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Tailoring low-dimensional structures of bismuth on monolayer epitaxial graphene.

Chen HH, Su SH, Chang SL, Cheng BY, Chen SW, Chen HY, Lin MF, Huang JC - Sci Rep (2015)

Bottom Line: Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms.When annealed to ~500 K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size.The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Cheng Kung University, Tainan, Taiwan 701, Taiwan.

ABSTRACT
To improve graphene-based multifunctional devices at nanoscale, a stepwise and controllable fabrication procedure must be elucidated. Here, a series of structural transition of bismuth (Bi) adatoms, adsorbed on monolayer epitaxial graphene (MEG), is explored at room temperature. Bi adatoms undergo a structural transition from one-dimensional (1D) linear structures to two-dimensional (2D) triangular islands and such 2D growth mode is affected by the corrugated substrate. Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms. When annealed to ~500 K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size. A well-controlled fabrication method is thus demonstrated. The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices.

No MeSH data available.


STM images of temperature effect.(a) STM image of 0.039 ML Bi coverage. (b) Annealed STM image of Fig. 4a. (c) Line profile measurements of (a) and (b). (d) dI/dV spectrum of Bi NCs at room temperature. The image size is 20 × 20 nm2 and the image conditions are Vs = 0.74 V, I = 0.15 nA for (a) and Vs = 0.85 V, I = 0.15 nA for (b).
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f4: STM images of temperature effect.(a) STM image of 0.039 ML Bi coverage. (b) Annealed STM image of Fig. 4a. (c) Line profile measurements of (a) and (b). (d) dI/dV spectrum of Bi NCs at room temperature. The image size is 20 × 20 nm2 and the image conditions are Vs = 0.74 V, I = 0.15 nA for (a) and Vs = 0.85 V, I = 0.15 nA for (b).

Mentions: To investigate the effect of temperature, the sample with 0.039 ML of Bi atoms was annealed to an elevated temperature of 500 K. Figure 4(a,b) display the STM images obtained before and after annealing, respectively. After annealing at 500 K for 10 minutes, 1D linear arrangement of Bi NCs, instead of the Bi adatoms in 2D triangular islands, is clearly observed. Interestingly, the Bi NCs are very uniform in size. Within line profile measurements [red and gray dashed lines in Fig. 4(a,b)], the Bi adatoms are ~0.24 nm height and the full width at half maximum (FWHM) ~1 nm in lateral size while Bi NCs are ~0.20 nm height and the FWHM ~2 nm in lateral size, as shown in Fig. 4(c). These results reveal that the Bi NCs are located closer to MEG than are the Bi adatoms. Each Bi NC is likely an aggregation of 3~4 Bi adatoms. Hence, the 2D triangular islands are transformed into the 1D Bi NCs by annealing. Based on the DFT calculations, the atomic model of 1D linear arrangement of Bi NCs are displayed in Fig. S2. Notably, Bi adatoms in NCs remain locating at B site. Moreover, both tri-atoms and quad-atoms configurations of the Bi NCs are possible according to the DFT results. Annealing at a higher elevated temperature ( > 600 K) causes Bi NCs to dissociate into Bi atoms, most of which evaporate from MEG. The spectrum of NCs, as shown in Fig. 4(d), reveal similar characteristic peak located at ~−0.72 eV (black arrow) to that in the dI/dV profile of the Bi adatom in hexagonal array, but with a lager FWHM, indicating stronger feature of the p-state of Bi atoms in NCs. Based on the above, a well-controlled method for forming Bi-based LDSs can be developed. However, further DFT calculations and experimental works to study the effect of corrugated substrate are needed to carry out in the future.


Tailoring low-dimensional structures of bismuth on monolayer epitaxial graphene.

Chen HH, Su SH, Chang SL, Cheng BY, Chen SW, Chen HY, Lin MF, Huang JC - Sci Rep (2015)

STM images of temperature effect.(a) STM image of 0.039 ML Bi coverage. (b) Annealed STM image of Fig. 4a. (c) Line profile measurements of (a) and (b). (d) dI/dV spectrum of Bi NCs at room temperature. The image size is 20 × 20 nm2 and the image conditions are Vs = 0.74 V, I = 0.15 nA for (a) and Vs = 0.85 V, I = 0.15 nA for (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477326&req=5

f4: STM images of temperature effect.(a) STM image of 0.039 ML Bi coverage. (b) Annealed STM image of Fig. 4a. (c) Line profile measurements of (a) and (b). (d) dI/dV spectrum of Bi NCs at room temperature. The image size is 20 × 20 nm2 and the image conditions are Vs = 0.74 V, I = 0.15 nA for (a) and Vs = 0.85 V, I = 0.15 nA for (b).
Mentions: To investigate the effect of temperature, the sample with 0.039 ML of Bi atoms was annealed to an elevated temperature of 500 K. Figure 4(a,b) display the STM images obtained before and after annealing, respectively. After annealing at 500 K for 10 minutes, 1D linear arrangement of Bi NCs, instead of the Bi adatoms in 2D triangular islands, is clearly observed. Interestingly, the Bi NCs are very uniform in size. Within line profile measurements [red and gray dashed lines in Fig. 4(a,b)], the Bi adatoms are ~0.24 nm height and the full width at half maximum (FWHM) ~1 nm in lateral size while Bi NCs are ~0.20 nm height and the FWHM ~2 nm in lateral size, as shown in Fig. 4(c). These results reveal that the Bi NCs are located closer to MEG than are the Bi adatoms. Each Bi NC is likely an aggregation of 3~4 Bi adatoms. Hence, the 2D triangular islands are transformed into the 1D Bi NCs by annealing. Based on the DFT calculations, the atomic model of 1D linear arrangement of Bi NCs are displayed in Fig. S2. Notably, Bi adatoms in NCs remain locating at B site. Moreover, both tri-atoms and quad-atoms configurations of the Bi NCs are possible according to the DFT results. Annealing at a higher elevated temperature ( > 600 K) causes Bi NCs to dissociate into Bi atoms, most of which evaporate from MEG. The spectrum of NCs, as shown in Fig. 4(d), reveal similar characteristic peak located at ~−0.72 eV (black arrow) to that in the dI/dV profile of the Bi adatom in hexagonal array, but with a lager FWHM, indicating stronger feature of the p-state of Bi atoms in NCs. Based on the above, a well-controlled method for forming Bi-based LDSs can be developed. However, further DFT calculations and experimental works to study the effect of corrugated substrate are needed to carry out in the future.

Bottom Line: Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms.When annealed to ~500 K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size.The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Cheng Kung University, Tainan, Taiwan 701, Taiwan.

ABSTRACT
To improve graphene-based multifunctional devices at nanoscale, a stepwise and controllable fabrication procedure must be elucidated. Here, a series of structural transition of bismuth (Bi) adatoms, adsorbed on monolayer epitaxial graphene (MEG), is explored at room temperature. Bi adatoms undergo a structural transition from one-dimensional (1D) linear structures to two-dimensional (2D) triangular islands and such 2D growth mode is affected by the corrugated substrate. Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms. When annealed to ~500 K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size. A well-controlled fabrication method is thus demonstrated. The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices.

No MeSH data available.