Resistive switching in Ni/SiO
/Si programmable metallization cells was investigated. The proposed switching mechanism is the formation and dissolution of Ni filaments. Under positive bias, Ni cations migrate through SiO
and are reduced at the cathode forming filaments. The filaments are dissolved by Joule-heating effect under positive or negative voltages. Promising resistive-switching characteristics, such as a large resistance ratio of ∼400, excellent data retention, and good immunity to read disturbance, are also revealed.