Memristive devices based on single ZnO nanowires - from material synthesis to neuromorphic functionalities

2022 ◽  
Author(s):  
Gianluca Milano ◽  
Luca Boarino ◽  
Ilia Valov ◽  
Carlo Ricciardi
Keyword(s):  
Resistive Switching ◽  
Large Scale ◽  
Chemical Vapor ◽  
Building Blocks ◽  
Model Systems ◽  
Top Down ◽  
Single Crystalline ◽  
Neuromorphic Systems ◽  
Pressure Chemical ◽  
Switching Devices

Abstract Memristive and resistive switching devices are considered promising building blocks for the realization of artificial neural networks and neuromorphic systems. Besides conventional top-down memristive devices based on thin films, resistive switching devices based on nanowires (NWs) have attracted great attention, not only for the possibility of going beyond current scaling limitations of the top-down approach, but also as model systems for the localization and investigation of the physical mechanism of switching. This work reports on the fabrication of memristive devices based on ZnO NWs, from NW synthesis to single NW-based memristive cell fabrication and characterization. The bottom-up synthesis of ZnO NWs was performed by low-pressure Chemical Vapor Deposition (LPCVD) according to a self-seeding Vapor-Solid (VS) mechanism on a Pt substrate over large scale (∼ cm2), without the requirement of previous seed deposition. The grown ZnO NWs are single crystalline with wurtzite crystal structure and are vertically aligned respect to the growth substrate. Single NWs were then contacted by means of asymmetric contacts, with an electrochemically active and an electrochemically inert electrode, to form NW-based electrochemical metallization memory (ECM) cells that show reproducible resistive switching behaviour and neuromorphic functionalities including short-term synaptic plasticity and Paired Pulse Facilitation (PPF). Besides representing building blocks for NW-based memristive and neuromorphic systems, these single crystalline devices can be exploited as model systems to study physicochemical processing underlaying memristive functionalities thanks to the high localization of switching events on the ZnO crystalline surface.

Dynamic resistive switching devices for neuromorphic computing

2021 ◽  
Author(s):  
Yuting Wu ◽  
Xinxin Wang ◽  
Wei Lu
Keyword(s):  
Resistive Switching ◽  
Large Scale ◽  
Internal State ◽  
Building Blocks ◽  
State Variables ◽  
Von Neumann ◽  
Internal State Variables ◽  
Switching Dynamics ◽  
Neuromorphic Systems ◽  
Neuronal Functions

Abstract Neuromorphic systems that can emulate the structure and the operations of biological neural circuits have long been viewed as a promising hardware solution to meet the ever-growing demands of big-data analysis and AI tasks. Recent studies on resistive switching or memristive devices have suggested such devices may form the building blocks of biorealistic neuromorphic systems. In a memristive device, the conductance is determined by a set of internal state variables, allowing the device to exhibit rich dynamics arising from the interplay between different physical processes. Not only can these devices be used for compute-in-memory architectures to tackle the von Neumann bottleneck, the switching dynamics of the devices can also be used to directly process temporal data in a biofaithful fashion. In this Review, we analyze the physical mechanisms that govern the dynamic switching behaviours and highlight how these properties can be utilized to efficiently implement synaptic and neuronal functions. Prototype systems that have been used in machine learning and brain-inspired network implementations will be covered, followed with discussions on the challenges for large scale implementations and opportunities for building bio-inspired, highly complex computing systems.

scholarly journals Direct Synthesis of Oxynitride Nanowires through Atmospheric Pressure Chemical Vapor Deposition

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2507
Author(s):  
Babak Adeli ◽  
Fariborz Taghipour
Keyword(s):  
Solid Solution ◽  
Vapor Deposition ◽  
Atmospheric Pressure ◽  
Wide Spectrum ◽  
Direct Synthesis ◽  
Chemical Vapor ◽  
Building Blocks ◽  
Operating Conditions ◽  
Wide Range ◽  
Pressure Chemical

Binary and ternary oxynitride solid alloys were studied extensively in the past decade due to their wide spectrum of applications, as well as their peculiar characteristics when compared to their bulk counterparts. Direct bottom-up synthesis of one-dimensional oxynitrides through solution-based routes cannot be realized because nitridation strategies are limited to high-temperature solid-state ammonolysis. Further, the facile fabrication of oxynitride thin films through vapor phase strategies has remained extremely challenging due to the low vapor pressure of gaseous building blocks at atmospheric pressure. Here, we present a direct and scalable catalytic vapor–liquid–solid epitaxy (VLSE) route for the fabrication of oxynitride solid solution nanowires from their oxide precursors through enhancing the local mass transfer flux of vapor deposition. For the model oxynitride material, we investigated the fabrication of gallium nitride and zinc oxide oxynitride solid solution (GaN:ZnO) thin film. GaN:ZnO nanowires were synthesized directly at atmospheric pressure, unlike the methods reported in the literature, which involved multiple-step processing and/or vacuum operating conditions. Moreover, the dimensions (i.e., diameters and length) of the synthesized nanowires were tailored within a wide range.

Growth of Large-Scale Praseodymium Hexaborides (PrB6) Nanowires and Enhanced Field-Emission Performance

2020 ◽  
Vol 15 (2) ◽  
pp. 276-283 ◽  
Author(s):  
Junqi Xu ◽  
Yanrui Wang ◽  
Wenjie Wang ◽  
Zijun Xu ◽  
Yonglei Jia ◽  
...  
Keyword(s):  
Field Emission ◽  
Electron Emission ◽  
Large Scale ◽  
Field Enhancement ◽  
Chemical Vapor ◽  
Field Electron Emission ◽  
Threshold Field ◽  
Analytical Instruments ◽  
Field Electron ◽  
Pressure Chemical

Large-scale PrB6 nanowires were fabricated by an effective, catalyst-free, and a simple low-pressure chemical vapor deposition (LPCVD) process. These nanowires, characterized in detail by various analytical instruments, demonstrated the large aspect ratio and high single-crystalline grown along the [001] crystal direction perpendicular to the (001) crystal plane. The field electron emission equipment tests manifest that the asgrown PrB6 products have a low turn-on field (Eto, 2.32 V/μm), a threshold field (Ethr, 4.28 V/μm), a high field enhancement factor (β, 2336), as well as a stable current-density (J) of field-emission. The relationships of the field electron emission parameters, such as J, Eto, and β versus cathode gap (d), have been established when d is increased from 500 μm to 800 μm. The outstanding properties suggest that the PrB6 products may be promising emitters in the cold-field-emission cathode application.

New Trends in Wide Bandgap Semiconductors: Synthesis of Single Crystalline Silicon Carbide Layers by Low Pressure Chemical Vapor Deposition Technique on P-Type Silicon (100 and/or 111) and their Characterization

2010 ◽  
Vol 442 ◽  
pp. 195-201
Author(s):  
F. Iqbal ◽  
A. Ali ◽  
A. Mehmood ◽  
M. Yasin ◽  
A. Raja ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Low Pressure ◽  
Single Crystalline ◽  
Type Silicon ◽  
Vapor Deposition Technique ◽  
Pressure Chemical ◽  
P Type

We report the growth of SiC layers on low cost p-type silicon (100 and/or 111) substrates maintained at constant temperature (1050 - 1350oC, ∆T=50oC) in a low pressure chemical vapor deposition reactor. Typical Fourier transform infrared spectrum showed a dominant peak at 800 cm-1 due to Si-C bond excitation. Large area x-ray diffraction spectra revealed single crystalline cubic structures of 3C-SiC(111) and 3C-SiC(200) on Si(111) and Si(100) substrates, respectively. Cross-sectional views exposed by scanning electron microscopy display upto 104 µm thick SiC layer. Energy dispersive spectroscopy of the layers demonstrated stiochiometric growth of SiC. Surface roughness and morphology of the films were also checked with the help of atomic force microscopy. Resistivity of the as-grown layers increases with increasing substrate temperature due to decrease of isolated intrinsic defects such as silicon and/or carbon vacanies having activation energy 0.59 ±0.02 eV.

scholarly journals Silicon Nitride Films Deposited by Atmospheric Pressure Chemical Vapor Deposition

1997 ◽  
Vol 495 ◽  
Author(s):  
Xian Lin ◽  
Denis Endisch ◽  
Xiaomeng Chen ◽  
Alain Kaloyeros
Keyword(s):  
Chemical Vapor Deposition ◽  
Silicon Nitride ◽  
Vapor Deposition ◽  
Atmospheric Pressure ◽  
Large Scale ◽  
Thin Film Transistor ◽  
Chemical Vapor ◽  
Silicon Nitride Films ◽  
Pressure Chemical ◽  
Scale Integration

ABSTRACTFilms of silicon nitride are widely used in semiconductor technologies for very large scale integration (VLSI), thin film transistor (TFT), and solar cell applications. Current production technologies for silicon nitride use low pressure chemical vapor deposition (LPCVD) at temperatures > 700 °C or plasma enhanced chemical vapor deposition (PECVD) at temperatures below 450 °C. In this report, successful deposition of silicon nitride films by the low temperature thermal atmospheric pressure chemical vapor deposition (APCVD) method is described. Using a novel precursor tetraiodosilane (SiI4), deposition of silicon nitride has been achieved at temperature as low as 400 °C. Data pertaining to the dependence of film properties on deposition temperature are presented, along with a evaluation of the deposition rate, composition, chemical structure, and conformality of the resulting films.

scholarly journals Improvement of Resistive Switching Performance in Sulfur-Doped HfOx-Based RRAM

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3330
Author(s):  
Zhenzhong Zhang ◽  
Fang Wang ◽  
Kai Hu ◽  
Yu She ◽  
Sannian Song ◽  
...  
Keyword(s):  
Resistive Switching ◽  
Photoelectron Spectroscopy ◽  
Oxygen Vacancies ◽  
Random Access ◽  
Chemical Vapor ◽  
Response Speed ◽  
Resistive Random Access Memory ◽  
Fast Response ◽  
Electrical Performance ◽  
Pressure Chemical

In order to improve the electrical performance of resistive random access memory (RRAM), sulfur (S)-doping technology for HfOx-based RRAM is systematically investigated in this paper. HfOx films with different S-doping contents are achieved by atmospheric pressure chemical vapor deposition (APCVD) under a series of preparation temperatures. The effect of S on crystallinity, surface topography, element composition of HfOx thin films and resistive switching (RS) performance of HfOx-based devices are discussed. Compared with an undoped device, the VSET/VRESET of the S-doped device with optimal S content (~1.66 At.%) is reduced, and the compliance current (Icc) is limited from 1 mA to 100 μA. Moreover, it also has high uniformity of resistance and voltage, stable endurance, good retention characteristics, fast response speed (SET 6.25 μs/RESET 7.50 μs) and low energy consumption (SET 9.08 nJ/RESET 6.72 nJ). Based on X-ray photoelectron spectroscopy (XPS) data and fitting of the high/low resistance state (HRS/LRS) conduction behavior, a switching mechanism is considered to explain the formation and rupture of conductive filaments (CFs) composed of oxygen vacancies in undoped and S-doped HfOx-based devices. Doping by sulfur is proposed to introduce the appropriate concentration oxygen vacancies into HfOx film and suppress the random formation of CFs in HfOx-based device, and thus improve the performance of the TiN/HfOx/ITO device.

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