In one example, a customizable nonlinear electrical device includes a first conductive layer, a second conductive layer, and a thin film metal-oxide layer sandwiched between the first conductive layer and the second conductive layer to form a first rectifying interface between the metal-oxide layer and the first conductive layer and a second rectifying interface between the metal-oxide layer and the second conductive layer. The metal-oxide layer includes an electrically conductive mixture of co-existing metal and metal oxides. A method forming a nonlinear electrical device is also provided.