Figure 2.

Characterisation of thermocouples. (a) Temperature increase induced by laser heating at different laser power s measured by the optical modulation method (wavelength λ = 830 nm; p-polarisation at slanted front-side incidence). Thermocouple Au-Ni was made on a slide glass. Sensitivity of 10.1 μV/K¹ determined for similar thermocouple was used for estimation of temperature changes; Au-Au junction was used as a reference. Illumination of the substrate was carried out from the side to contacts. (b) Temperature vs. laser power for 1 μm-thick Si₃N₄ membrane. The Au-Au reference electrodes had a Cr adhesion layer and formed a thermocouple which was experiencing a thermal gradient due to asymmetry of the primary contact pads during laser heating (see panel (c)). (c) An optical see-through image of the 400 × 400 μm² SiN-membrane region with thermocouple whose response is plotted in (b); laser spot was $\sim 100$ μm in diameter. Note a thermal asymmetry of this layout where the upper 100 × 100 μm² primary contact square pad was on the SiN membrane while the lower one on the Si substrate.