Bipolar Cu/HfO2/p++ Si Memristors by Sol-Gel Spin Coating Method and Their Application to Environmental Sensing

Abstract

In this paper, the memristive switching behavior of Cu/ HfO 2 /p ++ Si devices fabricated by an organic-polymer-assisted sol-gel spin-coating method, coupled with post-annealing and shadow-mask metal sputtering steps, is examined. HfO 2 layers of about 190 nm and 80 nm, are established using cost-effective spin-coating method, at deposition speeds of 2000 and 4000 rotations per minute (RPM), respectively. For two types of devices, the memristive characteristics ( V on , I on , and V reset ) and device-to-device electrical repeatability are primarily discussed in correlation with the oxide layer uniformity and thickness. The devices presented in this work exhibit an electroforming free and bipolar memory-resistive switching behavior that is typical of an Electrochemical Metallization (ECM) I-V fingerprint. The sample devices deposited at 4000 RPM generally show less variation in electrical performance parameters compared to those prepared at halved spin-coating speed. Typically, the samples prepared at 4000 RPM (n = 8) display a mean switching voltage V on of 3.0 V (±0.3) and mean reset voltage V reset of −1.1 V (±0.5) over 50 consecutive sweep cycles. These devices exhibit a large R off / R on window (up to 10 4 ), and sufficient electrical endurance and retention properties to be further examined for radiation sensing. As they exhibit less statistical uncertainty compared to the samples fabricated at 2000 RPM, the devices prepared at 4000 RPM are tested for the detection of soft gamma rays (emitted from low-activity Cs-137 and Am-241 radioactive sources), by assessing the variation in the on-state resistance value upon exposure. The analysis of the probability distributions of the logarithmic R on values measured over repeated ON-OFF cycles, before, during and after exposing the devices to radiation, demonstrate a statistical difference. These results pave the way for the fabrication and development of cost-effective soft-gamma ray detectors.

Highly durable and flexible gallium-based oxide conductive-bridging random access memory

“…For the OxRRAM, the formation and rupture of the filaments is formed by oxygen vacancies within the RRAM device 25–27 . CBRAM is also referred to as electrochemical metallization (ECM) memory, relying on the formation/dissolution of metallic filaments inside the switching layer 28–31 . CBRAM shows larger memory window and more power usage effectiveness compared to the OxRAM 32,33 .…”

Sputtering-deposited amorphous SrVOx-based memristor for use in neuromorphic computing

“…Various materials have been proposed for the active layer, such as binary oxides [21][22][23] , perovskite materials [24][25][26][27][28] , and organic materials 29,30 , and these materials exhibit different types of resistive switching mechanism under certain conditions. For instance, Pt/TiO 2 /Pt devices have been found to exhibit unipolar resistive switching behavior 31 , but modulation of the polarity of the electroforming in Pt/TiO 2 /Pt leads to bipolar reset 32 .…”

Recent Progress in Solution‐Based Metal Oxide Resistive Switching Devices

“…[ 35,41 ] Several studies using these active electrodes have been reported in solution‐based metal oxide RRAMs. [ 68,123,226,312 ] Cho and co‐workers studied the resistive switching behavior on solution‐based niobium pentoxide (Nb 2 O 5 ) thin films. [ 68 ] The resultant Pt/Nb 2 O 5 /Ag devices presented a unipolar switching, low operating voltage, fast switching speed (100 ns) and ultrahigh resistance window, ≥10 8 .…”

“…Another critical parameter on the synthesis process of resistive switching devices is the metal salt precursors, which are subdivided into three counter anions groups; [ 100 ] oxidants (hydrated nitrates), [ 72,79,80,98,101–121 ] reducers (alkoxides, [ 117,122–125 ] acetates, [ 72,76,78,79,104,105,109,111,113–118,126–153 ] and acetylacetonates [ 81,134,144,154–157 ] ), and neutrals (chlorine‐based). [ 63,71,103,107,110,112,116,119,125,132,158–164 ] Among these, oxidant counter ions are preferable due to the high oxidizing power (negative charge), greater solubility in water or polar organic solvents and low decomposition temperature, which are related to the electronic interactions between the metal and the nitrate group, as shown in Figure 9c.…”