Double charged surface layers in lead halide perovskite crystals by Goriely, A, Sarmah, S, Burlakov, V, Yengel, E, Murali, B, Alarousu, E, El-Zohry, A, Yang, C, Alias, M, Zhumekenov, A, Saidaminov, M, Chao, N, Wehbe, N, Mitra, S, Ajia, I, Dey, S, Mansue, A, Amassian, A, Roqan, I, Ooi, B, Bakr, O, Mohammed, O