Electric-field-induced photoconductivity and resistance switching in Fe-doped amorphous carbon/PMN-PT heterostructures

Amorphous carbon was thought to consume the energy of absorbed photons due to its disordered structure, and thus insensitive to the light illumination. Here, we observe a significant photoconductivity induced by a polarization-driven field in the Fe-doped amorphous carbon films grown on PMN-PT substrates (a-C:Fe/PMN-PT). In absence of an external electric field (E-field), the 532-nm light illumination generates less than 0.2% change in resistance. With a field applied across PMN-PT substrates, the value of (Rlight − Rdark)/Rdark reaches the maximum of 76.7%, exhibiting a large photoconductivity effect. Moreover, the a-C:Fe/PMN-PT heterostructures show a strong electric-field-induced modulation of carrier transport, and cause a resistance change up to the maximum of 70%. The samples switch from the high resistance state to low resistance state with the E-field overcoming a threshold field. A possible mechanism has been attributed to the separation of electron-hole pairs encouraged by the surface charge in the a-C:Fe/PMN-PT interface.