Improving the CO and CH4 Gas Sensor Response at Room Temperature of α-Fe2O3(0001) Epitaxial Thin Films Grown on SrTiO3(111) Incorporating Au(111) Islands

Abstract

In this work, the functional character of complex α-Fe2O3(0001)/SrTiO3(111) and Au(111) islands/α-Fe2O3(0001)/SrTiO3(111) heterostructures has been proven as gas sensors at room temperature. Epitaxial Au islands and α-Fe2O3 thin film are grown by pulsed laser deposition on SrTiO3(111) substrates. Intrinsic parameters such as the composition, particle size and epitaxial character are investigated for their influence on the gas sensing response. Both Au and α-Fe2O3 layer show an island-type growth with an average particle size of 40 and 62 nm, respectively. The epitaxial and incommensurate growth is evidenced, confirming a rotation of 30° between the in-plane crystallographic axes of α-Fe2O3(0001) structure and those of SrTiO3(111) substrate and between the in-plane crystallographic axes of Au(111) and those of α-Fe2O3(0001) structure. α-Fe2O3 is the only phase of iron oxide identified before and after its functionalization with Au nanoparticles. In addition, its structural characteristics are also preserved after Au deposition, with minor changes at short-range order. Conductance measurements of Au(111)/α-Fe2O3(0001)/SrTiO3(111) system show that the incorporation of epitaxial Au islands on top of the α-Fe2O3(0001) layer induces an enhancement of the gas-sensing activity of around 25% under CO and 35% under CH4 gas exposure, in comparison to a bare α-Fe2O3(0001) layer grown on SrTiO3(111) substrates. In addition, the response of the heterostructures to CO gas exposure is around 5–10% higher than to CH4 gas in each case.

Nanostructural evolution of hydrothermally grown SrTiO3 perovskite and its implementation in gaseous phase detection of ethanol

“…The real-time ethanol sensing was performed for all four morphologically variated SrTiO 3 nanostructured based at 150 °C in the presence of 80% RH. In figures 7(a)-(d), all the sensors responded in a positive direction of the y-axis unfolding the p-type semiconducting behavior of the SrTiO 3 nanostructures [24]. The p-type conductivity of the SrTiO 3 nanoforms possibly originated from the p-TiO 2 nanoparticles used in hydrothermal synthesis [29].…”

“…On the other hand, SrTiO 3 and its composites have been successfully employed in sensing different VOCs and gases such as H 2 [12,23], ethanol [3,9,11], O 2 [2,24], ozone [25] and NO 2 [26] but none of them have been focused on the morphology of the resulting sensing layer. The gas sensing performances of nanomaterials are greatly affected by their morphology, crystal structure, surface-to-volume ratio, porosity, oxygen functionality, etc [27].…”

The enhanced sensing properties of MOS-based resistive gas sensors by Au functionalization: a review

“…Chen et al 196 prepared Au-loaded In 2 O 3 /ZnSnO 3 nanofibers for acetone detection. At 200 °C, 50 ppm response was 19.3, with a fast response/recovery time of 10 s/13 s. Serrano et al 197 reported on α-Fe 2 O 3 epitaxial thin films grown on SrTiO 3 islands functionalized with Au for improved CO and CH 4 detection. The sensitivity of the composite material increased by about 35% and 25% under CH 4 and CO atmospheres, respectively.…”

Large Two-Magnon Raman Hysteresis Observed in a Magnetically Uncompensated Hematite Coating across the Morin Transition

“…In addition, hematite has several advantages related to the energy conversion as part of solar cells including a suitable gap [23], and it features a high corrosion resistance and low costs [24]. It also shows a high efficiency as a gas sensor due to the change in its electrical resistance when these compounds are deposited on its surface [25,26]. In paleomagnetism, the solid solutions between hematite and ilmenite (FeTiO 3 ) have interesting magnetic properties depending on the substituted degree of titanium in their structure, and it is used in theoretical and experimental models to explain the remanent magnetization found in magnetic rocks [27].…”