Electrical and Gas Sensing Properties of p-Type Co₃O₄ Loaded n-Type TiO₂ Nanotubes Heterostructures ^†

p-type Co₃O₄ particles loaded onto n-type TiO₂ nanotubes (NTs) with controlled Co₃O₄ density were synthesized using a two-step electrochemical deposition procedure. Morphology and structure of the fabricated samples were characterized by Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectroscopy and the X-ray Diffraction method. The effect of loading density on the electrical and gas sensing properties of the loaded n-type TiO₂ NTs was investigated. C-V and I-V characteristics were obtained and the heterojunction barrier height was determined. Sensor properties of hydrogen (H₂), NO₂ and VOCs with varying operation temperatures were measured. The results show that Co₃O₄ particle density on the surface of TiO₂ NTs directly affects the sensor performance such as selectivity and sensor response, even at low operation temperatures.