Electric field effect in ultrathin black phosphorus

Koenig, Steven P.; Doganov, Rostislav A.; Schmidt, Hennrik; Neto, A. H. Castro; Oezyilmaz, Barbaros

doi:10.1063/1.4868132

Cited by 1,196 publications

(1,185 citation statements)

References 38 publications

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“…The overall flake roughness distribution increases monotonically with time ( Fig. S6), consistent with an earlier report 13 and indicative of volumetric expansion. All of these factors suggest that structural or chemical changes are occurring in the BP flakes upon ambient exposure.…”

Section: Manuscriptsupporting

confidence: 90%

Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation

et al. 2014

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Unencapsulated, exfoliated black phosphorus (BP) flakes are found to chemically degrade upon exposure to ambient conditions. Atomic force microscopy, electrostatic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy are employed to characterize the structure and chemistry of the degradation process, suggesting that O2 saturated H2O irreversibly reacts with BP to form oxidized phosphorus species. This interpretation is further supported by the observation that BP degradation occurs more rapidly on hydrophobic octadecyltrichlorosilane self-assembled monolayers and on HSi(111), versus hydrophilic SiO2. For unencapsulated BP field-effect transistors, the ambient degradation causes large increases in threshold voltage after 6 hours in ambient, followed by a ~10 3 decrease in FET current on/off ratio and mobility after 48 hours. Atomic layer deposited AlOx overlayers effectively suppress ambient degradation, allowing encapsulated BP FETs to maintain high on/off ratios of ~10 3 and mobilities of ~100 cm 2 V -1 s -1 for over two weeks in ambient. This work shows that the ambient degradation of BP can be managed effectively when the flakes are sufficiently passivated. In turn, our strategy for enhancing BP environmental stability will accelerate efforts to implement BP in electronic and optoelectronic applications. On increased ambient exposure, the bubble density eventually decreases, evolving into wider and taller bubbles. These bubbles occur in BP, regardless of flake thickness (Fig. S2). In Fig. 2, we therefore use X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy to assess whether chemical modifications, such as the formation of additional chemical bonds or a change in oxidation state, occur in BP upon ambient exposure. Fig. 2A shows P 2p core level XPS spectra of as-exfoliated BP flakes on SiO2 for 0 hrs, 13 hrs, 1, day, 2 days, and 3 days, respectively, of ambient exposure. All spectra are calibrated to the binding energy of adventitious carbon (284.8 eV), and electrostatic charging is compensated using an Ar + flood gun (see Supporting Information for details). At 0 hrs of ambient exposure (black spectrum in Fig. 2A), the exfoliated BP exhibits a single spin-orbit split doublet at ~130 eV, consistent with previous XPS measurements on BP bulk crystals. 27, 28 Note that these spectra do not match those for red phosphorus (~129.8 eV), white phosphorus, or amorphous P-H. 27 A broad, s photoelectronSi satellite from the substrate 300 nm SiO2 appears at ~126.5 eV. After 13 hrs of ambient exposure (maroon spectrum), the full-width at half-maximum (FWHM) for the BP increases, characteristic of some loss of long range order. After 1, 2, and 3 days in ambient (green, navy, and gray spectra, respectively), an additional doublet appears at ~134 eV. This feature is best assigned to phosphate species, 9, 29 although many oxidized phosphorus compounds exhibit peaks near ~134-135 eV. 30, 31 The la...

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Section: Manuscriptsupporting

confidence: 90%

Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation

et al. 2014

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“…Monolayers of layered orthorhombic materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] can become disordered at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Disorder in Black Phosphorus and Monochalcogenide Monolayers

et al. 2016

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Ridged, orthorhombic two-dimensional atomic crystals with a bulk Pnma structure such as black phosphorus and monochalcogenide monolayers are an exciting and novel material platform for a host of applications. Key to their crystallinity, monolayers of these materials have a four-fold degenerate structural ground state, and a single energy scale E C (representing the * To whom correspondence should be addressed † Department of Physics. elastic energy required to switch the longer lattice vector along the x− or y−direction) determines how disordered these monolayers are at finite temperature. Disorder arises when nearest neighboring atoms become gently reassigned as the system is thermally excited beyond a critical temperature T c that is proportional to E C /k B . E C is tunable by chemical composition and it leads to a classification of these materials into two categories: (i) Those for which E C ≥ k B T m , and (ii) those having k B T m > E C ≥ 0, where T m is a given material's melting temperature. Black phosphorus and SiS monolayers belong to category (i): these materials do not display an intermediate order-disorder transition and melt directly. All other monochalcogenide monolayers with E C > 0 belonging to class (ii) will undergo a two-dimensional transition prior to melting. E C /k B is slightly larger than room temperature for GeS and GeSe, and smaller than 300 K for SnS and SnSe monolayers, so that these materials transition near room temperature. The onset of this generic atomistic phenomena is captured by a planar Potts model up to the orderdisorder transition. The order-disorder phase transition in two dimensions described here is at the origin of the Cmcm phase being discussed within the context of bulk layered SnSe.

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“…Different from semi-metallic graphene [6,7], these systems display a large band gap while still maintaining a high carrier mobility [3,[8][9][10][11]. Even though phosphorus and arsenic are both group V elements, they crystallize in different structures.…”

Section: Introductionmentioning

confidence: 99%

Structural Transition in Layered As_1–xP_x Compounds: A Computational Study

2015

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As a way to further improve the electronic properties of group V layered semiconductors, we propose to form in-layer 2D heterostructures of black phosphorus and grey arsenic. We use ab initio density functional theory to optimize the geometry, determine the electronic structure, and identify the most stable allotropes as a function of composition. Since pure black phosphorus and pure grey arsenic monolayers differ in their equilibrium structure, we predict a structural transition and a change in frontier states, including a change from a direct-gap to an indirect-gap semiconductor, with changing composition.

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Electric field effect in ultrathin black phosphorus

Cited by 1,196 publications

References 38 publications

Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation

Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation

Two-Dimensional Disorder in Black Phosphorus and Monochalcogenide Monolayers

Structural Transition in Layered As_1–xP_x Compounds: A Computational Study

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Electric field effect in ultrathin black phosphorus

Cited by 1,196 publications

References 38 publications

Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation

Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation

Two-Dimensional Disorder in Black Phosphorus and Monochalcogenide Monolayers

Structural Transition in Layered As1–xPx Compounds: A Computational Study

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Product

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Structural Transition in Layered As_1–xP_x Compounds: A Computational Study