以超快雷射製作石墨烯/二硫化鉬元件結構於氣體檢測

Abstract

本研究利用超快雷射製程 (Ultrafast laser processing technique)進行製作設計的微型加熱感測元件及其特性探討，同時整合二硫化鉬(Molybdenum disulfide, MoS2)材料，以開發異質結構(Heterostructure)元件於氣體檢測(Gas detection)應用。本研究是採以有限元素法(Finite element method, FEM)，在設計的串/並聯電路之微加熱結構元件，進行熱性能和電路的電流密度之預測。在實驗方面，是利用超快雷射直寫技術於石墨烯(Graphene)薄膜，其固定重複率為 300 kHz，在振鏡掃描速度為 300 mm/s及雷射能量密度為 2.19 J/cm2，進行製程路徑次數 2 次後，完成不同寬度的薄膜電極元件製作及其檢測元件特性分析。研究結果顯示：在施加相同電壓條件下，串聯電路結構的微加熱器穩態溫度較低，且穩態溫度受電路形狀的影響較大，其原因是串聯電路結構的電阻會明顯大於並聯電路結構，因此該元件通過的電流較小，產生的焦耳熱也較小。此外，本研究於石墨烯感測元件搭配MoS2溶液，以滴鍍(Drop casting)技術，開發MoS2/石墨烯微型加熱感測元件，並比較石墨烯微型加熱感測元件，進一步進行氣體檢測之靈敏度探討。本研究結果在石墨烯微型加熱感測元件方面，顯示在溫度於92 oC時，該元件偵測氣體濃度於100、300和500 ppm時，氣體響應值(Response)會分別為1.4 %、7.2 %和17.7 %。本研究結果在MoS2/石墨烯微型加熱感測元件方面，顯示在溫度於92 oC時，該元件偵測氣體濃度於100、300和500 ppm時，氣體響應值分會別為1.7 %、4.9 %和12.3 %。因此，本研究證明MoS2/石墨烯微型加熱感測元件具有良好的恢復性，在50 s內該元件的檢測電阻可以恢復至原始電阻。This study presents the ultrafast laser processing technique to fabricate the design of micro-heater devices and investigate on their device characteristics. At the same time, the study can integrate the molybdenum disulfide (MoS2) materials to develop heterostructure devices in applications for gas detection. The finite element method (FEM) of this study is used to predict the thermal performance and current density for the micro-heater devices with the design of series/parallel circuit structures. In terms of experiments, ultra-fast laser direct-writing technique is used on the graphene film with a fixed repetition rate of 300 kHz, a scanning speed of 300 mm/s in the galvanometer, and a required laser fluence of 2.19 J/cm2. After fabricating technique with path-process twice, the thin-film electrode devices with the different widths and the analysis of the sensing characteristics can be performed. The results of study showed that under the same voltage condition, the steady-state temperature of the series circuit structure of the micro-heater is lower, and the steady-state temperature is greatly affected by the shape of the electrode circuit. The resistance of the series circuit structure is obviously greater than that of the parallel circuit structure, so the current passing through the device is smaller where the Joule heat generated is also smaller. In addition, the technique of study can be used by with drop casting process with MoS2 solution on graphene sensing device for developing the MoS2/graphene heating sensing device. By compar to the graphene heating sensing device, the device study further can explore the sensitivity of gas detection. For the detection of NO gas on graphene heating sensing device, it indicates that the electrical response at the temperature of 92 oC can be 1.4, 7.2, and 17.7 % at the gas concentration of 100, 300, 500 ppm, respectively. For the detection of NO gas on MoS2/graphene heating sensing device, it shows that the electrical response at the temperature of 92 oC can be 1.7, 4.9, and 12.3 % at the gas concentration of 100 ppm, 300, 500 ppm, respectively. Therefore, it has good recoverability of MoS2/graphene heating sensing device on the sensing resistance to the original resistance within 50 s.