Coexistence of Grain‐Boundaries‐Assisted Bipolar and Threshold Resistive Switching in Multilayer Hexagonal Boron Nitride

Abstract

The use of two dimensional (2D) materials to improve the capabilities of electronic devices is a promising strategy that has recently gained much interest in both academy and industry. While the research on 2D metallic and semiconducting materials is well established, the knowledge and 2 applications of 2D insulators are still very scarce. In this report we study the presence of resistive switching (RS) in multilayer hexagonal boron nitride (h-BN) using different electrode materials, and we engineer a family of h-BN based resistive random access memories with tunable capabilities.The devices show the coexistence of forming-free bipolar and threshold type RS with low operation voltages down to 0.4 V, high current on/off ratios up to 10 6 , long retention times above 10 hours, as well as low variability. The RS is driven by the grain boundaries (GBs) in the polycrystalline h-BN stack, which allow the penetration of metallic ions from adjacent electrodes. This reaction can be boosted by the generation of B vacancies, which is more abundant at the GBs. To the best of our knowledge, h-BN is the first 2D material showing the coexistance of bipolar and threshold RS, which may open the door to additional functionalities and applications.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Bimodal Dielectric Breakdown in Electronic Devices Using Chemical Vapor Deposited Hexagonal Boron Nitride as Dielectric

“…A Cu substrate was introduced in a tube furnace, and a three-step growth process was followed: (i) the sample was annealed at 1000 °C under 10 sccm hydrogen atmosphere during 30 min for cleaning its surface; (ii) then the temperature was reduced to 750 °C and a mix of borazine (B 3 N 3 H 6 ) and hydrogen was introduced in the tube in a ratio 2/200 sccm during 10 min; and (iii) the sample was cooled down naturally. [26]. [53].…”

“…The small current fluctuations in Figure 2 should be related to trapping/ de-trapping effects in the h-BN stack, preferably at the GBs of the h-BN stack. [26] On the contrary, the small current steps marked as (3) in Figure 3b are an obvious sudden event (the sampling time in Figures 2 and 3 was the same) but, since it is too small to correspond to a t ox thinness of 0.3 nm, the only feasible explanation is a lateral propagation (in-plane defect formation).…”

“…The abrupt change in the conduction mechanism is associated to the BD of one or several h-BN layers in the stack (depending of the current limitation of the setup). The trapping/detrapping effects in the h-BN stack, preferably at the GBs of the h-BN stacks [26] may also generate small current fluctuations. [19,24,25] Figure 1b shows consecutive I-V curves measured up to the BD event.…”

Recommended Methods to Study Resistive Switching Devices

“…The SiO 2 /Si wafer should be covered with a metallic film as BE (the recommended thickness is >50 nm to withstand the high current densities in LRS). [63] It should be noted that (ultimately) the use of industry-compatible conductive alloys (TaN, TiN) is desired, although controlling the amount of oxygen may be challenging in laboratories of several universities and research institutes (in such case, using noble metals may lead to better quality interfaces). The use of noble metals (Au, Pt) as BE is more common than metals that can easily oxidize (Ti, Cu)-and recommendable when working in university labs without exhaustive air and humidity control-because they collect less oxygen from the atmosphere during the time between BE and RS medium deposition (although in the industry noble metals may not be used due to their high cost and etching issue).…”

2D Layered Materials for Memristive and Neuromorphic Applications

“…As shown in Figure 5a,b, Cu/bi-layer MoS 2 /Au memristive devices show low SET (0.25 V) and RESET (−0.15 V) voltages, [112] while the filament formation might be attributed to Cu 2+ diffusion through MoS 2 . [118] By pushing the thickness of active layer to atomic limit, Ge et al reported the first atomristor based on monolayer TMDs (i.e., MoS 2 , MoSe 2 , WS 2 , WSe 2 ). This issue could be surmounted by the use of insulating h-BN [117] as active layer.…”