Valleytronics公司
凝聚态物理
极化(电化学)
双层石墨烯
作者
Pramoda K. Nayak,Fan-Cheong Lin,Chao-Hui Yeh,Jer-Shing Huang,Po-Wen Chiu
出处
期刊:Nanoscale
[The Royal Society of Chemistry]
日期:2016-03-10
卷期号:8 (11): 6035-6042
被引量:60
摘要
We report robust room temperature valley polarization in chemical-vapor-deposition (CVD) grown monolayer and bilayer WS2via polarization-resolved photoluminescence measurements using excitation below the bandgap. We show that excitation with energy slightly below the bandgap of the multi-valleyed transition metal chalcogenides can effectively suppress the random redistribution of excited electrons and, thereby, greatly enhance the efficiency of valley polarization at room temperature. Compared to mechanically exfoliated WS2, our CVD grown WS2 films also show enhancement in the coupling of spin, layer and valley degree of freedom and, therefore, provide improved valley polarization. At room temperature, using below-bandgap excitation and CVD grown monolayer and bilayer WS2, we have reached a record-high valley polarization of 35% and 80%, respectively, exceeding the previously reported values of 10% and 65% for mechanically exfoliated WS2 layers using resonant excitation. This observation provides a new direction to enhance valley control at room temperature.
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