Solution-Processed Rare-Earth Oxide Thin Films for Alternative Gate Dielectric Application

Previous investigations on rare-earth oxides (REOs) reveal their high possibility as dielectric films in electronic devices, while complicated physical methods impede their developments and applications. Herein, we report a facile route to fabricate 16 REOs thin insulating films through a general solution process and their applications in low-voltage thin-film transistors as dielectrics. The formation and properties of REOs thin films are analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), spectroscopic ellipsometry, water contact angle measurement, X-ray photoemission spectroscopy (XPS), and electrical characterizations, respectively. Ultrasmooth, amorphous, and hydrophilic REO films with thickness around 10 nm have been obtained through a combined spin-coating and postannealing method. The compositional analysis results reveal the formation of RE hydrocarbonates on the surface and silicates at the interface of REOs films annealed on Si substrate. The dielectric properties of REO films are investigated by characterizing capacitors with a Si/Ln₂O₃/Au (Ln = La, Gd, and Er) structure. The observed low leakage current densities and large areal capacitances indicate these REO films can be employed as alternative gate dielectrics in transistors. Thus, we have successfully fabricated a series of low-voltage organic thin-film transistors based on such sol-gel derived REO films to demonstrate their application in electronics. The optimization of REOs dielectrics in transistors through further surface modification has also been studied. The current study provides a simple solution process approach to fabricate varieties of REOs insulating films, and the results reveal their promising applications as alternative gate dielectrics in thin-film transistors.