Step engineering for nucleation and domain orientation control in WSe2 epitaxy on c-plane sapphire

Zhu, Haoyue; Nayir, Nadire; Choudhury, Tanushree H.; Bansal, Anushka; Huet, Benjamin; Zhang, Kunyan; Puretzky, Alexander A.; Bachu, Saiphaneendra; York, Krystal; Knight, Thomas V. Mc; Trainor, Nicholas; Oberoi, Aaryan; Wang, Ke; Das, Saptarshi; Makin, Robert A.; Durbin, Steven M.; Huang, Shengxi; Alem, Nasim; Crespi, Vincent H.; Duin, Adri C. T. van; Redwing, Joan M.

doi:10.1038/s41565-023-01456-6

Cited by 29 publications

(17 citation statements)

References 53 publications

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“…For the 1° off-A-axis cut template, more than 85% of growing crystals align along the A-vector of the bulk sapphire, as determined by AFM. This insight in the early growth stage is in contrast to previous works, where the orientation of TMD domains is considered to be controlled by the step edge of the template, as the edges of TMD crystals were aligned along the step edge direction by AFM and/or scanning electron microscopy. − …”

Section: Results and Discussionmentioning

confidence: 64%

Chemical Vapor Deposition of a Single-Crystalline MoS₂ Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface

Kandybka,

Groven,

Medina Silva

et al. 2024

ACS Nano

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Recently, a step-flow growth mode has been proposed to break the inherent molybdenum disulfide (MoS 2 ) crystal domain bimodality and yield a single-crystalline MoS 2 monolayer on commonly employed sapphire substrates. This work reveals an alternative growth mechanism during the metal−organic chemical vapor deposition (MOCVD) of a single-crystalline MoS 2 monolayer through anisotropic 2D crystal growth. During early growth stages, the epitaxial symmetry and commensurability of sapphire terraces rather than the sapphire step inclination ultimately govern the MoS 2 crystal orientation. Strikingly, as the MoS 2 crystals continue to grow laterally, the sapphire steps transform the MoS 2 crystal geometry into diamond-shaped domains presumably by anisotropic diffusion of ad-species and facet development. Even though these MoS 2 domains nucleate on sapphire with predominantly bimodal 0 and 60°azimuthal rotation, the individual domains reach lateral dimensions of up to 200 nm before merging seamlessly into a single-crystalline MoS 2 monolayer upon coalescence. Plan-view transmission electron microscopy reveals the single-crystalline nature across 50 μm by 50 μm inspection areas. As a result, the median carrier mobility of MoS 2 monolayers peaks at 25 cm 2 V −1 s −1 with the highest value reaching 28 cm 2 V −1 s −1 . This work details synthesis−structure correlations and the possibilities to tune the structure and material properties through substrate topography toward various applications in nanoelectronics, catalysis, and nanotechnology. Moreover, shape modulation through anisotropic growth phenomena on stepped surfaces can provide opportunities for nanopatterning for a wide range of materials.

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Section: Results and Discussionmentioning

confidence: 64%

Chemical Vapor Deposition of a Single-Crystalline MoS₂ Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface

Kandybka,

Groven,

Medina Silva

et al. 2024

ACS Nano

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show abstract

“…3d and e). 53,62 DFT calculations also showed that S atoms have a rather negative adsorption energy and tend to adsorb onto the sapphire surface to form an S passivation layer. S passivation slightly increases the vdW interaction between MoS 2 and sapphires, and MoS 2 on S-passivated sapphires is also energetically stable.…”

Section: Growth Mechanism Of Tmds On Sapphiresmentioning

confidence: 99%

“…Zhu et al demonstrated that the growth conditions determine the extent of Al termination of the sapphire surface and the location of WSe 2 nucleation via theoretical calculations and CVD growth. 62 For sapphires with incomplete removal of OH, the oxygen remnants still present at the bottom terrace next to the step edge and WSe 2 are more inclined to nucleate at the top step edge, whereas for sapphire surfaces that are fully converted into Al termination and passivated with Se, WSe 2 stays at the bottom of the step edge. The preferred orientation of the WSe 2 structural domains is also altered due to the difference in surface termination of the sapphire substrate as well as the structure of the step edge.…”

Section: Influencing Factors Of Tmd Growth On Sapphiresmentioning

confidence: 99%

“…68 As the sapphire surface changes from OH termination to Al termination during heating, the release of H 2 O from the sapphire surface is not uniform at each location. 62 Based on the difference in oxygen dissociation energies at each position of the step, H 2 O is lost first at the top of the step and in the terrace region, and finally, at the bottom of the step. Zhu et al demonstrated that the growth conditions determine the extent of Al termination of the sapphire surface and the location of WSe 2 nucleation via theoretical calculations and CVD growth.…”

Section: Influencing Factors Of Tmd Growth On Sapphiresmentioning

confidence: 99%

“…The preferred orientation of the WSe 2 structural domains is also altered due to the difference in surface termination of the sapphire substrate as well as the structure of the step edge. 62 The surface of the substrate plays an important role in the epitaxy of TMDs. Mortelmans et al built a model that the nucleation of WSe 2 on (1 × 1) and reconstructed sapphires corresponds to different epitaxial relations.…”

Section: Influencing Factors Of Tmd Growth On Sapphiresmentioning

confidence: 99%

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Large-area single-crystal TMD growth modulated by sapphire substrates

Chen,

Cheng,

et al. 2024

Nanoscale

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Revisiting the Epitaxial Growth Mechanism of 2D TMDC Single Crystals

Li,

Zheng,

Min

et al. 2024

Advanced Materials

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Epitaxial growth of 2D transition metal dichalcogenides (TMDCs) on sapphire substrates has been recognized as a pivotal method for producing wafer‐scale single‐crystal films. Both step‐edges and symmetry of substrate surfaces have been proposed as controlling factors. However, the underlying fundamental still remains elusive. In this work, through the molybdenum disulfide (MoS2) growth on C/M sapphire, it is demonstrated that controlling the sulfur evaporation rate is crucial for dictating the switch between atomic‐edge guided epitaxy and van der Waals epitaxy. Low‐concentration sulfur condition preserves O/Al‐terminated step edges, fostering atomic‐edge epitaxy, while high‐concentration sulfur leads to S‐terminated edges, preferring van der Waals epitaxy. These experiments reveal that on a 2 in. wafer, the van der Waals epitaxy mechanism achieves better control in MoS2 alignment (≈99%) compared to the step edge mechanism (<85%). These findings shed light on the nuanced role of atomic‐level thermodynamics in controlling nucleation modes of TMDCs, thereby providing a pathway for the precise fabrication of single‐crystal 2D materials on a wafer scale.

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Step engineering for nucleation and domain orientation control in WSe2 epitaxy on c-plane sapphire

Cited by 29 publications

References 53 publications

Chemical Vapor Deposition of a Single-Crystalline MoS₂ Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface

Chemical Vapor Deposition of a Single-Crystalline MoS₂ Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface

Large-area single-crystal TMD growth modulated by sapphire substrates

Revisiting the Epitaxial Growth Mechanism of 2D TMDC Single Crystals

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Step engineering for nucleation and domain orientation control in WSe2 epitaxy on c-plane sapphire

Cited by 29 publications

References 53 publications

Chemical Vapor Deposition of a Single-Crystalline MoS2 Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface

Chemical Vapor Deposition of a Single-Crystalline MoS2 Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface

Large-area single-crystal TMD growth modulated by sapphire substrates

Revisiting the Epitaxial Growth Mechanism of 2D TMDC Single Crystals

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Product

Resources

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Chemical Vapor Deposition of a Single-Crystalline MoS₂ Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface

Chemical Vapor Deposition of a Single-Crystalline MoS₂ Monolayer through Anisotropic 2D Crystal Growth on Stepped Sapphire Surface