Fully dry PMMA transfer of graphene on
                    <i>h</i>
                    -BN using a heating/cooling system

Uwanno, Teerayut; Hattori, Yoshiaki; Taniguchi, Takashi; Nagashio, Kosuke

doi:10.1088/2053-1583/2/4/041002

Cited by 130 publications

(123 citation statements)

References 42 publications

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“…However, once BLG is encapsulated by h-BN crystals, interfacial bubbles did not aggregate with the subsequent annealing, unlike BLG on h-BN. 44 The selection of BLG with a width narrower than 2 m resulted in fewer bubbles being trapped in BLG channel area during encapsulation, as shown in Fig. S2.…”

Section: Resultsmentioning

confidence: 99%

Electrically Inert h-BN/Bilayer Graphene Interface in All-Two-Dimensional Heterostructure Field Effect Transistors

Uwanno

Taniguchi

Watanabe

et al. 2018

ACS Appl. Mater. Interfaces

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Bilayer graphene field effect transistors (BLG-FETs), unlike conventional semiconductors, are greatly sensitive to potential fluctuations because of the charged impurities in high- k gate stacks because the potential difference between two layers induced by the external perpendicular electrical filed is the physical origin behind the band gap opening. The assembly of BLG with layered h-BN insulators into a van der Waals heterostructure has been widely recognized to achieve the superior electrical transport properties. However, the carrier response properties at the h-BN/BLG heterointerface, which control the device performance, have not yet been revealed because of the inevitably large parasitic capacitance. In this study, the significant reduction of potential fluctuations to ∼1 meV is achieved in an all-two-dimensional heterostructure BLG-FET on a quartz substrate, which results in the suppression of the off-current to the measurement limit at a small band gap of ∼90 meV at 20 K. By capacitance measurement, we demonstrate that the electron trap/detrap response at such heterointerface is suppressed to undetectable level in the measurement frequency range. The electrically inert van der Waals heterointerface paves the way for the realization of future BLG electronics applications.

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Section: Resultsmentioning

confidence: 99%

Electrically Inert h-BN/Bilayer Graphene Interface in All-Two-Dimensional Heterostructure Field Effect Transistors

Uwanno

Taniguchi

Watanabe

et al. 2018

ACS Appl. Mater. Interfaces

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“…The optical image is also shown in Figure b. The details of the transfer process with negligible bubbles is explained in Figure S1 (Supporting Information) . The utilization of back‐gate graphite can help with increasing C ox (0.23 µF cm −2 with dielectric constant of 2.5 for h ‐BN) comparable to that for the high‐ k top gate by reducing the h ‐BN thickness to 9.5 nm, since the atomically flat surface of h ‐BN is guaranteed by the total thickness of graphite and h ‐BN (> 20 nm) (Figure S1, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Fang

Toyoda

Taniguchi

et al. 2019

Adv Funct Materials

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2D materials are promising to overcome the scaling limit of Si field-effect transistors (FETs). However, the insulator/2D channel interface severely degrades the performance of 2D FETs, and the origin of the degradation remains largely unexplored. Here, the full energy spectra of the interface state densities (D it ) are presented for both n-and p-MoS 2 FETs, based on the comprehensive and systematic studies, i.e., full rage of channel thickness and various gate stack structures with h-BN as well as high-k oxides. For n-MoS 2 , D it around the mid-gap is drastically reduced to 5 × 10 11 cm −2 eV −1 for the heterostructure FET with h-BN from 5 × 10 12 cm −2 eV −1 for the high-k top-gate. On the other hand, D it remains high, ≈10 13 cm −2 eV −1 , even for the heterostructure FET for p-MoS 2 . The systematic study elucidates that the strain induced externally through the substrate surface roughness and high-k deposition process is the origin for the interface degradation on conduction band side, while sulfur-vacancy-induced defect states dominate the interface degradation on valance band side. The present understanding of the interface properties provides the key to further improving the performance of 2D FETs.

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“…The detailed experiment is provided in Figure S1 of the Supporting Information. [27] Figure 1b shows the transfer characteristics of two types of back-gate-type WSe 2 FETs, where p + -type transfer characteristics are initially obtained for both cases. However, in the device fabrication process, p + -WSe 2 becomes p-WSe 2 .…”

Section: Stable P + -Wse 2 Formationmentioning

confidence: 99%

2D Tunnel Field Effect Transistors (FETs) with a Stable Charge‐Transfer‐Type p⁺‐WSe₂ Source

Fang

Nakamura

et al. 2018

Adv Elect Materials

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current, which can be expected from the tunneling process. To overcome this issue and improve the performance of TFETs, the reduction of tunneling distance and tunneling barrier height as well as the efficient gate controllability for the semiconductor channel are crucial.In these regards, the recent simulations [8][9][10] predict that 2D materials are highly promising as TFETs with both low SS and high drive current because the shorter tunnel distance and strong gate controllability can be expected from the van der Waals gap distance, and the atomically sharp heterointerface formed independently of lattice matching and the ideally dangling bond-free layered surface. Although many 2D-2D systems [11][12][13][14][15][16] such as MoS 2 /WSe 2 , [12] SnSe 2 /WSe 2 , [13] MoS 2 / black phosphorus (BP), [15] WSe 2 /SnSe 2 , [16] and BP/ReS 2 [17] have been investigated since the first experimental demonstration of band-to-band tunneling (BTBT) in an MoS 2 /WSe 2 diode, [11] the expectedly low SS using 2D-2D tunneling has not been realized. The dominant common problem is the lack of highly doped 2D materials with air stability as the sources, although there are many other issues to solve because of an early stage of 2D-TFET studies. Both BP and SnSe 2 used as the p + -source are notably unstable in air, which deteriorates the interface. [18,19] Therefore, the significantly low SS of 31.1 mV dec −1 for four orders has only been obtained from a conventional highly doped germanium source with a MoS 2 channel by using a liquid ion gate with extremely high capacitance. [20] This unfavorable circumstance for source selection in 2D-2D heterostructures results from the challenging situation that substitutional doping by the conventional ion implantation technique is not suitable for 2D materials because of defect formation. [21,22] Recently, a strong p + -WSe 2 has been demonstrated by charge-transfer doping from the self-limiting WO x surface oxide layer, which is formed by an ozone treatment. [23,24] If this charge-transfer-type p + -WSe 2 is used as the source in the 2D-2D TFET, the atomically sharp band alignment at the p + -2D/n-2D interface will be formed because the charge transfer occurs at the p + -2D/n-2D interface to cancel the energy difference in Fermi level (E F ), and the screening length determines the sharpness of the band alignment. [25] This procedure differs from the diffuse band alignment for the conventional depletion type interface, where substitutional ions are fixed in the lattice. Although the air exposure of p + -WSe 2 reduces the hole doping 2D materials are highly promising for tunnel field effect transistors (TFETs) with low subthreshold swing and high drive current because the shorter tunnel distance and strong gate controllability can be expected from the van der Waals gap distance and the atomically sharp heterointerface formed independently of lattice matching. However, the common problem for 2D-2D TFETs is the lack of highly doped 2D materials with the high process stability as the sources. In...

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Fully dry PMMA transfer of graphene on h -BN using a heating/cooling system

Cited by 130 publications

References 42 publications

Electrically Inert h-BN/Bilayer Graphene Interface in All-Two-Dimensional Heterostructure Field Effect Transistors

Electrically Inert h-BN/Bilayer Graphene Interface in All-Two-Dimensional Heterostructure Field Effect Transistors

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

2D Tunnel Field Effect Transistors (FETs) with a Stable Charge‐Transfer‐Type p⁺‐WSe₂ Source

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Fully dry PMMA transfer of graphene on h -BN using a heating/cooling system

Cited by 130 publications

References 42 publications

Electrically Inert h-BN/Bilayer Graphene Interface in All-Two-Dimensional Heterostructure Field Effect Transistors

Electrically Inert h-BN/Bilayer Graphene Interface in All-Two-Dimensional Heterostructure Field Effect Transistors

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS2 Field‐Effect Transistors

2D Tunnel Field Effect Transistors (FETs) with a Stable Charge‐Transfer‐Type p+‐WSe2 Source

Contact Info

Product

Resources

About

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

2D Tunnel Field Effect Transistors (FETs) with a Stable Charge‐Transfer‐Type p⁺‐WSe₂ Source