雷射削融法合成二硫化鎢量子點的光學特性與應用

Optical Properties and Applications of Tungsten Disulfide Quantum Dots Synthesized via Pulsed Laser Ablation

沈莉娜(Svette Reina Merden Santiago)

指導教授 ： 沈志霖

中原大學/理學院/物理研究所/博士(2020年)

https://doi.org/10.6840/cycu202000493

摘要

近年來，過渡金屬二硫化物如二硫化鎢量子點受到相當關注。在過渡金屬二硫化物中摻雜可以調整它們的光學和電學性質，並且有助於許多應用。我們開發出一種脈衝雷射削融法來合成二硫化鎢量子點，並藉由二乙烯三胺濃度來調控二硫化鎢量子點中的載子濃度，實現了高達8.27×1012 cm-2的電洞濃度。由於加入二乙烯三胺，二硫化鎢 量子點的光激螢光強度提高了72倍。本論文研究在二硫化鎢 量子點中的載子再結合動力學。 二硫化鎢量子點的輻射生命期隨著載子密度的增加而降低，這與眾所周知的ABC模型中的輻射生命期行為相似。在低和高載子濃度下的非輻射生命期，則分別由Shockley-Read-Hall（SRH）和Auger再結合主導。本論文也研究二硫化鎢量子點中的多體效應，發現二硫化鎢量子點在室溫下就可觀察到能隙重歸一化可達251 ± 16 meV並且激子束縛能可高達991 ± 33 meV。此外，當二硫化鎢量子點加入InGaN/GaN和InGaAs/AlGaAs量子井時，它們的光激螢光強度可增強，這歸因於從二硫化鎢量子點的光生電洞轉移。其中，二硫化鎢量子點穿隧到InGaN/GaN量子井的穿隧時間與位壘厚度呈現半經典的Wentzel-Kramers-Brillouin（WKB）模型。這些研究的結果，有助於過渡金屬二硫化物的光學特性了解與其在光電元件的應用。

關鍵字

光激螢光 ； 複合動力學 ； 多體效應 ； 載子轉移 ； 穿隧

並列摘要

Quantum dots (QDs) from transition metal dichalcogenides (TMDs) such as WS2 QDs has attracted much attention in recent years. Doping in TMDs have been found to modulate their optical and electrical properties and be beneficial in many applications. In this dissertation, we controlled the carrier density in WS2 QDs by pulsed laser ablation (PLA) synthesis with varying concentrations of diethylenetriamine (DETA). P-type doping of WS2 QDs was synthesized successfully and a hole concentration as high as 8.27 × 1012 cm−2 have been implemented. Introduction of DETA also displays an increase as high as 72 folds in the photoluminescence intensity of WS2 QDs. The carrier-density-dependent recombination dynamics in WS2 QDs has been investigated. The radiative lifetime of the WS2 QDs displays a decrease with increasing carrier densities, similar to the behavior of the radiative lifetime in the well-known ABC model. The nonradiative recombination was found to be dominated by Shockley-Read-Hall (SRH) and Auger recombination at the low and high carrier density, respectively. The many body effects in DETA-doped WS2 QDs were studied. The room-temperature band-gap renormalization as high as 251 ± 16 meV and an exciton binding energy up to 991 ± 33 meV in DETA-doped WS2 QDs were observed, displaying an agreement with the theory of many-body effects. The PL intensity enhancement in InGaN and AlgAas quantum wells (QWs) were observed after the introduction of WS2 QDs, which is attributed to the transfer of the photogenerated holes and tunneling of electrons from WS2 QDs to the QWs. The tunneling time as a function of the barrier thickness agrees well with the semiclassical Wentzel-Kramers-Brillouin (WKB) model. The above investigations are expected to provide useful insights for understanding the optical properties of TMD QDs and future applications in optoelectronics and energy conversion devices.

並列關鍵字

Photoluminescence ； Recombination Dynamics ； Many-Body Effects ； Carrier Transfer ； Tunneling

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