Zinc Oxide Thin Films for Memristive Devices: A Review

Laurenti, Marco; Porro, Samuele; Pirri, Candido; Ricciardi, Carlo; Chiolerio, Alessandro

doi:10.1080/10408436.2016.1192988

Cited by 89 publications

(55 citation statements)

References 104 publications

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“…[171][172][173][174][175][176][177][178][179] Even if resistive switching was previously observed in ZnO thin films grown by different techniques, [180][181][182] resistive switching in single crystalline ZnO nanowires with wurtzite structure grown by VLS technique was reported for the first time in 2011 by Chiang et al [171] In this case, the Ti/ZnO NW/Ti devices exhibited two well defined resistance states with high performances in terms of HRS/LRS ratio that was reported to be as high as 7.7 × 10 5 with an endurance of 100 cycles. [171][172][173][174][175][176][177][178][179] Even if resistive switching was previously observed in ZnO thin films grown by different techniques, [180][181][182] resistive switching in single crystalline ZnO nanowires with wurtzite structure grown by VLS technique was reported for the first time in 2011 by Chiang et al [171] In this case, the Ti/ZnO NW/Ti devices exhibited two well defined resistance states with high performances in terms of HRS/LRS ratio that was reported to be as high as 7.7 × 10 5 with an endurance of 100 cycles.…”

Section: Wwwadvelectronicmatdementioning

confidence: 99%

Recent Developments and Perspectives for Memristive Devices Based on Metal Oxide Nanowires

Milano

Porro

Valov

et al. 2019

Adv Elect Materials

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101

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Memristive devices are considered one of the most promising candidates to overcome technological limitations for realizing next‐generation memories, logic applications, and neuromorphic systems in the modern nanoelectronics and information technology. Despite the continuous efforts, understanding the resistive switching mechanism underlying memristive/neuromorphic behavior still represents a challenge. Metal oxide nanowire‐based memristors appear suitable model systems for a deeper understanding of the involved physical/chemical phenomena due the possibility for localizing and investigating the switching mechanism. In practical aspects, nanowire‐based devices can be grown using a bottom‐up approach, thus being considered reliable candidates for going beyond the current scaling limitations of the top‐down approach by the standard lithography. In addition, taking into advantage of the high surface‐to‐volume ratio of these nanostructures, new device functionalities can be achieved by exploiting surface effects. In the literature, a variety of nanowire‐based devices such as single nanowires, nanowire arrays, and networks are reported to exhibit memristive behavior, explained by different switching mechanisms. This work provides a comparative review and a comprehensive analysis of device performances and physical phenomena responsible for memristive and neuromorphic behavior in such nanostructures. The analysis of the state‐of‐art of memristor devices based on nanowires and nanorods represent a milestone toward the development of nanowire‐based artificial neural networks.

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Section: Wwwadvelectronicmatdementioning

confidence: 99%

Recent Developments and Perspectives for Memristive Devices Based on Metal Oxide Nanowires

Milano

Porro

Valov

et al. 2019

Adv Elect Materials

Self Cite

101

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“…In particular, ZnO thin films have attracted great interest due to their facile preparation approaches, excellent compatibility for device integration, and controllable electronic and optoelectronic behavior. [ 9 ] Their memristive behavior is primarily associated with the non‐equilibrium distribution of oxygen vacancies in response to an external electrical field. This switching mechanism allows robust cycling endurance, but it is always associated with low switching speed.…”

Section: Figurementioning

confidence: 99%

“…[ 12 ] Nevertheless, due to the unavailability of 2D oxides nanomaterials and the high entropy of introducing vacancies in 2D confined geometry, stable 2D oxide‐based memristors have yet to be demonstrated. [ 9 ]…”

Section: Figurementioning

confidence: 99%

Memristive Behavior Enabled by Amorphous–Crystalline 2D Oxide Heterostructure

et al. 2020

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broad selection of electrical properties. In particular, ZnO thin films have attracted great interest due to their facile preparation approaches, excellent compatibility for device integration, and controllable electronic and optoelectronic behavior. [9] Their memristive behavior is primarily associated with the non-equilibrium distribution of oxygen vacancies in response to an external electrical field. This switching mechanism allows robust cycling endurance, but it is always associated with low switching speed. [10] In contrast, 2D nanomaterials offer a quantum-confined medium which can have exceptional transport properties and substantially improved memristive behavior compared to conventional bulk materials. For example, single atomic layer 2D transition metal dichalcogenide memristors exhibited high-frequency switching with an extremely low power consumption, [6,11] and memristors based on ultrathin singlecrystalline SiGe layer demonstrated significantly improved reproducibility and low energy consumption. [3] Developing memory devices with low operating voltages and low energy consumption go in the direction of a connection between instrinsically neuromorphic devices and living neurons. [12] Nevertheless, due to the unavailability of 2D oxides nanomaterials and the high entropy of introducing vacancies in 2D confined geometry, stable 2D oxide-based memristors have yet to be demonstrated. [9] Recently, ionic layer epitaxy (ILE) was developed as a versatile solution-based approach for growing large-area oxide nanosheets on a liquid surface. [13] Atomically thin single-crystalline ZnO nanosheets were synthesized with sizes over 10 µm, enabling the study of the memristor properties based on 2D metal oxides. In this work, we show extraordinary memristive behavior enabled by interfacing atomically thin single crystalline ZnO nanosheets with a few-nm thick amorphous Al 2 O 3 layer. The conduction mechanism was attributed to the classic oxygen vacancy conductive channels in the lateral transistor module. In this configuration, the ZnO nanosheet provides a 2D host of oxygen vacancies, while the amorphous Al 2 O 3 facilitates the generation and stabilization of the oxygen vacancies. The 2D heterointerface brought a new promise for flexible nonvolatile and ultralow power memory devices.Atomically thin single-crystalline ZnO nanosheets were synthesized by ILE, [13,14] in which amphiphilic molecules (oleyl sulfate) self-assembled into a monolayer at the water-air The emergence of memristive behavior in amorphous-crystalline 2D oxide heterostructures, which are synthesized by atomic layer deposition (ALD) of a few-nanometer amorphous Al 2 O 3 layers onto atomically thin single-crystallineZnO nanosheets, is demonstrated. The conduction mechanism is identified based on classic oxygen vacancy conductive channels. ZnO nanosheets provide a 2D host for oxygen vacancies, while the amorphous Al 2 O 3 facilitates the generation and stabilization of the oxygen vacancies. The conduction mechanism in the high-resistance state follo...

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“…Among transition metal‐oxides, zinc oxide with its wide bandgap ( ≈ 3.37 eV at room temperature) is one of the most extensively investigated as a consequence of its outstanding properties such as piezoelectricity, transparency, and biocompatibility . Thanks to these characteristics, ZnO was employed for the fabrication of a wide range of electronic devices such as sensors, field‐effect transistors, resistive switching devices, photodetectors, and solar cells . Even if many efforts were spent in understanding the electronic transport mechanism and surface effects in a wide range of ZnO nanostructures including thin films and nanowires (NWs), a detailed understanding of the effect of moisture on electrical conductivity is still to be unambiguously elucidated.…”

Section: Introductionmentioning

confidence: 99%

Ionic Modulation of Electrical Conductivity of ZnO Due to Ambient Moisture

Milano

Luebben

Laurenti

et al. 2019

Adv Materials Inter

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only related to the fabrication of transistors [1] but mostly to the development of new generation devices named memristor, where metal-oxide thin films are usually exploited as active materials for resistive switching in a two-terminal configuration. [2][3][4][5] Regardless of the specific application, electrical conductivity of these compounds is unavoidably related to device functionalities. In this context, understanding the influence of the local environment on electrical conductivity is fundamental not only for the fabrication of reliable electronic devices but also for the development of sensors. [6,7] Electrical conductivity of metal-oxides is strongly affected by moisture and protons that can be incorporated in the oxide matrix as a consequence of sample exposure to ambient conditions or directly during the fabrication steps (e.g., material deposition, lithographic processes, surface treatments, etc.). However, it is not possible to establish a single general rule for explaining how moisture affects conductivity since its influence can be manifold, depending not only on the material composition and its defect chemistry but also on structural properties such as density and porosity. For this reason, chemical as well as structural properties have to be taken into account for explaining the moisture-dependent electrical characteristics of specific metal-oxide compounds.Moisture can strongly affect reliability and functionalities of a wide range of electronic devices based on metal-oxide semiconductors, where the electrical conductivity can be influenced by the deposition technique and the environment. In this work, the influence of moisture on electrical conductivity of zinc oxide (ZnO) is investigated, revealing that moisture and protons can impact not only the electronic conduction, but can provide additional ionic species that actively participate in the conduction mechanism. Single crystalline nanowires are exploited as model systems for investigating the effect of adsorbed species on ZnO surfaces, revealing that hydroxide species are responsible for the creation of a depletion region on the surface that decreases the electronic conductivity. The same mechanism is attributed to the decreasing of conductivity by increasing the moisture content in ZnO polycrystalline films, where moisture is adsorbed at grain boundaries. At high activities of moisture, it is observed that moisture-related species can migrate along the highly oriented grain boundaries resulting in an increase of the global conductivity due to the ionic current flowing in parallel to the electronic one. More generally, the results highlight the importance of the environment and the ionic contribution in determining the electrical conductivity of nanostructured devices.

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Zinc Oxide Thin Films for Memristive Devices: A Review

Cited by 89 publications

References 104 publications

Recent Developments and Perspectives for Memristive Devices Based on Metal Oxide Nanowires

Recent Developments and Perspectives for Memristive Devices Based on Metal Oxide Nanowires

Memristive Behavior Enabled by Amorphous–Crystalline 2D Oxide Heterostructure

Ionic Modulation of Electrical Conductivity of ZnO Due to Ambient Moisture

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