The present disclosure includes GCIB-treated resistive devices, devices utilizing GCIB-treated resistive devices (e.g., as switches, memory cells), and methods for forming the GCIB-treated resistive devices. One method of forming a GCIB-treated resistive device includes forming a lower electrode, and forming an oxide material on the lower electrode. The oxide material is exposed to a gas cluster ion beam (GCIB) until a change in resistance of a first portion of the oxide material relative to the resistance of a second portion of the oxide material. An upper electrode is formed on the first portion.