Fig. 4.

Substrate (graphite) 1D heat diffusion. Shown is the temperature change as a function of time considering 2 temporal ranges, up to 1 ns and 3 ns. The following values were used in the simulation: the full fluence of 24 mJ/cm², reflectivity of ∼30%, heat capacity of 1.33 J g⁻¹·K⁻¹ at the substrate initial temperature of 100 K (39), density of 2.266 g/cm³, thermal conductivity of 0.157 W cm⁻¹·K⁻¹ at 100 K (39), and penetration depth of 187 nm at the excitation wavelength of 800 nm (40). We note that the derived time constants are affected by the time range but the profiles are robust; see Text for discussion of the asymptotic value. The top trace is shifted by 10 K for clarity purpose.