Laser Synthesis of Transitional Metal Oxides in 2D Structure and Heterostructure for Thermo Sensors with High Seebeck Coefficient

Abstract

Ultraviolet photons of KrF-laser (λ = 248 nm) based on reactive pulsed laser deposition (RPLD) were used for the synthesis of chromium oxides (Cr3-XO3-Y), iron oxides (Fe2O3-X) 2D structures and Fe2O3-X/Cr3-XO3-Y 2D heterostructure with variable stoichiometry, electrical properties and thickness. 2D structures' depositions were carried out on <100>Si substrate at its temperature change in the range of 293-800 K. XRD analysis showed the evidence of these structures deposited on substrate had polycrystalline phases' content. All 2D structures and heterostructures demonstrated semiconductor temperature behaviour with variable band gap (Eg) less than 1.0 eV, depending on substrate temperature, oxygen pressure in the reactor and structure thickness. Thickness of all kinds' deposits (55-75 nm) depended on oxygen pressure, substrate temperature and the number of laser pulses. The optimum oxygen pressure and substrate temperature were found when thermo electromotive force coefficient (Seebeck coefficient, S) was high as 3.0-8.0 mV/K for Cr3-XO3-Y and for Fe2O3-X 2D structures, accordingly, in the range (280-330) K. The highest S coefficient obtained for 4 layered Fe2O3-X/Cr3-XO3-Y 2D heterostructures was about 15 mV/K in the range (280-330) K. This made these 2D structures and 2D heterostructures, synthesized by UV photons using RPLD method, an exceptionally strong candidate for effective thermo sensors operating at moderate temperature.