Thin-Film Optical Devices Based on Transparent Conducting Oxides: Physical Mechanisms and Applications

Abstract

This paper provides a review of optical devices based on a wide band-gap transparent conducting oxide (TCO) while discussing related physical mechanisms and potential applications. Intentionally using a light-induced metastability mechanism of oxygen defects in TCOs, it is allowed to detect even visible lights, eluding to a persistent photoconductivity (PPC) as an optical memory action. So, this PPC phenomenon is naturally useful for TCO-based optical memory applications, e.g., optical synaptic transistors, as well as photo-sensors along with an electrical controllability of a recovery speed with gate pulse or bias. Besides the role of TCO channel layer in thin-film transistor structure, a defective gate insulator can be another approach for a memory operation with assistance for gate bias and illuminations. In this respect, TCOs can be promising materials for a low-cost transparent optoelectronic application.

Effect of Annealing Temperature on Optoelectronic Performance of F- and Al-codoped ZnO Thin Films for Photosensor Applications

“…Transparent conductive oxide (TCO) films have many favorable properties, including high transmittance at visible wavelengths, high electrical conductivity, low resistivity, and high carrier density. (1)(2)(3) As a result, they are widely used in many different applications nowadays, including photosensors or gas sensors, thin-film solar cells, liquid crystal display monitors, and light-emitting diodes (LEDs). (4)(5)(6)(7)(8)(9) Among the various materials available for the fabrication of TCO films, indium oxide (In 2 O 3 ), tin oxide (SnO 2 ), and zinc oxide (ZnO) are among the most commonly used.…”

Structural and Optical Properties of ZnO:Al Thin Films Produced by Magnetron Sputtering with Different Oxygen Flow: An Experimental and Ab Initio Study

“…AZO, In 2 O 3 doped with Sn (ITO), and SnO 2 doped with Sb or F (ATO and FTO) make up the group of TCOs most studied and applied today. [ 14,15 ] AZO thin films have been studied, as it presents chemical stability, [ 16 ] a raw material of low economic value, [ 17 ] behaves similar to ferromagnetic material at room temperature, [ 18 ] in addition to the excellent balance between electrical and optical properties. Recent research on AZO films has converged on the understanding of the atomic and electronic structure, both theoretically [ 13 ] and experimentally.…”

Comparing metal oxide thin films as transparent p-type conductive electrodes

“…However, a class of oxide semiconductors named as transparent conductive oxides (TCOs) constitute an exception to this rule, because they are rather good conductors of electricity and simultaneously transparent in the visible region [1]. TCO materials in thin films are widely used in a variety of optoelectronic devices ranging from flat panel displays to smart windows or photovoltaic solar cells [2,3], and other advanced photo-sensors [4]. For these applications, transparent metal oxides with high n-type conductivity are commonly used, such as Sn-doped In 2 O 3 , Al-doped ZnO or Sb-doped SnO 2 [2].…”