Anodized ITO Thin‐Film Transistors

Abstract

1 www.MaterialsViews.com wileyonlinelibrary.com oxide semiconductor in itself and could be used as the active layers of TFTs. The high carrier density would prevent the devices from being switched-off normally; and the polycrystalline nature would bring about the poor device performance uniformity over large area.In an earlier effort to fabricate ITO TFTs, the sputtered ITO nano-clusters diffracting into the masked shadow regions were used to form an ultra-thin channel layer. [ 14 ] Clearly, this technique has a diffi culty in controlling the morphology of the self-assembled fi lm and is not compatible with the mainstream fl at panel display (FPD) technologies. An alternative effort to build the ITO TFTs was to make the TFTs have a junctionless structure. [ 15 ] In doing so, for turning the TFT off properly, the channel layer must be thin enough and the gate capacitance must be large enough to enable the channel layer depleted fully.Therefore, the feasible technology for ITO TFTs with a combination of simple process and high device performance has not been well established so far. On the other hand, a homojunction (HJ) structure with source/drain and channel layers made of the same material is a preferable structure for TFTs. In the case of poly-Si TFTs, this kind of structure can be easily obtained by a self-aligned ion implantation to dope the source/ drain regions. However, it is diffi cult to adopt this structure in the case of OS TFTs. In this work, an "All by ITO" TFT technology featuring the ideal homo-junction device structure is realized by introducing an anodic oxidation (anodization) technique to locally tailor the ITO properties for the fi rst time.The anodic oxidation technique has often been used to grow the metal oxide dielectrics due to the favorable features such as simple equipment requirement, low cost and high throughput. [16][17][18] The formation of anodic oxide fi lms has been a long discussion since 1934. [ 19 ] Although numerous models have been proposed to explain the kinetic, thermodynamic, structural and electronic properties, no single theory has yet emerged to provide comprehensive descriptions of the individual processes and explanations for the differences because of the complexity of various real metal-oxide systems. In spite of this, it is commonly recognized that a large number of metals when anodically polarized, exhibit the so-called high-fi eld conduction behavior which suggests a thermally activated, fi eld supporting hopping transport during the oxide growth. [ 20,21 ] Furthermore, the oxide fi lm growth is largely or exclusively resulted from the high-fi eld assisted inward movement of oxygen ions from the fi lm/solution interface to the metal/fi lm interface. [ 21 ] On the other hand, ITO is usually a highly degenerate n-type OS so that it acts more like a metal than a semiconductor. It Anodized ITO Thin-Film TransistorsYang Shao , Xiang Xiao , Longyan Wang , Yang Liu , and , and a subthreshold swing of 0.20 V per decade. This technology also allows a feasible V T adju...

Preparation of Cytocompatible ITO Neuroelectrodes with Enhanced Electrochemical Characteristics Using a Facile Anodic Oxidation Process

“…When subjected to anodic [39][40][41][42][43] and cathodic [42][43][44][45] polarization, ITO electrodes can undergo changes in chemical composition, [39][40][41][42][43][44][45] surface morphology, [39,40,[42][43][44][45] conductivity [39,40,[42][43][44][45] and optical transparency [41][42][43][44][45] . Such effects are largely influenced by i) the electrochemical parameters selected for electrode polarization and ii) composition of the electrolyte solution.…”

“…Such effects are largely influenced by i) the electrochemical parameters selected for electrode polarization and ii) composition of the electrolyte solution. [39][40][41][42][43][44][45] For example, polarization at high positive potentials (> 1.5 V vs. SCE) in aqueous electrolyte can cause substantial structural changes to the ITO electrode. [40] Similarly, polarization in strong acid (1 M HNO3) or strong base (1 M NaOH) can result in a dramatic reduction in electrochemical activity, electrical conductivity and optical transparency of the ITO electrode.…”

Direct writing of anodic oxides for plastic electronics

“…The semiconducting properties of oxides can be changed with the anodisation process itself, as previously shown for Indium-Tin-oxide. 55 Having demonstrated passive and active building blocks of flexible electronic circuits by direct writing, we now show that it is even possible to extend the patterning into the third dimension to further increase integration density.…”

Back Channel Anodization Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors Process

“…It is inferred that once after the Al: Nd is oxidized completely, the oxygen ions may penetrate through the Al 2 O 3 layer and enter the a-IGZO channel driven by the electric field across the Al 2 O 3 passivation layer if the anodization voltage increases further. The oxygen ions fill the oxygen vacancies there, thus reducing the carrier concentration of a-IGZO layer and leading to the increase of V T H [13]. The BCA a-IGZO TFT with V a = 65 V shows the best performances with μ sat , SS, V T H , and I on /I o f f of 6.1 cm 2 /V·s, 506 mV/dec, 3.23 V, and 3.7×10 8 , respectively.…”