TY - JOUR
T1 - Temperature Dependence of the Indirect Gap and the Direct Optical Transitions at the High-Symmetry Point of the Brillouin Zone and Band Nesting in MoS2, MoSe2, MoTe2, WS2, and WSe2Crystals
AU - Kopaczek, J.
AU - Zelewski, S.
AU - Yumigeta, K.
AU - Sailus, R.
AU - Tongay, S.
AU - Kudrawiec, R.
N1 - Funding Information:
This work was supported by the National Science Centre (NCN) Poland OPUS 11 No. 2016/21/B/ST3/00482. J.K. acknowledges support within the Bekker program from the Polish National Agency for Academic Exchange. S.J.Z. is a beneficiary of the START scholarship from the Foundation for Polish Science. S.T. acknowledges support from DOE-SC0020653, Applied Materials Inc., NSF CMMI 1825594, NSF DMR-1955889, NSF CMMI-1933214, NSF DMR-1904716, NSF 1935994, NSF ECCS 2052527, and DMR 2111812.
Funding Information:
This work was supported by the National Science Centre (NCN) Poland OPUS 11 No. 2016/21/B/ST3/00482. J.K. acknowledges support within the Bekker program from the Polish National Agency for Academic Exchange. S.J.Z. is a beneficiary of the START scholarship from the Foundation for Polish Science. S.T. acknowledges support from DOE-SC0020653 Applied Materials Inc., NSF CMMI 1825594, NSF DMR-1955889, NSF CMMI-1933214 NSF DMR-1904716, NSF 1935994, NSF ECCS 2052527, and DMR 2111812.
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/3/31
Y1 - 2022/3/31
N2 - Following the rise of interest in the properties of transition metal dichalcogenides, many experimental techniques were employed to research them. However, the temperature dependencies of optical transitions, especially those related to band nesting, were not analyzed in detail for many of them. Here, we present successful studies utilizing the photoreflectance method, which, due to its derivative and absorption-like character, allows investigating direct optical transitions at the high-symmetry point of the Brillouin zone and band nesting. By studying the mentioned optical transitions with temperature from 20 to 300 K, we tracked changes in the electronic band structure for the common transition metal dichalcogenides (TMDs), namely, MoS2, MoSe2, MoTe2, WS2, and WSe2. Moreover, transmission and photoacoustic spectroscopies were also employed to investigate the indirect gap in these crystals. For all observed optical transitions assigned to specific k-points of the Brillouin zone, their temperature dependencies were analyzed using the Varshni relation and Bose-Einstein expression. It was shown that the temperature energy shift for the transition associated with band nesting is smaller when compared with the one at high-symmetry point, revealing reduced average electron-phonon interaction strength.
AB - Following the rise of interest in the properties of transition metal dichalcogenides, many experimental techniques were employed to research them. However, the temperature dependencies of optical transitions, especially those related to band nesting, were not analyzed in detail for many of them. Here, we present successful studies utilizing the photoreflectance method, which, due to its derivative and absorption-like character, allows investigating direct optical transitions at the high-symmetry point of the Brillouin zone and band nesting. By studying the mentioned optical transitions with temperature from 20 to 300 K, we tracked changes in the electronic band structure for the common transition metal dichalcogenides (TMDs), namely, MoS2, MoSe2, MoTe2, WS2, and WSe2. Moreover, transmission and photoacoustic spectroscopies were also employed to investigate the indirect gap in these crystals. For all observed optical transitions assigned to specific k-points of the Brillouin zone, their temperature dependencies were analyzed using the Varshni relation and Bose-Einstein expression. It was shown that the temperature energy shift for the transition associated with band nesting is smaller when compared with the one at high-symmetry point, revealing reduced average electron-phonon interaction strength.
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U2 - 10.1021/acs.jpcc.2c01044
DO - 10.1021/acs.jpcc.2c01044
M3 - Article
AN - SCOPUS:85127309268
SN - 1932-7447
VL - 126
SP - 5665
EP - 5674
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 12
ER -