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[13a-PA3-2] Study on the thermal-diffusion-type Ga-doping in ZnO nanoparticles
aiming for TFT channel application.
Keywords:Thin Film Transistor, ZnO-NPs, Ga dopping, Thermal Diffusion
Using semiconductor nanoparticles (NPs) is one of the attractive techniques to obtain channel layer of thin-film transistors (TFTs), because of its exceptional properties. Recently, by using the ZnO-NPs synthesized in our laboratory, not only n-channel but also p-channel back-gate TFTs on Si/SiO2 substrates were successfully demonstrated by using the simple and easy spraying method, providing high expectation to realize complementary logic circuits using ZnO-based NP-layers. However, the resistivity of NP-layer was too high, preventing the progress of TFT performance. In this study, the thermal-diffusion-type Ga-doping in n-type ZnO-NPs were investigated with different ambient gases to obtain low resistive NP-layers aiming for TFT channel application.
From XRD the calculated crystallite sizes by Scherrer’s equation in (100) spectra are 41 nm, over 100 nm, 42 nm and 54 nm for ZnO, air, N2, and O2 respectively. The electrical resistivity of the ZnO-NP layers falls to a minimum value of approximately 200 Ω/sq by thermal treatment in air, while it decreased only a little in N2 or increased in O2. From XRD, a noticeable increase of crystallite size was detected only from the NPs thermally treated in air. A possible reason is the Ga incorporation into ZnO-NPs with substituting for Zn; i.e. Ga-doping was achieved effectively. By investigating the structural and electrical properties it is clear that the existence of moisture in the ambient gas tended to cause Zn-related defects making a substitution with Ga easier.
From XRD the calculated crystallite sizes by Scherrer’s equation in (100) spectra are 41 nm, over 100 nm, 42 nm and 54 nm for ZnO, air, N2, and O2 respectively. The electrical resistivity of the ZnO-NP layers falls to a minimum value of approximately 200 Ω/sq by thermal treatment in air, while it decreased only a little in N2 or increased in O2. From XRD, a noticeable increase of crystallite size was detected only from the NPs thermally treated in air. A possible reason is the Ga incorporation into ZnO-NPs with substituting for Zn; i.e. Ga-doping was achieved effectively. By investigating the structural and electrical properties it is clear that the existence of moisture in the ambient gas tended to cause Zn-related defects making a substitution with Ga easier.