Abstract:The preparation of nanocomposite as gate dielectric film was carried out by blending polyimide and nano-TiO 2 particle to enhance the capacitance of gate dielectric. When the concentration of the nano-TiO 2 particle was less than 2 vol % and was well dispersed in polyimide slurry, a nanocomposite film with a homogeneous distribution of nano-TiO 2 particles in polyimide and low roughness was obtained after curing at 200 C, resulting in low leakage current density of the nanocomposite film and high on/off ratio … Show more
“…These results revealed that the hydroxyl-free, nonpolar PMMA and COC materials form a more hydrophobic surface, facilitating crystalline growth. Moreover, the modified layer reduced the traps on the dielectric surface, thereby enhancing the OTFT performance [33–35]. Fig.…”
The organic material soluble polyimide (PI) and organic–inorganic hybrid PI–barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol–gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0–8.6 and 9.2–17.5 nF cm−2, respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10−1 cm2 V−1 s−1, and on/off current of 8.4 × 107.
“…These results revealed that the hydroxyl-free, nonpolar PMMA and COC materials form a more hydrophobic surface, facilitating crystalline growth. Moreover, the modified layer reduced the traps on the dielectric surface, thereby enhancing the OTFT performance [33–35]. Fig.…”
The organic material soluble polyimide (PI) and organic–inorganic hybrid PI–barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol–gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0–8.6 and 9.2–17.5 nF cm−2, respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10−1 cm2 V−1 s−1, and on/off current of 8.4 × 107.
“…And the leakage current density is still lower than that of the one with similar composition fabricated by atomic layer chemical vapor deposition (ALCVD). 15 The permittivity of composite system can be fitted by the Lichttenecker's mixing rule, 19 which provides a good approximation for composite system with mixed parallel and series contributions:…”
In this paper, a solution-processing method for fabrication of the titanium-aluminum oxide (TAO) was proposed. Variation of band gap, permittivity, and leakage current density and permittivity of TAO films with different Ti content were investigated. The permittivity and leakage current density of TAO films were proportion to the Ti content, while the bandgap did the reverse. A remarkable enhancement in permittivity (16.5) could be achieved at Ti:Al=0.4:0.6, meanwhile the leakage current density was ∼4 × 10 −7 A/cm 2 at 2 MV/cm.With the development of flat panel display (FPD), thin film transistors (TFTs) based on oxide semiconductors have received widespread attention. 1 Due to the increase of display resolution, large threshold and high operating voltages become a major limitation for mobile, battery-powered applications. The commonly used dielectrics such as SiO 2 and Si 3 N 4 usually result in high operation voltage because of the weak capacitive coupling between the gate electrode and active channel. Using a high-k dielectric is unarguably the most promising method since it can increase the capacitive couple because of its higher permittivity than SiO 2 (4). Besides, higher k dielectrics enable us to employ a thicker insulator but with the same capacitance as the requirement of SiO 2 , consequently, ensure the low leakage current. 2 There are already numerous candidates that could be employed as the gate dielectrics in TFTs, such as etc. Among the various high-k materials, Al 2 O 3 is well studied owing to its wide band gap (8.9 eV), low leakage current density, and good interface characteristics. However, the permittivity of 9 for Al 2 O 3 8 could be the fly in the ointment. TiO 2 is another well-known high-k material for the desirable permittivity of 155 9 with environment-friendly feature. Nevertheless, TiO 2 suffers from its high leakage current due to a narrow band gap (3.0-3.2 eV) and poor suppression of leakage. Auciello et al., and Shi et al. have reported the investigation of TiO 2 -Al 2 O 3 (TAO) dielectric films fabricated by sputtering and pulsed laser deposition, respectively. 10,11 However, many optical and electrical properties of TAO, such as bandgap, permittivity, leakage current density, still need to be studied. In this paper, solution-processing method is adopted to prepare the target films due to the component-controllability advantage. Variation of TAO band gap, permittivity, and leakage current density with different Ti content were investigated.
ExperimentalThe 0.4M precursor solution of TAO is prepared by dissolving Aluminum (III)-s-butoxide Al(C 4 H 9 O) 3 , tetrabutyl titanate Ti(C 4 H 9 O) 4 in 2-methoxyethanol (2ME) in turn, then hydrochloric acid is added dropwise till the solution becomes clear, the whole process is accompanied by intense oscillation. The mole ratio of Ti and Al is varied from 2:8 to 8:2. All the chemical reagents were bought from Sinopharm Chemical Reagent Co., Ltd. After a 6 h stirring resulting in a transparent solution, the TAO solution was aged in a contro...
“…[40][41][42] Our solution-processable hybrid dielectrics produce improved OTFTs characteristics because of an optimized combination of high dielectric constant inorganic oxide NPs and host PI matrix.…”
Section: Otfts Characteristics With Pi-btx Hybrids As Dielectricmentioning
We report on a systematic study of hydroxyl-containing polyimide (PI)-BaTiO 3 (BT) nanoparticle (NP) nanocomposite dielectric materials, to determine the effects of BT NPs loadings (X) for X ¼ 0, 2, 5, 8, 10, and 12 wt%, on p-type pentacene organic thin film transistors (OTFTs). A condensation reaction to produce well-dispersed BT NPs within the PI matrix was followed by spin-coating to form a dielectric thin film directly on a silicon substrate. The thermal, optical, surface, dielectric, and electrical properties of the PI-BPX hybrid dielectric composite correlated to BT content for each sample. The hybrid dielectric composites exhibit tunable insulating properties, including high dielectric constant values in the range 5.2-11.3, high capacitances from 3.1 to 27.9 nF cm À2 for a film thickness of approximately 350 nm, and low leakage current densities in the range of 1.85 Â 10 À7 to 2.76 Â 10 À6 A cm À2 at 2 MV cm À1 .Bottom-gate top-contact OTFTs fabricated using various PI-BTX hybrid dielectrics, exhibit low threshold voltages of À4.09-2.62 V, moderately high field-effect mobility rates of 3.36 Â 10 À2 $2.32 Â 10 À1 cm 2 V À1 s À1 , and high ON/OFF ratios of approximately 10 5 . This study opens a route towards transparent and highly stable hybrid dielectric materials with tunable dielectric properties, by careful selection of NPs and polymer matrix combinations.
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