摘要
This study reports on the mid-infrared （mid-IR） photothermal response of multilayer MoS2 thin films grown on crystalline （p-type silicon and c-axis- oriented single crystal sapphire） and amorphous （Si/SiO2 and Si/SiN） substrates by pulsed laser deposition （PLD）. The photothermal response of the MoS2 films is measured as the changes in the resistance of the MoS2 films when irradiated with a mid-IR （7 to 8.2 μm） source. We show that enhancing the temperature coefficient of resistance （TCR） of the MoS2 thin films is possible by controlling the film-substrate interface through a proper choice of substrate and growth conditions. The thin films grown by PLD are characterized using X-ray diffraction, Raman, atomic force microscopy, X-ray photoelectron microscopy, and transmission electron microscopy. The high-resolution transmission electron microscopy （HRTEM） images show that the MoS2 films grow on sapphire substrates in a layer-by-layer manner with misfit dislocations. The layer growth morphology is disrupted when the films are grown on substrates with a diamond cubic structure （e.g., silicon） because of twin growth formation. The growth morphology on amorphous substrates, such as Si/SiO2 or Si/SiN, is very different. The PLD-grown MoS2 films on silicon show higher TCR （-2.9% K^-1 at 296 K）, higher mid-IR sensitivity （△R/R = 5.2%）, and higher responsivity （8.7 V·W^-1） compared to both the PLD-grown films on other substrates and the mechanically exfoliated MoS2 flakes transferred to different substrates.
This study reports on the mid-infrared （mid-IR） photothermal response of multilayer MoS2 thin films grown on crystalline （p-type silicon and c-axis- oriented single crystal sapphire） and amorphous （Si/SiO2 and Si/SiN） substrates by pulsed laser deposition （PLD）. The photothermal response of the MoS2 films is measured as the changes in the resistance of the MoS2 films when irradiated with a mid-IR （7 to 8.2 μm） source. We show that enhancing the temperature coefficient of resistance （TCR） of the MoS2 thin films is possible by controlling the film-substrate interface through a proper choice of substrate and growth conditions. The thin films grown by PLD are characterized using X-ray diffraction, Raman, atomic force microscopy, X-ray photoelectron microscopy, and transmission electron microscopy. The high-resolution transmission electron microscopy （HRTEM） images show that the MoS2 films grow on sapphire substrates in a layer-by-layer manner with misfit dislocations. The layer growth morphology is disrupted when the films are grown on substrates with a diamond cubic structure （e.g., silicon） because of twin growth formation. The growth morphology on amorphous substrates, such as Si/SiO2 or Si/SiN, is very different. The PLD-grown MoS2 films on silicon show higher TCR （-2.9% K^-1 at 296 K）, higher mid-IR sensitivity （△R/R = 5.2%）, and higher responsivity （8.7 V·W^-1） compared to both the PLD-grown films on other substrates and the mechanically exfoliated MoS2 flakes transferred to different substrates.
