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Geometric influence of cylindrical surface curvature on the electrostatics of thin film transistors
摘要： Thin film transistor (TFTs) based integrated circuits on flexible substrates promise interesting approaches to human interface systems. TFTs have been fabricated on textured surfaces such as textiles, paper, artificially corrugated substrates and fibers. This can result in the metal-insulator-semiconductor (MIS) stack being significantly distorted from a planar geometry to having high curvature. Although the direct deposition on textured surfaces does not result in mechanical stress (as opposed to that seen during bending, buckling, wrinkling), the geometry of high curvature can influence the characteristics of the TFT. Here we present a closed form analytical model describing the impact of high curvature on the electrical performance of the TFT. Models are obtained from the solution to the Poisson-Boltzmann equation in polar co-ordinates and are limited to cylindrical surface (zero Gaussian curvature) with the ratio of radius of curvature of the semiconductor-insulator interface, rsi, to insulator thickness, ti, ranging from rsi/ti = 2 to rsi/ti = 50. Models are verified using Technology Computer-Aided Design (TCAD) simulations performed using amorphous galium indium zinc oxide (a-GIZO). Studies show that when the semiconductor-insulator interface is curved convex (normal vector into the gate) the interfacial free carrier concentration increases by 50% (for rsi/ti = 2) to 8.5% (for rsi/ti = 15) as compared to planar TFTs. On the other hand, when the curvature is concave, the free carrier concentration decreases by those percentages as compared to planar TFTs. Thus curvature can modulate TFT transconductance. Models show that the impact of curvature becomes negligible (< 4% variation) for rsi/ti > 25. Techniques to generalize the results to periodic cylindrical surfaces and other semiconducting materials are discussed along with experimental verification. This work forms an analytical basis to understand the behavior of TFTs fabricated on textured substrates.
关键词： textured surfaces,TCAD simulations,a-GIZO,flexible substrates,Thin film transistor,Poisson-Boltzmann equation
更新于2025-09-09 09:28:46
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Flexible silver nanowire transparent conductive films prepared by an electrostatic adsorption self-assembly process
摘要： In this work, we reported a facile approach to fabricate silver nanowire (AgNW) networks on ?exible substrates. Through immersing the modi?ed poly (ethylene terephthalate) with positively charged functional group into the AgNW dispersion with anionic dispersant, a ?exible AgNW transparent conductive ?lm was formed by electrostatic adsorption self-assembly process. Even without a post-treatment process, the as-prepared ?exible AgNW ?lms exhibited excellent optoelectrical property, low surface roughness and high reliability. It was shown that the insulating dispersant on AgNWs could be effectively removed by an ion bombardment method and then greatly decreased the sheet resistance of AgNW networks. Because of the nature of spontaneous adsorption, this preparation method can be suitable for an arbitrary shaped substrate, which will broaden the application of AgNW conductive ?lms in optoelectronic devices.
关键词： self-assembly,transparent conductive ?lms,silver nanowire,electrostatic adsorption,flexible substrates
更新于2025-09-04 15:30:14