Selective H2 sensing using lanthanum doped zinc oxide thin film: A study of temperature dependence H2 sensing effect on carrier reversal activity

Abstract

In the present work, we have demonstrated a highly sensitive H 2 gas sensor using a lanthanum doped ZnO (La_ZnO) thin film operated at 300 °C. Also, a p-type to n-type carrier reversal activity is revealed in the presence of H 2 gas species, which predominantly depends on the operating temperature and doping concentration of lanthanum. Pure and La_ZnO (1-10 at. %) thin films were successfully synthesized using a sol-gel route, where a 5 at. % lanthanum doped ZnO thin film shows an outstanding H 2 gas sensitivity (400%) among all other samples with an optimized temperature of 300 °C. Moreover, this sensor actively responds to a wide H 2 gas concentration (10-500 ppm) with a sensitivity of 0.9 (∼n). Additionally, H 2 gas sensing selectivity and mixed gas sensing performance were investigated in the presence of CO and CO 2 gas species at optimized temperature (300 °C). Results show that the pure and 1-3 at. % La_ZnO thin films exhibited n-type H 2 gas sensing, while p-type sensing behavior was observed for 5% and 10% La_ZnO thin films at 300 °C. It is further observed that O − species are extremely active to CO gas species operating at a high operating temperature (>250 °C). Therefore, despite the emerging p-type behavior of the sensor, the ejected electrons are expected to dominantly reduce the sensor resistance in the presence of CO gas species at 350 °C. The improvement of H 2 sensing is further interrelated with the defect levels using Raman spectroscopy.

Advanced NH3 Detection by 1D Nanostructured La:ZnO Sensors with Novel Intrinsic p–n Shifting and Ultrahigh Baseline Stability

“…A comparison of previously reported La-doped ZnO-based MOS gas sensors is made in Table . − Operated at a comparatively low temperature of 150 °C, the ZOL3 sensor of this work yielded the highest response of about 91 in exposure to the lowest level of 50 ppm of NH 3 gas. Moreover, compared to other sensors, the sensor showed superior results in regard to long-term stability in a span of 180 days during which it preserved about 98% of its initial performance.…”

Simultaneously Engineering Oxygen Defects and Heterojunction into Ho-Doped ZnO Nanoflowers for Enhancing n-Propanol Gas Detection

“…In the previous works of our group, an n -propanol gas sensor based on the LaFeO 3 /La 2 O 3 heterostructure exhibited a high response value of 4.3 toward 1 ppm n -propanol gas . From the aspect of element doping, the enhancement of gas-sensing performances, including response value − and stability, , through the doping of rare earth elements in metal oxides has been widely reported. − Meanwhile, ZnO, as an n-type semiconductor, finds diverse applications in catalysts, , nanogenerators, , electroluminescence, , and gas sensors. , Inspired by these advantages, a 5% La-ZnO film was prepared that demonstrated a higher response value (400%) to 500 ppm H 2 gas compared to pure ZnO (80%) . Zhao et al prepared Ce-doped ZnO nanowires, which were exposed to 100 ppm ethanol, and exhibited a higher response (25.3) than pure ZnO (7.4) .…”

Enhanced Sensing Performance of an Ammonia Gas Sensor Based on Ag‐Decorated ZnO Nanorods / Polyaniline Nanocomposite

“…[39,40] Moreover, studies suggest that gas sensing properties of ZnO nanostructure depends on surface characteristics that can be controlled by the fabrication process. [41] In the past, our group studied NH 3 sensing performance of PANiÀ Cu nanocomposites doped with HCl that showed selective response. [42] In particular, the addition of n-type oxide semiconductor nanoparticles in p-type PANi could lead to the formation of the regions with p-n junctions.…”

“…Among the SMOs, ZnO has several advantages over other metal oxides, such as high electron mobility, high thermal and chemical stability, low cost; making it is an appropriate candidate for gas sensing applications [39,40] . Moreover, studies suggest that gas sensing properties of ZnO nanostructure depends on surface characteristics that can be controlled by the fabrication process [41] …”