Exploring Electron Transport and Memristive Switching in Nanoscale Au/WO_x/W Multijunctions Based on Anodically Oxidized Al/W Metal Layers

Abstract

size effect. [1][2][3] Eventual functionalization of WO x nanostructures through modifying the surface and interfacial properties by combining, doping, or decorating the pure oxide with other nanomaterials creates additional metal/semiconductor or semiconductor/semiconductor interfaces and grain boundaries capable of further infl uencing the sensing, electrical, optical, and opto-electronic properties or even introducing novel unique functionalities. [4][5][6] Contrarily to WO x nanostructures with no directional orientation of its morphological units, like disordered 1D nanowires or nanorods grown by vapor-and liquid-phase methods, [ 1,7 ] oriented 1D WO x nanostructures, self-organized and upright-standing on a conducting substrate, without mutually intersecting with each other are expected to bring more advantages for practical applications in nanoscale electrochromic, [ 8,9 ] fi eldemission, [ 10 ] gas-sensing, [ 11 ] and photonic devices. Moreover, substrate-supported 1D nanostructures assembled in an array would enable the use of their integral properties, especially electrical, optical, or mechanical in contrast with the formation and application of single nanowires relying on their individual characteristics. [ 12,13 ] Synthesis of WO x nanostructures regularly aligned on substrates has been an active and competitive area of nanoscience and nanotechnology as the arrays of 1D structures often suffer from mechanical weakness and randomly dispersed physical contacts between neighboring units, limiting their performance in a device. Besides, creating welldefi ned nanoscale metal/semiconductor electrical and thermal interfaces and boundaries by contacting the tops of 1D nanostructures assembled in an array in a reliable and reproducible manner to benefi t from the characteristics measured along the nanostructures and across relevant interfaces has been a challenge. [8][9][10][11][14][15][16][17] Surface engineering of aluminum [ 18 ] and porous anodic alumina (PAA) fi lms grown by anodic oxidation (anodizing) of aluminum have been of increasing interest for lithography-free templating of metals, dielectrics, and semiconductors. [19][20][21][22] PAA-assisted anodization [ 23 ] of certain valve metals sputtered on substrates, including tungsten, [24][25][26] has proven its potential as a reproducible method for electrochemically forming self-organized vertically aligned spatially separated 1D nanostructures (nanocolumns, rods, or tubes), being nearly ideally electrically and mechanically bonded at their bottoms either to the substrate metal [ 26 ] or to a continuous solid layer of similar metal oxide that grows at the columns/substrate-metal interface. [ 24,25 ] On the way An array of semiconducting tungsten-oxide (WO x ) nanorods, 100 nm wide and 700 nm long, is synthesized via the porous-anodic-alumina-assisted anodization of tungsten on a substrate and is modifi ed by annealing in air and vacuum. The rods buried in the alumina nanopores are self-anchored to the tungsten layer while their tops are interconnec...

Memristor Arrays Formed by Reversible Formation and Breakdown of Nanoscale Silica Layers on Si–H Surfaces

“…The resistance change is a result of ion motion, similar to that observed in biological synapses and neurons. Their unique features make memristors a natural choice for the building blocks of neural networks with a broad spectrum of applications such as computer vision, speech recognition, autonomous vehicles, robotics, and medicine. ,,− …”

Electrochemical Tantalum Oxide for Resistive Switching Memories

“…[23][24][25][26][27][28][29] In the case of anodizing of metallic alloys, resulting oxide will be a mixed oxide in which the atomic ratio between partner metals can be different with respect to the underlying alloys depending on transport numbers of involved cations. To date, there are several papers in which porous anodic aluminum oxide is used as a matrix for the fabrication of ReRAMs [30][31][32][33] or anodic nanostructured oxides are used as solid electrolytes, [34][35][36][37][38] but only few papers discuss on ReRAMs devices with barriertype anodic oxides however not showing some particular promises. [39][40][41][42] Here we demonstrate Ta/Ta 2 O 5 /Pt system with electrochemically grown Ta Increasing the voltage over + 3 V leads to a formation of filament i.e.…”

Electrochemically anodized one-dimensional semiconductors: a fruitful platform for solar energy conversion

“…It was found that these metal (Au, Ag, Pt) NPs can serve as electron traps to boost separation of photoinduced electrons and holes leading to markedly enhanced photoactivities. Apart from LbL assembly approach, other synthetic strategy was developed to achieve decoration of Au NPs on the anodized tungsten-oxide (Au/WO x ) nanostructures [132].…”