Chemiresistors Based on Li-Doped CuO–TiO2 Films

Abstract

Chemiresistors based on thin films of the Li-doped CuO–TiO2 heterojunctions were synthesized by a 2-step method: (i) repeated ion beam sputtering of the building elements (on the Si substrates and multisensor platforms); and (ii) thermal annealing in flowing air. The structure and composition of the films were analyzed by several methods: Rutherford Backscattering (RBS), Neutron Depth Profiling (NDP), Secondary Ion Mass Spectrometry (SIMS), and Atomic Force Microscopy (AFM), and their sensitivity to gaseous analytes was evaluated using a specific lab-made device operating in a continuous gas flow mode. The obtained results showed that the Li doping significantly increased the sensitivity of the sensors to oxidizing gases, such as NO2, O3, and Cl2, but not to reducing H2. The sensing response of the CuO–TiO2–Li chemiresistors improved with increasing Li content. For the best sensors with about 15% Li atoms, the detection limits were as follows: NO2 → 0.5 ppm, O3→ 10 ppb, and Cl2→ 0.1 ppm. The Li-doped sensors showed excellent sensing performance at a lower operating temperature (200 ∘C); however, even though their response time was only a few minutes, their recovery was slow (up to a few hours) and incomplete.

Effect of Li Doping on Structural, Optical, and Electrical Properties of CuO Thin Films Produced by Spray Pyrolysis Method

“…The battery industry relies on lithium for its high energy density and storage capacity. This is why scientists have been interested in mixing lithium with numerous metal oxides such as CuO [9] and SnO 2 [10], as these materials play an effective role in battery applications and energy storage. Studies have shown that lithium has a significant effect on the electrical and optical properties of metal oxides [11,12].…”

Hydrogen Gas Sensing Properties of Mixed Copper–Titanium Oxide Thin Films

“…Similarly, Lupan et al [32] obtained an enhanced gas response to ethanol compared to hydrogen in the temperature range between 523 and 623 K, which was opposite the result of Barreca et al [40], who showed that the response to hydrogen is about two times higher than that of ethanol. Furthermore, a mixed oxide of 50% TiO 2 and 50% CuO was found to be more sensitive to NO 2 than to H 2 , and could be further improved by adding Li to the mixture [41,42].…”