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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. Full article