Extended Data Fig. 7: Further Raman and HD-SFG measurements.
From: Spontaneous ordering of identical materials into a triboelectric series
a, Raman spectroscopy reveals no molecular changes within all samples. The insets highlight an Si–O mode and two C–H modes from left to right, respectively. b, For HD-SFG, no differences are detected in the symmetric and asymmetric peaks between pristine and contacted samples. However, the plasma-treated sample clearly shows a much lower signal for the symmetric and asymmetric modes at 2,900 cm−1 and 2,960 cm−1, respectively.
