Raman and infrared reflection spectroscopy in black phosphorus

Sugai, S.; Shirotani, Ichimin

doi:10.1016/0038-1098(85)90213-3

Cited by 221 publications

(213 citation statements)

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“…As carbon atoms in graphene, each phosphorus atom is connected to three adjacent phosphorus atoms in BP to form a stable, linked ring structure, with each ring consisting of six phosphorus atoms. However, the puckered BP structure has reduced symmetry compared with graphite, resulting in its unique angle-dependent in-plane conductivities [33][34][35][36] . The adjacent layer spacing is around 0.53 nm and the lattice constant in this orthorhombic system along the z direction is 1.05 nm.…”

Section: Resultsmentioning

confidence: 99%

Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics

2014

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Graphene and transition metal dichalcogenides (TMDCs) are the two major types of layered materials under intensive investigation. However, the zero-bandgap nature of graphene and the relatively low mobility in TMDCs limit their applications. Here we reintroduce black phosphorus (BP), the most stable allotrope of phosphorus with strong intrinsic in-plane anisotropy, to the layered-material family. For 15-nm-thick BP, we measure a Hall mobility of 1,000 and 600 cm 2 V À 1 s À 1 for holes along the light (x) and heavy (y) effective mass directions at 120 K. BP thin films also exhibit large and anisotropic in-plane optical conductivity from 2 to 5 mm. Field-effect transistors using 5 nm BP along x direction exhibit an on-off current ratio exceeding 10 5 , a field-effect mobility of 205 cm 2 V À 1 s À 1 , and good current saturation characteristics all at room temperature. BP shows great potential for thin-film electronics, infrared optoelectronics and novel devices in which anisotropic properties are desirable.

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Section: Resultsmentioning

confidence: 99%

Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics

2014

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“…Moreover, it is found that their excitation laser polarization dependence can be used to determine the crystal orientation of BP 45,47 . However, the frequencies of HF intralayer modes are found to exhibit almost no dependence on film thickness [44][45][46][47] . Clearly, the 4 study of the LF interlayer phonon modes in few-layer BP (Fig.…”

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Low-Frequency Interlayer Breathing Modes in Few-Layer Black Phosphorus

et al. 2015

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As a new two-dimensional layered material, black phosphorus (BP) is a promising material for nanoelectronics and nano-optoelectronics. We use Raman spectroscopy and first-principles theory to report our findings related to low-frequency (LF) interlayer breathing modes (<100 cm -1 ) in few-layer BP for the first time. The breathing modes are assigned to Ag symmetry by the laser polarization dependence study and group theory analysis. Compared to the high-frequency (HF) Raman modes, the LF breathing modes are much more sensitive to interlayer coupling and thus their frequencies show much stronger dependence on the number of layers. Hence, they could be used as effective means to probe both the crystalline orientation and thickness for fewlayer BP. Furthermore, the temperature dependence study shows that the breathing modes have a harmonic behavior, in contrast to HF Raman modes which are known to exhibit anharmonicity. 2 Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.3 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. 2Orthorhombic black phosphorus (BP) is the most stable allotrope of phosphorus. It features a layered structure with puckered monolayers stacked by van der Waals (vdW) force 1 . Few-or single-layer BP can be mechanically exfoliated from bulk BP [2][3][4][5] . Due to BP's intrinsic thicknessdependent direct bandgap (ranging from 0.3 eV to 2.0 eV) and relatively high carrier mobility (up to ~1,000 cm 2 V -1 s -1 at room temperature) 2,4,[6][7][8][9] , it is expected to have promising applications in nanoelectronic devices [2][3][4]10 , and near and mid-infrared photodetector [11][12][13][14][15][16][17][18][19] . Recently, high performance thermoelectric devices were also predicted based on BP thin films [20][21][22] . With the surge of interest in two-dimensional (2D) materials (such as graphene and transition metal dichalcogenides (TMDs)) 23,24 , BP has become a new attraction since 2014 because it bridges the gap between graphene and TMDs, and offers the best trade-off between mobility and on-off ratio 3 . Moreover, the unique anisotropic puckered honeycomb lattice of BP leads to many novel in-plane anisotropic properties, which could lead to more applications based on BP 3,9,25,26 .Phonon behaviors play an important role in the diverse properties of materials 27 , which has been intensively studied in vdW layered materials, such as graphene and TMDs [28][29][30][31][32][33][34][35] . Raman spectroscopy is a powerful non-destructive tool to investigate the phonons and their coupling to electrons, and has been successfully applied to vdW layered materials [36][37][38][39][40] . Due to the lattice dynamics of vdW layered compounds, the phonon modes in these materials can be classified as high-frequency (HF) intralayer modes and low-frequency (LF) interlayer modes 27 . Intralayer modes involve vibrations from the intralayer chemical bonds (Fig. 1c), and the associated frequencies ...

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“…[18,19] For incident and scattered light propagating normal to the planes of the flakes, the selection rules 4 permit observation of three modes [19] To orient our encapsulated BP samples prior to thermal measurement, we take angleresolved, parallel polarized Raman spectra, as shown in Figure 2 and Figure S2. We subtract polynomial baselines from the spectra, Lorentzian fit them, and then normalize their peak intensity values.…”

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“…[18,19] For incident and scattered light propagating normal to the planes of the flakes, the selection rules 4 permit observation of three modes [19] A intensities depend on the polarization direction in the a-c plane and can be used to determine the crystal orientation. [19] Further, we note that the Raman intensity of the Si TO phonon (~521 cm −1 ) varies with sample orientation, as both the intrinsic Si Raman tensor and BP's optical constants are angle-dependent.…”

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Anisotropic Thermal Conductivity of Exfoliated Black Phosphorus

et al. 2015

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We ascertain the anisotropic thermal conductivity of passivated black phosphorus (BP), a reactive 2D nanomaterial with strong in-plane anisotropy. We measure the room temperature thermal conductivity by time-domain thermoreflectance for three crystalline axes of exfoliated BP. The thermal conductivity along the zigzag direction (86 ± 8 W m −1 K −1 ) is ~2.5 times higher than that of the armchair direction (34 ± 4 W m −1 K −1 ). TOC Figure 2Black phosphorus (BP), a stable phosphorus allotrope at ambient temperature and pressure, [1] is a two-dimensional electronic material with desirable properties for transistor, [2, 3] thermoelectric, [4] and optical sensing [5] applications. Few-layer BP flakes can be exfoliated from bulk crystals due to weak interlayer bonding. [2, 3,6] In contrast to the planar character of graphite and transition metal dichalcogenides, BP has a puckered, honeycomb structure, leading to heightened chemical reactivity [7] and pronounced in-plane anisotropy.Experimental and theoretical examinations of the electrical, [3, 4,6] optical, [3,8] mechanical, [9] and thermal [4,10,11,12] properties reveal distinct anisotropy along BP's two high-symmetry, inplane directions. These symmetry axes are commonly referred to as the zigzag and armchair directions, with lattice constants of a = 3.314 Å and c = 4.376 Å, respectively. [1] Understanding an electronic material's thermal conductivity is critical for the thermal management of small-scale devices and for exploring potential thermoelectric applications.Despite extensive electrical characterization of exfoliated BP, experimental measurements of BP's thermal properties are few. [12,13] First-principles calculations of the anisotropic thermal conductivity of monolayer BP, that is, phosphorene, predict that the thermal conductivity along the zigzag direction is two-or three-fold higher [10,11] than along the armchair direction; for example, ref. 11 finds 110 and 36 W m −1 K −1 , respectively, in the two directions. Of this, the electronic contribution to the thermal conductivity is markedly small, less than 3 W m −1 K −1 , even at a high carrier concentration of ~10 12 cm −2 . [11] Experimentally, Slack found the thermal conductivity of bulk, polycrystalline BP to be 10 W m −1 K −1 at room temperature, [13] but no anisotropic effects were examined. Only mechanically exfoliated BP flakes, with defined symmetry axes, allow an assessment of anisotropic thermal properties in all three high symmetry directions of the crystal. A recent preprint [12] reports the in-plane, anisotropic thermal transport for exfoliated, few-layer BP using micro-Raman spectroscopy; still, the extracted values were much smaller than theoretically predicted for phosphorene. For thinner (<15 nm) BP samples, the measured BP thermal conductivity is modified by phonon scattering from oxidized regions, substrates, and surface imperfections. By contrast, thermal measurements on thicker (>100 nm) BP flakes, especially those protected against ambient oxidation, provide an intrinsic ...

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Raman and infrared reflection spectroscopy in black phosphorus

Cited by 221 publications

References 18 publications

Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics

Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics

Low-Frequency Interlayer Breathing Modes in Few-Layer Black Phosphorus

Anisotropic Thermal Conductivity of Exfoliated Black Phosphorus

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