Dielectric ceramics/TiO2/single-crystalline silicon nanomembrane heterostructure for high performance flexible thin-film transistors on plastic substrates

A dielectric ceramics/TiO2/single-crystalline silicon nanomembrane (SiNM) heterostructure is designed and fabricated for high performance flexible thin-film transistors (TFTs). Both the dielectric ceramics (Nb2O3–Bi2O3–MgO) and TiO2 are deposited by radio frequency (RF) magnetron sputtering at room temperature, which is compatible with flexible plastic substrates. And the single-crystalline SiNM is transferred and attached to the dielectric ceramics/TiO2 layers to form the heterostructure. The experimental results demonstrate that the room temperature processed heterostructure has high quality because: (1) the Nb2O3–Bi2O3–MgO/TiO2 heterostructure has a high dielectric constant (∼76.6) and low leakage current. (2) The TiO2/single-crystalline SiNM structure has a relatively low interface trap density. (3) The band gap of the Nb2O3–Bi2O3–MgO/TiO2 heterostructure is wider than TiO2, which increases the conduction band offset between Si and TiO2, lowering the leakage current. Flexible TFTs have been fabricated with the Nb2O3–Bi2O3–MgO/TiO2/SiNM heterostructure on plastic substrates and show a current on/off ratio over 104, threshold voltage of ∼1.2 V, subthreshold swing (SS) as low as ∼0.2 V dec−1, and interface trap density of ∼1012 eV−1 cm−2. The results indicate that the dielectric ceramics/TiO2/SiNM heterostructure has great potential for high performance TFTs.