Electrically tunable localized states in sub-band of bilayer graphene nanoribbon

Wang, Zhongwang; Sun, Jian; Muruganathan, Manoharan; Mizuta, Hiroshi

doi:10.1063/1.5042696

Cited by 4 publications

(6 citation statements)

References 22 publications

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“…Surface charge transfer doping is commonly employed for 2D materials as a nondestructive and efficient doping technique. [69][70][71] Fang et al have reported p-type and n-type doping to TMDs at contact regions using NO 2 and potassium as surface dopants, respectively. [72,73] Degenerate doping concentrations of 1.0 × 10 13 and 2.5 × 10 12 cm −2 were obtained for potassium-doped MoS 2 and WSe 2 , respectively.…”

Section: Surface-charge-transfer-doped Tmdsmentioning

confidence: 99%

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Fermi Level Pinning Dependent 2D Semiconductor Devices: Challenges and Prospects

et al. 2022

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Motivated by the high expectation for efficient electrostatic modulation of charge transport at very low voltages, atomically thin 2D materials with a range of bandgaps are investigated extensively for use in future semiconductor devices. However, researchers face formidable challenges in 2D device processing mainly originated from the out‐of‐plane van der Waals (vdW) structure of ultrathin 2D materials. As major challenges, untunable Schottky barrier height and the corresponding strong Fermi level pinning (FLP) at metal interfaces are observed unexpectedly with 2D vdW materials, giving rise to unmodulated semiconductor polarity, high contact resistance, and lowered device mobility. Here, FLP observed from recently developed 2D semiconductor devices is addressed differently from those observed from conventional semiconductor devices. It is understood that the observed FLP is attributed to inefficient doping into 2D materials, vdW gap present at the metal interface, and hybridized compounds formed under contacting metals. To provide readers with practical guidelines for the design of 2D devices, the impact of FLP occurring in 2D semiconductor devices is further reviewed by exploring various origins responsible for the FLP, effects of FLP on 2D device performances, and methods for improving metallic contact to 2D materials.

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Section: Surface-charge-transfer-doped Tmdsmentioning

confidence: 99%

“…Surface charge transfer doping is commonly employed for 2D materials as a nondestructive and efficient doping technique. [ 69–71 ] Fang et al. have reported p‐type and n‐type doping to TMDs at contact regions using NO 2 and potassium as surface dopants, respectively.…”

Section: Flp‐related Contact Strategies For 2d Tmd Devicesmentioning

confidence: 99%

Fermi Level Pinning Dependent 2D Semiconductor Devices: Challenges and Prospects

et al. 2022

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“…However, the structure with such small dimensions is inevitably subjected to the disorders originating from fabrication residues, substrate defects, − and edge roughness. Subsequently, these disorders vary the spatial distribution of the chemical potential in the GNR, resulting in small unintended QDs − and parasitic charged puddles . These localized states therefore smear out the anticipated single QD features.…”

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confidence: 99%

Quantum Dot Formation in Controllably Doped Graphene Nanoribbon

et al. 2019

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We introduce the controllable doping from hydrogen silsesquioxane (HSQ) to graphene by changing its electron-beam exposure dose. Using HSQ as the dopant, a fine-resolution electron-beam resist allows us to selectively dope graphene with an extremely high spatial resolution of a few nanometers. Therefore, we can design and demonstrate the single quantum dot (QD)-like transport in the graphene nanoribbon (GNR) with the opening of the energy gap. Moreover, we suggest a rough geometric design rule in which a relatively short and wide GNR is required for observing the single QD-like transport. We envisage that this method can be utilized for other materials and for other applications, such as p–n junctions and tunnel field-effect transistors.

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“…Normally, to efficiently generate complementary dopants from HSQ, i.e., to cleave both Si─H and Si─O bonds, a temperature much higher than 500 C is normally required. [22,23] First, we examine that the current annealing is capable to cleave Si─O bonds. Here, we perform the current annealing in an as-fabricated graphene device placed on the thermal SiO 2 substrate without HSQ capping, which is carried out by applying a large dc source-drain bias to the device.…”

Section: Resultsmentioning

confidence: 99%

“…We expect that the graphene channel can be fully p-doped with longer annealing. [23] The temporal change of doping concentration n eff can be quantitatively extracted from the transfer curves using the equation n eff ¼ C ox V cnp /e. Here, C ox is the capacitance per unit area of the 300 nm thick silicon dioxide, e is the elementary charge, and V cnp is the position of CNP.…”

Section: Resultsmentioning

confidence: 99%

Current‐Induced Complementary Doping to Graphene from Hydrogen Silsesquioxane Passivation Layer

Wang

Yuan

Liu

et al. 2021

Physica Rapid Research Ltrs

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Hydrogen silsesquioxane (HSQ) is a high-resolution negative-tone e-beam resist. Apart from that, it also frequently uses a complementary dopant to 2D materials. So far, most of the studies on an HSQ complementary doping process have been performed by electron beam exposure during the device fabrication. Doping induced by post-treatment after device fabrication has not been investigated. Herein, current annealing is reported as an easy access to induce controlled complementary doping from the capping HSQ to the graphene. Joule heating caused by the current is able to break silicon─hydrogen and silicon─oxygen bonds in HSQ. Subsequently, hydrogen and oxygen atoms generated are trapped at the HSQ-graphene interface, therefore, n-type and p-type doping graphene, respectively. The doping polarity and strength can be controlled by current strength and annealing duration.

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Electrically tunable localized states in sub-band of bilayer graphene nanoribbon

Cited by 4 publications

References 22 publications

Fermi Level Pinning Dependent 2D Semiconductor Devices: Challenges and Prospects

Fermi Level Pinning Dependent 2D Semiconductor Devices: Challenges and Prospects

Quantum Dot Formation in Controllably Doped Graphene Nanoribbon

Current‐Induced Complementary Doping to Graphene from Hydrogen Silsesquioxane Passivation Layer

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