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arXiv 1907.03342cond-mat.mes-hallcond-mat.mtrl-sci
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化学气相沉积法制备高光学质量的MoS2单分子膜

Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition

Shivangi Shree, Antony George, Tibor Lehnert, Christof Neumann, Meryem Benelajla, Cedric Robert, Xavier Marie, Kenji Watanabe, Takashi Taniguchi, Ute Kaiser, Be… 展开作者

Shivangi Shree, Antony George, Tibor Lehnert, Christof Neumann, Meryem Benelajla, Cedric Robert, Xavier Marie, Kenji Watanabe, Takashi Taniguchi, Ute Kaiser, Bernhard Urbaszek, Andrey Turchanin

摘要:

化学气相沉积(CVD)允许在廉价衬底上的大表面积上生长过渡金属二硫属化物(TMD)。在这项工作中,我们相关的CVD生长的MoS $_2$单层(ML)的结构质量的SiO $_2$ /Si晶片的高分辨率透射电子显微镜(HRTEM)研究显示,在低温到环境温度的光发射和吸收的高光学质量。我们用高分辨透射电子显微镜测定了样品的缺陷浓度为10 $^{13}$ cm $^{-2}$。为了获得ML的固有光学质量,我们从SiO $_2$生长衬底中去除ML,并将其封装在具有低缺陷密度的hBN薄片中,以减少介电无序的不利影响。在低温下(T= 4K),自由激子的发射和吸收光谱的光跃迁线宽为5 meV.这与通过散装材料的机械剥离获得的最佳ML样品相当。CVD生长的MoS $_2$ ML的光致发光主要由自由激子而不是缺陷,即使在低温下。高的光学质量的样品进一步证实了观察激发激子态的里德伯系列。我们在CVD生长的MoS $_2$层中光学地产生谷相干性和谷极化,显示了研究大表面积CVD样品中自旋和谷物理的可能性。

英文摘要:

Chemical vapor deposition (CVD) allows growing transition metal dichalcogenides (TMDs) over large surface areas on inexpensive substrates. In this work, we correlate the structural quality of CVD grown MoS$_2$ monolayers (MLs) on SiO$_2$/Si wafers studied by high-resolution transmission electron microscopy (HRTEM) with high optical quality revealed in optical emission and absorption from cryogenic to ambient temperatures. We determine a defect concentration of the order of 10$^{13}$ cm$^{-2}$ for our samples with HRTEM. To have access to the intrinsic optical quality of the MLs, we remove the MLs from the SiO$_2$ growth substrate and encapsulate them in hBN flakes with low defect density, to reduce the detrimental impact of dielectric disorder. We show optical transition linewidth of 5 meV at low temperature (T=4 K) for the free excitons in emission and absorption. This is comparable to the best ML samples obtained by mechanical exfoliation of bulk material. The CVD grown MoS$_2$ ML photoluminescence is dominated by free excitons and not defects even at low temperature. High optical quality of the samples is further confirmed by the observation of excited exciton states of the Rydberg series. We optically generate valley coherence and valley polarization in our CVD grown MoS$_2$ layers, showing the possibility for studying spin and valley physics in CVD samples of large surface area.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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