Investigation on electrical properties of indium tin oxide thin films by effective control of crystallographic orientation

Influence of Substrate Orientation and Oxygen Partial Pressure on the Morphology, Structure, and Electrical Property of Epitaxial Indium Tin Oxide Films

“…For example, the hole mobility in a [110] plane is 78% enhanced compared to the [100] plane; the difference of the hole mobility is due to the anisotropy of the hole effective mass. − We speculate that ITO may have similar anisotropic transport properties. In addition, Zhuo et al prepared polycrystalline ITO films with different (100)- and (111)-grain densities by metal organic chemical vapor deposition and found that the averaged grain boundary barrier height increased with the (100)-grain density . This may also be the reason for the differences in the carrier mobility of ITO films with different orientations.…”

“…Because of the high transparency in the visible region and excellent electrical conductivity, ITO films have been widely employed in various research fields such as biosensing technology, , electroanalysis, liquid crystal displays, , photovoltaic devices, , and light-emitting diodes. − In addition to this, ITO films with flat surfaces could be used as conductive substrates for specific characterization techniques such as ultraviolet photoelectron spectroscopy and scanning tunneling microscopy . Various techniques are available for ITO film preparation, including sol–gel process, spray pyrolysis, vacuum evaporation, , electron beam evaporation, magnetron sputtering, − pulsed laser deposition, − ion beam sputtering, chemical vapor deposition, − atomic layer deposition, and so forth. Generally, amorphous or nonepitaxial polycrystalline ITO films are usually obtained on the commonly used substrates for ITO deposition such as quartz, corning glass, polymer, and silicon substrates, while the orientation-controlled or epitaxial ITO films can be obtained on yttria-stabilized zirconia (YSZ) or sapphire (Al 2 O 3 ) substrates under specific preparation conditions because of the low lattice mismatch between ITO films and the substrates. ,,,,− …”

“…Various techniques are available for ITO film preparation, including sol–gel process, spray pyrolysis, vacuum evaporation, , electron beam evaporation, magnetron sputtering, − pulsed laser deposition, − ion beam sputtering, chemical vapor deposition, − atomic layer deposition, and so forth. Generally, amorphous or nonepitaxial polycrystalline ITO films are usually obtained on the commonly used substrates for ITO deposition such as quartz, corning glass, polymer, and silicon substrates, while the orientation-controlled or epitaxial ITO films can be obtained on yttria-stabilized zirconia (YSZ) or sapphire (Al 2 O 3 ) substrates under specific preparation conditions because of the low lattice mismatch between ITO films and the substrates. ,,,,− …”

“…In the early studies, researchers believed that there was no significant difference in the electrical properties between polycrystalline and epitaxial ITO films . However, in recent years, many researchers found that the preferred orientation could influence the electrical/optical properties in polycrystalline ITO films, and the correlation between relative intensities of typical XRD peaks, such as (222), (400), (440), and (622), and resistivity/mobility/transparency was often discussed. ,,− For example, Zhuo et al found that the increase of (100)-oriented grains was accompanied by the decrease of carrier mobility . It means that the crystal orientations will affect the electrical properties of ITO films.…”

“…It means that the crystal orientations will affect the electrical properties of ITO films. But in most of the previous studies, changes in preferred crystal orientations often went along with the changes of deposition conditions, such as oxygen partial pressure, , deposition time, , thermally treated temperature, , precursor flow rates, Sn concentration, sputtering power, deposition angles, and deposition rates, and so on. In order to eliminate the influence of preparation conditions and clarify the correlations between crystalline orientation and electrical properties, in this work, the epitaxial ITO thin films along the different crystal orientations were deposited on low-index YSZ substrates by direct current (DC) magnetron sputtering.…”