Preparation And Properties Of Graphene Field Effect Transistor With BNTM Ferroelectric Gate

As the basic memory cell of the ferroelectric memory, ferroelectric field effect transistor(FeFET) has many advantages such as anti-radiation, high density storage, low power consumption and compatible with the process of integrated circuit which has attracted considerable interests(IC). However, FeFET has some problem such as its relatively short retention time,and how to reduce the power consumption and improve the stability of the system on chip will prove to be a problem for people. Due to its superior transparency, high mobility and excellent mechanical properties, graphene could become a new favorite channel material. In this thesis, A novel graphene field effect transistor(G-FET) based on Bi3.15Nd0.85Ti2.99Mn0.01O12(BNTM) ferroelectric gate dielectric and graphene channel is demonstrated. The main research contents and obtained results are summarized as follows:1. Preparation and characterization of BNTM gate dielectricThe BNTM thin films were fabricatied on Pt/Ti/SiO2/Si substrated by sol-gel process,The microstructure and electrical properties of BNTM thin films were investigated in detail by X-ray diffractometer, scanning electron microscopy, raman spectroscopy and ferroelectric test systems respectively. These results suggest that the thin film were well crystallized and favorable grains with well-defined boundaries can be identified, the thicknesse of the thin film are measured to be approximately 420 nm, the prepared BNTM thin films exhibit excellent ferroelectricity and high dielectric constant, which meet the standards of insulation layer for FeFET.2. Preparation and characterization of graphenethe few-layer and monolayer graphene was fabricated by micromechanical exfoliation and chemical vaporous depositon method, and transferred to the BNTM ferroelectric layer thin film which was used as the gate dielectric. The microstructure,thickness and electrical properties of graphene thin films were investigated in detail by optical microscope, scanning electron microscopy, raman spectroscopy and UV-Vis spectrophotometer respectively. These results suggest that large area and uniform monolayer graphene film with good quality is obtained on the copper foil by chemical vaporous depositon and it has few cracks and impurities on the surface. The light transmittance of graphene is about 97.3% which indicated its monolayer properties.3. Preparation and characterization of G-FET with BNTM ferroelectric gateThe process parameters of graphene field effect transistor(G-FET) based onBi3.15Nd0.85Ti2.99Mn0.01O12(BNTM) ferroelectric gate dielectric and graphene channel is studied. The process parameters of the metal electrodes and channel graphic are optimized. The results showed that graphene contact well with metal electrodes, due to the polarization of the BNTM ferroelectric materials, the obviously memory window approximately 1.8 V, It can be seen that the memory window is almost changed after 50 loops, which shows the good retention performance of the device.