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. 2025 Jan 13;5(1):1–8. doi: 10.1021/acsnanoscienceau.4c00050

Phase Controlled Metalorganic Chemical Vapor Deposition Growth of Wafer-Scale Molybdenum Ditelluride

Bum Jun Kim †,‡, Derick Tseng †, David Dang §, Jiayun Liang †, Vitali Soukhoveev ∥, Andrei Osinsky ∥, Ke Wang ⊥, Ho Wai Howard Lee §,#, Zakaria Y Al Balushi †,‡,*
PMCID: PMC11843501  PMID: 39990112

Abstract

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Metalorganic chemical vapor deposition (MOCVD) has become a pivotal technique for developing wafer-scale transition metal dichalcogenide (TMD) 2D materials. This study investigates the impact of MOCVD growth conditions on achieving uniform and selective polymorph phase control of MoTe2 over large wafers. We demonstrated the controlled and uniform growth of few-layer MoTe2 in pure 2H, 1T′, and mixed phases at various temperatures on up to 4 in. C-plane sapphire wafers with hexagonal boron nitride templates. At 600 °C, high-quality 2H-MoTe2 was obtained within a narrow temperature window, verified with absorption and TEM analysis. In addition, we observed strong exciton–phonon coupling effects in multiwavelength Raman spectroscopy when the excitation wavelength was in resonance with the C-exciton. Our findings indicate that temperature-induced Te vacancies play a crucial role in determining the MoTe2 phase. This study highlights the importance of precise control over the MOCVD growth temperature to engineer the MoTe2 phase of interest for device applications.

Keywords: MOCVD, MoTe2, polymorph, exciton−phonon coupling, vacancies

Two-dimensional (2D) materials, with thicknesses of only a few atoms and dominated by van der Waals (vdW) interactions, have attracted considerable attention due to their extraordinary nanoscale properties, which are not observable in bulk materials. Among these materials, transition metal dichalcogenides (TMDs) like molybdenum ditelluride (MoTe2) have been extensively studied due to their numerous stable polymorphs, particularly the 2H semiconducting and 1T′ metallic phases.1 The 2H semiconducting phase, characterized by a hexagonal crystal structure, exhibits an indirect-to-direct bandgap transition, shifting from ∼0.8 eV in the bulk to ∼1.1 eV at the monolayer limit.2 This direct bandgap makes 2H-MoTe2 a viable candidate for next-generation optoelectronic devices. Conversely, the 1T′ metallic phase, which possesses an orthorhombic crystal structure and higher electrical conductivity, demonstrates intriguing properties, especially during its transition to the Td phase at low temperatures.3 In TMDs, the thermodynamic stability of a given polymorph is ascribed by the ground state filling of the transition metal d orbitals.4 Each TMD polymorph displays a unique situational filling on the basis of crystal field theory. Notably, MoTe2 has the lowest energy difference between the 2H and 1T′ phases among the TMDs,5,6 making it a promising 2D material for achieving reversible phase switching via strain, charge, and electric fields.7−10 These transformations are crucial for the development of energy efficient logic and nonvolatile memory devices,11 as reducing the energy barrier between the phases is expected to lower their device operating voltages. Although the 2H phase of MoTe2 is the most thermodynamically stable polymorph, the controlled growth of MoTe2 thin films over large wafers remains limited.

Metalorganic chemical vapor deposition (MOCVD) has emerged as a crucial method for the advanced manufacturing of wafer-scale 2D materials for devices.12 However, the growth of transition metal ditellurides by MOCVD has been limited.13−16 One of the major challenges in the growth of TMDs by MOCVD is the significant effect of the temperature on the adatom surface mobility of transition metals and surface desorption rate of chalcogen species during thin film growth. Generally, transition metals exhibit high melting points and extremely low vapor pressures, while chalcogens possess high vapor pressures and low melting points. High temperatures are necessary to enhance the surface mobility of transition metals, thereby improving the domain size and the crystallinity of coalesced films over large wafer areas. However, these high temperatures also result in significant desorption of chalcogen adatoms from the surface, creating chalcogen vacancies in the crystal. Evidently, tellurium (Te) vacancies in bulk crystals can regulate the phase stability of the 2H and 1T′ polymorphs in MoTe2.17 This influence of vacancies on phase stability was first corroborated in laser annealing experiments by Cho et al., where laser treatment of exfoliated bulk crystals led to the creation of Te vacancies that induced a transformation of the 2H phase of MoTe2 to the 1T′ phase once a threshold vacancy concentration of Te was surpassed.18 Binding energy calculations of the 2H and 1T′ phases of MoTe2 as a function of the Te vacancy concentration in the crystal also show that the 1T′ polymorph phase becomes more stable than the 2H phase once the vacancy concentration in the monolayer exceeds ∼3%.19,20 During the growth of TMDs by MOCVD, it is possible to compensate for the formation of chalcogen vacancies, since their equilibrium concentration can be altered by (1) the growth temperature and (2) the chalcogen-to-transition metal source flux ratios. These parameters can be precisely controlled in various MOCVD reactor designs. This precise control is why MOCVD is considered the best method for growing MoTe2 over large wafers.

In this study, we investigated the impact of temperature on the growth of MoTe2 by MOCVD to achieve a uniform and selective phase control over large wafers. We demonstrate the controlled, uniform growth of few-layer MoTe2 thin films of pure 2H, 1T′, and mixed polymorphs at various growth temperatures on ultraflat templates of hexagonal boron nitride (hBN) produced on 4-in. C-plane sapphire (Al2O3) substrates.21 A high-speed rotating disc MOCVD reactor was utilized to grow MoTe2 using di-isopropyl telluride ((i-C3H7)2Te) and molybdenum hexacarbonyl (Mo(CO)6) as precursor sources and hydrogen as the carrier gas. We observed a noticeable color change across samples grown at 450–800 °C, indicating changes in the optical absorption properties and thus polymorph purity. These observations were corroborated using Raman spectroscopy as well as X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) of sample cross sections. Our findings indicate that Te vacancies, induced by temperature, play a crucial role in determining the phase of MoTe2. This work highlights the importance of temperature control and uniformity in precisely engineering the polymorph phase of MoTe2, paving the way for its potential applications in nanoscale devices.22

Results and Discussion

The growth of MoTe2 on our hBN/sapphire templates is governed by single-atom vacancies that enhance nucleation density, leading to accelerated growth, similar to observations reported in MOCVD growth of WSe2 by Zhang et al.24 We systematically investigated the influence of the growth temperature on the optical properties of MoTe2 thin films through a series of controlled MOCVD experiments. After a 30 min MOCVD growth of MoTe2 on 4-in. hBN templates produced on single-side polished sapphire wafers (see the Experimental Methods), we observed a noticeable color change between samples grown at 600 and 700 °C, transitioning from a darker brown color at 600 °C (Figure 1a) to a pink hue at 700 °C (Figure 1a, inset). This change suggests variations in the optical properties within this temperature range. A more detailed analysis of the color change from grown samples is shown in Supporting Figure S1. Figure 1b shows the absorption spectra of MoTe2 obtained from room-temperature angle-dependent transmission–reflection measurements. A schematic of the setup is highlighted in Figure S2. The measurements were conducted on samples grown at 600 and 700 °C on hBN templates atop double-side polished sapphire. The spectra were observed at angles of 6° and 30°. All samples were encapsulated with poly(methyl methacrylate) (PMMA) to prevent oxidation during measurements. The results, analyzed within the energy range of 1 to 3 eV, reveal excitonic features in the absorption spectra indicative of the 2H phase of MoTe2. Specifically, the A-exciton is located around 1.09 eV, the B-exciton around 1.37 eV, and the C-exciton around 1.82 eV. These exciton features are blue-shifted compared to ab initio calculated values for monolayer 2H-MoTe2 (Figure 1b, dashed lines),23,26 likely due to variations in thickness, strain, and changes in the dielectric environment. Notably, the B-exciton feature observed in our absorption spectra is significantly diminished. Ab initio calculations suggest that the oscillator strength of the B-exciton is highly sensitive to doping,26 which may arise from tellurium vacancies or excess tellurium in our films. The high tellurium-to-transition metal ratio, ∼1500, used in the growth of these samples could also result in p-doping, commonly observed in bulk crystal growths of MoTe2.27,28 Thus, the pronounced excitonic behavior observed in MoTe2 grown at 600 °C indicates high crystallinity in the grown 2H phase of MoTe2. In contrast, the lack of noticeable excitonic behavior in MoTe2 grown at 700 °C suggests the formation of the 1T′ phase.

Figure 1.

Figure 1

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(a) Images of grown MoTe2 on 4 in. hBN/sapphire wafers at 600 °C, with the inset showing the sample grown at 700 °C. (b) Angle-dependent absorption spectrum of the MoTe2 sample grown at 600 °C (red) and 700 °C (blue). The dashed lines in the absorption spectrum (b) indicate the positions of ab initio calculated A-, B-, and C-excitons in undoped monolayer 2H-MoTe2 from ref (23).

To understand the impact of temperature on the phase stability of MoTe2, we conducted angle-dependent absorption and multiwavelength Raman studies on thin film samples grown at temperatures ranging from 450 to 800 °C. The absorption measurements are summarized in Figure 2. In the graph, solid lines represent results measured at 6°, while dotted lines indicate results measured at 30°. The differences caused by the transmission–reflection angle are minimal. In samples grown at 450 and 500 °C, no significant peaks were observed, indicating the absence of excitons typically associated with the 2H phase of MoTe2. However, samples grown at 550 and 600 °C displayed clear peaks corresponding to the A-exciton and C-exciton, suggesting the successful formation of the 2H phase of MoTe2. For samples grown at temperatures from 650 to 800 °C, exciton peaks associated with the 2H phase of MoTe2 were not observed. It is suspected that at temperatures above 600 °C a phase transition to the 1T′ phase of MoTe2 occurs, causing the disappearance of excitonic behavior. At lower temperatures, the absence of exciton features could be attributed to the poor crystalline quality of the samples, possibly due to limited adatom surface mobility. These findings underscore the narrow temperature window required to stabilize the semiconducting 2H phase of MoTe2 in MOCVD grown thin films.

Figure 2.

Figure 2

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Absorption spectrum of MoTe2 samples grown at temperatures ranging from 450 to 800 °C. The inset highlights the red shift of the C-exciton for samples grown at 600 °C compared to those grown at 550 °C.

Notably, a comparison between samples grown at 550 and 600 °C reveals a red shift in the C-exciton peak position with increasing temperature (Figure 2, inset). This shift, along with the full width at half-maximum (fwhm) of the C-exciton peak, serves as a valuable probe for gaining fundamental insights into the evolution of polymorphs during synthesis and understanding the complex chemical processes present throughout the growth of TMDs. It has been shown that distinct optical signatures in the C-exciton peak are related to the edge states of evolving TMD domains.29,30 Bond stretching due to strain should shift the C-exciton peak to lower energies, while bond deformation can affect the fwhm.29 Additionally, an increase in the number of layers can also lead to a shift of the C-exciton peak position to lower energies.30,31 To elucidate the origin of the observed red shift, we analyzed the surface morphology of the films using atomic force microscopy (AFM) and measured the root-mean-square (RMS) roughness of each sample (Figure S3). Samples grown at 450 and 500 °C were relatively flat, with an RMS roughness value of ∼0.39 nm. However, samples grown at 550 and 600 °C, which exhibited clear exciton features for the 2H phase of MoTe2, showed distinct differences. At 550 °C, the RMS roughness was ∼0.94 nm, with small equiaxed domains observable. At 600 °C, the RMS roughness increased to ∼1.95 nm, indicative of grain growth. The red shift in the C-exciton peak position at 600 °C can thus be attributed to strain effects resulting from the enhanced grain size. Overall, both A- and C-exciton shifts are highly sensitive to external factors (e.g., lattice structure strain and temperature). However, due to the differences in their origins within the electronic band structure, the C-exciton is more sensitive to changes in strain due to the band nesting effect as investigated by Mennel et al. in exfoliated monolayers.30

Raman spectroscopy is a powerful technique for probing the vibrational and optical properties of 2D materials, especially under resonant excitation, which enables the investigation of symmetry-dependent exciton–phonon coupling.32,33 To distinguish between the 2H and 1T′ phases in our samples, we conducted multiwavelength Raman analysis using three laser wavelengths: 785, 660, and 488 nm. Notably, the 660 nm laser coincides near the C-exciton peak position in our MoTe2 samples grown at 550 and 600 °C (Figure 2a). All measurements were performed with PMMA-encapsulation under low laser excitation (∼6.5 mW) and short exposure times (5 s) to prevent photoinduced sample heating and degradation. The Raman spectrum of 2H-MoTe2 typically displays prominent first-order peaks from the out-of-plane A1g and in-plane E12g modes.34 These first-order Raman modes were clearly observed in our samples grown at 600 °C (Figure 3a), with both the A1g and E12g modes present, as detailed in Supporting Table S1. Interestingly, the intensity of the out-of-plane A1g mode was significantly stronger at longer wavelengths (660 and 785 nm) compared to the in-plane E12g mode under 488 nm laser excitation. This resonant out-of-plane phonon behavior, consistent with studies of TMDs,34−37 suggests that the A1g mode becomes more pronounced at excitation energies near the C-exciton. In fact, optical pump–probe measurements of 2H-MoTe2 revealed intense, long-lived coherent oscillations within the spectral range of excitons, attributed to the excitation of the out-of-plane A1g mode, highlighting strong coupling between excitons at ∼1.8 eV and coherent phonons in MoTe2.38,39 While the study by Sayers et al. was attributed to resonant enhancement of the B-exciton,38 our results align with the C-exciton peak position of ∼1.8 eV, as calculated by Champagne et al. which is also located at the same energy.23 Moreover, in samples grown at 600 °C and excited with the 785 nm laser, we observed a second-order Raman peak between ∼137 and 142 cm–1, attributed to a second-order E12g(M)-LA(M) mode,40−42 and a broad peak between ∼205 and 207 cm–1, potentially attributed to 2LA(M), which represent in-plane collective movements of lattice atoms.43 These second-order Raman modes may be amplified by strain-induced band nesting effects,30,31 resulting in enhanced optical absorption through indirect electronic transitions or strong electron–phonon coupling. Unlike samples grown at 600 °C, the 700 °C samples showed only the 1Ag and 2Ag peaks of the 1T′ phase of MoTe2 (Figure 3a, 488 nm, Table S2). These peaks were gradually quenched in intensity under 660 and 785 nm laser excitation.

Figure 3.

Figure 3

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(a) Multiwavelength (488, 660, and 785 nm) Raman investigation of MoTe2 films grown at 600 and 700 °C. (b) Raman analysis of the 1T′-to-2H transformation by monitoring the evolution of the A1g, 1Ag, and E12g(M)-LA(M) modes. (c) Evolution of the E12g, A1g, and 1Ag modes in samples grown at 450 to 600 °C. (b) and (c) utilize 785 and 488 nm laser excitations, respectively. (d) Raman analysis of the 2H-to-1T′ transformation by monitoring the 1Ag and 2Ag modes in samples grown at 650 to 800 °C using 488 nm laser excitation. Red symbols = 1T′; blue symbols = 2H; yellow symbols = Te.

To assess the phase evolution of MoTe2, we conducted Raman measurements across the growth temperature range from 450 to 800 °C. Under 785 nm excitation (Figure 3b and Table S3), the sample grown at 450 °C exhibited the A1g mode (170.03 cm–1) associated with the 2H phase of MoTe2 with a shoulder peak ∼162.48 cm–1 (1Ag) indicating the 1T′ phase in addition to the peak at 124.27 cm–1 related to excess Te on the sample surface.44 As the growth temperature increased to 600 °C, the A1g mode intensity was enhanced, along with the appearance of the second-order E12g(M)-LA(M) mode, indicating the dominance of the 2H phase. This suggests that, at lower temperatures, the samples exhibit mixed phases, with the 2H phase becoming more prominent as the growth temperature rises. A similar trend is observed for the E12g mode collected under 488 nm excitation (Figure 3c, Table S4). However, at temperatures above 650 °C (Figure 3d, Table S5), the A1g and E12g peaks disappeared, replaced by the 1Ag (163.92 cm–1) and 2Ag (257.1 cm–1) peaks characteristic of the 1T′ phase of MoTe2. No significant changes were noted in the Raman spectra between 650 and 750 °C. However, at 800 °C, the peaks became weaker and broader, indicating degradation of the sample, likely due to increased Te vacancy formation at elevated growth temperatures. This was corroborated by AFM results (Figure S3), showing increased RMS roughness and poor surface morphology. These findings suggest that, at low temperatures, a mixed 1T′/2H phase can be stabilized, similar to films produced by low temperature tellurization of molybdenum in previous studies.45,46 However, the 2H phase tends to dominate at 550 and 600 °C in our MOCVD grown samples, as evidenced by clear excitonic features in our absorption measurements (Figure 2). At temperatures above 650 °C, the 1T′ phase becomes dominant, consistent with previous observation in bulk grown single crystals.

To elucidate the chemical states of our grown MoTe2 thin films, we conducted an XPS analysis of our grown samples. The binding energies of Mo 3d and Te 3d core levels are presented in Figures 4a and 4b, respectively. For samples grown at 600 °C, the Mo 3d3/2 and Mo 3d5/2 peaks are positioned at 228.3 eV (red curve) and 231.4 eV (blue curve), consistent with the 2H phase of MoTe2.47 Additionally, the reduced intensity of oxides in the Mo and Te 3d peaks at 600 °C indicates the high chemical stability of the 2H phase of MoTe2. Below 600 °C, while oxide peaks become more prominent, the 1T′ phase of MoTe2 also becomes more apparent in the Mo 3d5/2 and 3d3/2 core levels, suggesting that MoTe2 at these temperatures exhibits a mixed 2H/1T′ phase as corroborated by our Raman measurements (Figure 3b). Our XPS analysis also highlights that the enhanced phase fraction of the 1T′ phase at lower temperatures makes the films more susceptible to oxidation. Interestingly, at 650 °C, a mixed 2H/1T′ phase is also seen, with both 2H and 1T′ Mo 3d5/2 and 3d3/2 peaks coexisting and the Te 3d (Figure 4b), with peaks located at 573.1 eV (red-curve) and 583.5 eV (blue-curve), further confirming these observations. Samples grown at 650 °C and above show peaks corresponding to the 1T′ phase, specifically the Mo 3d5/2 and 3d3/2 peaks at 228.3 eV (orange-curve) and 572.9 eV (purple-curve), with the intensity of the 2H phase peaks diminishing in samples grown beyond 700 °C. This indicates that, at higher temperatures, the 1T′ phase becomes thermodynamically favorable, likely due to the enhanced formation of Te vacancies at elevated growth temperatures. Our findings corroborate our Raman and absorption measurements, which show that mixed phases dominate at lower growth temperatures. Growing samples beyond the narrow growth window required to stabilize the 2H phase leads to the stabilization of the 1T′ phase. However, whenever the phase fraction of the 1T′ phase increases in the sample, either at lower or higher temperatures, the samples become more prone to oxidation due to the high chemical reactivity of the 1T′ phase of MoTe2.

Figure 4.

Figure 4

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(a) and (b) XPS spectra of Mo 3d and Te 3d core levels, respectively. Deconvolution fittings were performed to identify the fractions of 2H- and 1T′ phases based on the binding energy positions of Mo (3d3/2, 3d5/2) and Te (3d3/2, 3d5/2).

Moreover, we performed STEM analysis on cross-sectional samples of MoTe2 grown at 600 and 700 °C to assess their structural quality. These samples show good uniformity across the wafer, as evident from large area ellipsometry and Raman mapping (Figure S4). Figure 5a demonstrates that the 2H phase of MoTe2 grown at 600 °C for 30 min exhibits well-crystallized bi-to-trilayers on hBN/sapphire templates. The energy-dispersive X-ray spectroscopy (EDX) mapping of the 2H phase of the MoTe2 cross section shows a uniform distribution of Mo and Te within the layers (Figure 5b). Although STEM analysis shows bi-to-trilayer formation after 30 min of growth, our Raman analysis of the in-plane E12g mode as a function of growth time indicates an initial measurable Raman signal after 5 min (Figure S5a), with a clear signal after ∼10 min of growth time, suggesting that a monolayer can form within this time frame on hBN/sapphire templates. We also monitored the Raman shift and fwhm of the A1g and E12g modes as a function of the growth time (Figures S5b and S5c). As the growth time increases, the out-of-plane A1g mode shifts to higher wavenumbers with a relatively constant fwhm, indicating an increase in the number of layers with growth time.34 However, the in-plane E12g mode decreases initially but then shifts to higher wavenumbers with a decreasing fwhm, likely due to compressive stress from grain growth as observed in the AFM images (Figure S3).48,49 In contrast, Figure 5c shows that the STEM cross section of the 1T′ phase of MoTe2 grown at 700 °C forms nonuniform layers even though the EDX maps indicate uniform Mo and Te elemental distribution (Figure 5d). The poor contrast in STEM 1T′ cross sections suggests that the films are not phase pure and suffer significant oxidation, likely due to the high chemical reactivity of the 1T′ phase, corroborating our XPS analysis (Figure 4).

Figure 5.

Figure 5

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(a, b) Cross-sectional TEM images of the 2H phase of MoTe2 grown at 600 °C, along with corresponding EDX mapping images showing the elemental distribution of Mo and Te. (c, d) Cross-sectional TEM images of the 1T′ phase of MoTe2 grown at 700 °C, along with corresponding EDX mapping images showing the elemental distribution of Mo and Te.

Conclusions

In summary, we successfully grew uniform MoTe2 thin films with controlled 2H and 1T′ phase purities on up to 4-in. hBN/sapphire substrates using MOCVD. Our findings reveal that temperature-driven changes in Te content and vacancy formation are key factors in controlling the phase and quality of MoTe2. At 600 °C, we obtained a high-quality 2H phase of MoTe2 characterized by clear A- and C-excitonic behavior. We found that the 2H phase of MoTe2 has a relatively narrow temperature window for inducing phase stability and to achieve films with high crystalline quality, with observed exciton–phonon coupling effects when the Raman laser wavelength resonates with the C-exciton peak position. Conversely, at lower growth temperatures and above 650 °C, MoTe2 transitions to the 1T′ phase, displaying distinct optical and structural properties. Achieving precise control over the MoTe2 polymorph phase on large wafers requires meticulously controlled growth conditions, which is possible in high-speed rotating disk MOCVD reactor designs. This work underscores the importance of precise phase engineering of MoTe2, paving the way for its potential applications in electronic and optoelectronic devices.

Acknowledgments

The growth of the films was primarily funded by the National Science Foundation under award# 2145022 CAREER: Phase Control in Synthetic Two-Dimensional Materials. The exciton–phonon coupling study with multiwavelength Raman was funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Contract No. DE-AC02-05-CH11231 in the Phonon Control for NextGeneration Superconducting Systems and Sensors FWP (KCAS23). We thank Agnitron Technology Inc. for providing hexagonal boron nitride (hBN) templates on sapphire for this study, and Agnitron Technology Inc. acknowledges the support of the AFWEX SBIR project FA864922P0963 for developing these hBN templates. We also thank Dr. Somilkumar Rathi for helping with ellipsometry measurements.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnanoscienceau.4c00050.

  • Description of experimental methods and supplemental figures and tables related to growth and characterization of samples (PDF)

Author Contributions

B.J.K. and D.T. performed growth and characterization of the samples, including Raman spectroscopy. Both authors contributed extensively to this work, including in the analysis and interpretation of the results. D.D. and H.W.H.L. performed transmission–reflection measurements. V.S. and A.O. provided the hBN templates for this study. J.L. performed XPS measurements. K.W. performed transmission electron microscopy sample preparation and measurements. Z.Y.A. conceived the idea, supervised the project, and wrote the manuscript with B.J.K. and D.T. All authors discussed, revised, and approved the manuscript. CRediT: Bum Jun Kim data curation, formal analysis, investigation, methodology, visualization, writing - original draft, writing - review & editing; Derick Tseng data curation, formal analysis, methodology, visualization, writing - review & editing; David Dang data curation, methodology; Jiayun Liang data curation, methodology; Vitali Soukhoveev data curation, methodology, resources; Andrei Osinsky funding acquisition, resources; Ke Wang data curation; Ho Wai Howard Lee data curation, methodology, resources; Zakaria Y. Al Balushi conceptualization, formal analysis, funding acquisition, investigation, methodology, project administration, resources, supervision, validation, visualization, writing - original draft, writing - review & editing.

The authors declare no competing financial interest.

Special Issue

Published as part of ACS Nanoscience Auspecial issue “Advances in Energy Conversion and Storage at the Nanoscale”.

Supplementary Material

ng4c00050_si_001.pdf (3MB, pdf)

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