Abstract
Glancing angle deposition technique was used to fabricate Ag nanoparticles (NPs) capped TiO2 Nanowire (NW) array structure for capacitive memory application. Electron microscopes confirmed the sandwiched structure of Ag NPs between TiO2 thin-film (TF) and NW. The average length of the vertical TiO2 NW and diameter of Ag NPs (with density ~ 1012 cm2) were found to be ~ 350 ± 5 nm and ~ 3.2 ± 0.4 nm, respectively. An enhanced photoluminescence was observed in case of Ag NPs capped TiO2 NWs due to the presence of high carriers as compared to bare TiO2 NW. The capacitance (C)–voltage (V) hysteresis was measured for both Ag NPs capped TiO2 NW and bare TiO2 NW at different sweeping voltage (± 3– ± 10 V) at 1 MHz frequency. A high capacitive memory window of 7.12 V was obtained for Ag NP capped TiO2 NW at ± 10 V with an excellent endurance upto 1000 cycle. Significantly lesser charge loss of 23% was obtained after a span of 104 s with a hole and electron loss of 10.6% and 17.8% respectively. The program and erase process in the device was explained with the help of a band diagram.
Highlights
Metal nanoparticle (NP) (Ag, Au etc.) based non-volatile memory (NVM) have drawn much attention because of their ability of showing high non-volatile characteristics in terms of higher retention, endurance and scalability [1]
Uncapped TiO2 NW (figure 6(b)) shows almost a constant counter clock-wise hysteresis with increase in sweep voltage, which signifies that the charge storage/trapping capability is lacking in this case
The memory window versus the sweeping voltage is plotted in figure 7 (a) which clearly shows that the Ag NPs capped TiO2 NWs had better window as compared to the bared TiO2 NW
Summary
Metal nanoparticle (NP) (Ag, Au etc.) based non-volatile memory (NVM) have drawn much attention because of their ability of showing high non-volatile characteristics in terms of higher retention, endurance and scalability [1]. Enhanced memory window using metal NPs decorated high-k dielectric based capacitive memory was reported [15][16] but all of the above memory needs a significant improvement. No reports are so far available on the demonstration of charge trapping structure for capacitive memory applications using TiO2/Ag NPs decorated over the tip of TiO2 NW which can further enhance the NVM performance. This novel structure with Ag NP sandwiched in between TiO2 NW and TF can significantly introduce intermediate states in between TiO2 creating charge trapping centers and inject higher charges which can improve the NVM characteristics
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