Tailoring Vacancies Far Beyond Intrinsic Levels Changes the Carrier Type and Optical Response in Monolayer MoSe2−x Crystals

详细信息    查看全文

• 作者：Masoud Mahjouri-Samani ; Liangbo Liang ; Akinola Oyedele ; Yong-Sung Kim ; Mengkun Tian ; Nicholas Cross ; Kai Wang ; Ming-Wei Lin ; Abdelaziz Boulesbaa ; Christopher M. Rouleau ; Alexander A. Puretzky ; Kai Xiao ; Mina Yoon ; Gyula Eres ; Gerd Duscher ; Bobby G. Sumpter ; David B. Geohegan
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：August 10, 2016
• 年：2016
• 卷：16
• 期：8
• 页码：5213-5220
• 全文大小：513K
• 年卷期：0
• ISSN：1530-6992

文摘

Defect engineering has been a critical step in controlling the transport characteristics of electronic devices, and the ability to create, tune, and annihilate defects is essential to enable the range of next-generation devices. Whereas defect formation has been well-demonstrated in three-dimensional semiconductors, similar exploration of the heterogeneity in atomically thin two-dimensional semiconductors and the link between their atomic structures, defects, and properties has not yet been extensively studied. Here, we demonstrate the growth of MoSe_2–x single crystals with selenium (Se) vacancies far beyond intrinsic levels, up to ∼20%, that exhibit a remarkable transition in electrical transport properties from n- to p-type character with increasing Se vacancy concentration. A new defect-activated phonon band at ∼250 cm⁻¹ appears, and the A_1g Raman characteristic mode at 240 cm⁻¹ softens toward ∼230 cm⁻¹ which serves as a fingerprint of vacancy concentration in the crystals. We show that post-selenization using pulsed laser evaporated Se atoms can repair Se-vacant sites to nearly recover the properties of the pristine crystals. First-principles calculations reveal the underlying mechanisms for the corresponding vacancy-induced electrical and optical transitions.