2D Heterostructures with Bi2S3 Nanowire and MoS2

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Co-Nucleus 1D/2D Heterostructures with Bi2S3 Nanowire and MoS2 Monolayer#One-Step Growth and Its Defect-Induced Formation Mechanism Yongtao Li, Le Huang, Bo Li, Xiaoting Wang, Ziqi Zhou, Jingbo Li, and Zhongming Wei ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.6b04952 • Publication Date (Web): 29 Aug 2016 Downloaded from http://pubs.acs.org on August 29, 2016

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Co-Nucleus 1D/2D Heterostructures with Bi2S3 Nanowire and MoS2 Monolayer：One-Step Growth and Its Defect-Induced Formation Mechanism Yongtao Li,‡ Le Huang,‡ Bo Li, Xiaoting Wang, Ziqi Zhou, Jingbo Li,* and Zhongming Wei* State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, P. R. China Corresponding Author. E-mail: [email protected] (Jingbo Li); [email protected] (Zhongming Wei) KEYWORDS. Heterostructure, 1D/2D, CVD growth, MoS2, Bi2S3

ABSTRACT. Heterostructures constructed by low-dimensional (such as 0D, 1D and 2D) materials have opened up the opportunities for exploring interesting physical properties and versatile (opto)electronics. Recently, the 2D/2D heterostructures, especially the atomically thin materials graphene and transition-metal dichalcogenides (TMDs) including graphene/MoS2, WSe2/MoS2 and WS2/WSe2, were efficiently prepared (by the methods of transfer technique, and chemical vapor deposition (CVD) growth, etc.) and systematically studied. But on contrast, the investigation of 1D/2D heterostructures was still very challenging and rarely reported, and the

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understanding of such heterostructures was also not well established. Herein, we demonstrate the one-step growth of heterostructure on the basis of 1D-Bi2S3 nanowire and 2D-MoS2 monolayer through the chemical vapor deposition method. Multi-means were employed and the results proved the separated growth of Bi2S3 nanowire and MoS2 sheet in heterostructure rather than forming BixMo1-xSy alloy due to their large lattice mismatch. Defect-induced co-nucleus growth, which was an important growth mode in 1D/2D heterostructures, has also been experimentally confirmed and systematically investigated in our research. Such 1D/2D heterostructures were further fabricated and utilized in the (opto)electronic devices as field-effect transistor (FET) and photodetector, and revealed its potential for multifunctional design in electrical properties. The direct growth of such nanostructure will help us to gain a better comprehension of these specific configurations, and allow device functionalities in the prospective applications.

Hetero-connection in different two-dimensional materials has attracted a lot of attentions for its interesting functions in nanoelectronics and optoelectronics. The common strategies to build heterostructures mainly involve “top down” manual layer-by-layer stacking and “bottom up” epitaxial growth by chemical vapor deposition method.1-2 In the manual stacking approach, it provides us quite a large space to design and realize the contact between many different 2D materials such as graphene/hBN, MoS2/WSe2 and MoS2/WS2, in which some great physical phenomena have also been reported.3-5 For example, van der Waals (vdWs) stacking n-type MoS2 and p-type WSe2 revealed apparent rectifying characteristic on account of their intrinsic type-II band alignment.6 Ultrafast charge transfer from MoS2 to WS2 and long lifetime of indirect excitons in MoSe2/WSe2 heterojunctions were also demonstrated.5, 7 The direct CVD


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growth of heterostructure, in comparison to manual stacking approach, possesses its own advantages which can hardly be achieved by manual manipulation or even with the help of precise instruments. The transfer process for graphene/h-BN heterostructures introduced structural uncertainties due to the random stacking between graphene and h-BN substrate.3 While precise alignment was observed for the epitaxial growth of single-domain graphene on h-BN.8-9 Lateral junction of WSe2/MoS2, where MoS2 was edge epitaxially grown along the front of monolayer WSe2 flake with atomically sharp transition in compositions, was achieved using a two-step growth method.10 A one-step growth strategy for the creation of high-quality vertically stacked as well as in-plane interconnected heterostructures of WS2/MoS2 mainly via control of the growth temperature was also reported.11 Besides the “bottom up” 2D/2D heterostructures of layered materials mentioned above, hetero-contacted 2D/3D, 1D/3D, 1D/1D and 0D/0D junctions have also been synthesized by varieties of approaches.12 For example, aligned monolayer MoS2 sheets were able to directly grow on gallium nitride (GaN) substrates, forming the lattice-matched 2D/3D vertical heterostructures.13 1D nanowires or nanorods (such as InxGa1-xAs, InAsyP1-y, ZnO and so on) were also obtained on bulk semiconductor substrates.14-16 Moreover, core-shell nanowires and nanoparticles, which composed of different components in core and in shell respectively, formed the classical 1D/1D and 0D/0D appearances in the previous researches.17-18 In the case of 1D/2D nanostructure, even though several groups have reported the InxGa1−xAs nanowires grown on transferred graphene in metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) systems,19-21 more such heterostructures could only fabricated via manual stacking or hybridizing methods.22-24 Indeed, to date, the synchronous growth of 1D/2D nanostructures was rarely reported in comparison to the other heterojunctions mentioned above,


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and the understanding of forming mechanism and physical properties of such heterostructures were still not well established. 1D semiconducting Bi2S3 nanowire was reported to possess distinct gate-tunable drainsource current behaviour and excellent photosensitive performance with fast photoresponse speed,25-26 revealing its great potential in (opto)electronic devices. On the other hand, 2D MoS2 monolayer, which consists of a layer of Mo atoms sandwiched between two layers of sulfur atoms, was also demonstrated the prominent electrical properties with high mobility of more than 200 cm2/(V·s) and on/off ratio of 108.27 Based on these knowledge, we considered that the synthesis of specific 1D/2D heterostructure with such two materials might lead an interesting way to multifunctional design for electrical properties such as band alignment (Figure S1), rectification, photodetector, etc. In broad terms, the direct growth of 1D/2D heterojunctions will also help us to gain a better comprehension of these specific configurations and allow device functionalities and properties in the prospective applications. Here, we demonstrate the one-step growth of heterostructure from 1D-Bi2S3 nanowire and 2D-MoS2 monolayer by chemical vapor deposition method. Scanning electron microscope (SEM) and atomic force microscope (AFM) revealed the fact that Bi2S3 nanowire grew above MoS2 monolayer. X-ray photoelectron spectroscopy (XPS) confirmed the existence of both MoS2 and Bi2S3, and micro-area characterization by the Auger electron spectroscopy (AES) further recognized the nanowires to be Bi2S3 while triangle sheets to be MoS2. Moreover, Raman spectra collected from the nanowire and sheet showed distinct signatures of Bi2S3 and MoS2, respectively, just in keeping with their individual growing products. High-resolution transmission electron microscope (HR-TEM) presented clear lattice morphology as well as diffraction patterns of MoS2 and Bi2S3, in which we found that Bi2S3 nanowires grew along the


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[001] direction (c-axis in orthorhombic crystal system, space group of Pbnm, JCPDS card of No. 75-1306). Detailed AFM characteristics demonstrated that the nanowire and sheet contacted with each other only at the nucleation site of the triangle MoS2 single crystal while grew separately in other area, implying the co-nucleus growth mode in the 1D-Bi2S3 nanowire/2DMoS2 monolayer heterostructure. HR-TEM characteristic illustrated that multi-defects and irregular morphology in the nucleation site gave rise to the co-nucleus behaviour in 1D/2D heterostructures, and the forming mechanism for such special performance was also investigated using first principle calculations. Such 1D/2D heterostructures were also further fabricated and utilized in the (opto)electronic devices including field-effect transistor (FET) and photodetector, and revealed their good potential in future application. RESULTS AND DISDUSSION The growing process was conducted in a CVD system, where mixture powder of MoO3 and Bi2O3 reacted with Sulfur vapor at high temperature (650 °C) and synthetized the 1DBi2S3/2D-MoS2 heterostructures on SiO2/Si substrate (Figure 1a and 1b, and detailed growing process can be seen in methods section). Typical morphologies of the heterostructure is presented in Figure 1c and S2, where we can clearly see nanowires locate on triangle sheets from the distinct differences in brightness. AFM measurement was performed and confirmed that thickness of the sheet to be about 0.98 nm (Figure 1d), illustrating monolayer nature of the sheets. Figure 1d also shows that length and diameter of the nanowire is 7.3 µm and 120 nm, respectively, and the aspect ratio is more than 60. Our experimental results reveal that the nanowires will grow longer rather than thicker for extended growing time (Figure S3). Statistical growth rate of the Bi2S3 nanowires and MoS2 sheets were counted to be 1~3 µm/min and 1~4


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µm/min respectively, in which relative growth rate of such two materials depended on relative mass ratio of Bi2O3/MoO3 sources, and higher temperature would lead to their faster growth. Meanwhile, it is worth noting that mass ratio of Bi2O3/MoO3 also plays an important role in morphology of the heterostrucutes, where too low Bi2O3/MoO3 mass ratio can only grow MoS2 sheets, while too high ratio results in thicker wires in heterostructures, Bi2O3/MoO3 mass ratio of 2~3 is a suitable range in our experiments (Figure S4). Moreover, our statistic from hundreds of heterostructures reveals that the nanowires may rotate random angle with respect to the triangle sheet. While relatively more cases are that the nanowires tend to be parallel to (~0°) or perpendicular to (~30°) one edge of the triangle sheets (Figure 1e), these two prior results may be caused by their relatively lower forming energy in such special rotating configurations,13, 28-30 and the reason for other random rotational angles will also be discussed in the following section in regard to defects.


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Figure 1. Growth and morphologies of Bi2S3/MoS2 heterostructures. (a) Schematic illustration of synthesis process for the heterostructures, in which mixture of MoO3 and Bi2O3 served as solid source and reacted with S vapor at high temperature. (b) Model of the heterostructures grown on SiO2/Si substrate, where Bi2S3 nanowires locate above triangle MoS2 sheets. (c) SEM image of typical 1D-Bi2S3/2D-MoS2 heterostructure on SiO2/Si substrate. (d) Optical image, SEM image as well as its corresponding AFM height and phase images of the nanostructure. (e) Statistical diagram of the included angle between nanowires and edges of triangle sheets, and the ellipsis indicate the repeating statistic part exceeding period of 30°.


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Figure 2. Elemental characteristics by XPS and micro-area AES measurement. (a-c) XPS spectra of the samples on SiO2/Si substrate, indicting the existence MoS2 and Bi2S3. (d-f) Microarea Auger mapping of element: S, Mo and Bi, respectively, where we can see that the triangle sheet is consisted of Mo and S atoms while the nanowire is consisted of Bi and S ones. (g) Corresponding SEM image of the MoS2/Bi2S3 heterostructrue in (d-f). (i) Detailed Auger spectrum corrected from the spot 1 (nanowire) and spot 2 (triangle sheet) in (g), and clear Bi signal appeared in the spectrum from nanowire. X-ray photoelectron spectroscopy (XPS) was utilized to identify elemental composition in the synthetic samples. The measurement revealed the existence of Mo, S and Bi elements on substrate, in which prominent peaks at 232.97 eV, 229.87 eV, 227.32 eV, 163.87 eV, 162.82 eV, and 158.57 eV were assigned to Mo (3d3/2), Mo (3d5/2), S (2s), S (2p1/2), S (2p3/2), and Bi (4f7), respectively (Figure 2a-2c). Moreover, micro-area AES mapping (Figure 2d-2f) was used for gaining the detailed elements distribution in 1D/2D heterostructure, where elements S and Mo were found to cover the whole triangle sheet while Bi appeared only in the position of nanowire. As we can see in Figure 2i and 2j, the AES spectra corrected from spot 1 (in Figure 2g) showed evident signal of Bi (at ~105 eV) while no Bi signal was detected in spot 2. Such result provided the strong evidence that triangle sheet was MoS2 while the nanowire was made up of Bi2S3. Raman and PL spectroscopy were also employed to further characterize the 1D/2D heterostructures. As showed in Figure 3a, black Raman spectrum collected from black spot (in Figure 3d) revealed intensity peaks at about 187.1 cm-1, 236.0 cm-1, 260.3 cm-1, which were just in according with Raman peaks (red line in Figure 3a) of our CVD synthetized individual Bi2S3 nanowires (Figure S5a) and previous reports.31-32 Moreover, the Raman spectrum from the green


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spot (in Figure 3d) presented the classical E2g1 and A1g peaks of MoS2, which were also in keeping with the results from our CVD growing pure MoS2 monolayer (red line in Figure 3b and samples image in Figure S5b).33 The PL emission from green spot (in Figure 3d) possessed an intensity peak at 1.84 eV. To give more visual images, Raman mappings according to the -

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intensity at 404.4 cm 1 and 236.0 cm 1 were performed and exhibited the clear morphologies of triangle sheet of MoS2 and wire-shape of Bi2S3. Indeed, the specific fingerprints of various materials attained from Raman spectroscopy provide us a definite way to identify uncertain substances. And as a consequence, both elemental and Raman results illustrate the fact of 1DBi2S3 nanowire and 2D-MoS2 monolayer in heterostructure, rather than a compound of BixMo1xSy.

Figure 3. Raman and PL characterization of Bi2S3/MoS2 heterostructure. (a) Black-line Raman spectrum was corrected at the black spot in (d), and red-line Raman spectrum was corrected from pure Bi2S3 nanowires grown by CVD method individually. (b) Green-line Raman spectrum was


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corrected at the green spot in (d) and red-line Raman spectrum was corrected from pure MoS2 monolayer grown by CVD method individually. (c) Photoluminescence spectrum taken at the green spot in (d). (d) Optical image of a Bi2S3/MoS2 heterostructure used for Raman -

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characterization. (e and f) Raman intensity mapping collected at 404.4 cm 1 and 236.0 cm 1, respectively. The measurements were performed with 532 nm laser excitation at room temperature. We transferred the samples onto Cu grid and performed HR-TEM and electron diffraction studies to gain the fine crystal morphologies of MoS2 monolayer as well as Bi2S3 nanowire in heterostructure. SAED pattern taken from the sheet displayed a typical six-fold symmetry (Figure 4a), whose set of hexagonally arranged diffraction spots could be indexed to the (001) zone plane of MoS2 layered structures.34 HR-TEM image of the flake in Figure 4b also showed the lattice structure of MoS2 monolayer where the bright spots corresponded to Mo atoms while S atoms were not displayed for their smaller atomic bulk.35-36 The bright spots of Mo illustrated distinct periodic arrangement, and distance between adjacent Mo atoms was measured to be 0.3158 nm, just was in line with that of 0.316 nm in optimized MoS2 lattice constant (Figure 4c). On the other hand, our measurement showed that nanowire in the heterostructure possessed a classical orthorhombic crystal lattice, where the SAED pattern in Figure 4d presented periodical orthogonal feature. Careful analysis of these diffraction spots revealed (001) and (020) lattice plane spacing of 0.401 nm and 0.566 nm in the nanowire. Included angle between the plane (020) and (021) was 54.7°, and plane (001) was perpendicular to plane (020). Such results were exactly in agreement with lattice structure of Bi2S3 (Figure 4f).37-39 Besides, both SAED and HR-TEM demonstrated the [001] growing direction of the Bi2S3 nanowire, whose low magnified TEM image was also showed in inset of Figure 4e. Even


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though nanowires in heterostructures grew along the specific direction, we should also note that different lattice plane of Bi2S3 could settle on the MoS2 sheets, such as the (100) plane in Figure 4e and (-110) plane in Figure S6.

The above characteristics provide us a path to gain more insight into the growth of Bi2S3/MoS2 heterostructures in CVD system. Indeed, several products, such as BixMo1-xSy alloy,40-42 2D-layered Bi2S3/MoS2 stacking heterostructure,11,

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and 1D-Bi2S3/2D-MoS2

heterostructure, have been conjectured before we conducted the synthesis experiment using mixture of Bi2O3/MoO3 as solid sources. The final outcomes revealed the fact that only 1DBi2S3/2D-MoS2 heterostructrues could be obtained by this method. The underlying mechanism of this result is believed to induced by the large difference in lattice forms of such two materials, where MoS2 belongs to hexagonal crystal system with the lattice parameters of a=0.316 nm, b=0.316 nm, c=1.820 nm, α=90°, β=90°, γ=120° (Figure 4c), while Bi2S3 belongs to orthorhombic crystal system with the lattice parameters of a=1.112 nm, b=1.125 nm, c=0.397 nm, α=90°, β=90°, γ=90° (Figure 4f). The large lattice gap made them tend to grow into MoS2 sheet and Bi2S3 nanowire individually, which have also been confirmed by AES as well as Raman characteristics in our experiments. On the other side, for purpose of simulating edgesynthetic situation for larger-area MoS2 monolayer (Figure S7),our theoretical calculation also indicates the binding energy of 17.77 eV and 5.17 eV for Mo and Bi atom filling at the Movacancy in MoS2 sheet, using the formula ∆ = − ( ) − , where ∆E is the binding energy between the individual Mo (or Bi atom) and Mo-vacancy MoS2, Etotal is the energy of the whole system, Emo(Bi) is the energy of individual Mo or Bi atom, and EMo-vacancy MoS2 is energy of the Mo-vacancy MoS2 monolayer.43-45 Obviously, the calculation result reveals that


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MoS2 sheet prefers to combine with Mo atoms rather than Bi atoms for growing larger in CVD chamber.

Figure 4. Atomic structure of the MoS2 monolayer and Bi2S3 nanowire. (a and b) SAED pattern and HR-TEM image of the nanosheet in heterostructure, where the clear honeycomb configuration matches MoS2 lattice well. (c) Optimized lattice structure of monolayer MoS2. (d) SAED pattern of the Bi2S3 nanowire in heterostructure. The exact corresponding lattice planes


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can be obtained on the basis of the measured spots distance as well as included angle, and lattice plane (001), (021) and (020) are demarcated. (e) High resolution TEM image of the nanowire, and its large area TEM image is also showed in the inset. Growing direction of the nanowire can be demarcated as [001] in the light of (d) and (e). (f) Schematic of orthorhombic crystal Bi2S3. Indeed, connection mode between Bi2S3 nanowire and MoS2 monolayer is another important issue in the 1D/2D heterostructures that has been rarely reported before. It may wonder us whether Bi2S3 nanowire connects MoS2 monolayer by line all over the area beneath the nanowire or just by one specific spot. It was fortunate for us to find the answer by means of scratching the nanowire away using a probe and exposing the underlying area so that we could obtain the exact information. Optical images of a typical Bi2S3/MoS2 heterostructure before and after being scratched were presented in Figure 5a, and AFM height and phase measurement were utilized to characterize the local region as showed in Figure 5b and 5c, respectively. The blue dashed frame indicated the area covered by nanowire before, and the green dashed circle pointed out nucleation region of the triangle MoS2 single crystal. It is clear in the AFM image that only nucleation site of the MoS2 monolayer was teared away together with the Bi2S3 nanowire and exposed the underlying SiO2 substrate, while there is no damage in the other area beneath the nanowire. Inset at the bottom right of Figure 5b illustrated AFM height profile of the black line passing through edge of the MoS2 monolayer as well as area under the nanowire, and no evident variation of height was found in the specific area, which was in accord with the result in phase image where phase of region in blue frame stayed the same as other area of the MoS2 monolayer, meaning the same component of them. Besides, further evidences were also obtained when we grew Bi2S3 nanowires individually on SiO2/Si substrate, where not only nanowires were found on the surface of substrate (Figure S5a), some suspended nanowires could also be seen at the


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edge of substrate (Figure S8). Such results provide a lesson that it is possible for Bi2S3 nanowire and MoS2 monolayer to grow individually except for a co-nucleus spot, establishing the connection in the 1D/2D heterostructures.

Figure 5. Contact and nucleation condition of the Bi2S3/MoS2 heterostructurre characterized by AFM. (a) Optical image of a typical heterostructure before and after being scratched by probe, where part of the nanowire was scratched away so that the underlying as well as nucleation region was exposed. (b) AFM height image of the magnifying red-frame area in (a). The nucleation area is marked in green dash circular ring and the blue dash frame reveals the area ever been covered by Bi2S3 nanowire. The bottom-right inset also presents the height profile along black line, indicating that no connection between the nanowire and MoS2 monolayer except for the nucleation site. (c) AFM phase image of the same area in (b), the area in green dash circular clearly shows the underlying SiO2 substrate after Bi2S3 nanowire was scratched away together with part of adjacent MoS2 nanosheet for their connection in the nucleation site.


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Figure 6. Nucleation spot of the heterostructurre characterized by HR-TEM and the energy level of heterostructures obtained using first principles calculation. (a) Optical image of typical MoS2 sheet transferred onto TEM grid. (b) HR-TEM image of MoS2 monolayer at red frame A in (a). The inset presented FFT pattern of the TEM morphology. (c-d) HR-TEM morphology of the nucleation site at the red frame B in (a). (e) Schematic illustration of MoS2 supercell with one S atom vacancy as showed as a red circle. And the yellow and grey balls denote S and Mo atoms, respectively. (f and g) Optimized model of a Bi atom located, respectively, above a common sulfur atom away from the defect and a sulfur vacancy on the basis of supercell in (e). (h) Energy level comparison of (e), (f) and (g) systems from first principles calculations. (i) Schematic illustration of MoS2 supercell with one Mo (blue circle) and two S (red circle) atom (1Mo-2S) vacancies. (j and k) Optimized model of a Bi atom located, respectively, above a sulfur atom


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away from the defect and around the 1Mo-2S vacancy on the basis of supercell in (i). (l) Energy level comparison of (i), (j) and (k). Further investigation was performed so as to gain a deeper insight into the co-nucleus behavior in 1D/2D heterostructures. The study above have indicated that Bi2S3 nanowire and MoS2 monolayer would prefer to grow individually rather than turning into alloy of BixMo1-xSy. However, previous reports have demonstrated that defects in 2D material possessed enhanced chemical reactivity with dangling bonds compared to their perfect crystal structures,35, 46-48 which was easy to form a new hybrid structures with foreign material in the defect sites. In fact, in our synthesis experiments, most of the Bi2S3 nanowires were found to connect with the MoS2 sheets in the nucleation sites (Figure S9). Accordingly, a typical triangle MoS2 sheet without Bi2S3 nanowire on was transferred onto Cu grid and characterized by HR-TEM in order to learn the nucleation situation in MoS2 sheets as well as heterostructures. Amplifying TEM images of the region A and B (in Figure 6a) were presented in Figure 6b-6d, respectively. Obvious difference can be seen from the two area where the nucleation region appears to be multilayer MoS2 with disordered morphology while the other areas are homogeneous MoS2 monolayer. In general, it is a nature for crystal to nucleate at location with higher chemical reactivity, and the disordered morphology as well as the concomitant defects (Figure S10) in nucleation site of MoS2 sheet exactly offers such a suitable surroundings to Bi2S3 nanocluster for its initial nucleation and the following growing longer into nanowire. Indeed, this forming mechanism also accounts for the various rotational angles between Bi2S3 nanowire and MoS2 triangle, where defects break the stable rotating configuration between them. And in a few cases, multi-defects in the nucleation site can also lead to the multiple nanowires grown on top of a single MoS2 triangle (Figure S11).


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Meanwhile, for a better understanding about how the defects in nucleation spot give rise to the co-nucleus behavior between MoS2 and Bi2S3 in such 1D/2D heterostructure, two types of classical defects, including one sulfur atom vacancy (Figure 6e) and 1Mo-2S atoms vacancy (Figure 6i), were taken into theoretical calculation.49 The computational works were performed using first principle method, in which comparison of energy in the system could provide us an effective way to evaluate stability of a certain structural configuration. Comparison of a Bi atom located above a common sulfur atom away from the defect region or just above the sulfur vacancy in defect spot were calculated for the case in Figure 6e-6g, the computed result in Figure 6h clearly illustrated energy level of 1.57 eV lower in system in Figure 6f than in 6e, and it was even 4.27eV lower when a Bi atom located on the defect via chemical bonds. Indeed, the lower energy level also meant a more stable existence in the system. And it is similar to the case for Bi atom associating with 1Mo-2S defect MoS2 sheet in Figure 6i-6l. Such result reflects the knowledge that it is more favorable for Bi atoms to combine with defects rather than other common sulfur sites in MoS2, and high temperature in the furnace will also boost migration of Bi atoms toward the defect sites, which promotes the following nucleation of Bi2S3 nanowires, and also results in the growth of co-nucleus Bi2S3/MoS2 heterostructures. As a matter of fact, for more cases in our experimental results, defect-induced co-nucleus growth of Bi2S3 and MoS2 might occur almost simultaneously at the initial stage on account of the relatively high chemical reactivity between them (Figure S12). Different devices have also been fabricated and measurement was systematically performed to evaluate the electrical transport and photoresponse properties of the Bi2S3/MoS2 heterojunction. Nevertheless, the fact was that no valid electric signals could be probed for devices with a pair of Au electrodes contacting Bi2S3 nanowire and MoS2 monolayer,


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respectively (Figure S13a and S13b). Such result was mainly originated from several reasons involving relatively inferior defect-induced connection and small point-contacted area between nanowire and sheet which has been illustrated in Figure 5 and Figure 6. Moreover, large

resistance, obtained from electrical resistance formula R = ρ , also revealed the relatively poor conductivity in Bi2S3 nanowire for its high ratio of l/A (as showed in Figure 1d). Bi2S3-on-MoS2 devices were also fabricated and room temperature electrical property of the device was presented in Figure S14, where the variation of output behavior under different back gate voltages declared the distinct adjustment of our device by electric field. The device showed a typical n-type channel in the Id-Vg plot which was scanned from -40 to 40 V with Vd =5 V (Figure S14c). Current on/off ratio of the FET reached up to 103 with an off current of about 7.8×10-11 A. Field-effect mobility of the device was extracted to be approximately 0.1 cm2/(V·s), which was comparable to the results in earlier reports about MoS2 sheets synthesized by CVD method but much lower than the samples from mechanical exfoliation.27,

34, 50-52

Moreover,

comparison of performance of individual Bi2S3 and MoS2 device (in Figure S15) demonstrated that MoS2 monolayer played the dominated role in the Bi2S3-on-MoS2 FET while Bi2S3 nanowire also contributed it secondary electrical transport effect. This result was mainly caused by the relatively larger conducting area of MoS2 than Bi2S3 in the heterostructure device. The electrical response to illumination of 532 nm laser was showed in Figure S14d, where power density of the light source was about 3.4 mW/cm2. The photoconductivity has obviously increased under illumination for inducing photo-generated electron-hole pairs and current of the device increased from 2 nA to 4.5 nA as the laser switching to the “ON” state, giving a photoswitching ratio (Ilight/Idark) of 2.25. These results showed the good optoelectronic performance of the 1D/2D heterostructures and also confirmed their high quality.


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CONCLUSIONS In summary, we have reported the one-step growth of 1D/2D heterostructure from Bi2S3 nanowire and MoS2 monolayer by CVD method. Different types of characteristic methods, such as AFM, Raman, TEM, etc., proved the separated synthesis of Bi2S3 nanowire and MoS2 sheet in heterostructure. Moreover, co-nucleus growth, which is an important growth mode in 1D/2D heterostructures, has been confirmed and investigated from our experiments as well as theoretical calculation, which also provided us a way to gain more systematic understanding of growing mechanism in these peculiar heterostructures. Multifunctional design for electrical properties, such as band alignment, rectification, photodetector, etc. might also be achieved in these 1D/2D heterostructures by using various low-dimensional nanowire, nanorod and fewlayered materials. METHODS Synthesis of 1D-Bi2S3/2D-MoS2 heterostructure. Typically, a mixture of Bi2O3 and MoO3 nanopowder was placed on a quartz boat in the center of a horizontal quartz tube furnace, with a clean SiO2/Si substrate being put inversely above the solid source. Another small quartz boat containing pure sulfur (0.5-1 g) was placed upstream in a cooler zone which was 12 cm away from substrate. After that, high flow of pure N2 blew across the quartz tube for about 5 min so as to drive away the air in the tube. During the growing process, flow of N2 was remained 20 sccm (standard cubic centimeter per minute), temperature of the furnace was heated up to 650 °C within 16 min and stayed for 6 min for growing the Bi2S3/MoS2 heterostructures. The furnace was finally shut down and uncapped after finishing the growth. More details can be seen in


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Figure S16. The growth of individual Bi2S3 nanowire and MoS2 monolayer follows similar process with only Bi2O3 and MoO3 source, respectively. Transfer process. The as-grown Bi2S3/MoS2 heterostructures were transferred by wet transferring method. First, polymethyl methacrylate (PMMA) was spin coated onto the substrate and then baked on heating plate at 150 °C for 30 min. After that the substrate with PMMA was soaked into NaOH solution until the PMMA film with heterostructures separated from the substrate and floated on the solution surface. The PMMA film was rinsed with deionized water for several times and then transferred onto TEM grid and dried. Finally, the PMMA film was dissolved in acetone for half an hour. Fabrication of devices. The devices were fabricated using electron beam lithography method. Devices were first spin-coated a layer of 4% 950K PMMA solution onto SiO2/Si substrate with 4000 rpm. After baking on 200 oC heating plate for 4min, the substrate was scanned and patterned by 50 µC/cm2 electron beam in EBL machine. A developing solution of methyl isobutyl ketone and isopropyl alcohol in a 1:2 (v/v) ratio was subsequently used to develop the features. And 60nm gold layer was deposited onto the substrate. The final devices were gained after submersed in acetone to remove the remaining PMMA. The devices were then measured in air atmosphere at room temperature using Agilent B2902A. Density Functional Theory Calculations. The calculations were conducted using the projector augmented wave (PAW) method with the generalized gradient approximation of the PerdewBurke-Ernzerhof (GGA-PBE) exchange–correlation functional in the VASP. The energy cutoff for plane-wave expansion was set at 450 eV. A vacuum layer thickness more than 12 Å was employed to prevent the correlation between adjacent layers. Brillouin zone (BZ) sampling was


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processed with Monkhorst Pack (MP) special k point meshes and a k-point grid of 5 × 5 × 1 was chosen for the calculations. All the structures were fully relaxed using the conjugated gradient method until the Hellmann-Feynman force on each atom was less than 0.02 eV/Å. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (Jingbo Li); [email protected] (Zhongming Wei)

Author Contributions ‡

Yongtao Li and Le Huang contributed equally.

ACKNOWLEDGMENT The authors acknowledge Dr. Lu Fangyuan for his help of experimental supports on individual Bi2S3 nanowire devices fabrication and measurement. This work was financially supported by the “Hundred Talents Program” of Chinese Academy of Sciences (CAS), the National Natural Science Foundation of China (grant no. 61571415, 51502283), and the CAS/SAFEA International Partnership Program for Creative Research Teams. ASSOCIATED CONTENT Supporting Information. Additional experimental details and Figure S1-S16. This material is available free of charge via the Internet at http://pubs.acs.org. REFERENCES 1. Lotsch, B. V., Vertical 2D Heterostructures. Annu. Rev. Mater. Res. 2014, 45, 85-109. 2. Geim, A. K.; Grigorieva, I. V., Van Der Waals Heterostructures. Nature 2013, 499, 419425. 3. Dean, C. R.; Young, A. F.; Meric, I.; Lee, C.; Wang, L.; Sorgenfrei, S.; Watanabe, K.; Taniguchi, T.; Kim, P.; Shepard, K. L., Boron Nitride Substrates for High-Quality Graphene


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Page 22 of 26

Electronics. Nat. Nanotechnol. 2010, 5, 722-726. 4. Nourbakhsh, A.; Zubair, A.; Dresselhaus, M. S.; Palacios, T., Transport Properties of a MoS2/WSe2 Heterojunction Transistor and Its Potential for Application. Nano Lett. 2016, 16, 1359-1366. 5. Hong, X.; Kim, J.; Shi, S. F.; Zhang, Y.; Jin, C.; Sun, Y.; Tongay, S.; Wu, J.; Zhang, Y.; Wang, F., Ultrafast Charge Transfer in Atomically Thin MoS2/WS2 Heterostructures. Nat. Nanotechnol. 2014, 9, 682-686. 6. Huo, N.; Tongay, S.; Guo, W.; Li, R.; Fan, C.; Lu, F.; Yang, J.; Li, B.; Li, Y.; Wei, Z., Novel Optical and Electrical Transport Properties in Atomically Thin WSe2/MoS2 P–N Heterostructures. Adv. Electron. Mater. 2015, 1, 1400066. 7. Rivera, P.; Schaibley, J. R.; Jones, A. M.; Ross, J. S.; Wu, S.; Aivazian, G.; Klement, P.; Seyler, K.; Clark, G.; Ghimire, N. J., Observation of Long-Lived Interlayer Excitons in Monolayer MoSe2-WSe2 Heterostructures. Nat. Commun. 2014, 6, 6242. 8. Tang, S.; Wang, H.; Zhang, Y.; Li, A.; Xie, H.; Liu, X.; Liu, L.; Li, T.; Huang, F.; Xie, X., Precisely Aligned Graphene Grown on Hexagonal Boron Nitride by Catalyst Free Chemical Vapor Deposition. Sci. Rep. 2013, 3, 2666. 9. Roth, S.; Matsui, F.; Greber, T.; Osterwalder, J., Chemical Vapor Deposition and Characterization of Aligned and Incommensurate Graphene/Hexagonal Boron Nitride Heterostack on Cu (111). Nano Lett. 2013, 13, 2668-2675. 10. Li, M. Y.; Shi, Y. M.; Cheng, C. C.; Lu, L. S.; Lin, Y. C.; Tang, H. L.; Tsai, M. L.; Chu, C. W.; Wei, K. H.; He, J. H.; CHANG, W. H.; Suenaga, K.; Li, L. J., Epitaxial Growth of A Monolayer WSe2-MoS2 Lateral Pn Junction with An Atomically Sharp Interface. Science 2015, 349, 524-528. 11. Gong, Y.; Lin, J.; Wang, X.; Shi, G.; Lei, S.; Lin, Z.; Zou, X.; Ye, G.; Vajtai, R.; Yakobson, B. I.; Terrones, H.; Terrones, M.; Tay, B. K.; Lou, J.; Pantelides, S. T.; Liu, Z.; Zhou, W.; Ajayan, P. M., Vertical and In-Plane Heterostructures from WS2/MoS2 Monolayers. Nat. Mater. 2014, 13, 1135-1142. 12. Liu, Y.; Weiss, N. O.; Duan, X.; Cheng, H.-C.; Huang, Y.; Duan, X., Van Der Waals Heterostructures and Devices. Nat. Rev. Mater. 2016, 16042. 13. Ruzmetov, D.; Zhang, K.; Stan, G.; Kalanyan, B.; Bhimanapati, G. R.; Eichfeld, S. M.; Burke, R. A.; Shah, P. B.; O'Regan, T. P.; Crowne, F. J.; Birdwell, A. G.; Robinson, J. A.; Davydov, A. V.; Ivanov, T. G., Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride. ACS Nano 2016, 10, 3580-3588. 14. Shin, J. C.; Kim, K. H.; Yu, K. J.; Hu, H.; Yin, L.; Ning, C. Z.; Rogers, J. A.; Zuo, J. M.; Li, X., InxGa1-xAs Nanowires on Silicon: One-Dimensional Heterogeneous Epitaxy, Bandgap Engineering, and Photovoltaics. Nano Lett. 2011, 11, 4831-4838. 15. Shin, J. C.; Lee, A.; Mohseni, P. K.; Kim, d. Y.; Yu, L.; Kim, J. H.; Kim, H. J.; Choi, W. J.; Wasserman, D.; Choi, K. J., Wafer-Scale Production of Uniform InAs(y)P(1-y) Nanowire Array on Silicon for Heterogeneous Integration. ACS Nano 2013, 7, 5463-5471. 16. Yang, P.; Yan, H.; Mao, S.; Russo, R.; Johnson, J.; Saykally, R.; Morris, N.; Pham, J.; He, R.; Choi, H. J., Controlled Growth of ZnO Nanowires and Their Optical Properties. Adv. Funct. Mater. 2002, 12, 323–331. 17. Lauhon, L. J.; Gudiksen, M. S.; Wang, D.; Lieber, C. M., Epitaxial Core-Shell and CoreMultishell Nanowire Heterostructures. Nature 2002, 420, 57-61. 18. Ghosh, C. R.; Paria, S., Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications. Chem. Rev. 2011, 112, 2373-2433.


22

Page 23 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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19. Mohseni, P. K.; Behnam, A.; Wood, J. D.; English, C. D.; Lyding, J. W.; Pop, E.; Li, X., In(x)Ga(1-x)As Nanowire Growth on Graphene: Van Der Waals Epitaxy Induced Phase Segregation. Nano Lett. 2013, 13, 1153-1161. 20. Munshi, A. M.; Dheeraj, D. L.; Fauske, V. T.; Kim, D.-C.; Van Helvoort, A. T.; Fimland, B.-O.; Weman, H., Vertically Aligned GaAs Nanowires on Graphite and Few-Layer Graphene: Generic Model and Epitaxial Growth. Nano Lett. 2012, 12, 4570-4576. 21. Hong, Y. J.; Lee, W. H.; Wu, Y.; Ruoff, R. S.; Fukui, T., Van Der Waals Epitaxy of InAs Nanowires Vertically Aligned on Single-Layer Graphene. Nano Lett. 2012, 12, 1431-1436. 22. Jariwala, D.; Sangwan, V. K.; Wu, C. C.; Prabhumirashi, P. L.; Geier, M. L.; Marks, T. J.; Lauhon, L. J.; Hersam, M. C., Gate-Tunable Carbon Nanotube-MoS2 Heterojunction P-N Diode. Proc. Natl. Acad. Sci. U S A 2013, 110, 18076-18080. 23. Zhou, W.; Zhou, Y.; Peng, Y.; Zhang, Y.; Yin, Y.; Tang, D., Ultrahigh Sensitivity and Gain White Light Photodetector Based on GaTe/Sn:CdS Nanoflake/Nanowire Heterostructures. Nanotechnol. 2014, 25, 445202. 24. Liu, Y.; Wang, F.; Wang, X.; Wang, X.; Flahaut, E.; Liu, X.; Li, Y.; Wang, X.; Xu, Y.; Shi, Y.; Zhang, R., Planar Carbon Nanotube-Graphene Hybrid Films for High-Performance Broadband Photodetectors. Nat. Commun. 2015, 6, 8589. 25. Lu, F.; Li, R.; Li, Y.; Huo, N.; Yang, J.; Li, Y.; Li, B.; Yang, S.; Wei, Z.; Li, J., Improving the Field-Effect Performance of Bi2S3 Single Nanowires by An Asymmetric Device Fabrication. ChemPhysChem 2015, 16, 99-103. 26. Li, Y.; Wei, F.; Ma, Y.; Zhang, H.; Gao, Z.; Dai, L.; Qin, G., Selected-Control Hydrothermal Synthesis and Photoresponse Properties of Bi2S3 Micro/Nanocrystals. CrystEngComm 2013, 15, 6611-6616. 27. Radisavljevic, B.; Radenovic, A.; Brivio, J.; Giacometti, i. V.; Kis, A., Single-Layer MoS2 Transistors. Nat. Nanotechnol. 2011, 6, 147-150. 28. Zhang, Q.; Xiao, X.; Zhao, R.; Lv, D.; Xu, G.; Lu, Z.; Sun, L.; Lin, S.; Gao, X.; Zhou, J., Two‐Dimensional Layered Heterostructures Synthesized from Core–Shell Nanowires. Angew. Chem. Int. Ed. 2015, 54, 8957-8960. 29. Liu, K.; Zhang, L.; Cao, T.; Jin, C.; Qiu, D.; Zhou, Q.; Zettl, A.; Yang, P.; Louie, S. G.; Wang, F., Evolution of Interlayer Coupling in Twisted Molybdenum Disulfide Bilayers. Nat. Commun. 2014, 5, 4966. 30. Dumcenco, D.; Ovchinnikov, D.; Marinov, K.; Lazic, P.; Gibertini, M.; Marzari, N.; Sanchez, O. L.; Kung, Y. C.; Krasnozhon, D.; Chen, M. W., Large-Area Epitaxial Monolayer MoS2. ACS Nano 2015, 9, 4611-4620. 31. Zumeta-Dubé, I.; Ortiz-Quiñonez, J. L.; Díaz, D.; Trallero-Giner, C.; Ruiz-Ruiz, V. F., First Order Raman Scattering in Bulk Bi2S3 and Quantum Dots: Reconsidering Controversial Interpretations. J. Phys. Chem. C 2014, 118, 30244-30252. 32. Kaltenhauser, V., Bismuth Sulphide–Polymer Nanocomposites from A Highly Soluble Bismuth Xanthate Precursor. J. Mater. Chem. C 2013, 1, 7825-7832. 33. Li, H.; Zhang, Q.; Yap, C. C. R.; Tay, B. K.; Edwin, T. H. T.; Olivier, A.; Baillargeat, D., From Bulk to Monolayer MoS2: Evolution of Raman Scattering. Adv. Funct. Mater. 2012, 22, 1385-1390. 34. Lee, Y. H.; Zhang, X. Q.; Zhang, W.; Chang, M. T.; Lin, C. T.; Chang, K. D.; Yu, Y. C.; Wang, J. T.; Chang, C. S.; Li, L. J.; Lin, T. W., Synthesis of Large-Area MoS2 Atomic Layers with Chemical Vapor Deposition. Adv. Mater. 2012, 24, 2320-2325. 35. Van Der Zande, A. M.; Huang, P. Y.; Chenet, D. A.; Berkelbach, T. C.; You, Y.; Lee, G.-


23

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Page 24 of 26

H.; Heinz, T. F.; Reichman, D. R.; Muller, D. A.; Hone, J. C., Grains and Grain Boundaries in Highly Crystalline Monolayer Molybdenum Disulphide. Nat. Mater. 2013, 12, 554-561. 36. Castro-Guerrero, C. F.; Deepak, F. L.; Ponce, A.; Cruz-Reyes, J.; Del Valle-Granados, M.; Fuentes-Moyado, S.; Galvan, D.; José-Yacamán, M., Structure and Catalytic Properties of Hexagonal Molybdenum Disulfide Nanoplates. Catal. Sci. Technol. 2011, 1, 1024-1031. 37. Sigman, M. B.; Korgel, B. A., Solventless Synthesis of Bi2S3 (Bismuthinite) Nanorods, Nanowires, and Nanofabric. Chem. Mater. 2005, 17, 1655-1660. 38. Whittaker-Brooks, L.; Gao, J.; Hailey, A. K.; Thomas, C. R.; Yao, N.; Loo, Y.-L., Bi2S3 Nanowire Networks as Electron Acceptor Layers in Solution-Processed Hybrid Solar Cells. J. Mater. Chem. C 2015, 3, 2686-2692. 39. Wang, Y.; Chen, J.; Wang, P.; Chen, L.; Chen, Y.-B.; Wu, L.-M., Syntheses, Growth Mechanism, and Optical Properties of [001] Growing Bi2S3 Nanorods. J. Phys. Chem. C 2009, 113, 16009-16014. 40. Zeng, Q.; Wang, H.; Fu, W.; Gong, Y.; Zhou, W.; Ajayan, P. M.; Lou, J.; Liu, Z., Band Engineering for Novel Two‐Dimensional Atomic Layers. Small 2015, 11, 1868-1884. 41. Song, J.-G.; Ryu, G. H.; Lee, S. J.; Sim, S.; Lee, C. W.; Choi, T.; Jung, H.; Kim, Y.; Lee, Z.; Myoung, J.-M., Controllable Synthesis of Molybdenum Tungsten Disulfide Alloy for Vertically Composition-Controlled Multilayer. Nat. Commun. 2015, 6, 7817. 42. Zheng, S.; Sun, L.; Yin, T.; Dubrovkin, A. M.; Liu, F.; Liu, Z.; Shen, Z. X.; Fan, H. J., Monolayers of WxMo1− xS2 Alloy Heterostructure with In-Plane Composition Variations. Appl. Phys. Lett. 2015, 106, 063113. 43. Yue, Q.; Chang, S.; Qin, S.; Li, J., Functionalization of Monolayer MoS2 by Substitutional Doping: A First-Principles Study. Phys. Lett. A 2013, 377, 1362-1367. 44. Liem, S.; Kresse, G.; Clarke, J., First Principles Calculation of Oxygen Adsorption and Reconstruction of Cu (110) Surface. Surf. Sci. 1998, 415, 194-211. 45. Wang, X.; Huang, L.; Jiang, X.-W.; Li, Y.; Wei, Z.; Li, J., Large Scale ZrS2 Atomically Thin Layers. J. Mater. Chem. C 2016, 4, 3143-3148. 46. Kim, K.; Lee, H. B.; Johnson, R. W.; Tanskanen, J. T.; Liu, N.; Kim, M. G.; Pang, C.; Ahn, C.; Bent, S. F.; Bao, Z., Selective Metal Deposition at Graphene Line Defects by Atomic Layer Deposition. Nat. Commun. 2014, 5, 4781. 47. Park, K. S.; Kim, S.; Kim, H.; Kwon, D.; Lee, Y. E.; Min, S. W.; Im, S.; Choi, H. J.; Lim, S.; Shin, H.; Koo, S. M.; Sung, M. M., Wafer-Scale Single-Domain-Like Graphene by DefectSelective Atomic Layer Deposition of Hexagonal ZnO. Nanoscale 2015, 7, 17702-17709. 48. Jeong, H. Y.; Lee, S. Y.; Ly, T. H.; Han, G. H.; Kim, H.; Nam, H.; Jiong, Z.; Shin, B. G.; Yun, S. J.; Kim, J.; Kim, U. J.; Hwang, S.; Lee, Y. H., Visualizing Point Defects in TransitionMetal Dichalcogenides Using Optical Microscopy. ACS Nano 2016, 10, 770-777. 49. Sun, X.; Wang, Z.; Fu, Y., Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide. Sci. Rep. 2015, 5, 18712. 50. Ionescu, R.; Wang, W.; Chai, Y.; Mutlu, Z.; Ruiz, I.; Favors, Z.; Wickramaratne, D.; Neupane, M.; Zavala, L.; Lake, R., Synthesis of Atomically Thin Triangles and Hexagrams and Their Electrical Transport Properties. IEEE Trans. Nanotechnol. 2014, 13, 749-754. 51. Zhan, Y.; Liu, Z.; Najmaei, S.; Ajayan, P. M.; Lou, J., Large‐Area Vapor‐Phase Growth and Characterization of MoS2 Atomic Layers on A SiO2 Substrate. Small 2012, 8, 966971. 52. Liu, K.-K.; Zhang, W.; Lee, Y.-H.; Lin, Y.-C.; Chang, M.-T.; Su, C.-Y.; Chang, C.-S.; Li, H.; Shi, Y.; Zhang, H., Growth of Large-Area and Highly Crystalline MoS2 Thin Layers on


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Insulating Substrates. Nano Lett. 2012, 12, 1538-1544.


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