Focused Review on Print‐Patterned Contact Electrodes for Metal‐Oxide Thin‐Film Transistors

Abstract

mechanical flexibility, higher charge-carrier mobility than that of organic materials or amorphous silicon, and low processing temperature as compared to amorphous and polycrystalline silicon TFTs. [18][19][20][21] Parallel to the achievements of metaloxide TFTs, organic materials, carbon nanotubes (CNTs), and 2D materials have also been constantly developed. For recent reviews, see refs. [22,23]. The material approaches differ in their characteristics such as charge-carrier type (electrons or holes), charge-carrier mobility, environmental and electrical stability, mechanical flexibility, operation voltage, thermal budget of processing, technology readiness level for high-throughput fabrication, and sustainability (environmental footprint of materials and processes). There are also approaches that combine different material classes, for example, to implement complementary logic by combining the predominantly n-type oxide TFTs with p-type organic TFTs. [24] In this paper, we focus on the metal-oxide TFTs that are among the highest-performing alternatives for flexible thin-film devices that can be patterned by printing and that have already reached the maturity of being used in product fabrication (e.g., flat-panel displays). [2] The first metal-oxide-based TFT employed tin oxide (SnO 2 ) as the semiconductor and was invented by Klasens et al. in 1964, opening the door for research into transparent metal oxide TFTs. [25] Owing to the technology and material-processing limitations at that time, only a few studies focused on this area until 2003. During that year, zinc-oxide-based (ZnO) TFTs with mobility of µ = 2.5 cm 2 V −1 s −1 were successfully manufactured by Hoffman et al., Carcia et al., In the same year, Nomura et al. made a breakthrough with the first use of the quaternary-oxide semiconductor IGZO in a single-crystalline form to fabricate the TFTs, rather than some more conventional binary oxides such as ZnO, indium oxide (In 2 O 3 ), and SnO 2 . This kind of device that required annealing at 1400 °C displayed better electrical properties than its binary counterparts, with 80 cm 2 V −1 s −1 mobility and a 10 6 on/off ratio. [29] The following year in 2004, they reported flexible TFTs fabricated at room temperature on polymer film based on amorphous IGZO (a-IGZO) with saturation mobility of ≈6-9 cm 2 V −1 s −1 . [30] The discovery of a-IGZO raised substantial interest in research on amorphous metal-oxide TFTs and their low-temperature Metal-oxide-semiconductor-based thin-film transistors (TFTs) are exploited in display backplanes and X-ray detectors fabricated by vacuum deposition and lithographic patterning. However, there is growing interest to use scalable printing technologies to lower the environmental impact and cost of processing. There have been substantial research efforts on oxide dielectric and semiconductor materials and their interfaces. Materials for the source/ drain (S/D) contact electrodes and their interface to the semiconductor have received less attention, particularly concerning the usa...

Direct Patterned Printing Method of Top-Contact ITO Electrodes for Solution-Processed Metal Oxide Thin-film Transistors

“…Additionally, Figure S3 displays the dependence of the sheet resistance and resistivity of the fabricated ITO film on the process temperature for various ITO inks with different mixed solvents. According to a previous study related to printed morphological issues, beneficial methods include the usage of cosolvents exhibiting different viscosities and boiling points. , Different solvent boiling points (2-methoxy ethanol: 126 °C; ethylene glycol: 197 °C) and viscosities (2-methoxy ethanol: 1.7 mPa s; ethylene glycol: 20 mP a s at 20 °C) were beneficial to obtain the ideal shapes for this printing process.…”

“…27,28 The contact resistivity of oxide TFTs at the interface between the semiconductor and source/drain electrodes is known to be higher due to the problems of large contact resistance, poor adhesion, and material migration. 8 In this research, a novel and spontaneous direct printing approach was devised for directly printing In−Sn−O (ITO) electrodes used in solution-processed TFTs. The method coats the metal oxide semiconductor with a basic bar coater, a layer of photopatterned surface modification, and selective wettability.…”

“…Printed electronics is a promising research topic, based on which a wide variety of futuristic human-interactive devices can be obtained by replacing traditional and expensive silicon-based electronics. The key benefits of printed electronics include efficient production, cost-effectiveness, minimal energy usage, and the ability to scale up over large areas. − A facile printing process that does not require vacuum equipment can considerably reduce manufacturing costs and energy consumption. Various printed devices for displays, , smart sensors, − radio frequency identification tags, and integrated circuits , using thin-film transistors (TFTs) have been proposed and actively researched as a promising next-generation technology.…”

“…Such innovative solution-processed metal oxide TFT technologies have been reported, but most of the research has focused on solution-processed semiconductors that use metal electrodes fabricated through vacuum deposition and patterned using photolithography. ,− In order to fully benefit from solution processing, a simple method that applies solution processing to conductors and other TFT components as well as semiconductors is required. The conductors used as source and drain contact electrodes in n-type metal oxide semiconductors such as IGZO and IZO must be carefully chosen based on their high conductivity, good adhesiveness, appropriate work function for ohmic contact, and the capacity to suppress interfacial trap states. , The contact resistivity of oxide TFTs at the interface between the semiconductor and source/drain electrodes is known to be higher due to the problems of large contact resistance, poor adhesion, and material migration …”

Printable metal oxide nanostructures based chemiresistive non-biological analyte sensors

“…Printable chemical sensors have emerged as innovative tools in the field of analytical chemistry, offering versatile and adaptable means of detecting and quantifying non-biological analytes. Harnessing the principles of materials science and nanotechnology, printable chemical sensors are fabricated using advanced printable materials such as conductive polymers [1], metal oxides (MOs) [2], carbon nanotubes [3], graphene [4], and functionalized nanoparticles. These materials offer the advantage of being easily deposited onto various substrates, including flexible and low-cost surfaces, through techniques like inkjet printing, screen printing, and aerosol jet printing [5].…”