Resonant Raman spectroscopy study of swift heavy ion irradiated MoS₂

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• 作者：Hang Guo^a ; ^b ; Youmei Sun^a ; Pengfei Zhai^a ; Jian Zeng^a ; Shengxia Zhang^a ; ^b ; Peipei Hu^a ; ^b ; Huijun Yao^a ; Jinglai Duan^a ; Mingdong Hou^a ; Jie Liu^a ; ^{j.liu@impcas.ac.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Resonant Raman spectroscopy ; Molybdenum disulphide ; Swift heavy ion irradiation
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2016
• 出版时间：15 August 2016
• 年：2016
• 卷：381
• 期：Complete
• 页码：1-5
• 全文大小：1736 K

文摘

Molybdenum disulphide (MoS₂) crystal samples were irradiated by swift heavy ions (²⁰⁹Bi and ⁵⁶Fe). Hillock-like latent tracks were observed on the surface of irradiated MoS₂ by atomic force microscopy. The modifications of properties of irradiated MoS₂ were investigated by resonant Raman spectroscopy and ultraviolet–visible spectroscopy (UV–Vis). A new peak ($E_{1u}^2\text{,}$ ∼385.7 cm⁻¹) occurs near the in-plane $E_{2g}^1$ peak (∼383.7 cm⁻¹) after irradiation. The two peaks shift towards lower frequency and broaden due to structural defects and stress with increasing fluence. When irradiated with high fluence, two other new peaks appear at ∼ 190 and ∼ 230 cm⁻¹. The peak at ∼230 cm⁻¹ is disorder-induced LA(M) mode. The presence of this mode indicates defects induced by irradiation. The feature at ∼460 cm⁻¹ is composed of 2LA(M) (∼458 cm⁻¹) and A_2u$A_{2u}$ (∼466 cm⁻¹) mode. With increasing fluence, the integrated intensity ratio between 2LA(M  ) and A_2u$A_{2u}$ increases. The relative enhancement of 2LA(M) mode is in agreement with the appearance of LA(M) mode, which both demonstrate structural disorder in irradiated MoS₂. The ∼423-cm⁻¹ peak shifts toward lower frequency due to the decrease in exciton energy of MoS₂, and this was demonstrated by the results of UV–Vis spectra. The decrease in exciton energy could be due to introduction of defect levels into band gap.