Ultrathin Van der Waals Lanthanum Oxychloride Dielectric for 2D Field‐Effect Transistors

Abstract

Downsizing silicon‐based transistors can result in lower power consumption, faster speeds, and greater computational capacity, although it is accompanied by the appearance of short‐channel effects. The integration of high‐mobility 2D semiconductor channels with ultrathin high dielectric constant (high‐κ) dielectric in transistors is expected to suppress the effect. Nevertheless, the absence of a high‐κ dielectric layer featuring an atomically smooth surface devoid of dangling bonds poses a significant obstacle in the advancement of 2D electronics. Here, ultrathin van der Waals (vdW) lanthanum oxychloride (LaOCl) dielectrics are successfully synthesized by precisely controlling the growth kinetics. These dielectrics demonstrate an impressive high‐κ value of 10.8 and exhibit a remarkable breakdown field strength (Ebd) exceeding 10 MV cm−1. Remarkably, the conventional molybdenum disulfide (MoS2) field‐effect transistor (FET) featuring a dielectric made of LaOCl showcases an almost negligible hysteresis when compared to FETs employing alternative gate dielectrics. This can be attributed to the flawlessly formed vdW interface and excellent compatibility established between LaOCl and MoS2. These findings will motivate the further exploration of rare‐earth oxychlorides and the development of more‐than‐Moore nanoelectronic devices.

Controllable Synthesis of Transferable Ultrathin Bi2Ge(Si)O5 Dielectric Alloys with Composition-Tunable High-κ Properties

“…To illustrate the superior high-κ characteristic of the BiGe(Si)O 5 dielectric alloy, we benchmark the value with the reported representative vdW dielectrics. 15,18,20−24,34−42 As shown in Figure 3f, the ε r of >40 in Bi 2 GeO 5 is almost the highest value among CVD-grown 2D single-crystalline insulators (exemplified by ε r = 3.3 for h-BN 42 and ε r = 10.8 for LaOCl 23 ) and is apparently higher than the commercial atomic-layer-deposited (ALD) high-κ dielectrics, such as HfO 2 (ε r ≈ 16) and Al 2 O 3 (ε r ≈ 9). One of the most well-known functions for a high-κ singlecrystalline dielectric is acting as the h-BN-like vdW encapsulation layer to enhance the carrier mobility of 2D materials.…”

“…The observed composition-varied dielectric constants and breakdown field strength are consistent with the fact that Bi 2 SiO 5 has a larger band gap but lower dielectric constant than Bi 2 GeO 5 . To illustrate the superior high-κ characteristic of the BiGe­(Si)­O 5 dielectric alloy, we benchmark the value with the reported representative vdW dielectrics. ,,− ,− As shown in Figure f, the ε r of >40 in Bi 2 GeO 5 is almost the highest value among CVD-grown 2D single-crystalline insulators (exemplified by ε r = 3.3 for h -BN and ε r = 10.8 for LaOCl) and is apparently higher than the commercial atomic-layer-deposited (ALD) high-κ dielectrics, such as HfO 2 (ε r ≈ 16) and Al 2 O 3 (ε r ≈ 9).…”

“…Thanks to the advantages of enhancing the carrier mobility and reducing gate hysteresis of 2D transistors, − a variety of van der Waals (vdW) single-crystalline 2D insulators with high-κ nature are identified as the gate dielectrics to fabricate high-performance devices, including CaF 2 (ε r = 8.4), Bi 2 SeO 5 (ε r = 15.6), VOCl (ε r = 11.7), LaOCl (ε r = 10.8), and ZrO 2 (ε r = 8–19) . Even so, the reported 2D insulators that meet the requirements to form uniform solid solutions are still rare, since the formation of insulating dielectric alloys usually needs a mixture of two or more constituent phases with similar physicochemical properties and crystal structures.…”

Entropy-Engineered Middle-In Synthesis of Dual Single-Atom Compounds for Nitrate Reduction Reaction

“…The core–electron interactions were described by the projector augmented wave (PAW) method, and the Perdew–Burke–Ernzerhof (PBE) functional was applied for the exchange-correlation interactions. A plane wave energy cutoff of 450 eV was chosen. , The large-enough convergence criteria − were set to 10 –6 eV for electronic iterations and a force threshold of 0.02 eV/Å for ionic relaxations. The DFT-D3 dispersion correction was incorporated to account for van der Waals interactions.…”

“…A plane wave energy cutoff of 450 eV was chosen. 80,81 The large-enough convergence criteria 82−84 were set to 10 −6 eV for electronic iterations and a force threshold of 0.02 eV/Å for ionic relaxations. The DFT-D3 dispersion correction was incorporated to account for van der Waals interactions.…”