Preparation Of Perovskite Transistors Based On High Dielectric Constant Oxides

Metal halide perovskite has attracted widespread attention in light emitting diodes and solar cells due to its excellent photoelectric performance and simple expandable processing.Two-dimensional perovskite materials with layered structures and relatively large organic cations can be used to effectively inhibit ion migration and improve stability in field effect transistors requiring horizontal charge transfer.At the same time,silicon dioxide is traditionally used as the dielectric layer of TFT.In order to reduce the size of transistors,the thickness of dielectric layer is often reduced to increase the capacitance and improve the carrier mobility of devices.Too thin dielectric layer often results in quantum tunneling effect,which affects transistor performance.High permittivity oxide as dielectric layer can effectively avoid quantum tunneling effect.The specific content of the thesis is divided into the following three aspects:Al₂O₃films were prepared by using ALD on p-doped monocrystalline silicon.The material properties and phase composition of the samples were analyzed by AFM,SEM,XPS,XRD and dielectric properties experiments.The effects of deposition temperature and cycle morphology on film morphology and electrical properties were observed.The results show that Al₂O₃film prepared by ALD technology has good flatness and mainly exists in amorphous form.The deposition temperature mainly affects the dielectric constant and leakage current density of the sample film.The higher the deposition temperature is,the dielectric constant increases and the leakage current density decreases.There is a linear correlation between deposition cycle number and film thickness.When the process parameters were determined:deposition temperature 225℃,pulse time 0.2 s and deposition cycle 250 cycles,the dielectric property of the film was the best,and theAl₂O₃ films were prepared by using ALD on p-doped monocrystalline silicon.The material properties and phase composition of the samples were investigated by AFM,SEM,XPS,XRD and dielectric properties experiments.The effects of deposition temperature and cycle morphology on film morphology and electrical properties were observed.The results show that Al₂O₃ film prepared by ALD technology has good flatness and mainly exists in amorphous form.The deposition temperature mainly affects the dielectric constant and leakage current density of the sample film.The higher the deposition temperature is,the dielectric constant increases and the leakage current density decreases.There is a linear correlation between deposition cycle number and film thickness.When the process parameters are deposition temperature 225℃and deposition250 cycles,the dielectric property of the film is the best,and the dielectric constant is7.33.（PEA）₂SnI₄ perovskite thin films were prepared by one-step spin coating method.The effects of solvent ratio of precursor,annealing temperature,spin coating speed and other factors on the morphology,crystallinity and optical properties of the thin films were observed.The crystallization of（PEA）₂SnI₄ perovskite films was controlled by solvent method.The films were characterized by SEM,UV-VIS and XRD.The experimental results showed that adding chlorobenzene（CB）into the traditional precursor solvent N,N-dimethylformamide（DMF）was beneficial to the nucleation and film formation of perovskite solution.Compared with pure DMF or DMF and DMSO mixed solution,the perovskite film prepared by adding a certain volume of CB solution is more compact and smoother,and has a higher light absorption intensity.The volume ratio of CB to DMF is1:5,anneal at 100℃,the film is smooth and the thickness is about 100 nm a 4000 rpm.It is suitable for the preparation of thin film FET.Al₂O₃ with high dielectric constant prepared by atomic layer deposition（ALD）is used as dielectric layer instead of Si O₂,and（PEA）₂SnI₄ perovskite is used as active layer to prepare high performance phototransistors.On this basis,the transistor is prepared.The mobility of carriers is improved obviously and the response to light is also enhanced.The best performance parameters of thin film transistor carrier mobility 3.3 cm~2 V^-1 s^-1,current on/off ratio increased to 10~6.The optical response parameter is 1.3×10~5AW^-1.