Strategy for Controlling the Electrical Conductivity of Indium Tin Oxide (ITO) Nanobranches

Abstract

be avoided if the ITO is grown into nanobranch structures. [11,12] The second issue is related to controlling the conductivity of ITO in order to form the building blocks of many electronic devices. This is due to the fact that the ideal efficacy of electronic devices strongly depends on the conductivity of the building block materials. For example, TCO requires high conductivity, whereas electronic sensors require slightly high resistivity for high sensitivity. [13][14][15] Essentially, the conductivity of ITO can be controlled by changing the doping concentration (experimental 10% tin-doped ITO is known to have the highest electrical conductivity) based on classical ceramic processes such as ball milling, calcination, and sintering. [16,17] However, after fixing the stoichiometric ratio between indium and tin, it is difficult to control the conductivity. While it is possible to change the electrical conductivity by controlling the oxygen vacancies through annealing or plasma treatment, this option is not suitable for flexible devices because high temperature and ionic plasma energy can cause damage to the devices. [18][19][20] As shown in Figure 1a,b, this research proposed two methods for controlling the electrical conductivity of flexible ITO nanobranches. First, the orientation and connectivity of the ITO nanobranches were controlled by selecting a suitable substrate. In this study, we used the yttria-stabilized zirconia (YSZ) (100) and (111) substrates that have a very small lattice mismatch with ITO. [21,22] Second, this work involved forming a depletion layer on the surface of ITO nanobranches using heterojunction metal oxide nanoparticles that have a lower electron concentration compared to ITO. [23][24][25] To decorate ITO with metal oxide nanoparticles at a low temperature for application in flexible devices, we used a metal chloride coating and annealing in an oxygen atmosphere. By controlling electrical characteristics using these proposed methods, ITO nanobranches could be applied as electrodes and active materials in the fabrication of various flexible electronic devices. Results and DiscussionTo control the growth direction and connectivity of the nanobranches, we deposited ITO nanobranches on YSZ (100) and (111) substrates as shown in Figure 2a. The crystal structure of The electronic properties of indium tin oxide (ITO) nanobranches fabricated by electron beam evaporation are controlled using the following two methods: i) The growth direction of the rods and branches is controlled by an epitaxial relationship with a yttria-stabilized zirconia substrate. The aligned growth of ITO nanobranches causes low sheet resistance because of the high density and good connectivity of the branches. ii) Heterojunction metal-oxide nanoparticles are coated on the surface of the nanobranches to form a depletion region in the near surface for band bending. The morphology of the metal oxide also affects the electronic properties of the nanobranches.

Enhanced ultra high frequency EMI shielding with controlled ITO nano-branch width via different tin material types

“…When Fe 2 O 3 is coated along the surface of the ITO NBs, a depletion layer forms at the interface. 29 This implies that the resistance increases as the concentration of conductive electrons decreases. In Fig.…”

Transparent and Flexible Electromagnetic Interference Shielding Film Using ITO Nanobranches by Internal Scattering

“…In this study, a TF-EMIS film was developed using indium tin oxide (ITO; Sn-doped In 2 O 3 ), which is well known as a transparent conductive oxide. When the conductive oxide is used, the reflective shielding effect by free electrons and an additional shielding effect due to a specific dielectric constant can be expected simultaneously (Re­(ε r ) and Im­(ε i ) ≈ 10 5 of a 100 nm thick ITO thin film at 1–20 GHz; the EMI shielding effect of ITO is known to be 14 dB at 0.3–3 GHz). − The mechanical brittleness of ceramic materials, which is problematic during the fabrication of flexible devices, was overcome by synthesizing ITO with nanobranches (Figure a), which has been proven experimentally. , Thus, a highly efficient TF-EMIS film using an ITO nanostructure was fabricated. Because the EM wave absorption continuously occurs through internal scattering, excellent shielding properties can be expected (Figure b).…”

“…43−45 The mechanical brittleness of ceramic materials, which is problematic during the fabrication of flexible devices, was overcome by synthesizing ITO with nanobranches (Figure 1a), which has been proven experimentally. 46,47 Thus, a highly efficient TF-EMIS film using an ITO nanostructure was fabricated. Because the EM wave absorption continuously occurs through internal scattering, excellent shielding properties can be expected (Figure 1b).…”

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

“…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. ,,,,− …”