Direct Analysis of Stacked Au/Ti/In₂O₃/Al₂O₃/p⁺-Si Transport Mechanisms Using Operando Hard X-ray Photoelectron Spectroscopy

Oxygen transport mechanisms for two different Au/Ti/In 2 O 3 /Al 2 O 3 /p + -Si samples were experimentally evaluated by hard X-ray photoelectron spectroscopy (HAXPES). The deposition temperature for atomic layer deposition of In 2 O 3, as well as the bias voltages applied on the entire stacked structures, were the main parameters used in the work. Chemical analyses of the In 2 O 3 layers deposited at 150 and 200 °C for the samples named T_150 and T_200, respectively, revealed a decreased carbon impurity content in the host In 2 O 3 used as a dopant. Ex situ interfacial analysis of In 2 O 3 /Al 2 O 3 also indicated oxygen transport from Al 2 O 3 to In 2 O 3 . Moreover, we observed that the Ti adhesion metal attracted oxygen and carbon from In 2 O 3 to form TiO 2 and TiC conductive interlayers. Furthermore, operando-HAXPES under an applied bias voltage also revealed that In 2 O 3 underwent phase separation, likely due to variations in the space charge (carriers) around the In 2 O 3 /Al 2 O 3 interface for the T_150 sample. Finally, our results emphasize the prominent roles of migration for the ionic oxygen/carbon species and the uncompensated interfacial charge formed by the bias voltage for the metal–semiconductor-oxide stacked structure.