Fast, Sensitive, and Miniaturized Temperature Sensor Based on CuO-Decorated Fe₂O₃ Nanostructures

In this research, highly sensitive temperature sensors based on copper oxide (CuO)-decorated iron oxide (Fe2O3) nanostructures (NSs) were successfully fabricated. The Fe2O3 NSs were synthesized through a facile for 12 h at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~^{\circ }$ </tex-math></inline-formula>C hydrothermal method, and subsequently, they were coated on an alumina substrate equipped with Pt electrodes. Then, thin layers (5, 10, 50, and 100 nm) of Cu were decorated on the Fe2O3 NSs by sputtering device and annealing at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400~^{\circ }$ </tex-math></inline-formula>C for 1 h, CuO-decorated Fe2O3 NSs temperature sensors were prepared. After extracting the results, it was found that the sensor with 5-nm CuO decoration has the best performance. Using an integrated microheater, the sensor temperature was controlled. Upon variation of the temperature, resistance was changed and the sensor was able to detect temperature variations in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$30~^{\circ }$ </tex-math></inline-formula>C–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$140~^{\circ }$ </tex-math></inline-formula>C. The temperature has been detected from the ambient temperature to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$140~^{\circ }$ </tex-math></inline-formula>C. It showed a temperature coefficient ratio (TCR) of -0.9% °C<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> and a sensitivity of -107.19 M<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega ~^{\circ }$ </tex-math></inline-formula>C<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula>, which demonstrated the highly sensitive nature of the developed sensor. Furthermore, it showed fast dynamics along with high stability. The results demonstrate the possibility of the realization of a highly sensitive and portable temperature sensor using CuO-decorated Fe2O3 NSs.