Anisotropic Optical and Vibrational Properties of GeS
The optical response of bulk germanium sulfide (GeS) is investigated systematically using different polarization-resolved experimental techniques, such as photoluminescence (PL), reflectance contrast (RC), and Raman scattering (RS). It is shown that while the low-temperature (<i>T</i> =...
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| Autores principales: | , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/e461a722866a4ee98d9202aabe2fb7cd |
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| Sumario: | The optical response of bulk germanium sulfide (GeS) is investigated systematically using different polarization-resolved experimental techniques, such as photoluminescence (PL), reflectance contrast (RC), and Raman scattering (RS). It is shown that while the low-temperature (<i>T</i> = 5 K) optical band-gap absorption is governed by a single resonance related to the neutral exciton, the corresponding emission is dominated by the disorder/impurity- and/or phonon-assisted recombination processes. Both the RC and PL spectra are found to be linearly polarized along the armchair direction. The measured RS spectra over a broad range from 5 to 300 K consist of six Raman peaks identified with the help of Density Functional Theory (DFT) calculations: A<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mi mathvariant="normal">g</mi><mn>1</mn></msubsup></semantics></math></inline-formula>, A<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mi mathvariant="normal">g</mi><mn>2</mn></msubsup></semantics></math></inline-formula>, A<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mi mathvariant="normal">g</mi><mn>3</mn></msubsup></semantics></math></inline-formula>, A<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mi mathvariant="normal">g</mi><mn>4</mn></msubsup></semantics></math></inline-formula>, B<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mrow><mn>1</mn><mi mathvariant="normal">g</mi></mrow><mn>1</mn></msubsup></semantics></math></inline-formula>, and B<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mrow><mn>1</mn><mi mathvariant="normal">g</mi></mrow><mn>2</mn></msubsup></semantics></math></inline-formula>, which polarization properties are studied under four different excitation energies. We found that the polarization orientations of the A<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mi mathvariant="normal">g</mi><mn>2</mn></msubsup></semantics></math></inline-formula> and A<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow></mrow><mi mathvariant="normal">g</mi><mn>4</mn></msubsup></semantics></math></inline-formula> modes under specific excitation energy can be useful tools to determine the GeS crystallographic directions: armchair and zigzag. |
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