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High-quality sandwiched black phosphorus heterostructure and its quantum oscillations.

Chen X, Wu Y, Wu Z, Han Y, Xu S, Wang L, Ye W, Han T, He Y, Cai Y, Wang N - Nat Commun (2015)

Bottom Line: Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices.Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ∼1,350 cm(2)V(-1) s(-1) at room temperature and on-off ratios exceeding 10(5).At low temperatures, the mobility even reaches ∼2,700 cm(2)V(-1) s(-1) and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.

ABSTRACT
Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices. The family of two-dimensional materials was recently joined by atomically thin black phosphorus which possesses high theoretical mobility and tunable bandgap structure. However, degradation of properties under atmospheric conditions and high-density charge traps in black phosphorus have largely limited its actual mobility thus hindering its future applications. Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ∼1,350 cm(2)V(-1) s(-1) at room temperature and on-off ratios exceeding 10(5). At low temperatures, the mobility even reaches ∼2,700 cm(2)V(-1) s(-1) and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields. Importantly, the sandwiched heterostructures ensure that the quality of black phosphorus remains high under ambient conditions.

No MeSH data available.


Related in: MedlinePlus

Mobility and stability of the BN–BP–BN heterostructure devices.(a) The I–Vds curves obtained at different gate voltages at 1.7 K. The inset is the optical image of Sample A with the following geometrical parameters: L14=16 μm, L23=10 μm and W=3 μm. (b) The resistivity determined from four-terminal (green line) and two-terminal configurations (orange line) at 1.7 K. (c) Variation of the contact resistivity. (d) The conductivity of Sample A measured at with a room temperature and 1.7 K. The inset shows the ambipolarity of the BP conductance. (e,f) Temperature dependence of the field-effect μF (open dots) and Hall mobilityμh (solid dots) at Vg=−70 V) of Sample A and Sample B (15 nm thick). The dashed lines serve as guidelines for the μ∼T−γ relation. (g) The room temperature conductivity showing no hysteresis in Sample A. (h) The mobility and on–off ratio of Sample A as a functions of ambient exposure time. No quality degradation is observed even after exposure for an entire week.
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f2: Mobility and stability of the BN–BP–BN heterostructure devices.(a) The I–Vds curves obtained at different gate voltages at 1.7 K. The inset is the optical image of Sample A with the following geometrical parameters: L14=16 μm, L23=10 μm and W=3 μm. (b) The resistivity determined from four-terminal (green line) and two-terminal configurations (orange line) at 1.7 K. (c) Variation of the contact resistivity. (d) The conductivity of Sample A measured at with a room temperature and 1.7 K. The inset shows the ambipolarity of the BP conductance. (e,f) Temperature dependence of the field-effect μF (open dots) and Hall mobilityμh (solid dots) at Vg=−70 V) of Sample A and Sample B (15 nm thick). The dashed lines serve as guidelines for the μ∼T−γ relation. (g) The room temperature conductivity showing no hysteresis in Sample A. (h) The mobility and on–off ratio of Sample A as a functions of ambient exposure time. No quality degradation is observed even after exposure for an entire week.

Mentions: To achieve both high mobility and stability of BP FETs under atmospheric conditions, the BN–BP–BN configuration and high-temperature annealing are the two key factors. The ultra-clean BN–BP interfaces are ensured by adopting the polymer-free van der Waals transfer technique32 as shown in Fig. 1a. The few-layer BP mechanically exfoliated on a 300-nm SiO2/Si substrate was first picked up by a thin BN flake (6–20 nm thick). Then the BN–BP sample was transferred to a BN flake supported on a SiO2/Si substrate to form the BN–BP–BN heterostructure. The atomically thin BP was completely encapsulated by two BN layers, thus allowing us to anneal the sample at temperatures up to 500 °C in an argon atmosphere to further improve the sample quality. Without the BN protective layers, few-layer BP breaks down easily at 350 °C (see Supplementary Note 1 and Supplementary Fig. 1). In addition, the annealing process can significantly reduce the charge trap density in BP as no hysteresis effect is observed at room temperature (Fig. 2g and Supplementary Fig. 2).


High-quality sandwiched black phosphorus heterostructure and its quantum oscillations.

Chen X, Wu Y, Wu Z, Han Y, Xu S, Wang L, Ye W, Han T, He Y, Cai Y, Wang N - Nat Commun (2015)

Mobility and stability of the BN–BP–BN heterostructure devices.(a) The I–Vds curves obtained at different gate voltages at 1.7 K. The inset is the optical image of Sample A with the following geometrical parameters: L14=16 μm, L23=10 μm and W=3 μm. (b) The resistivity determined from four-terminal (green line) and two-terminal configurations (orange line) at 1.7 K. (c) Variation of the contact resistivity. (d) The conductivity of Sample A measured at with a room temperature and 1.7 K. The inset shows the ambipolarity of the BP conductance. (e,f) Temperature dependence of the field-effect μF (open dots) and Hall mobilityμh (solid dots) at Vg=−70 V) of Sample A and Sample B (15 nm thick). The dashed lines serve as guidelines for the μ∼T−γ relation. (g) The room temperature conductivity showing no hysteresis in Sample A. (h) The mobility and on–off ratio of Sample A as a functions of ambient exposure time. No quality degradation is observed even after exposure for an entire week.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557360&req=5

f2: Mobility and stability of the BN–BP–BN heterostructure devices.(a) The I–Vds curves obtained at different gate voltages at 1.7 K. The inset is the optical image of Sample A with the following geometrical parameters: L14=16 μm, L23=10 μm and W=3 μm. (b) The resistivity determined from four-terminal (green line) and two-terminal configurations (orange line) at 1.7 K. (c) Variation of the contact resistivity. (d) The conductivity of Sample A measured at with a room temperature and 1.7 K. The inset shows the ambipolarity of the BP conductance. (e,f) Temperature dependence of the field-effect μF (open dots) and Hall mobilityμh (solid dots) at Vg=−70 V) of Sample A and Sample B (15 nm thick). The dashed lines serve as guidelines for the μ∼T−γ relation. (g) The room temperature conductivity showing no hysteresis in Sample A. (h) The mobility and on–off ratio of Sample A as a functions of ambient exposure time. No quality degradation is observed even after exposure for an entire week.
Mentions: To achieve both high mobility and stability of BP FETs under atmospheric conditions, the BN–BP–BN configuration and high-temperature annealing are the two key factors. The ultra-clean BN–BP interfaces are ensured by adopting the polymer-free van der Waals transfer technique32 as shown in Fig. 1a. The few-layer BP mechanically exfoliated on a 300-nm SiO2/Si substrate was first picked up by a thin BN flake (6–20 nm thick). Then the BN–BP sample was transferred to a BN flake supported on a SiO2/Si substrate to form the BN–BP–BN heterostructure. The atomically thin BP was completely encapsulated by two BN layers, thus allowing us to anneal the sample at temperatures up to 500 °C in an argon atmosphere to further improve the sample quality. Without the BN protective layers, few-layer BP breaks down easily at 350 °C (see Supplementary Note 1 and Supplementary Fig. 1). In addition, the annealing process can significantly reduce the charge trap density in BP as no hysteresis effect is observed at room temperature (Fig. 2g and Supplementary Fig. 2).

Bottom Line: Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices.Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ∼1,350 cm(2)V(-1) s(-1) at room temperature and on-off ratios exceeding 10(5).At low temperatures, the mobility even reaches ∼2,700 cm(2)V(-1) s(-1) and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and the William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.

ABSTRACT
Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices. The family of two-dimensional materials was recently joined by atomically thin black phosphorus which possesses high theoretical mobility and tunable bandgap structure. However, degradation of properties under atmospheric conditions and high-density charge traps in black phosphorus have largely limited its actual mobility thus hindering its future applications. Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ∼1,350 cm(2)V(-1) s(-1) at room temperature and on-off ratios exceeding 10(5). At low temperatures, the mobility even reaches ∼2,700 cm(2)V(-1) s(-1) and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields. Importantly, the sandwiched heterostructures ensure that the quality of black phosphorus remains high under ambient conditions.

No MeSH data available.


Related in: MedlinePlus