Abstract:Emerging two-dimensional gallium chalcogenides, such as gallium telluride (GaTe), are considered promising layered semiconductors that can serve as vital building blocks towards the implementation of nanodevices in the fields of nanoelectronics, optoelectronics, and quantum photonics. However, oxidation-induced electronic, structural, and optical changes observed in ambient-exposed gallium chalcogenides need to be further investigated and addressed. Herein, we report on the thickness-dependent effect of air ex… Show more
“…Typical room temperature photoluminescence (PL) spectrum was shown in Fig. 1 d, where a strong peak at 1.66 eV, in good agreement with the previously reported direct bandgap of GaTe, was observed 28 , 29 , 33 . All the results shown in Fig.…”
Section: Resultssupporting
confidence: 88%
“…1 b, where eleven A g modes and two B g modes were observed in the spectral range from 20 to 300 cm −1 . It is noteworthy that our Raman spectrum did not show peaks around 132 cm −1 and 146 cm −1 , which were known to exist in oxygen-contaminated GaTe samples 28 , 29 . Figure 1 ( a ) Crystal structure of GaTe, shown in perspective view, side view, and top view of three stacked layers.…”
Section: Resultsmentioning
confidence: 65%
“…It has a monoclinic structure whose space group is C2/m. In this work, we will use the conventional crystallographic axes of GaTe, where the x-axis is the direction of the stacked layers, also known as [ ] direction 25 , 28 . On the layer plane, the y-axis is the direction of a series of Ga-Ga binding chains.…”
Gallium Telluride (GaTe), a layered material with monoclinic crystal structure, has recently attracted a lot of attention due to its unique physical properties and potential applications for angle-resolved photonics and electronics, where optical anisotropies are important. Despite a few reports on the in-plane anisotropies of GaTe, a comprehensive understanding of them remained unsatisfactory to date. In this work, we investigated thickness-dependent in-plane anisotropies of the 13 Raman-active modes and one Raman-inactive mode of GaTe by using angle-resolved polarized Raman spectroscopy, under both parallel and perpendicular polarization configurations in the spectral range from 20 to 300 cm−1. Raman modes of GaTe revealed distinctly different thickness-dependent anisotropies in parallel polarization configuration while nearly unchanged for the perpendicular configuration. Especially, three Ag modes at 40.2 ($${\text{A}}_{\text{g}}^{1}$$
A
g
1
), 152.5 ($${\text{A}}_{\text{g}}^{7}$$
A
g
7
), and 283.8 ($${\text{A}}_{\text{g}}^{12}$$
A
g
12
) cm−1 exhibited an evident variation in anisotropic behavior as decreasing thickness down to 9 nm. The observed anisotropies were thoroughly explained by adopting the calculated interference effect and the semiclassical complex Raman tensor analysis.
“…Typical room temperature photoluminescence (PL) spectrum was shown in Fig. 1 d, where a strong peak at 1.66 eV, in good agreement with the previously reported direct bandgap of GaTe, was observed 28 , 29 , 33 . All the results shown in Fig.…”
Section: Resultssupporting
confidence: 88%
“…1 b, where eleven A g modes and two B g modes were observed in the spectral range from 20 to 300 cm −1 . It is noteworthy that our Raman spectrum did not show peaks around 132 cm −1 and 146 cm −1 , which were known to exist in oxygen-contaminated GaTe samples 28 , 29 . Figure 1 ( a ) Crystal structure of GaTe, shown in perspective view, side view, and top view of three stacked layers.…”
Section: Resultsmentioning
confidence: 65%
“…It has a monoclinic structure whose space group is C2/m. In this work, we will use the conventional crystallographic axes of GaTe, where the x-axis is the direction of the stacked layers, also known as [ ] direction 25 , 28 . On the layer plane, the y-axis is the direction of a series of Ga-Ga binding chains.…”
Gallium Telluride (GaTe), a layered material with monoclinic crystal structure, has recently attracted a lot of attention due to its unique physical properties and potential applications for angle-resolved photonics and electronics, where optical anisotropies are important. Despite a few reports on the in-plane anisotropies of GaTe, a comprehensive understanding of them remained unsatisfactory to date. In this work, we investigated thickness-dependent in-plane anisotropies of the 13 Raman-active modes and one Raman-inactive mode of GaTe by using angle-resolved polarized Raman spectroscopy, under both parallel and perpendicular polarization configurations in the spectral range from 20 to 300 cm−1. Raman modes of GaTe revealed distinctly different thickness-dependent anisotropies in parallel polarization configuration while nearly unchanged for the perpendicular configuration. Especially, three Ag modes at 40.2 ($${\text{A}}_{\text{g}}^{1}$$
A
g
1
), 152.5 ($${\text{A}}_{\text{g}}^{7}$$
A
g
7
), and 283.8 ($${\text{A}}_{\text{g}}^{12}$$
A
g
12
) cm−1 exhibited an evident variation in anisotropic behavior as decreasing thickness down to 9 nm. The observed anisotropies were thoroughly explained by adopting the calculated interference effect and the semiclassical complex Raman tensor analysis.
“…Notably, the Raman analysis indicates that O 2 intercalation happens spontaneously during this complicated preparing process in air, similar with that in the self‐intercalation process in some 2D materials, [ 25 ] different from that in their bulk counterpart, which needs a couple of days for the O 2 concentrates in the bulk. [ 15 , 26 ] In addition, only two broad Raman vibration modes at 126 and 142 cm −1 are obvious for as exfoliated thinner GaTe flakes (≈11 nm), which indicates that this few‐layer GaTe flake is fully transformed during the exfoliation process.…”
Low symmetric two dimensional (2D) semiconductors are of great significance for their potential applications in polarization‐sensitive photodetection and quantum information devices. However, their real applications are limited by their photo‐detecting wavelength ranges, which are restricted by their fundamental optical bandgaps. Recently, intercalation has been demonstrated to be a powerful strategy to modulate the optical bandgaps of 2D semiconductors. Here, the authors report the self‐driven oxygen (O2) intercalation induced bandgap reduction from 1.75 to 1.19 eV in gallium telluride (GaTe) in air. This bandgap shrinkage provides the long‐wavelength detection threshold above ≈1100 nm for O2 intercalated GaTe (referred to as GaTeO2), well beyond the cut‐off wavelength at ≈708 nm for pristine GaTe. The GaTeO2 photodetectors have a high photoresponsivity, and highly anisotropic photodetection behavior to even sub‐waveband radiation. The dichroic ratio (Imax/Imin) of photocurrent is about 1.39 and 2.9 for 600 nm and 1100 nm, respectively. This findings demonstrates a broadband photodetector utilizing GaTe after breaking through its bandgap limitation by self‐driven O2 intercalation in air and further reveal its photoconductivity anisotropic nature. This provides design strategies of 2D materials‐based high‐performance broadband photodetectors for the exploration of polarized state information.
“…We observed a PL peak at 1.66 eV (Figure 2b), which is the reported room-temperature direct bandgap for monoclinic GaTe. [18,26] For polarization-resolved Raman measurements, we primarily monitored the intense A g -Raman peak at 115 cm À1 . The excitation polarization-dependent PL spectra obtained using the parallel configuration (Figure 1d) are as shown in Figure 2c.…”
Section: Determination Of Crystal B-axis Through Optical Transmission Electron Microscopy (Tem) and Diffraction Studiesmentioning
2D layered materials have attracted extensive interest due to their direct electronic bandgap, efficient light-matter coupling, and exciting anisotropic material properties. The anisotropic optical and electronic properties in these materials are vital for the creation of polarization-sensitive optoelectronic devices, such as polarization-dependent photodetectors, sensors, and sources. [1] Currently, most photodetectors provide information about the brightness and color of an object obtained from the intensity and wavelength of absorbed light. However, another fundamental property of light, the polarization of the electric field, can offer enhanced details about an image that is unobtainable from traditional thermal or visible imaging. As a result, polarization-resolved imaging has gained interest for use in applications in various fields, spanning from vehicle navigation, [2] finger printing, [3] and the study of astronomical objects [4] to facial recognition, obstacle detection, and military surveillance. [5,6] In addition, polarizationsensitive imaging has been used in the biomedical field for the study of microcirculation in humans, [7] imaging for retinal surgery, [8] and detection of cancer at early stages. [9] In addition to detection of polarized light, it is essential to control both the polarization and directionality of light emission for several applications, such as sensing, polarized light emission, and optical communication. [10,11] Resolving the polarization state of light requires additional elements that are otherwise unneeded in a photodetector, such as gratings or polarizers. Consequently, these systems require sophisticated integration schemes to enable proper alignment of these elements during device patterning. [12] Conversely, a class of 2D materials with strong inherent structural and optical anisotropy caused by their chain-formation structure extending in one crystal direction can potentially enable the fabrication of flexible stretchable polarization-sensitive devices, lifting some of the current stringent fabrication requirements. This class of materials includes transition metal monochalcogenides, GeS, [13] GeSe, [14] dichalcogenides, such as ReS 2 , [12] ReSe 2 , [15] and GeSe 2 , [16] and trichalcogenides ZrS 3 . [17] Most recently monoclinic gallium telluride (GaTe) [18][19][20] has emerged as a promising material platform for polarizationsensitive photodetection applications. The in-plane optical anisotropy behavior of monoclinic GaTe is caused by its pseudo-1D nature, as each layer comprises a chain-like structure extending along the b-axis direction. Furthermore, a study by Wang et al. [21] has reported that layered GaTe flakes exhibit in-plane anisotropic resistance and can be used to create direction-sensitive data storage devices/sensors. The measured ratios of electrical conductivity along directions parallel and perpendicular to the b-axis (chain direction) can reach up to an order of 10 3 based on the applied gate voltage. So far, no study translating these anisotropic pr...
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