  Here we report mid infrared (mid-IR) photothermal response of multi layer
MoS2 thin film grown on crystalline (p-type silicon and c-axis oriented single
crystal sapphire) and amorphous substrates (Si/SiO2 and Si/SiN) by pulsed laser
deposition (PLD) technique. The photothermal response of the MoS2 films was
measured as changes in the resistance of MoS2 films when irradiated with mid IR
(7 to 8.2 {\mu}m) source. We show that it is possible to enhance the
temperature coefficient of resistance (TCR) of the MoS2 thin film by
controlling the interface through proper choice of substrate and growth
conditions. The thin films grown by PLD were characterized using XRD, Raman,
AFM, XPS and TEM. High-resolution transmission electron microscopy (HRTEM)
images show that the MoS2 films grow on sapphire substrate in a layer-by-layer
manner with misfit dislocations. Layer growth morphology is disrupted when
grown on substrates with diamond cubic structure such as silicon due to growth
twin formation. The growth morphology is very different on amorphous substrates
such as Si/SiO2 or Si/SiN. The MoS2 film grown on silicon shows a very high TCR
(-2.9% K-1), mid IR sensitivity (delR/R=5.2 %) and responsivity (8.7 V/W) as
compared to films on other substrates.
