Exploration of Monolayer MoS<sub>2</sub> Template-Induced Growth of GaN Thin Films via Plasma-Enhanced Atomic Layer Deposition

Song, Yimeng; He, Yingfeng; Li, Yangfeng; Wei, Huiyun; Qiu, Peng; Huang, Q.; He, Zhiquan; Die, Junhui; Peng, Mingzeng; Zheng, Xin

doi:10.1021/acs.cgd.0c01650

Cited by 9 publications

(10 citation statements)

References 43 publications

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“…Heterostructures of these materials offer large untapped technological opportunities; their realization and utility rely on understanding of the material interface both for MoS 2 grown on GaN and, ultimately, the reverse. Several recent publications explored them. − Here, we offer detailed insight into the optimization of the former interface using a broad range of surface science and ex situ techniques.…”

Section: Introductionmentioning

confidence: 99%

Epitaxial Molybdenum Disulfide/Gallium Nitride Junctions: Low-Knee-Voltage Schottky-Diode Behavior at Optimized Interfaces

Yang

Coyle

Wurch

et al. 2021

ACS Appl. Mater. Interfaces

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Low turn-on (knee) voltage (∼0.3 V) Schottky-diode behavior of a four-layer (4L) MoS2/GaN junction is achieved by optimizing the in situ interface preparation of the GaN substrate prior to MoS2 overlayer growth in a vacuum system using metallic molybdenum and hydrogen sulfide gas as precursors. The process leads to a clean nitrogen-terminated GaN surface that bonds well to the MoS2 film revealing a 2 × 2 reconstruction at the interface observed in low-energy electron diffraction (LEED). Atomic force microscopy and X-ray photoelectron spectroscopy provide clear images of the GaN terraces through the MoS2 overlayer confirming close adhesion and absence of oxygen and other contaminants. Density functional theory calculations predict the formation of the 2 × 2 superstructure at a clean interface. Transport measurements show diode behavior at an on/off ratio of ∼105 for ±1 V with a forward direction for the positive voltage applied to the MoS2 layer. Combining transport and photoelectron spectroscopy measurements with theory, we deduce a Fermi-level position in the MoS2 gap consistent with interface charge transfer from MoS2 to the substrate. The high performance of the MoS2/Gan diode highlights the technological potential of devices based on GaN/MoS2 interfaces.

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Section: Introductionmentioning

confidence: 99%

Epitaxial Molybdenum Disulfide/Gallium Nitride Junctions: Low-Knee-Voltage Schottky-Diode Behavior at Optimized Interfaces

Yang

Coyle

Wurch

et al. 2021

ACS Appl. Mater. Interfaces

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“…Panels a and b in Figures show the schematic structures of S1 and S2, respectively. Because the film’s characteristics under direct deposition at 260 °C have been studied, S0 is used here just to make a quick comparison. Figure c shows XRD spectra of three samples.…”

Section: Resultsmentioning

confidence: 99%

“…A larger version of S2 (see Figure d) shows a boundary above the substrate of 3.56 nm. The deposition rate (also called growth per cycle, GPC) of GaN at 260 °C was found to be around 0.65 nm/cycle . Therefore, the 3.56 nm thick layer adjacent to the substrate is considered grown through the first 60-cycle growth at the low temperature.…”

Section: Resultsmentioning

confidence: 99%

“…Standard triethylgallium (TEGa) and Ar/N 2 /H 2 (1:3:6) plasma gas were used as precursors with a flow rate of 5 sccm, the plasma power was 60 W. A detailed PEALD experimental process and the parameters applicable to GaN/mono-MoS 2 system have been reported in our previous work . For S0 and S1, all else being equal, 360-cycle GaN was directly deposited on the substrate at 260 °C (according to ref ) and 320 °C, respectively. The known TEGa homogeneous pyrolysis temperature is ∼350 °C, and thus 320 °C was adopted to avoid the decomposition.…”

Section: Methodsmentioning

confidence: 99%

“…Here, using mono-MoS 2 as the substrate for the PEALD-GaN growth has succeeded in living up to the expectation of suppressing the interfacial layer. In our previous work, we had attempted the direct deposition of ultrathin GaN films (0.5–40 nm) on mono-MoS 2 layers by PEALD using triethylgallium and Ar/N 2 /H 2 plasma precursors at 260 °C . It was found that GaN crystallized on MoS 2 without any interfacial layer and shows a clear interface structure.…”

Section: Introductionmentioning

confidence: 99%

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Two-Step Deposition of an Ultrathin GaN Film on a Monolayer MoS₂ Template

Song

et al. 2022

ACS Appl. Mater. Interfaces

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Ultrathin gallium nitride (GaN) application can be profoundly influenced by its quality, especially the issue of amorphous interfacial layers formed on conventional substrates. Herein, we report a two-step deposition of an ultrathin GaN film via the plasma-enhanced atomic layer deposition (PEALD) technique on a mono-MoS2 template over a SiO2/Si substrate for quality improvement, by starting the deposition temperature at 260 °C and then ramping it to 320 °C. It was found that a lower initiating deposition temperature could be conducive to maintaining the mono-MoS2 template to support the subsequent growth of GaN. Compared to the control group of one-step high-temperature deposition at 320 °C, ideal layer-by-layer film growth is achieved at the low temperature of the two-step method instead of island formation, leading to the direct crystallization of GaN on the substrate with a rather sharp interface. Structural and chemical characterizations show that this two-step method produces a preferred [0001] orientation of the film originating from the interface region. Additionally, the improved two-step ultrathin GaN displays a smooth surface roughness as low as 0.58 nm, a low oxygen impurity concentration of 3.6%, and a nearly balanced Ga/N stoichiometry of 0.95:1. Our work paves a possible way to the feasible fabrication of ultrathin high-quality PEALD-GaN, and it is promising for better performance of relevant devices.

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Tunable Encapsulation and Doping of Monolayer MoS₂ by In Situ Probing of Excitonic Properties During Atomic Layer Deposition

Henning

Levashov

Qian

et al. 2023

Adv Materials Inter

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suppressed, they may replace or augment silicon (Si) to overcome scaling and performance limitations of current semiconductor technologies. [5] However, few-and single-layer 2D materials are supremely sensitive to their dielectric environments, which must be controlled on the atomic level in a scalable manner to make full use of their intrinsic properties in optical and electronic device applications. [4] This represents a considerable challenge, since most conventional techniques used for dielectric or metal integration in semiconductor technology, such as high-temperature oxidation, sputtering, evaporation, and chemical vapor deposition (CVD), can degrade the 2D crystal as a consequence of high energy atoms impacting the surface [6] or gas-phase reactants interacting with the 2D material at elevated temperatures. In contrast, atomic layer deposition (ALD) relies on the sequential injection of gasphase reactants into a reactor chamber at moderate temperatures (<300 °C) and provides a delicate route to the controlled and large-scale deposition of thin films on sensitive substrates.Although ALD offers considerable advantages for 2D/3D materials integration, conformal deposition on 2D materials without the introduction of defects has proven to be challenging due to the lack of reactive sites on the fully coordinated basal planes of vdW materials. [7] For the realization of continuous and ultrathin coatings by ALD, seed layers on 2D nanosheets have been demonstrated to facilitate nucleation and yield uniform ALD coatings, [8] but their application is incompatible with large-scale manufacturing and may reduce interface stability during device operation. As an alternative, gas-phase surface activation prior to or during ALD, including (UV) ozone treatment [7a,9] or plasma-assisted approaches, [10] can be easily combined with the growth process. However, such treatments can be deleterious to the 2D crystal and introduce additional defects. [11] In this regard, there is a pressing need to understand the evolution of the optoelectronic characteristics of 2D materials during growth of films on their surfaces, and especially during the critical stage of nucleation when the basal plane is exposed to the reactive gas environment.Despite the importance of the initial growth regime in defining both interface and film, in situ investigations during Here, it is shown that in situ spectroscopic ellipsometry (SE) is a powerful method for probing the effects of reactant adsorption and film formation on the excitonic properties of 2D materials during atomic layer deposition (ALD), thus allowing optimization of both film growth and opto(electronic) characteristics in real time. Facilitated by in situ SE during ALD on monolayer MoS 2 , a low temperature (40 °C) process for encapsulation of the 2D material with a nanometer-thin alumina (AlO x ) layer is investigated, which results in a 2D/3D interface governed by van der Waals interactions rather than chemical bonding. Charge transfer doping of MoS 2 by AlO x is found to be an inte...

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Exploration of Monolayer MoS₂ Template-Induced Growth of GaN Thin Films via Plasma-Enhanced Atomic Layer Deposition

Cited by 9 publications

References 43 publications

Epitaxial Molybdenum Disulfide/Gallium Nitride Junctions: Low-Knee-Voltage Schottky-Diode Behavior at Optimized Interfaces

Epitaxial Molybdenum Disulfide/Gallium Nitride Junctions: Low-Knee-Voltage Schottky-Diode Behavior at Optimized Interfaces

Two-Step Deposition of an Ultrathin GaN Film on a Monolayer MoS₂ Template

Tunable Encapsulation and Doping of Monolayer MoS₂ by In Situ Probing of Excitonic Properties During Atomic Layer Deposition

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Exploration of Monolayer MoS2 Template-Induced Growth of GaN Thin Films via Plasma-Enhanced Atomic Layer Deposition

Cited by 9 publications

References 43 publications

Epitaxial Molybdenum Disulfide/Gallium Nitride Junctions: Low-Knee-Voltage Schottky-Diode Behavior at Optimized Interfaces

Epitaxial Molybdenum Disulfide/Gallium Nitride Junctions: Low-Knee-Voltage Schottky-Diode Behavior at Optimized Interfaces

Two-Step Deposition of an Ultrathin GaN Film on a Monolayer MoS2 Template

Tunable Encapsulation and Doping of Monolayer MoS2 by In Situ Probing of Excitonic Properties During Atomic Layer Deposition

Contact Info

Product

Resources

About

Exploration of Monolayer MoS₂ Template-Induced Growth of GaN Thin Films via Plasma-Enhanced Atomic Layer Deposition

Two-Step Deposition of an Ultrathin GaN Film on a Monolayer MoS₂ Template

Tunable Encapsulation and Doping of Monolayer MoS₂ by In Situ Probing of Excitonic Properties During Atomic Layer Deposition