Observation of new Raman lines in GeSe and SnSe at low temperatures

Fukunaga, T.; Sugai, S.; Kinosada, T.; Murase, K.

doi:10.1016/0038-1098(81)90015-6

Cited by 43 publications

(41 citation statements)

References 14 publications

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“…3, the pronounced sublinear pressure response of the RL A g shear mode results from pressure-enhanced mode mixing of a nearly RL vibration. This pressure-induced breakdown of the RL approximation can be found in other [15] at 20 K, c [16] at 20 K, d present work at 10 K. RL modes (e.g. compressive B 2g mode) with symmetry-allowed coupling of eigenvector components.…”

Section: Vibrational Response In Anisotropic Solidssupporting

confidence: 81%

“…As a prototype of quasi-two-dimensional layered materials, the isostructural semiconductors GeS and GeSe adopt a double-layered orthorhombic crystal structure with space group Pcmn (D 16 2h at ambient pressure [1 to 5] . Choosing the c-axis to be perpendicular to the plane of layers, the locations of the four Ge (or chalcogen) atoms are defined by the additional specification of two free atomic positional parameters (u and v) and are expressed as AEuY 1 4 Y v and AE 1 2 À uY 1 4 Y 1 2 v. On the other hand, the ambient structure of the quasi-molecular crystal AsI 3 is rhombohedral with space group C 2 3i (R " 3) [4,5].…”

Section: Introductionmentioning

confidence: 99%

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Compression Mechanisms in Highly Anisotropic Semiconductors

Hsueh

Crain

1999

phys. stat. sol. (b)

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Section: Vibrational Response In Anisotropic Solidssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Compression Mechanisms in Highly Anisotropic Semiconductors

Hsueh

Crain

1999

phys. stat. sol. (b)

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“…Nevertheless, it is important to keep in mind the effecto fs uch al arge change of strain at high temperatures, for example, in the mechanical stability of thermoelectric devices. [20] As pointed out by some of the same authors of the aforementioned studies, no indications of any structural phase transition have been found by meanso fd iffractiont echniques. This infers that some kind of structural rearrangement, for example, rearrangement of defects, takes place in the same range of temperature at which Wiedemeier and Siemers report thermala nomalies.…”

Section: Resultsmentioning

confidence: 91%

High‐Temperature Crystal Structure and Chemical Bonding in Thermoelectric Germanium Selenide (GeSe)

Sist

Gatti

Nørby

et al. 2017

Chemistry A European J

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The discovery of the ultra-high thermoelectric figure of merit of 2.6 in SnSe has drawn attention to other lead-free IV-VI orthorhombic semiconductors. GeSe has been predicted to possess thermoelectric performances comparable to SnSe. Here, a complete structural study is reported of GeSe with temperature by means of high-resolution synchrotron powder X-ray diffraction. In the orthorhombic phase, the evolution of the bond distances with temperature is shown to deviate significantly with respect to SnSe. Analysis of the chemical bonding within the Quantum Theory of Atoms in Molecules shows that GeSe is ionic with van der Waals interlayer interactions. The signature of the N shell lone pair of Ge is also evident from both the electron density Laplacian and the ELF topologies.

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“…The clearly observed peaks at 83 and 188cm -1 are associated with the Ag 1 and Ag 2 modes, while the peak at 151cm -1 is assigned to B3g mode; a result in good agreement with previous work. 22,23 Figure 3d shows the measured and fitted intensity of Ag and B3g modes as a function of the angle between the incident light polarization and the receiver polarizer, α. We can see that the intensities of Ag and B3g modes have a variation period of 180 o .…”

Section: Polarized Raman and Crystal Orientationmentioning

confidence: 99%

Layered material GeSe and vertical GeSe/MoS2 p-n heterojunctions

et al. 2017

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Beyond graphene, transition metal dichalcogenides (TMDCs) and black phosphorus (BP), group-IV monochalcogenides are emerging as a unique class of layered materials. We report in this paper experimental and theoretical investigations of germanium selenide (GeSe) and its heterostructures. We find that GeSe has a prominent anisotropic electronic transport with maximum conductance along the armchair direction. Density functional theory (DFT) calculations reveal that the effective mass along the zigzag direction is 2.7 times larger than that in the armchair direction, and the anisotropic effective mass explains the observed anisotropic conductance. The crystallographic direction of the GeSe is confirmed by angle-resolved polarized Raman measurement, which is further supported by calculated Raman tensors for the orthorhombic structure. Novel GeSe/MoS2 pn heterojunctions are created, taking advantage of the natural p-type doping in GeSe and n-type doping in MoS2. The temperature-dependence of the junction current measurement reveals that GeSe and MoS2 form a type II band alignment with a conduction band offset of ~ 0.234 eV. The anisotropic conductance in GeSe may enable a new series of electronic and optoelectronic devices such as plasmonic devices with resonance frequency continuously tunable with light polarization direction and high-efficiency thermoelectric devices. The unique GeSe/MoS2 pn junctions with type II alignment will be an essential building block for vertical tunneling field-effect transistors for low power applications. This new p-type layered material GeSe can also be combined with ntype TMDCs to form heterogeneous complementary metal oxide semiconductor (CMOS) circuits.Keywords: monochalcogenides, germanium selenide, anisotropic conductance, polarized Raman, pn heterojunction. ------------------------------------------------------------* These authors contributed equally to this paper. # Corresponding author's email: wjzhu@illinois.edu 2 Layered group-IV monochalcogenides are a newly emerging materials platform. As compared to graphene, transition metal dichalcogenides (TMDCs) and black phosphorus (BP), layered monochalcogenides such as SnS, SnSe, GeS and GeSe have many unique electrical, thermal, and optical properties that could prove useful for diverse applications. In particular, layered monochalcogenides have an orthorhombic (distorted rock-salt) structure and feature anomalously high Grüneisen parameters, which lead to ultralow thermal conductivity and an exceptionally high thermoelectric figure of merit, 1, 2 which makes them promising for thermoelectric applications. At high temperatures, layered monochalcogenides undergo a displacive phase transition from a lower symmetry Pnma space group to a higher symmetry Cmcm space group, 1, 3 which makes them an interesting candidate for phase change memory. The bandgap of layered group-IV monochalcogenides is in the range of 0.5 to 1.5eV, 4 lining up fairly well with the solar spectrum, which makes them attractive for solar cells and photodete...

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Observation of new Raman lines in GeSe and SnSe at low temperatures

Cited by 43 publications

References 14 publications

Compression Mechanisms in Highly Anisotropic Semiconductors

Compression Mechanisms in Highly Anisotropic Semiconductors

High‐Temperature Crystal Structure and Chemical Bonding in Thermoelectric Germanium Selenide (GeSe)

Layered material GeSe and vertical GeSe/MoS2 p-n heterojunctions

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