Oxygen migration at Pt/HfO2/Pt interface under bias operation

The interfacial electronic states of a Pt/HfO2/Pt diode were investigated by using hard x-ray photoelectron spectroscopy under bias operation. The application of a forward bias to the Pt/HfO2/Pt diode increased the Pt-O bonding peak, providing evidence of Pt electrode oxidization and oxygen vacancy formation around the Pt/HfO2 interface. Under a reverse bias, hafnium was drawn to the Pt electrode, where it took part in Hf-Pt bonding. We achieved the direct observation of oxygen migration at a Pt/HfO2 interface under device operation, which is the key to controlling the electrical properties of metals on oxides.