Electrical and Optical Properties of Amorphous Indium-Zinc-Tin Oxide Thin Films: Oxygen Flow Dependence

• Published in: Journal of the Korean Physical Society Vol. 76; no. 8; pp. 750 - 756
• Main Authors: So, Hyeon Seob, Jung, Dae Ho, Seok, Hae-Jun, Kim, Han-Ki, Lee, Hosun
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01.04.2020; Springer Nature B.V; 한국물리학회
• Subjects: Absorptivity; Carrier density; Conduction bands; Dependence; Ellipsometry; Flow velocity; Gas flow; Grain boundaries; Indium; Mathematical and Computational Physics; Optical properties; Oxygen; Particle and Nuclear Physics; Physics; Physics and Astronomy; Theoretical; Thin films; Tin oxides; Zinc; 물리학; Oxygen flow; Sputtering deposition; Mobility; Indium-zinc-tin oxide; Effective mass; Optical constants; Drude tail
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.76.750

In this study, the electrical and the optical properties of the amorphous indium-zinc-tin oxide (IZTO) thin films that had been grown using a cosputtering system were investigated as a function of the oxygen flow rate during growth. The optical constants of the IZTO thin films were obtained by applying the Drude and the parametric optical constant models to the ellipsometric angles, Ψ and Δ. We estimated the optical gap energies of the IZTO thin films from their absorption coefficients (α). The Drude tail amplitudes in the optical spectra were found to decrease under the deposition condition of increasing oxygen flow. The resistivity of the IZTO films was measured to be as low as 0.547 mΩ·cm at an oxygen flow rate of 0.3 sccm. Further, the Hall carrier concentrations and the mobilities were measured. We determined the effective masses of the IZTO thin films by using a combination of their optical and electrical parameters. The effective mass of the amorphous IZTO thin films decreased from 0.61 to 0.44 m 0 as the oxygen gas flow rate was increased. Assuming a linear dependence of the effective mass on the carrier concentration, we estimated the effective mass at the conduction band minimum. The optically and electrically measured resistivities and mobilities of the amorphous IZTO thin films were equal because the films were free of grain boundaries; therefore, no scattering of free carriers from such grain boundaries had to be considered.