Low pressure CVD growth of 2D PdSe₂ thin film and its application in PdSe₂-MoSe₂ vertical heterostructure

Abstract

Palladium diselenide (PdSe2) is a novel member of the transition metal dichalcogenide (TMD) family with layer dependent bandgap in the infrared (IR) regime with potential applications in many electronic and optoelectronic devices. Low pressure CVD (LPCVD) could be an effective way to synthesize large area 2D PdSe2 materials at low growth temperatures creating new opportunities for the widescale applications of PdSe2. Here, we report LPCVD growth of PdSe2 for the first time at a growth temperature down to 250 oC, which is significantly lower than what was previously reported. The 2 nm Pd films became 8 nm PdSe2 after selenization in the temperature range of 250 - 375 oC and no thickness variation with growth temperature was observed in our AFM study. Raman study showed narrowing of PdSe2 related peaks with increasing growth temperature suggesting improved structural quality of the films. XPS study confirmed complete selenization of the thin films to the lowest growth temperature of 250 oC. Electrical transport properties study showed resistance of the devices decrease with increasing growth temperature possibly due to the improvement of crystallinity. We also found that the devices show p-type behavior with mobilities up to 1 cm2/Vs. The good electrical quality of the film was further confirmed by demonstrating its application in fabricating PdSe2/MoSe2 vertical heterojunction which showed rectification behavior with a rectification ratio of up to 232. Kelvin probe force microscopy confirmed that the rectification behavior was originated from the work function difference of 0.76 eV between MoSe2 and PdSe2.

Gate-Tunable Responsivity of PdSe2 Nanosheet-Based Bolometric Photodetectors for Mid-Infrared Light Detection

“…The thickness of the PdSe 2 flake was measured to be about 11 nm by atomic force microscopy (AFM, Figure c). The Raman spectrum of the channel shows (Figure d) four characteristic peaks at 145.3, 208.1, 223.7, and 259.8 cm –1 , corresponding to the A g 1 , A g 2 , B 1 g 2 and A g 3 Raman modes of PdSe 2 , respectively, confirming that the channel material is multilayer PdSe 2 . – Ohmic-like contact is achieved as indicated from the linear output curves in Figure e. Due to the existence of charge traps arising from interface defects, intrinsic defects in 2D material, and gas molecular absorption, etc., FETs always show hysteresis in the transfer curve when dual gate voltage sweep is applied (Figure S1, Supporting Information).…”

Controllable Selenization Transformation from MoO2 to MoSe2 by Gas Pressure‐Mediated Chemical Vapor Deposition

“…[15,16] Although great progress has been made in the CVD optimization of MoSe 2 flakes, it is still a great challenge to grow large-area 2D MoSe 2 with uniform selenization and good quality by CVD synthesis. [17][18][19] In the selenization reaction of 2D MoSe 2 , the gas pressure of CVD chamber acts as a crucial parameter to modulate the reaction rate and diffusion rate of MoO 3 and Se precursors. It is favorable for systematically understanding the nucleation, selenization, and growth of 2D MoSe 2 .…”

“…[ 15,16 ] Although great progress has been made in the CVD optimization of MoSe 2 flakes, it is still a great challenge to grow large‐area 2D MoSe 2 with uniform selenization and good quality by CVD synthesis. [ 17–19 ]…”

Phase Engineering of Palladium Selenide Using Chalcogen Flux Control

“…PdSe 2 displays a tunable band gap from near-zero at bulk to 1.3 eV in the monolayer, making it an exciting candidate for infrared optoelectronic devices. 8 Additionally, theoretical studies predict an indirect band gap of 0.45 eV for Pd 2 Se 3 . The moderate band gap, anisotropic transport properties, and wide absorption in the solar spectrum make Pd 2 Se 3 highly desirable for optoelectronic applications.…”

“…Pd 17 Se 15 has been recently used in the hydrogen evolution reaction and as counter electrodes in dye-sensitized solar cells, illustrating thermal stability and superconducting properties due to its rich metal character. PdSe 2 displays a tunable band gap from near-zero at bulk to 1.3 eV in the monolayer, making it an exciting candidate for infrared optoelectronic devices . Additionally, theoretical studies predict an indirect band gap of 0.45 eV for Pd 2 Se 3 .…”