FOV of the specimen with a limited number of crystallites could be captured per image.