Direct observation of single-atom defects in monolayer two-dimensional materials by using electron ptychography at 200 kV acceleration voltage

Before conducting reconstruction, we performed data binning from 512\(\,\times\,\)512 to 256\(\,\times\,\)256 to enhance the signal-to-noise (S/N) ratio and padded zeros to the pattern size, extending it to 501p to achieve an increased oversampling ratio. Two mixed-stated probes participated during the reconstruction process by the following equation:

$$\begin{aligned}&O_r^{\prime }=O_r+\frac{\alpha }{\max \left( \sum _k\left| P_r^{(k)}\right| ^2\right) } \sum _k P_r^{(k) *} \times \left( \psi _r^{(k)}-P_r^{(k)} O_r\right) \\&P_r^{(k)^{\prime }}=P_r^{(k)}+\frac{\beta }{\max \left( \left|…

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