Dong-won Choi

Highly Conducting, Transparent, and Flexible Indium Oxide Thin Film Prepared by Atomic Layer Deposition Using a New Liquid Precursor Et2InN(SiMe3)2

Highly conductive indium oxide films, electrically more conductive than commercial sputtered indium tin oxide films films, were deposited using a new liquid precursor Et2InN(SiMe3)2 and H2O by atomic layer deposition (ALD) at 225-250 °C. Film resistivity can be as low as 2.3 × 10(-4)-5.16 × 10(-5) Ω·cm (when deposited at 225-250 °C). Optical transparency of >80% at wavelengths of 400-700 nm was obtained for all the deposited films. A self-limiting ALD growth mode was found 0.7 Å/cycle at 175-250 °C. X-ray photoelectron spectroscopy depth profile analysis showed pure indium oxide thin film without carbon or any other impurity. The physical and chemical properties were systematically analyzed by transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, optical spectrometer, and hall measurement; it was found that the enhanced electrical conductivity is attributed to the oxygen deficient InOx phases.

The effect of the annealing temperature on the transition from conductor to semiconductor behavior in zinc tin oxide deposited atomic layer deposition

We investigated the electrical properties of zinc tin oxide (ZTO) films deposited via atomic layer deposition and compared them to ZnO and SnO2 films as a function of the annealing temperature. The ZTO and ZnO, except for SnO2, films exhibited an electrical transition from a metal to semiconductor characteristics when annealed above 300 °C. The X-ray photoelectron spectroscopy analyses indicate that the relative area of the oxygen vacancy-related peak decreased from 58% to 41% when annealing at temperatures above 400 °C. Thin film transistors incorporating ZTO active layers demonstrated a mobility of 13.2 cm2/V s and a negative bias instability of −0.2 V.

A Study on the Growth Behavior and Stability of Molecular Layer Deposited Alucone Films Using Diethylene Glycol and Trimethyl Aluminum Precursors, and the Enhancement of Diffusion Barrier Properties by Atomic Layer Deposited Al2O3 Capping

As a route to the production of organic-inorganic hybrid multilayers, the growth behavior of molecular layer deposited (MLD) alucone and atomic layer deposited (ALD) Al2O3 films on top of each other was examined. MLD alucone films were prepared using trimethyl aluminum and diethylene glycol precursors, the latter resulting in faster growth rates than ethylene glycol precursors. The sensitivity of individual alucone films with respect to ambient exposure was found to be related to moisture permeation and hydration reactions, of which the mechanism is studied by density functional theory calculations. Deleterious effects such as thickness reduction over time could be suppressed by applying a protective Al2O3 layer on top of alucone. A preliminary nucleation period was required in the ALD process of Al2O3 films on alucone surfaces, prior to reaching a linear regime where the thickness increases linearly with respect to the number of ALD cycles. The same behavior was observed for alucone growing on Al2O3. The protective Al2O3 films were found to effectively suppress moisture permeation, thus isolating the underlying alucone from the surrounding environment. The water vapor transmission rate was greatly reduced when an Al2O3/alucone/Al2O3 multilayer stack was formed, which suggests that proper combinations of organic/inorganic hybrid structures may provide chemically stable platforms, especially for mechanically flexible applications.

Performance modulation of transparent ALD indium oxide films on flexible substrates: transition between metal-like conductor and high performance semiconductor states

Indium oxide (InOx) films are grown by atomic layer deposition (ALD) using [1,1,1-trimethyl-N-(trimethylsilyl)silanaminato]-indium (InCA-1) as the metal precursor and hydrogen peroxide (H2O2) as the oxidant. It is found that the electrical properties of the indium oxide layers strongly depend on the ALD growth temperature. Relatively low electrical resistivity (∼10−4 Ω cm) and high optical transparency (>85%) are obtained at growth temperatures higher than 200 °C, which make the indium oxide film suitable for transparent conducting oxide (TCO) applications. On the other hand, at relatively low growth temperatures below 150 °C, indium oxide behaves as a transparent semiconducting oxide (TSO). Thin film transistors (TFTs) incorporating this material as the active layer exhibit reasonably high performance with saturation mobility exceeding 10 cm2 V−1 s−1 and a threshold voltage near 0 V.

Efficient Planar Perovskite Solar Cells Using Passivated Tin Oxide as an Electron Transport Layer

Abstract Planar perovskite solar cells using low‐temperature atomic layer deposition (ALD) of the SnO2 electron transporting layer (ETL), with excellent electron extraction and hole‐blocking ability, offer significant advantages compared with high‐temperature deposition methods. The optical, chemical, and electrical properties of the ALD SnO2 layer and its influence on the device performance are investigated. It is found that surface passivation of SnO2 is essential to reduce charge recombination at the perovskite and ETL interface and show that the fabricated planar perovskite solar cells exhibit high reproducibility, stability, and power conversion efficiency of 20%.

Anti-reflective conducting indium oxide layer on nanostructured substrate as a function of aspect ratio

Antireflective conducting indium oxide layers were deposited using atomic layer deposition on a transparent nanostructured substrate grown using colloidal lithography. In order to explain the changes in the electrical resistivity and the optical transmittance of conducting indium oxide layers depending on various aspect ratios of the nanostructured substrates, we investigated the surface area and refractive index of the indium oxide layers in the film depth direction as a function of aspect ratio. The conformal indium oxide layer on a transparent nanostructured substrate with optimized geometry exhibited transmittance of 88% and resistivity of 7.32 × 10−4 Ω cm. The enhancement of electrical resistivity is strongly correlated with the surface area of the indium oxide layer depending on the aspect ratio of the nanostructured substrates. In addition, the improvement in transparency was explained by the gradual changes of the refractive index in the film depth direction according to the aspect ratio of the nanostructures.