Frequency-Dependent Complex Conductivities and Dielectric Responses of Indium Tin Oxide Thin Films From the Visible to the Far-Infrared

• Published in: IEEE journal of quantum electronics Vol. 46; no. 12; pp. 1746 - 1754
• Main Authors: CHEN, Ching-Wei, LIN, Yen-Cheng, CHANG, Chia-Hua, PEICHEN YU, SHIEH, Jia-Min, PAN, Ci-Ling
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-12-2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Carrier density; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity; Dielectric function; Dielectrics; drude free-electron model; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Indium tin oxide; Mathematical models; optical constants; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical films; Optical materials; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Optics; Optoelectronic devices; Physics; Plasma frequencies; plasma frequency; Refractive index; scattering time; Spectroscopy; Substrates; terahertz time domain spectroscopy; Thin films; Time frequency analysis; Plasma; drude free-electron model; Electrical properties; Dielectric materials; Optoelectronic devices; indium tin oxide; plasma frequency; Indium oxide; Thin films; Reflectivity; Dielectric function; THz range; terahertz time domain spectroscopy; Tin; fs range; ITO layers; Free electron; Optical materials; scattering time; Optical constants
• ISSN: 0018-9197; 1558-1713
• DOI: 10.1109/JQE.2010.2063696

Transparent and conducting indium tin oxide (ITO) thin films form an integral part for various optoelectronic devices. In this paper, we report the frequency-dependent complex conductivities and dielectric responses of several sputtered ITO thin films with thicknesses in the range of 189-962 nm by using terahertz time domain spectroscopy (THz-TDS), optical reflectance spectroscopy, and electrical measurements. The plasma frequencies are verified to be from 1590 to 1930 rad·THz, while the scattering times are in the range 6-7 fs based on the Drude free-electron model. The mobilities of the above ITO thin films are calculated to be 32.7-34.2 cm 2 V -1 s -1 , whereas the carrier concentrations lie in the range 2.79-4.10× 10 20 cm -3 . The electrical properties derived from the THz-TDS technique agree well with those determined by Hall measurement. Parameters for the complex dielectric function suitable for ITO in the range 0.2-2 and 4-450 THz are also determined.