Atomic Layer Deposition of Iridium Using a Tricarbonyl Cyclopropenyl Precursor and Oxygen

Abstract

Atomic layer deposition (ALD) is an advanced technology that can be used to deposit extremely thin and conformal films of iridium (Ir). However, ALD techniques for Ir coating are not well-developed. In particular, new Ir precursors with high reactivity at a suitable low temperature are essentially required. In this study, we report a novel ALD precursor with improved reactivity by introducing a cyclopropenyl ligand. Tricarbonyl (1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl iridium (C 18 H 27 IrO 3 or TICP) is used as an ALD precursor with molecular O 2 as a reactant. Ir films are grown by ALD on a Si substrate at deposition temperatures ranging from 200 to 325 °C, and an ALD window of 250−275 °C and self-limiting growth at a rate of 0.52 Å cycle −1 at 250 °C are observed. The negligible O impurity content (<2 at. %) and low resistivity (13 μΩ cm) indicate that pure metallic Ir films are formed. The differential delay of nucleation depending on the substrate surface is explained in terms of the dominant surface functional group, indicating possible application of the current ALD process toward area-selective deposition of Ir. Density functional theory calculations show that the adsorption of the Ir precursor is feasible on Si and Ru but is unfavorable on hydroxyl-terminated SiO 2 . Ru is adopted as the seed layer for conformal deposition on a SiO 2 trench, and a step coverage of ∼100% is obtained. Finally, an Ir thin film grown on a threedimensional titanium substrate shows overpotentials (at 10 mA cm −2 ) of ∼65 mV for the hydrogen evolution reaction and ∼336 mV for the oxygen evolution reaction in an acid electrolyte, which suggest its potential application as a water-splitting catalyst.

Atomically dispersed iridium catalysts on silicon photoanode for efficient photoelectrochemical water splitting

“…To construct the NiO/Ni thin film, Ni layer with the thickness of 2 nm was deposited and the surface of Ni is oxidized by oxygen supplied as a secondary precursor vapor for Ir deposition during the ALD process. Then, atomically dispersed Ir single atoms are anchored into the NiO lattice via a single cycle ALD process, utilizing tricarbonyl (1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl iridium (C 18 H 27 IrO 3 or TICP) and O 2 as a precursor vapor 28 . The cross-sectional high-resolution TEM image in Fig.…”

Nucleation and Layer Closure Behavior of Iridium Films Grown Using Atomic Layer Deposition

“…Assuming that the ALD-grown Ir films have a theoretical density of 22.56 g/cm 3 , the steady-state GPC corresponds to 0.052 nm/cycle, which is comparable to the previously reported value for ALD-grown Ir. 25 The invariance of the steady-state GPC with temperature was also verified using quartz crystal microbalance (QCM) analyses, as shown in Figure 1b. The change in the mass deposited per cycle at 200−300 °C was in a narrow range of 0.115−0.125 μg cm −2 cycle −1 .…”

Process Controlled Ruthenium on 2D Engineered V‐MXene via Atomic Layer Deposition for Human Healthcare Monitoring

“…ALD is an emerging atomic‐level control technique to deposit the precious or rarest noble metals (Pt, Ir, Os, Pd, Rh, and Ru) as single metal atoms or clusters or a few nanometers uniforms and high‐quality thin films through their self‐limiting growth and precision. [ 10 ] The selective deposition of Ru on V‐MXene in its atomic or cluster form could significantly alter the surface chemistry and overall electronic properties. Also, the connectivity among the V‐MXene layers facilitates better electrical contact throughout the structure through the metal‐MXene embedded heterostructure.…”