materials Article
A Simple Method for High-Performance, Solution-Processed, Amorphous ZrO2 Gate Insulator TFT with a High Concentration Precursor Wei Cai 1 , Zhennan Zhu 1 , Jinglin Wei 1 , Zhiqiang Fang 1 , Honglong Ning 1, * Shangxiong Zhou 1 , Rihui Yao 1, * ID , Junbiao Peng 1 and Xubing Lu 2 1
2
*
ID
, Zeke Zheng 1 ,
Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China;
[email protected] (W.C.);
[email protected] (Z.Z.);
[email protected] (J.W.);
[email protected] (Z.F.);
[email protected] (Z.Z.);
[email protected] (S.Z.);
[email protected] (J.P.) Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China;
[email protected] Correspondence:
[email protected] (H.N.);
[email protected] (R.Y.)
Received: 22 June 2017; Accepted: 15 August 2017; Published: 21 August 2017
Abstract: Solution-processed high-k dielectric TFTs attract much attention since they cost relatively little and have a simple fabrication process. However, it is still a challenge to reduce the leakage of the current density of solution-processed dielectric TFTs. Here, a simple solution method is presented towards enhanced performance of ZrO2 films by intentionally increasing the concentration of precursor. The ZrO2 films not only exhibit a low leakage current density of 10−6 A/cm2 at 10 V and a breakdown field of 2.5 MV/cm, but also demonstrate a saturation mobility of 12.6 cm2 ·V−1 ·s−1 and a Ion /Ioff ratio of 106 in DC pulse sputtering IGZO-TFTs based on these films. Moreover, the underlying mechanism of influence of precursor concentration on film formation is presented. Higher concentration precursor results in a thicker film within same coating times with reduced ZrO2 /IGZO interface defects and roughness. It shows the importance of thickness, roughness, and annealing temperature in solution-processed dielectric oxide TFT and provides an approach to precisely control solution-processed oxide films thickness. Keywords: solution-processed ZrO2 ; low leakage current density; precursor concentration; control thickness
1. Introduction The development of high mobility, thin film transistors (TFTs) depends heavily on the selection of dielectric materials with appropriate characteristics, including low leakage current and high breakdown voltage [1,2]. High-k dielectrics have been widely employed into facilitating TFT due to its high capacitance, which is beneficial to a large Ion /Ioff ratio and low-voltage operation. Although the vacuum-based deposition methods have their own advantages, their high fabrication cost restricts the areas of their applications [3,4]. Deposition with solution-based approaches has been reported as an alternative for a few material systems, including HfO2 , ZrO2 , and Y2 O3 [5]. Solution-processed gate dielectrics are required to have a low leakage current (
