Oxygen vacancy concentration as a function of cycling and polarization state in TiN/Hf 0.5 Zr 0.5 O 2 /TiN ferroelectric capacitors studied by x-ray photoemission electron microscopy
Abstract
We have studied the field cycling behavior of microscopic TiN/Hf 0.5 Zr 0.5 O 2 /TiN ferroelectric capacitors using synchrotron-based soft x-ray photoemission electron microscopy. The oxygen vacancy ([Formula: see text]) concentration near the top TiN/Hf 0.5 Zr 0.5 O 2 interface is estimated from the reduction of Hf 4+ to Hf 3+ as measured in the Hf 4f core level spectra. The [Formula: see text] concentration increases with field cycling and redistributes under the effect of the internal field due to the polarization. Upward pointing polarization slightly depletes the concentration near the top interface, whereas downward polarization causes [Formula: see text] drift toward the top interface. The [Formula: see text] redistribution after wake-up is consistent with shifts in the I–V switching peak. The Schottky barrier height for electrons decreases systematically with cycling in polarization states, reflecting the overall increase in [Formula: see text].