Abstract
This study aims to discuss the sheet resistance of ultrathin indium tin oxide (ITO) transparent conductive films during the postannealing treatment. The thickness of the ultrathin ITO films is 20 nm. They are prepared on B270 glass substrates at room temperature by a direct-current pulsed magnetron sputtering system. Ultrathin ITO films with high sheet resistance are commonly used for touch panel applications. As the annealing temperature is increased, the structure of the ultrathin ITO film changes from amorphous to polycrystalline. The crystalline of ultrathin ITO films becomes stronger with an increase of annealing temperature, which further leads to the effect of enhanced Hall mobility. A postannealing treatment in an atmosphere can enhance the optical transmittance owing to the filling of oxygen vacancies, but the sheet resistance rises sharply. However, a higher annealing temperature, above 250°C, results in a decrease in the sheet resistance of ultrathin ITO films, because more Sn ions become an effective dopant. An optimum sheet resistance of 336 Ω/sqr was obtained for ultrathin ITO films at 400°C with an average optical transmittance of 86.8% for touch sensor applications.
Highlights
Transparent conducting oxide (TCO) thin films have drawn a great deal of attention in recent years and have been widely applied in various optoelectronic devices such as solar cells [1, 2], flat panel displays [3, 4], organic light emitting devices (OLED) [5,6,7], and a variety of handheld devices
The sheet resistance of the ultrathin indium tin oxide (ITO) films increases with an increased annealing temperature, reaching a maximum value of 1075 Ω/sqr at an annealing temperature of 250∘C
Ultrathin ITO films were prepared on B270 glass substrates at room temperature by the dc pulsed magnetron sputtering method
Summary
Transparent conducting oxide (TCO) thin films have drawn a great deal of attention in recent years and have been widely applied in various optoelectronic devices such as solar cells [1, 2], flat panel displays [3, 4], organic light emitting devices (OLED) [5,6,7], and a variety of handheld devices. Tin-doped In2O3 (indium tin oxide, ITO) has been the most widely used of the TCO materials because of its low resistivity (less than 10−3 Ω-cm) and good optical transmittance (more than 80%) in the visible region [8]. It is a degenerate ntype semiconductor with a wide energy band gap (3.7 eV) and possesses the qualities of high mechanical hardness and chemical inertness [9]. A pulsed dc magnetron sputtering method is the most common technology for the deposition of ITO films, because it is an easy way to get high quality thin films [16]. The properties of ITO films are dependent on the process parameters like the oxygen partial pressure, substrate temperature, and postannealing temperature and different substrates, such as glass and PET [17,18,19,20]
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