High-temperature optical properties of indium tin oxide thin-films

Abstract

Indium tin oxide (ITO) is one of the most widely used transparent conductors in optoelectronic device applications. We investigated the optical properties of ITO thin films at high temperatures up to 800 °C using spectroscopic ellipsometry. As temperature increases, amorphous ITO thin films undergo a phase transition at ~ 200 °C and develop polycrystalline phases with increased optical gap energies. The optical gap energies of both polycrystalline and epitaxial ITO thin films decrease with increasing temperature due to electron-phonon interactions. Depending on the background oxygen partial pressure, however, we observed that the optical gap energies exhibit reversible changes, implying that the oxidation and reduction processes occur vigorously due to the low oxidation and reduction potential energies of the ITO thin films at high temperatures. This result suggests that the electronic structure of ITO thin films strongly depends on temperature and oxygen partial pressure while they remain optically transparent, i.e., optical gap energies > 3.6 eV.

Non‐Volatile Reconfigurable Integrated Photonics Enabled by Broadband Low‐Loss Phase Change Material

“…The DC sweep allows extended period for long range atomic diffusion, during which the atoms can settle in the most energetically favorable positions. The red shift is a result of PCM phase transition because it was found that the refractive index of amorphous ITO remains relatively constant upon heating up to 773 K [ 51 ] while the thermo‐optic effect is volatile. The spectral shift of 0.4 nm matches very well with the predicted shift of 0.39 nm based on simulation of rib waveguide (see Section S4, Supporting information) but lower than what was measured from fully etched waveguide (0.48 nm) due to less mode confinement.…”

Revealing the Three-Dimensional Orientation and Interplay between Plasmons and Interband Transitions for Single Gold Bipyramids by Photoluminescence Excitation Pattern Imaging

“…Figure b is a time series of the PL spectra of AuBP 1 acquired with 530 nm excitation over a time period of 50 s. The intensity of the spectrum is stable over a long time period, while the peak of the PL spectra blue-shifts from 704 to 700 nm according to Lorentzian fits. This slight blue-shift could be a thermal effect due to the change of the refractive index caused by continued laser excitation . The thermal effect or damage to the AuBP is unlikely to be responsible for the ∼10 nm difference between the dark-field scattering and LPR-induced emission excited at 488 and 530 nm, however, as the PL spectrum using 633 nm excitation is acquired after the short-wavelength excitation.…”

High Power Impulse Magnetron Sputtering of In2O3/Sn Cold Sprayed Composite Target

“…Nevertheless, in this study thermal energy necessary for crystallization was dissipated by short pulse durations [ 57 ]. ITO thin films undergo an amorphous—polycrystalline phase transition at ~200 °C [ 58 ], which increases optical and electrical properties [ 59 ]. On the other hand, amorphous structure can be desirable due to solving ITO etching residue problems in large-size 3D display devices [ 60 ].…”