Dynamic observation of oxygen vacancies in hafnia layer by in situ transmission electron microscopy

The trapping process of charge trapping flash with HfO2 film as the charge capture layer has been investigated by in situ electron energy-loss spectroscopy and in situ energy filter image under external positive bias. The results show that oxygen vacancies can be generated inhomogeneously in HfO2 trapping layer during the program process. The distribution of the oxygen vacancy is not same as the reported location of the trapped electrons, implying that the trapping process is more complex. Those bias-induced oxygen defects may influence the performance of the devices such as the lifetime. This phenomenon should be considered in the models used to describe the trapping process.