摻雜二亞乙基三胺二硫化鉬量子點的螢光能谷偏極化與復合機制

Valley polarized luminescence and recombination mechanism in diethylenetriamine doped MoS2 quantum dots

王泓鈞(HONG-JYUN WANG)

指導教授 ： 沈志霖

中原大學/理學院/物理學系/碩士(2021年)

https://doi.org/10.6840/cycu202201150

摘要

此論文透過脈衝雷射剝離法 (Pulsed Laser Ablation (PLA) Method) 成功地製備含二亞乙基三胺 (Diethylenetriamine; DETA)的二硫化鉬量子點。透過量測時間解析螢光光譜，發現隨著載子濃度的增加，量子點的輻射復合生命期會逐漸減少。而非輻射復合生命期隨著載子濃度的變化，可由肖克萊瑞德-霍爾(Shockley-Read-Hall)復合和奧杰(Auger)復合來解釋。此外，發現增加氨水的濃度會使得光致發光強度逐漸下降，透過量測光致發光和時間解析光致發光，證明二硫化鉬量子點和氨水有著高靈敏度的變化，因此，二硫化鉬量子點有可能作為氨水的螢光感測器。
此論文藉由用光致發光與時間解析光致發光研究在室溫的二硫化鉬量子點能谷偏極化率。一般而言，在常溫下能夠維持在奈秒以上尺度的只有過渡金屬二硫化物的異質結構。透過光譜分析，發現含二亞乙基三胺二硫化鉬量子點的 A 激子與 B 激子在室溫約各有 10%與 15%的能谷偏極化率。另外，透過量測載子在能谷生命期可得出能谷偏極化率生命期，得到其生命期可以達到約 20-45 奈秒。此時間長度是單層的過金屬二鹵化物在低溫下能谷偏極化率生命期的幾十倍甚至到幾百倍。為了能夠更了解能谷中所發生的現象，利用交換交互作用的能間散射模型 (Intervalley Scattering Model)來模擬能谷偏極化率生命期。發現同層不同能谷激子間的能谷間交互作用 (Intervalley Interaction)所產生的能谷間散射 (Intervalley Scattering)可以讓能谷偏極化生命期維持更久的時間，此模擬得出的數據符合實驗的能谷偏極 化率生命期，因此證明了上述模型是正確的。此二硫化鉬量子點能谷偏極化 率的研究將有幫助於在能谷電子學以及量子資訊等領域的元件應用。

關鍵字

二硫化鉬量子點

並列摘要

The quantum dots (QDs) functionalized with Diethylenetriamine was successfully produced by the pulsed laser ablation (PLA). We investigate the carrier concentration and recombination lifetime of the TMD QDs through TRPL. Here, the change in nonradiative recombination lifetime is found to be due to Auger and Shockley-Read Hall (SRH) recombination. Also, the sensing capability of the QDs was studied. Here, the change in PL emission intensity of QDs with introduction of ammonium hydroxide was measured. Using PL and TRPL, the QDs demonstrates good sensitivity to the ammonium hydroxide, hence, showing that the QDs can be used as ammonium hydroxide fluorescent detector.
Further, by measuring the polarized resolved photoluminescence (PL) spectra and polarized-time resolved PL (PTRPL), the valley polarization under ambient temperature can be observed. Basically, valley polarization lifetime can be achieved in the range of nanoseconds under room temperature and was only observed in the heterostructure transition metal dichalcogenides (TMDs). Through analyzation by PL measurements, the B- and A-exciton of our TMD QDs
have been found to demonstrate a valley polarization of 10 % and 15 %,
respectively. By measuring the PTRPL, the carrier lifetime in the different valley can be observed with range of 20 to 45 ns. The scale of the valley polarization lifetime observed in QDs under ambient temperature is longer than ten to hundreds times of that in monolayer TMD under low temperature. To
understand the phenomenon in the valley, we simulate the carrier lifetime in the
valley by using an intervalley scattering model. Here, the simulated model versus the experimental data demonstrates an agreement. This describes the intervalley interaction can result in intervalley scattering that affects the valley polarization lifetime. This research of the valley polarization lifetime of TMD QDs can be helpful to valleytronics studies and the application of quantum information devices.

並列關鍵字

MoS2 quantum dot

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