Ultraviolet-assisted direct patterning and low-temperature formation of flexible ZrO₂ resistive switching arrays on PET/ITO substrates

Abstract

We demonstrate a low-cost and facile photochemical solution method to prepare the ZrO resistive switching arrays as memristive units on flexible PET/ITO substrates. ZrO solution sensitive to UV light of 337 nm was synthesized using zirconium n-butyl alcohol as the precursor, and benzoylacetone as the complexing agent. After the dip-coated ZrO gel films were irradiated through a mask under the UV lamp (with wavelength of 325-365 nm) at room temperature and rinsed in ethanol, the ZrO gel arrays were obtained on PET/ITO substrates. Subsequently, the ZrO gel arrays were irradiated by deep UV light of 254 and 185 nm at 150 °C, resulting in the amorphous ZrO memristive micro-arrays. The ZrO units on flexible PET/ITO substrates exhibited excellent memristive properties. A high ratio of 10 of on-state and off-state resistance was obtained. The resistive switching behavior of the flexible device remained stable after being bent for 10 times. The device showed stable flexibility up to a minimum bending diameter of 1.25 cm.

Recent Progress in Solution‐Based Metal Oxide Resistive Switching Devices

“…Other resistive switching materials such as TiO 2 and ZrO 2 were subjected to the same post-treatment and used as resistive switching layers in flexible substrates based on PET/ITO. [174,198] Both devices presented good retention and endurance characteristics even after being bent 1000 times, which is quite promising for further flexible applications. Another advantage related to solution-based metal oxide thin films processed at low temperature is the presence of an amorphous oxide, which is highly desirable for flexible S-RRAMs, since electronic performance does not depend on the degree of films' disorder and the materials have ultrasmooth surfaces for suppressing interface traps and scattering centers.…”

“…Various initiation sources such as furnace [219,223] or oven, [184,190,224] rapid thermal annealing (RTA), [131,140,202,204,225,226] microwave, [119,122,124,227] ultraviolet (UV) photochemical activation (lamp [118,174,198,228] and laser [229] ), and hotplate [98,185] have been used for the solution-based metal oxides films' conversion for RRAM devices. From these, the most common initiation sources are based on conventional thermal annealing (CTA), like furnace/oven and hotplate annealing.…”

“…2017 [198] ZrO Further work on printed materials is highly demanded to provide scalability (R2R compatibility), reduction of chemical waste, direct writing of the oxide materials (i.e., patterning without lithography processes), and higher reproducibility. Thus, in the future a substantial effort should be done on solution-based metal oxides processed at low temperature in low cost flexible substrates (i.e., PET, PEN, and PES) to afford their implementation and scale-up for R2R-based techniques.…”

“…It constitutes a substantial portion of the oxide precursor solutions: around 98% and 90% for lower and higher concentrations, respectively. The most common solvents in solution‐based metal oxide RRAMs are 2‐methoxyethanol (2‐ME), [ 63,72,79,80,98,102,104,105,107,109,112,113,115–119,121,127,129,130,133,134,137,139,142,144,150–153,158,159,168–185 ] ethanol, [ 72,77,78,82,103,108,113,114,120,126,132,135,136,138,145,147,157,162–164,168,186–200 ] deionized (DI) water, [ 73,101,116,120,123,148,162,163,190,201 ] acetic acid, [ 103,121,129–131,134,140,142,144,149,150,152,154,173,179,180,183,202 ] and isopropanol [ 23,123,125,128,136,169,181,203 ] among others (ethylene glycol, [ 141,204 ] 2‐butoxyethanol, [ 205 ] acetylacetone, [ 149 ] and acetonitrile […”

“…Other resistive switching materials such as TiO 2 and ZrO 2 were subjected to the same post‐treatment and used as resistive switching layers in flexible substrates based on PET/ITO. [ 174,198 ] Both devices presented good retention and endurance characteristics even after being bent 1000 times, which is quite promising for further flexible applications.…”