期刊
PHYSICAL REVIEW B
卷 90, 期 3, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.90.035308
关键词
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资金
- Major State Basic Research Development Program of China [2011CB922200, 2013CB922300]
- Natural and Science Foundation of China [11374097, 61376129]
- Science and Technology Commission of Shanghai Municipality [14XD1401500, 13JC1402100, 13JC1404200]
- Shanghai Institutions of Higher Learning
Temperature-dependent interband transitions and exciton excitations of sol-gel derived CuCr1-x MgxO2 (2% <= x <= 8%) films have been investigated by transmittance spectra (8-300 K) and photoluminescence (PL) spectra (77-300 K). An abnormal dependence of the optical band gap with the temperature has been found for the films with x = 0.02 and 0.04. At the low-temperature region, the gap energy shows a redshift trend with decreasing temperature. It is due to the strong Cr 3d-O 2p-Cu 3d interaction in the upper part of the valence band, which can be weaken by heavily Mg doping. The spin-orbit interactions of Cr3+ ions in an octahedral environment make the 3d states more disperse, which can contribute to the relatively high conductivity. A well-defined low-energy absorption has been assigned to the spin-allowed 3d -> 3d transition. Moreover, a strong exciton excitation around 1.8 eV has been observed due to the naturally low-dimensional structure of the delafossite, which can be modulated by temperature and hole concentration.
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