脉冲激光沉积在SiO₂上生长的单层和少层MoS₂的多波长拉曼研究
Multiwavelength Raman investigation of mono- and few-layer MoS2 grown by Pulsed Laser Deposition on SiO2
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中文总结 AI 辅助
研究利用室温脉冲激光沉积在SiO₂衬底上生长MoS₂，通过多波长拉曼光谱研究其生长及激子 - 声子耦合。控制参数可调控层数，发现E₂g¹和A₁g模式拉曼位移差与缺陷密度随脉冲数变化，还证实对称依赖的激子 - 声子耦合，为二维MoS₂生长及相互作用研究提供依据。
中文摘要 AI 辅助
二硫化钼（MoS₂）是一种半导体，其振动和激子特性对层数和结构无序高度敏感。我们展示了使用室温脉冲激光沉积（PLD）在惰性、电子兼容的SiO₂衬底上生长MoS₂单层。通过控制工艺参数可实现从单层到多层膜的调控，并通过多波长拉曼光谱进行研究。E₂g¹和A₁g模式之间拉曼位移差的演变以及缺陷密度评估跟踪了薄膜生长与沉积激光脉冲数的关系。我们提供了PLD生长的单层MoS₂中对称依赖的激子 - 声子耦合的实验证据，观察到面外A₁g和面内E₂g¹模式共振行为的调制，与它们与不同激子的耦合有关。与机械剥离的单层比较揭示了生长诱导缺陷在调节这些相互作用中的作用。这些发现确立了室温PLD作为在惰性、电子兼容衬底上生长二维MoS₂的可行方法，并深入了解二维MoS₂中激子共振与生长诱导无序之间的相互作用。
英文摘要
Molybdenum disulfide (MoS$_2$) is a semiconductor whose vibrational and excitonic properties are highly sensitive to layer number and structural disorder. We demonstrate the growth of MoS$_2$ monolayers on inert, electronics-compatible SiO$_2$ substrates using room-temperature pulsed laser deposition (PLD). Control of the process parameters enables tuning from monolayer to multilayer films, which we investigate by multiwavelength Raman spectroscopy. The evolution of the Raman-shift difference between the $E_{2g}^{1}$ and $A_{1g}$ modes, combined with an assessment of defect density, tracks film growth as a function of the number of deposition laser pulses. Although excitonic effects strongly influence the optical response of two-dimensional transition-metal dichalcogenides, experimental reports of symmetry-selective exciton-phonon coupling remain limited. We provide experimental evidence of symmetry-dependent exciton-phonon coupling in PLD-grown monolayer MoS$_2$. Specifically, we observe modulation of the resonant behaviour of the out-of-plane $A_{1g}$ and in-plane $E_{2g}^{1}$ modes, related to their different coupling to A excitons, predominantly derived from Mo $d_{z^2}$ orbitals, and C excitons, characterized by mixed orbital contributions from Mo $d_{z^2}$ and S $p_x$ and $p_y$ states. Comparison with mechanically exfoliated monolayers reveals the role of growth-induced defects in modulating these interactions. These findings establish room-temperature PLD as a viable approach for growing two-dimensional MoS$_2$ on inert, electronics-compatible substrates and provide insight into the interplay between excitonic resonances and growth-induced disorder in two-dimensional MoS$_2$.
