**2. Resistive system and type of physical mechanism**

Following the systematic and consistent study of RRAM devices, it has been realized that the resistive switching material (I) embedded between two metal electrodes (M) plays a key role in switching phenomenon in the metal–insulator–metal (MIM) stratified device structures. In general, MIM devices are referred to sandwiched stacks/layers of metals and insulator. In a simplistic way, the resistive switching effect can be identified phenomenology as the different switching occurring within stratified MIM layered structure. For such device structures, it is comprehensible to understand the different locations of switching while moving vertically from one metal electrode to other. Therefore, there can be following possible switching locations (**Figure 1**):


#### **Figure 1.**

*Different types of resistive switching in which the formation of an interfacial layer between metal electrode and oxide plays a key role in device performance.*

*Effect of Surface Variations on Resistive Switching DOI: http://dx.doi.org/10.5772/intechopen.97562*

On the other hand, switching locations are also possible along perpendicular direction i.e. in the plane of device cross section (lateral direction). Due to this, following switching types are induced:

