Hybrid Gate Dielectric of MoS₂ Transistors for Enhanced Photo‐Electronic Stability

Abstract

promising channel materials for nextgeneration thin-film transistors (TFTs) because of their outstanding characteristics, such as high mobility, on/off current ratio, and saturation velocity. [1][2][3][4] Moreover, MoS 2 TFTs can potentially be used as future scaled devices because of their atomically thin nature to overcome shortchannel effects that hinder future scaling of metal-oxide-semiconductor field-effect transistors using bulk-type materials. [4][5][6] From the viewpoint of organic lightemitting diodes (OLED), MoS 2 TFTs are expected to be applied as driving transistors based on their superior performance and their potential use as flexible displays, as compared to relatively brittle materials, such as amorphous silicon and oxide semiconductors. [7][8][9] However, the device characteristics of MoS 2 TFTs heavily rely on not only the contact between MoS 2 and metal, [10] but also the interface between MoS 2 and the gate dielectric because of the atomically thin nature. Previous studies have revealed that carrier mobility, saturation velocity, hysteresis, and thermal stability of MoS 2 TFTs depend on the gate dielectric, and a suitable dielectric is required for the optimized device performance and the proper application. [11] Previous studies have reported that high-κ dielectric layer boosts the carrier mobility of MoS 2 TFTs by the charge screening effect. [12] Therefore, several high-κ dielectric layers, such as Al 2 O 3 and HfO 2 , were applied, but high-κ dielectrics inherently have functional groups including hydroxyl groups (OH − ) at the surface that are critical to the device performance.The gate dielectrics of MoS 2 TFTs are normally deposited by atomic layer deposition (ALD), which produces uniform large-scale films with highly controllable thickness at relatively low temperatures. ALD produces a wide range of dielectrics for MoS 2 TFTs based on various precursors and reactants. Recently, polymer dielectrics, such as poly(1,3,5-trimethyl-1,3,5trivinyl cyclotrisiloxane) (pV3D3), based on initiated chemical vapor deposition (iCVD) have emerged. They exhibit high uniformity, purity, low leakage, high chemical stability, and large band-gap with low-κ. [13] Therefore, iCVD-grown polymer dielectrics are used in various applications such as gate dielectrics of TMDs-based transistors, tunneling dielectrics of flash memory cells, flexible devices, and neuromorphic computing systems. [14][15][16][17]

Combination of Polymer Gate Dielectric and Two-Dimensional Semiconductor for Emerging Field-Effect Transistors

“…In addition, with the reduced interface charge trap density and top-gate geometry, the 2D MoS 2 FETs with P(V4D4-co-CHMA) showed enhanced operational and environmental stability. Similar results were reported by Park et al [ 107 ], who deposited poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (PV3D3) via iCVD between the 2D MoS 2 and Al 2 O 3 . An improved μ value was obtained in the 2D MoS 2 FETs containing the interfacial PV3D3 (~10.4 cm 2 /Vs) with reduced hysteresis in the transfer curve compared to those without PV3D3 (~6.3 cm 2 /Vs).…”

“…Moreover, this process is based on physical adsorption, which makes it possible to form a uniform, ultrathin (a few tens of nanometers) polymer dielectric film on top of dangling bond-free 2D semiconductors [ 47 , 94 ]. Therefore, by using a low processing temperature, iCVD-based polymer dielectrics enabled the fabrication of 2D semiconductor FETs with a top-gate geometry [ 40 , 106 , 107 , 108 , 109 ].…”

“…Copyright © 2018, American Chemical Society. ( f ) The V T shift with the stress time for the 2D MoS 2 FETs with the hybrid dielectric (PV3D3/Al 2 O 3 ) compared to those without the PV3D3 dielectric in NBIS measurements [ 107 ]. Copyright © 2021, John Wiley and Sons.…”

Sequential Infiltration Synthesis with Organic Co-reactants for Extensively Swollen Organic–Inorganic Hybrid Thin Films

“…Organic–inorganic hybrid thin films serve as key materials in different components including encapsulating layers , or hybrid gate dielectrics, , in electronic/optoelectronic devices, electrode protection coatings in batteries, , and active layers in solar cells. , Therefore, the deposition of these various organic–inorganic thin films constitutes one of the major categories in the field of material deposition, in which molecular layer deposition (MLD) is one of the leading techniques . MLD is similar to atomic layer deposition (ALD), a well-established method for the deposition of inorganic thin films, in which the precursors are sequentially introduced to a reactor chamber, leading to self-limiting reactions on the surface.…”

“…O rganic−inorganic hybrid thin films serve as key materials in different components including encapsulating layers 1,2 or hybrid gate dielectrics, 3,4 in electronic/optoelectronic devices, electrode protection coatings in batteries, 5,6 and active layers in solar cells. 7,8 Therefore, the deposition of these various organic−inorganic thin films constitutes one of the major categories in the field of material deposition, in which molecular layer deposition (MLD) is one of the leading techniques.…”