Fabrication conditions for solution-processed high-mobility ZnO thin-film transistors

Li, Chensha; Yu-ning, Li; Wu, Yiliang; Ong, B.S.; Loutfy, Rafik O.

doi:10.1039/b812047a

Cited by 108 publications

(88 citation statements)

References 76 publications

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“…Metal salts are cheap, stable, and easy to use which makes them ideal precursors for the mass production of ZnO lms. Zinc sulfate, 36 zinc nitrate, 37,38 zinc chloride 39,40 and zinc acetate 41,42 are some of the common metal salts used to synthesize thin lms and nanoparticles of ZnO by solution-based techniques. A non-trivial problem in using metal salt precursors containing inorganic counterions in non-aqueous media is removing the anion from the lm while organic counterions such as acetate offer the advantage of producing volatile by-products upon sol pyrolysis.…”

Section: Introductionmentioning

confidence: 99%

Effect of sol stabilizer on the structure and electronic properties of solution-processed ZnO thin films

et al. 2015

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ZnO is an increasingly important wide bandgap semiconductor for optoelectronic applications. Solution processing provides a facile and inexpensive method to form ZnO thin films with high throughput. The sol stabilizer used in the solution processing of ZnO functions variously as a sol homogenizer, chelating agent, wettability improver and capping agent. In spite of its obvious importance in influencing ZnO film properties, a restricted set of short chain alkaline sol stabilizers have been used in prior reports. We examined the effect of six different sol stabilizers, including acidic and longer chain species, along with a recipe without any stabilizer, on the grain size, crystallographic texture, and resistivity of solution processed ZnO films on thermal oxide-coated silicon substrates, and found large variations in the structural and electrical properties as a consequence of the choice of sol stabilizer. We found that ZnO films formed using oleic acid as the sol stabilizer possessed a strong (002) preferred orientation with a Lotgering factor as high as 0.86. The key insight we obtained is that the sol stabilizer strongly influences the film surface area and activation energy barrier for inter-grain transport. We comprehensively studied the steady state and transient behavior of ZnO films deposited using different stabilizers and compared their lifetime and mobility-lifetime products. When exposed to illumination, the conductivity of the deposited films increased by several orders of magnitude. This is attributed to the trapping of the nonequilibrium holes by the surface adsorbed oxide species, which produces equivalent number of excess electrons in the conduction band. Impedance spectroscopy and C-V measurements were performed to calculate the doping of the ZnO thin films. ZnO thin film transistors were also fabricated and the effects of the sol stabilizer on the different parameters of the TFT like mobility and threshold voltage were investigated.

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Section: Introductionmentioning

confidence: 99%

Effect of sol stabilizer on the structure and electronic properties of solution-processed ZnO thin films

et al. 2015

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“…[6][7][8] Therefore, reactive mesogen (RM) was added to the YIZO system to obtain high electrical performance by inducing the channel material to become positioned along the source-drain direction. When a hybrid YIZO film is irradiated with UV radiation, a uniaxial directivity of the channel material is formed because RM is sensitive to UV light.…”

Section: Uv-cured Reactive Mesogen-yinzno Hybrid Materials Asmentioning

confidence: 99%

UV-Cured Reactive Mesogen-YInZnO Hybrid Materials as Semiconducting Channels in Thin-Film Transistors Using a Solution-Process

Kim

Jung

Cho

et al. 2015

ECS Solid State Letters

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Electrical performance of thin-film transistors (TFTs) is important for their applications. Solution-processed TFTs have low mobility and high sub-threshold swings (S.Ss) because there are many pores and pin-holes in the films. These characteristics are attributed to electron trapping in the YInZnO (YIZO) channel, the SiO 2 gate insulator, or their interface. We fabricated hybrid YIZO TFTs with and without UV radiation, and observed that UV-curing of the film affected TFT performance through promoting a response to reactive mesogen (RM). The UV irradiated TFT showed better performance because of the alignment of the channel materials in the source-drain direction. The Recently, amorphous oxide semiconductors (AOSs) have been researched extensively for a use as the channel layer in thin-film transistors (TFTs), 1-3 which exhibit superior electrical and optical characteristics to amorphous Si (a-Si) TFTs. a-Si TFTs have a relatively low mobility of approximately 0.5 cm 2 /Vs because of the angular distortion of the strongly directive sp 3 orbital. 1 In contrast, AOSs have a different carrier-path mechanism that permits them to achieve high mobility, as demonstrated by Nomura et al.1 They proposed a unique mechanism: direct overlapping between neighboring s orbitals that have insensitive angular distortion because of the chemical bonding between heavy-metal ions, such as the In in the InGaZnO (IGZO) system. Thus, despite the amorphous phase, AOSs have mobility that is almost comparable to that of the crystalline phase. 4 Previously, Shin et al. studied using YInZnO (YIZO) for the TFT channels by replacing the Ga in the IGZO system with Y.5 Y has a lower standard electrode potential (SEP) (−2.372 eV) and a lower electronegativity (1.22) than those of Ga; therefore, Y can easily form chemical bonds with oxygen, thereby decreasing the oxygen vacancies.Solution-processed TFTs have low electrical performance in terms of characteristics such as low mobility and high sub-threshold swing (S.S) because they contain many pores and pin-holes, which lead to electron trapping.6-8 Therefore, reactive mesogen (RM) was added to the YIZO system to obtain high electrical performance by inducing the channel material to become positioned along the source-drain direction. When a hybrid YIZO film is irradiated with UV radiation, a uniaxial directivity of the channel material is formed because RM is sensitive to UV light. [9][10][11] In this study, we produced hybrid YIZO TFTs using a solutionprocess with and without UV irradiation and investigated the role of UV-irradiated RM in the hybrid YIZO system in attaining high electrical performance.A 0. in 2-methoxyethanol (2ME). The molar ratio of Y:In:Zn was fixed at 2:11:7. To ensure a stable and homogeneous solution, we added mono-ethanolamine (MEA) and acetic acid as stabilizers. The solution was stirred at 75• C for 2 h and then aged for 1 day. Prior to the deposition, parallel-aligned RM(RMS03-015, Merck) was added to the YIZO system making a weight ratio of RM and YIZO to be 1:9. z E-m...

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“…[ 1,2 ] To date, many alternatives, including zinc oxide (ZnO), [3][4][5][6] zinc tin oxide, [ 6,7 ] indium zinc oxide (IZO), [8][9][10] and indium gallium zinc oxide, [11][12][13][14][15] have been widely demonstrated for use as active materials in TFTs based on the sol-gel processes with easy accessibility to a variety of compositional oxides. To boost fi eld-effect mobilities, the indispensable element, indium has been employed as a mobility enhancer in oxide semiconductors; [ 16 ] however, the incorporation of this highly expensive element has significantly shadowed the crucial advantage in cost-effectiveness of solution-processable functional materials.…”

mentioning

confidence: 99%

Chemically Functionalized, Well‐Dispersed Carbon Nanotubes in Lithium‐Doped Zinc Oxide for Low‐Cost, High‐Performance Thin‐Film Transistors

Son

Chee

Jun

et al. 2016

Small

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Surface-functionalized carbon nanotubes (CNTs) are introduced into lithium-doped ZnO thin-film transistors (TFTs) as an alternative to the conventional incorporation of an expensive element, indium. The crucial role of surface functionalization of CNTs is clarified with the demonstration of indium-free ZnO-based TFTs with a field-effect mobility of 28.6 cm(2) V(-1) s(-1) and an on/off current ratio of 9 × 10(6) for low-cost, high-performance electronics.

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Fabrication conditions for solution-processed high-mobility ZnO thin-film transistors

Cited by 108 publications

References 76 publications

Effect of sol stabilizer on the structure and electronic properties of solution-processed ZnO thin films

Effect of sol stabilizer on the structure and electronic properties of solution-processed ZnO thin films

UV-Cured Reactive Mesogen-YInZnO Hybrid Materials as Semiconducting Channels in Thin-Film Transistors Using a Solution-Process

Chemically Functionalized, Well‐Dispersed Carbon Nanotubes in Lithium‐Doped Zinc Oxide for Low‐Cost, High‐Performance Thin‐Film Transistors

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