A Systematic Study of the Temperature Dependence of the Dielectric Function of GaSe Uniaxial Crystals from 27 to 300 K.
- Resource Type
- Academic Journal
- Authors
- Le LV; Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam.; Nguyen TT; Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam.; Nguyen XA; Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea.; Cuong DD; Faculty of Physics and Engineering Physics, University of Science, VNU-HCM, Ho Chi Minh City 700000, Vietnam.; Nguyen TH; Department of Physics, Nha Trang University, Nha Trang 650000, Vietnam.; Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea.; Nguyen VQ; Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea.; Advanced Process Development Team, ISAC Research Inc., Techno2ro 340, Tabrip-dong, Yuseong-gu, Daejeon 34036, Republic of Korea.; Cho S; Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea.; Kim YD; Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea.; Kim TJ; Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea.
- Source
- Publisher: MDPI AG Country of Publication: Switzerland NLM ID: 101610216 Publication Model: Electronic Cited Medium: Print ISSN: 2079-4991 (Print) Linking ISSN: 20794991 NLM ISO Abbreviation: Nanomaterials (Basel) Subsets: PubMed not MEDLINE
- Subject
- Language
- English
- ISSN
- 2079-4991
We report the temperature dependences of the dielectric function ε = ε 1 + i ε 2 and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to 300 K using spectroscopic ellipsometry. The fundamental bandgap and strong exciton effect near 2.1 eV are detected only in the c-direction, which is perpendicular to the cleavage plane of the crystal. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that incorporates the Bose-Einstein statistical factor and the temperature coefficient to describe the electron-phonon interaction. To determine the origin of this anisotropy, we perform first-principles calculations using the mBJ method for bandgap correction. The results clearly demonstrate that the anisotropic dielectric characteristics can be directly attributed to the inherent anisotropy of p orbitals. More specifically, this prominent excitonic feature and fundamental bandgap are derived from the band-to-band transition between s and p z orbitals at the Γ-point.