| Memories with higher quality are needed in order to develop the excellentperformance of electronics as we enter the information age. Ferroelectric field effecttransistors (FeFET) have received much attention as the basic cell of nonvolatileferroelectric random memory. The FeFET with structure of thin film transistor (TFT)are popular among the different kinds of FeFET because of its simple technology,easy integration with large area, achieving fully epitaxial growth and being fullytransparent and flexible device. In this paper, we fabricated BIT thin film by doping atA site and B site to improve its performance and characterize the performance, firstly.Then the optimum content of Nb in Bi3.15Nd0.85Ti(3-x)NbxO12(BNTNx)is analyzed andstudied. At last, the excellent performance of BNTN0.03is applied in ZnO TFT as gatedielectric layer. We compared the performance of transistors with and withoutdielectric layer. The main research work and results are as follows:Firstly, we fabricated the BIT and BNTN0.01thin film on Pt/Ti/SiO2/Si(100) byChemical Solution Deposition method (CSD). Then the optional annealingtemperatures (650℃,750℃and850℃) were studied. The microstructures of thesample were investigated by X-ray Diffraction (XRD) and Scanning ElectronMicroscopy (SEM) and the ferroelectric characteristics were also investigated. Theresults of SEM and XRD present the grains of the films grow with the rise ofannealing temperature, but the grains at750℃are more uniform. At the same time,the ferroelectricity increases initially and then decreases with the rise of annealingtemperature.Secondly, The BIT and BNTNx(x=0,0.01,0.03,0.05,0.07) thin films wereannealed at750℃to study the optimum content of Nb in BNTNx. The microstructure,ferroelctrical and dielectricall properties of the prepared films were investigated. Theresults show that the crystal structures of the films are not transformed after A-sitedoped with Nd and B-site doped with Nb in the films. The size of grains reduce withthe increase of x in BNTNx，while the2Ec(coercive field) are changed on the contrary.The2Prof the films increase with x at first， then decreases after x≥0.03. The leakagecurrents of the BNTN0.03thin film reach the lowest, C-V characteristics are the best,and dielectric constants are the largest.Lastly, the ZnO/BNTN0.03ferroelectrical thin film transistor (FeTFT) was deposited on Pt/Ti/SiO2/Si(100) by CSD, and the BNTN0.03thin film was applied asdielectric layer. The ZnO-based TFT was fabricated on SiO2/Si(100) as contrast. Then,the transfer, output and retention characteristics were tested. The results show that thetransistors with and without dielectric layer both have typical n-channelcharacteristics. The ZnO/BNTN0.03FeTFT shows better transfer and outputcharacteristic.and the threshold voltage, channel mobility, memory window and on/offratio of the ZnO/BNTN0.03TFT reach to2.5V,5.68cm2/Vs,1.5V and1.8×105,respectively. Notably, the device shows large drain-current on/off ratio of about105after a24h data retention test which far exceeds the memory recognizablerequirements103. These results suggest that the ZnO/BNTNxFeTFT has superiorretention characteristics because of the polarization interaction and the relatively goodinterface properties between the ZnO film and the BNTN0.03thin film. |
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