A metal vanadium film is used as an extraction electrode contacting with a vanadium oxide or doped vanadium oxide film. The electrode material is adapted for a detector, sensor and optical switch based on a vanadium oxide or doped vanadium oxide film. The metal vanadium film is in favor of reducing the thermal conductivity of the support structure of the array unit. The preparation process of the vanadium film using the metal vanadium as the source material is more easily controlled than that of NiCr film using the NiCr alloy as the source material. The extraction electrode of the present invention easily obtains an excellent metal-semiconductor contact characteristic. The preparation process and patterning process of the metal vanadium film have an excellent technology compatibility with the IC and MEMS manufacturing processes.