Figure 2

The LC alignment on the oxidized BP due to the ambient exposure and the Raman analysis. (a) The freshly cleaved BP flake. (b) The oxidized BP flake which was exposed to the ambient and the oxidation is visible. (c) The LC coated BP in which the oxidation remnants of a thin heavily oxidized flake are visible next to a triangular flake. (d) The Raman Spectra at three points indicated by the stars. The red star indicates the Raman taken on the BP flake while the black and the green stars indicate the Raman at completely oxidized region with and without the LC. The BP flakes show three sharp signature characteristic peaks, which indicate a bulk flake. A small broad peak at 800–900 cm⁻¹ on the BP corresponds to the mixed phosphorus oxides vibrations. At the completely oxidized regions which are indicated by the red and the green stars, there is a relatively intense peak at 900–1000 cm⁻¹. This corresponds to the mix signals from the phosphoric acids and the phosphorus oxides species. The offset is zoomed for the peaks that emerged in the range of 750 to 1100 cm⁻¹.