Schottky diodes composed of palladium deposited on silicon carbide (Pd/SiC) detect hydrogen and hydrocarbon gases at elevated temperatures with high sensitivity. Previous examination of the properties of the Pd/SiC structure indicated that its forward current responded to the presence of hydrogen even after extended annealing at 425 °C. However, drift in the sensor properties suggested that stabilization of the diode structure was necessary. In this work, we examine the effects of placing a thin layer of silicon dioxide (SiO2) between the Pd and the SiC. Both Pd/SiC and Pd/SiO2/SiC diodes are annealed at 425 °C for 140 h and the electronic and interfacial properties of the annealed diodes are compared. The electronic properties and sensitivity to hydrogen of both diodes change significantly due to the annealing. Scanning electron microscopy and Auger electron spectroscopy indicate that the surface and interfacial properties of the diodes are very different. The Pd/SiC diode has a broad interface region wi...