Lead-free thin films for memory devices
doi:10.1038/nindia.2015.39 Published online 26 March 2015
Researchers have fabricated thin films from lead-free ferroelectric materials. These films could be used to fabricate non-volatile memory devices, which are potentially useful for high-speed, low-power electronic applications1.
The researchers synthesised ferroelectric materials from barium carbonate and oxides of titanium, niobium and copper. They then used a laser to deposit a thin ferroelectric film on a hafnium-oxide-coated silicon substrate in an oxygen-rich environment at high temperature.
By applying an external voltage to the films, the scientists investigated their effectiveness for use in non-volatile memory devices. At positive voltages, silicon released free electrons, which were trapped in the ferroelectric film. These trapped charge carriers could be used to program memory devices. At negative voltages, electrons trapped in the ferroelectric film moved back to silicon. This property could be used to erase programs from memory devices.
The films did not show any change in memory window and exhibited little charge leakage at high voltages. The films also had good charge retention, with high and low capacitances remaining after 11 days.
The researchers say that this study opens up the possibility of embedding memory devices based on ferroelectric thin films in any electronic device by using current metal–oxide–semiconductor processing technology.
1. Kundu, S. et al. Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications. Sci. Rep. 5, 8494 (2015)