Atomic layer deposition of two-dimensional layered zirconium sulfide

Abstract

Zirconium disulfide (ZrS2) is a two-dimensional (2D) layered transition metal dichalcogenide (TMDC) and has important implications in optoelectronics and energy storage. Despite some research efforts reported to date for synthesizing 2D ZrS2, there still lacks a method to grow large-scale continuous ZrS2 thin films. In this study, we developed a low temperature vapor-phase process for controllably growing zirconium sulfide (ZrSx) films via atomic layer deposition (ALD), using tetrakis (dimethylamido)zirconium (TDMA-Zr) and H2S as the precursors in the range of 75–300 °C. We verified the self-limiting growth behavior of the ZrSx ALD using an in-situ quartz crystal microbalance (QCM). Furthermore, we characterized the resultant ZrSx films using a suite of instruments, including scanning electron microscopy (SEM), synchrotron X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). The results showed that the growth per cycle (GPC) of the ZrSx films varies with temperature and decreases from ∼1.2 Å/cycle at 75 °C to ∼0.3 Å/cycle at 300 °C. The as-deposited films are mainly amorphous in all the temperatures and have an S/Zr ratio varying from ∼2 to 1. Very interestingly, our in situ annealing HR-TEM analyses revealed that the resultant films could transform from an amorphous layer into a layer of crystalline nanoparticles of 2D ZrS2 with increasing temperatures up to 1000 °C. We also confirmed that the as-deposited ZrSx films are electrochemically active and show promising capability as an anode material for lithium-ion batteries (LIBs). Thus, this study represents a new ALD process for ZrSx, which may have important applications in multiple areas.