Figure 2: STM images of the (2✓3 × 2✓3)R30° Sn structures on n-type and p-type Si(111).
From: Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping
Notice the transition from the (2✓3 × 2✓3)R30° to (4✓3 × 2✓3)R30° phase for the p-type (B-2✓3Sn) interface in b,d. No such transition is observed for the n-type interface (a,c). Scale bars in (a–d) are 5 nm; scale bar in e is 1 nm. Scanning parameters (Vs and It) are 2 V, 0.2 nA (a), 1 V, 0.2 nA (a inset), 2 V, 0.5 nA (b), 2 V 0.3 nA (b inset), −2.3 V, 0.5 nA (c), +1.5 V, 0.02 nA (d) and +1.2 V, 0.15 nA (e). (e) Zoomed-in image of the surface area marked in d. Dashed lines mark the primitive (2✓3 × 2✓3)R30° and (4✓3 × 2✓3)R30° unit cells of the B-2✓3Sn and B-4✓3Sn phase, respectively, while solid lines mark the corresponding centred-rectangular and rectangular unit cells. Up-dimers are marked by ovals. (f) Area fractions of the B-4✓3Sn (solid squares) and p-4✓3Sn (solid triangles) surface phases as a function of temperature. To determine the change in transition temperature, the p-4✓3Sn data were rigidly shifted and superposed with the B-4✓3Sn data (hollow triangles). Each data point is obtained from a surface area that is at least 14,000 nm2 in size, and is fully converged as a function of image size. Areas close to step edges and domain boundaries were excluded from the statistics.
