Thickness-Dependent Low Lattice Thermal Conductivity of Chemical Vapor-Deposited SnSe₂ Nanosheets

SnSe₂ is a layered semiconductor with intrinsically low thermal conductivity, making it a promising candidate for thermoelectric and thermal management applications. However, detailed measurements of the intrinsic thermal conductivity of SnSe₂ nanosheets grown by chemical vapor deposition (CVD) remain scarce. Here, monocrystalline SnSe₂ nanosheets were synthesized by CVD, with systematic investigation of thickness-dependent in-plane thermal conductivity. A noncontact photothermal Raman technique revealed an ultralow lattice thermal conductivity increasing from 1.63 ± 0.26 W/mK in 4 nm SnSe₂ to 3.61 ± 0.11 W/mK in 130 nm samples, approaching the bulk value. Complementary vacuum calibrations and measurements verified that air convection shifts the extracted thermal conductivity by only 5-10%, preserving the thickness-dependent trend. Substrate effects produced distinct heat-transport behavior in suspended versus supported regions, and strain-induced lattice tilting at suspension edges led to reduced thermal conductivity. Moreover, independent measurements with a thermal bridge device confirmed the temperature dependence of the thermal conductivity and validated the Raman results.