Limits...
Large Area Fabrication of Semiconducting Phosphorene by Langmuir-Blodgett Assembly

View Article: PubMed Central - PubMed

ABSTRACT

Phosphorene is a recently new member of the family of two dimensional (2D) inorganic materials. Besides its synthesis it is of utmost importance to deposit this material as thin film in a way that represents a general applicability for 2D materials. Although a considerable number of solvent based methodologies have been developed for exfoliating black phosphorus, so far there are no reports on controlled organization of these exfoliated nanosheets on substrates. Here, for the first time to the best of our knowledge, a mixture of N-methyl-2-pyrrolidone and deoxygenated water is employed as a subphase in Langmuir-Blodgett trough for assembling the nanosheets followed by their deposition on substrates and studied its field-effect transistor characteristics. Electron microscopy reveals the presence of densely aligned, crystalline, ultra-thin sheets of pristine phosphorene having lateral dimensions larger than hundred of microns. Furthermore, these assembled nanosheets retain their electronic properties and show a high current modulation of 104 at room temperature in field-effect transistor devices. The proposed technique provides semiconducting phosphorene thin films that are amenable for large area applications.

No MeSH data available.


Surface morphology of LB assembled phosphorene nanosheets on SiO2/Si substrate.(a) FESEM of small nanosheets (S-Ex BP) deposited at a surface pressure of 40 mN/m. (b) Magnified FESEM image S-Ex BP. (c) AFM of S-Ex BP. Inset: Height profile of nanosheets. (d) FESEM of large nanosheets (L-Ex BP) deposited at a surface pressure of 40 mN/m. (e) Magnified FESEM image of L-Ex BP. (f) AFM of L-Ex BP. Inset: Height profile of nanosheets.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5037434&req=5

f2: Surface morphology of LB assembled phosphorene nanosheets on SiO2/Si substrate.(a) FESEM of small nanosheets (S-Ex BP) deposited at a surface pressure of 40 mN/m. (b) Magnified FESEM image S-Ex BP. (c) AFM of S-Ex BP. Inset: Height profile of nanosheets. (d) FESEM of large nanosheets (L-Ex BP) deposited at a surface pressure of 40 mN/m. (e) Magnified FESEM image of L-Ex BP. (f) AFM of L-Ex BP. Inset: Height profile of nanosheets.

Mentions: Field emission scanning electron microscope (FESEM) was used to characterize the morphology of LB assembled nanosheets on SiO2/Si substrates. Figure 2a shows a representative, low-magnification FESEM image (0.3 × 0.3 mm2) revealing a high density deposition of small nanosheets (S-Ex BP, centrifuged at 10,000 r.p.m). Such a compact spatial arrangement of aligned nanosheets over such a large area cannot be achieved through drop-cast method as illustrated above. It can only be used where the small microscopic area (in microns) is of interest, hence cannot be used to produce thin films of phosphorene. The magnified image (Fig. 2b), indicates nanosheets were flat and have lateral dimensions in the order of few microns. Figure 2c shows its AFM image, reveals thickness of these nanosheets varies from 3–5 nm. No flake having thickness more than 5 nm was found is an indicative of the presence of few layer phosphorene (Supplemetary information, Figure S6). Also this range of height was comparable with the thickness of the nanosheets deposited by drop-cast method ensures that during the assembly procedure, the nanosheets were neither oxidized nor underwent any degradation. Further, LB films made by using large nanosheets suspension (L-Ex BP, centrifuged at 3000 r.p.m) shows an enrichment of ultra-large nanosheets (>10,000 μm2, Supplementary information, Figure S7) on the substrate as depicted in Fig. 2d which represents a low magnification image (0.8 × 0.8 mm2). The continuity in the nanosheets is clearly shown in its magnified image (Fig. 2e) over several microns. However, small dark contrast features (marked by circle in Fig. 2d) were attributed to be formed from the curling or rolling of these large nanosheets during LB assembly under high surface pressure. Figure 2f shows the AFM image of L-Ex BP, which shows that these large nanosheets have thickness ≈4 nm. Thus, LB assembly technique can result in the production of controllable deposition of large area phosphorene nanosheets with high reproducibility.


Large Area Fabrication of Semiconducting Phosphorene by Langmuir-Blodgett Assembly
Surface morphology of LB assembled phosphorene nanosheets on SiO2/Si substrate.(a) FESEM of small nanosheets (S-Ex BP) deposited at a surface pressure of 40 mN/m. (b) Magnified FESEM image S-Ex BP. (c) AFM of S-Ex BP. Inset: Height profile of nanosheets. (d) FESEM of large nanosheets (L-Ex BP) deposited at a surface pressure of 40 mN/m. (e) Magnified FESEM image of L-Ex BP. (f) AFM of L-Ex BP. Inset: Height profile of nanosheets.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037434&req=5

f2: Surface morphology of LB assembled phosphorene nanosheets on SiO2/Si substrate.(a) FESEM of small nanosheets (S-Ex BP) deposited at a surface pressure of 40 mN/m. (b) Magnified FESEM image S-Ex BP. (c) AFM of S-Ex BP. Inset: Height profile of nanosheets. (d) FESEM of large nanosheets (L-Ex BP) deposited at a surface pressure of 40 mN/m. (e) Magnified FESEM image of L-Ex BP. (f) AFM of L-Ex BP. Inset: Height profile of nanosheets.
Mentions: Field emission scanning electron microscope (FESEM) was used to characterize the morphology of LB assembled nanosheets on SiO2/Si substrates. Figure 2a shows a representative, low-magnification FESEM image (0.3 × 0.3 mm2) revealing a high density deposition of small nanosheets (S-Ex BP, centrifuged at 10,000 r.p.m). Such a compact spatial arrangement of aligned nanosheets over such a large area cannot be achieved through drop-cast method as illustrated above. It can only be used where the small microscopic area (in microns) is of interest, hence cannot be used to produce thin films of phosphorene. The magnified image (Fig. 2b), indicates nanosheets were flat and have lateral dimensions in the order of few microns. Figure 2c shows its AFM image, reveals thickness of these nanosheets varies from 3–5 nm. No flake having thickness more than 5 nm was found is an indicative of the presence of few layer phosphorene (Supplemetary information, Figure S6). Also this range of height was comparable with the thickness of the nanosheets deposited by drop-cast method ensures that during the assembly procedure, the nanosheets were neither oxidized nor underwent any degradation. Further, LB films made by using large nanosheets suspension (L-Ex BP, centrifuged at 3000 r.p.m) shows an enrichment of ultra-large nanosheets (>10,000 μm2, Supplementary information, Figure S7) on the substrate as depicted in Fig. 2d which represents a low magnification image (0.8 × 0.8 mm2). The continuity in the nanosheets is clearly shown in its magnified image (Fig. 2e) over several microns. However, small dark contrast features (marked by circle in Fig. 2d) were attributed to be formed from the curling or rolling of these large nanosheets during LB assembly under high surface pressure. Figure 2f shows the AFM image of L-Ex BP, which shows that these large nanosheets have thickness ≈4 nm. Thus, LB assembly technique can result in the production of controllable deposition of large area phosphorene nanosheets with high reproducibility.

View Article: PubMed Central - PubMed

ABSTRACT

Phosphorene is a recently new member of the family of two dimensional (2D) inorganic materials. Besides its synthesis it is of utmost importance to deposit this material as thin film in a way that represents a general applicability for 2D materials. Although a considerable number of solvent based methodologies have been developed for exfoliating black phosphorus, so far there are no reports on controlled organization of these exfoliated nanosheets on substrates. Here, for the first time to the best of our knowledge, a mixture of N-methyl-2-pyrrolidone and deoxygenated water is employed as a subphase in Langmuir-Blodgett trough for assembling the nanosheets followed by their deposition on substrates and studied its field-effect transistor characteristics. Electron microscopy reveals the presence of densely aligned, crystalline, ultra-thin sheets of pristine phosphorene having lateral dimensions larger than hundred of microns. Furthermore, these assembled nanosheets retain their electronic properties and show a high current modulation of 104 at room temperature in field-effect transistor devices. The proposed technique provides semiconducting phosphorene thin films that are amenable for large area applications.

No MeSH data available.