Horizontal-to-Vertical Transition of 2D Layer Orientation in Low-Temperature Chemical Vapor Deposition-Grown PtSe₂ and Its Influences on Electrical Properties and Device Applications

Abstract

Two-dimensional (2D) transition-metal dichalcogenides (2D TMDs) in the form of MX2 (M: transition metal, X: chalcogen) exhibit intrinsically anisotropic layered crystallinity wherein their material properties are determined by constituting M and X elements. 2D platinum diselenide (2D PtSe2) is a relatively unexplored class of 2D TMDs with noble-metal Pt as M, offering distinct advantages over conventional 2D TMDs such as higher carrier mobility and lower growth temperatures. Despite the projected promise, much of its fundamental structural and electrical properties and their interrelation have not been clarified, and so its full technological potential remains mostly unexplored. In this work, we investigate the structural evolution of large-area chemical vapor deposition (CVD)-grown 2D PtSe2 layers of tailored morphology and clarify its influence on resulting electrical properties. Specifically, we unveil the coupled transition of structural–electrical properties in 2D PtSe2 layers grown at a low temperature (i.e., 400 °C). The layer orientation of 2D PtSe2 grown by the CVD selenization of seed Pt films exhibits horizontal-to-vertical transition with increasing Pt thickness. While vertically aligned 2D PtSe2 layers present metallic transports, field-effect-transistor gate responses were observed with thin horizontally aligned 2D PtSe2 layers prepared with Pt of small thickness. Density functional theory calculation identifies the electronic structures of 2D PtSe2 layers undergoing the transition of horizontal-to-vertical layer orientation, further confirming the presence of this uniquely coupled structural-electrical transition. The advantage of low-temperature growth was further demonstrated by directly growing 2D PtSe2 layers of controlled orientation on polyimide polymeric substrates and fabricating their Kirigami structures, further strengthening the application potential of this material. Discussions on the growth mechanism behind the horizontal-to-vertical 2D layer transition are also presented.

Two-Dimensional Platinum Diselenide: Synthesis, Emerging Applications, and Future Challenges

“…In 2015, Wang et al [25] firstly fabricated a single crystal monolayer PtSe 2 by direct selenization of Pt (111). Han et al [114] prepared large-scale 2D PtSe 2 with different thickness on SiO 2 /Si substrate. Figure 8b shows the photograph of the PtSe 2 film with different thickness on SiO 2 /Si substrate.…”

“…Since the pre-deposition process and post-selenization process are carried out in relatively mild condition, the PtSe 2 film can be prepared on arbitrary substrates. Besides the conventional Si [33,115,116], Si/SiO 2 [32,33,55,94,112,114,[117][118][119][120][121][122][123][124], and Sapphire substrate [81,125,126], 2D PtSe 2 film has been successfully grown on fused quartz [31,84,125], fluorine-doped tin oxide (FTO) [127,128], gallium nitride (GaN) [129], and polyimide [114]. Figure 8c shows the PtSe 2 on the surface of flexible polyimide [41,114].…”

Tuning the orientation of few-layer MoS2 films using one-zone sulfurization

“…13 A similar mechanism is proposed also for PtSe 2 lms grown by rapid selenization. 16 Shang et al 36 proposed a mechanism controlling vertical versus lateral growth of 2D MoS 2 islands where the thermodynamic growth window is guiding the deposition of MoS 2 thin lms. They pointed out that the key factors that control the growth of MoS 2 includes temperature, pressure, substrate and chemical potentials.…”

Layered PtSe2 for Sensing, Photonic, and (Opto‐)Electronic Applications

“…[38] To obtain this layered PtSe 2 with high crystal quality, diverse synthesis methods have been developed. [7,12,24,29,[39][40][41][42][43][44][45][46][47][48] In this section, we will introduce these methods and compare their advantages and disadvantages, providing a reference for the development and fabrication of PtSe 2 -based devices.…”