Electronic Self-Passivation of Single Vacancy in Black Phosphorus via Ionization

Identification and Manipulation of Defects in Black Phosphorus

“…However, we see that defect A remains a dumbbell at negative bias after application of the STM pulse. We note that this finding is in marked contrast to a very recent report in the literature, 17 where the authors found that their dumbbell-shaped features (identified as neutral MVs) changed to bright dots (identified as negatively charged MVs) upon application of a pulse.…”

“…At negative bias, these defects have an asymmetric dumbbell shape oriented along the armchair direction and extending over ∼8 nm. Such features have been remarked on by previous authors. ,,, Importantly, we observe that, on going from negative to positive bias, there is a contrast reversal (see Figure e and f) and shape change, so that these same defects (labeled as type- A defects) now appear as dark circles; this has not been noted previously in the literature. We identify five salient features of defect A : (1) bright contrast (higher LDOS with respect to pristine BP) at negative bias, (2) dumbbell shape at negative bias, (3) comparatively dark center (see magenta marker) between the lobes of the dumbbell at negative bias, (4) dark contrast (lower LDOS) with respect to pristine BP at positive bias, and (5) circular shape at positive bias.…”

“…Note that Sn is used in the synthesis procedure; its presence is confirmed by X-ray photoemission spectroscopy (Figure S5 of the Supporting Information). We note that, though there have been previous DFT calculations on different types of BP defects, ,,− only 5656-MV-1 and Sn-1 configurations have been previously considered as candidates to explain dumbbell features seen in STM experiments. ,,, …”

“…Defects on the BP surface have been imaged using scanning tunneling microscopy (STM). − A commonly observed defect feature is an asymmetric dumbbell shape, extending several nanometers along the armchair direction; this has also been associated as the source of p-doping found in BP crystals. However, there is hitherto no consensus in the literature on the type of defect corresponding to such a dumbbell feature: some authors have identified the dumbbells as arising from monovacancies (MVs), ,, whereas others have concluded they arise from neutral or charged Sn substitutional defects. , Further confusion has arisen from scanning tunneling spectroscopy (STS) data on these defects from different groups showing peaks at different energies. ,, …”

“…We note that, though there have been previous DFT calculations on different types of BP defects, 11,12,20−31 only 5656-MV-1 and Sn-1 configurations have been previously considered as candidates to explain dumbbell features seen in STM experiments. 11,12,16,17 Our identification approach involves correlating the salient features in the experimental STM images of a given defect type with those in simulated images 32 of candidate defects at both bias polarities, for a precise identification. As an example, Figure 3a contains a table listing five characteristic features of the experimental image of defect A; see also the markers in Figure 1e,f.…”