# Rare Mononuclear Lithium–Carbene Complex for Atomic Layer Deposition of Lithium Containing Thin Films

## TL;DR

A new lithium complex is developed for atomic layer deposition, enabling precise fabrication of lithium-containing thin films with promising thermal and structural properties.

## Contribution

A rare mononuclear NHC-stabilized lithium complex is introduced as a novel ALD precursor with favorable volatility and thermal properties.

## Key findings

- The new lithium complex has a low melting point and suitable volatility for ALD applications.
- ALD trials using the complex successfully deposited lithium silicate films with a growth per cycle of 0.95 Å.

## Abstract

Lithium is the core material of modern battery technologies and fabricating the lithium‐containing materials with atomic layer deposition (ALD) confers significant benefits in control of film composition and thickness. In this work, a new mononuclear N‐heterocyclic carbene (NHC) stabilized lithium complex, [Li(tBuNHC)(hmds)], is introduced as a promising precursor for ALD of lithium‐containing thin films. Structural characterization is performed, comparing density functional theory (DFT) and single‐crystal X‐ray diffraction (SC‐XRD), confirming a rare mononuclear structure. Favorable thermal properties for ALD applications are evidenced by thermogravimetric analysis (TGA). The compound exhibits a low melting point, clean evaporation, and its volatility parameters are encouraging compared to other lithium precursors. ALD trials using [Li(tBuNHC)(hmds)] with ozone demonstrate its effectiveness in depositing LiSi
x
O
y
films. The ALD process exhibits a saturated growth per cycle (GPC) of 0.95 Å. Compositional analysis using Rutherford backscattering spectrometry/nuclear reaction analysis (RBS/NRA), X‐ray photoelectron spectrometry (XPS), and glow discharge optical emission spectrometry (GD‐OES), confirms the presence of lithium and silicon in the expected ratios. This work not only presents a new ALD precursor but also contributes to the understanding of lithium chemistry, offering insights into the intriguing coordination chemistry and thermal behavior of lithium complexes stabilized by NHC ligands.

A new N‐heterocyclic carbene (NHC) stabilized lithium complex is introduced as a thermally stable atomic layer deposition (ALD) precursor. It features a rare mononuclear structure, suitable volatility, and a low melting point of 55 °C. ALD trials yielded lithium silicate films. This study opens new directions for NHC‐ligand chemistry in thin‐film deposition applications.