Laser synthesis of non-volatile memristor structures based on tantalum oxide thin films

Abstract

The amorphous thin TaOx films (x ≤ 5) of different thicknesses with different levels of oxygen vacancy content, which are promising for use as an active region of non-volatile memristors, were fabricated by the pulsed laser deposition in a drop-free mode on the c-sapphire substrates. The films were obtained from tantalum metal targets at substrate temperatures of 25 °C and 350 °C in the oxygen pressure range from 0.5 to 50 mTorr. The relationship between the partial oxygen pressure and the optical, electrical, and chemical properties of the films was studied. It was found that the amorphous TaOx phase, which is a source of defects associated with oxygen deficiency, required for the creation of memristors, appears only at low oxygen pressures in the chamber (~ 5 × 10−4 Torr), this leads to low values resistivity in the films (~ 10−3 Ohm · cm). Memristor structures Ag(Pt)/TaOx/TaOy/Ta/c-Al2O3 (x > y) in cross-bar geometry have been created that do not require electroforming, due to the choice of design and deposition conditions. Memristor using two mechanisms of resistive switching based on oxygen vacancies and silver cations showed very reliable RS performance with memory window performance RON/ROFF ~ 103 and RESET operating voltage ~ 1 V.