Depth profiles by x-ray photoelectron spectroscopy have been used in conjunction with current-voltage measurements to study the thermal stability of a 50-nm-thick Pt contact to n-4H-SiC substrate. A reaction between the Pt and the SiC substrate is observed at temperatures of 600°C and above. Annealing below that temperature improves the ideality and the uniformity of the Schottky characteristics, while annealing above this temperature degrades the electrical performance and uniformity. Thermodynamic stability is not reached even after annealing for 1 h at 900°C. A local improvement of the characteristics at 800°C is correlated with the formation of a second graphite film in the Pt-SiC reaction.