“…Many experimental results on resistive switching materials have been interpreted in terms of conduction through atom-sized filamentary structures [ 127 ]. This is the case of a wide variety of binary and ternary oxides such as SiO x [ 128 , 129 , 130 , 131 ], HfO 2 [ 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 ], Ta 2 O 5 [ 140 , 141 , 142 ], NiO [ 143 , 144 ], ZnO [ 145 , 146 ], a-Si:H [ 147 ], TiO 2 [ 148 ], V 2 O 5 [ 149 ], YO x [ 150 ], and BiVO 4 [ 151 ]. Nonlinear effects in HfO 2 were also reported by Degraeve et al [ 152 ] and in CeO x /SiO 2 -based structures by Miranda et al [ 153 ].…”