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...