Sputtering Effect on Amorphous Ga–In–Zn–O Thin-Film Surface: Occurrence of Subgap and Metallic States

Abstract

The chemical states of Ne + -ion-sputtered amorphous Ga-In-Zn-O ͑a-GIZO͒ thin films were investigated by high-resolution X-ray photoelectron spectroscopy. The sputtering reduced the Zn and In contents relative to that of Ga and generated a subgap state above the valence band maximum. Further sputtering resulted in metallic states at the In3d and In4d orbitals and at the Fermi energy edge, more so for the lower Zn-and In-content film. Locally generated metallic In is suggested to contribute to the metallic states.

Effects of Substrate Temperature on Structural, Electrical and Optical Properties of Amorphous In-Ga-Zn-O Thin Films

“…Each O 1s spectrum could be deconvoluted into the same three components: 'O 1 ', 'O 2 ', and 'O 3 '. 24 Each spectrum was curve-fitted using Voigt functions with the Lorentzian width fixed to 0.2 eV and with Shirley-type backgrounds. For all of the spectra (a)-(d), the peak positions were the same, and the peak separation between O Binding Energy (eV) as the one representing the In-Ga-Zn-O quaternary system, since it was the main component for all of the samples 20 and was more dominant for the sample deposited at low temperature.…”

“…The O 3 component (at 532.23 eV), which appeared at a higher BE than the O 1 component, represents oxygen atoms whose local environment are away from quaternary system. 20,24 This O 3 component represents nonstoichiometric or distorted a-IGZO structure, which represents the oxygen atoms which are close to oxygen vacancies and also probably the defects, interstitial oxygen, etc. As shown in the Fig.…”

Blue shift in the optical band gap of amorphous Hf–In–Zn–O thin films deposited by RF sputtering

“…The oxygen vacancies can act as shallow donors and supply conduction electrons in a-HIZO films, meanwhile the vacancies or defects can also act as scattering centers, reducing some amount of charge carrier conduction [15]. The oxygen vacancies and surface defect states can also induce deep subgap state (DSS) [16][17][18]. The density of the DSS was estimated to be ∼10 21 /cm 3 [18], which may effectively increase the charge carrier density.…”