本實驗在氧化鋅奈米柱上修飾硫化鉬，將其應用於二氧化氮感測。逐步探討修飾對氧化鋅造成的影響，於氣體感測方面，修飾後材料對二氧化氮之靈敏度有大幅的提升。感測材料及元件合成方面，首先使用黃光微影和電子束蒸鍍在矽晶圓上沉積金/鈦電極，接著利用低溫水熱法合成氧化鋅奈米柱，而後分別利用濺鍍、光沉積兩種方法修飾硫化鉬材料於氧化鋅上。
利用掃描式電子顯微鏡(SEM)觀察材料表面形貌，氧化鋅奈米柱的長度約2 μm，直徑大小約100 nm，呈現六角柱結構。濺鍍修飾硫化鉬後，修飾材料在氧化鋅奈米柱的側壁及頂端，成長出奈米顆粒，並隨著濺鍍時間增加聚合於奈米柱頂端，形成直徑數百奈米之奈米球。我們接著對濺鍍之硫化鉬修飾物進行材料分析，發現濺鍍的修飾材料會與基底氧化鋅鍵結，形成一結構缺陷之二硫化鉬，經XPS分析後得知化學成分為MoSxOy (x=2~3, y=0~1)，此化合物為一非晶結構，並根據鉬與硫的比例判斷其為一p型半導體。
使用光沉積法修飾硫化鉬後的表面形貌，則是會與氧化鋅形成核殼結構。此硫化鉬修飾物經XPS分析後為MoS3 ，並產生副產物S8。我們也發現若先修飾銅氧化物再修飾硫化鉬於氧化鋅上，此時光沉積硫化鉬產物則為MoSx (x=2,3)伴隨著副產物S8產生。
以紫外光激活模式在室溫下對材料進行NO2感測，氧化鋅奈米柱對於500 ppb之NO2有124%的響應。而經過濺鍍修飾後，由於p型MoSxOy與n 型氧化鋅接合，p-n 接面的形成，使載子再結合機率下降，此外也觀察到修飾材料與氧化鋅產生鍵結後，氧化鋅內部的施體缺陷增加，此兩原因使材料對500 ppb之NO2響應提升至448%。
利用光沉積法修飾MoS3於氧化鋅上則是會使材料對500 ppb之NO2響應下降至102%，原因為沉積之MoS3與氧化鋅形成核殼結構，造成氧化鋅感測面積下降，使得響應降低。有趣的是，若在光沉積修飾硫化鉬前先修飾銅氧化物，此時修飾之MoSx將會造成響應值的提升。p型銅氧化物會先與n型氧化鋅產生p-n 接面，使得感測材料對500 ppb之NO2響應提升至416%，若此時再修飾MoSx(MoS3、MoS2)，修飾物與氧化鋅產生的核殼結構將使氧化鋅感測面積下降，但也將使披覆於銅氧化物上的MoS2與氧化鋅接合，p型MoS2與n 型氧化鋅形成新的p-n 接面，再度促進電子電洞對分離，而感測面積下降及新的p-n 接面形成兩者影響抗衡下，將使材料對500 ppb之NO2響應提升至582%。
本實驗利用成本低廉且製程簡單的方式，合成出對二氧化氮具有高靈敏度的感測材料。在500 ppb二氧化氮感測下，濺鍍修飾MoSxOy後材料具有比氧化鋅基材高上3.6倍的二氧化氮氣體響應，而光沉積之MoSx/CuxO共修飾材料更具有比氧化鋅基材高上4.7倍的響應，此兩種材料於低濃度二氧化氮感測應用展現極大的潛力。

In this work, molybdenum sulfide modified ZnO nanorods(NRs) were produced for nitrogen dioxide gas sensing application. A series of material characterizations were performed to investigate the properties of the synthesized materials. It was found that the gas sensing sensitivity greatly improved after the modification. For preparing sensing materials and devices, first, Au/Ti electrodes were made by photolithography and e-gun evaporation on a 4-inch Si wafer. ZnO NRs were grown by a low-temperature hydrothermal method. In the last, modified materials were grown on the ZnO NRs by a sputtering system and a photodeposition method.
The morphologies of the materials were observed by the scanning electron microscope. The results showed that the length of the ZnO NRs were about 2 μm and the diameter were about 100 nm, presenting a hexagonal column structure. After sputtering, nanoparticles grew on the sidewalls and top of the ZnO NRs. They
aggregated on the top of the NRs as the sputtering time increased, forming nanospheres with a diameter of a few hundreds of nanometers. From X-ray photoelectron spectroscopy (XPS) analysis, the chemical composition of the sputtered material was MoSxOy(x=2~3, y=0~1). This compound had an amorphous structure and was judged to be a p-type semiconductor with molybdenum vacancies based on the ratio of molybdenum to sulfur in the XPS results.
The morphologies of photodeposition modified materials formed a core-shell structure with ZnO NRs. By using XPS analysis, amorphous MoS3 with by-product S8 were found in the photodeposition modified materials. For ZnO NRs first modified with copper oxide and then molybdenum sulfide, MoS2 could actually be obtained. The formed materials of the photodeposition processes were MoSx (x=2,3) and S8.
The gas sensing experiments were performed at 500 ppb NO2 under the UV-activation mode. The response for ZnO NRs was 124%, whereas the response for MoSxOy modified ZnO NRs increased to 448%. After MoSxOy modification, p-n heterojunctions were created between MoSxOy and ZnO NRs, reducing the carrier recombination rate. It was also observed that the internal donor defects of ZnO increased after the modified material bonded with ZnO. The two reasons led to a rise in the average response.
On the other hand, the reduction of the average response to 102% was observed for the photodeposited MoS3 modified ZnO NRs. This phenomenon could be explained by the reduction of the sensing area after MoS3 and ZnO NRs formed a core-shell structure. Interestingly, if copper oxide was photodeposited prior to molybdenum sulfide modification, the core-shell structure reduced the ZnO sensing area as mentioned above, but also created MoS2/ZnO p-n heterojunctions. Under the effects of the two influencing factors, the response to 500 ppb NO2, which was 582%, increased again compared with that of the copper oxide modified ZnO NRs, which was 416%.
To summarize, a facile and cost-effective fabrication method was used to synthesize sensing materials with high sensitivities to nitrogen dioxide. At 500 ppb NO2, the response of sputtered MoSxOy modified ZnO NRs was 3.6 times as high as that of the ZnO NRs, and the response of the photodeposited MoSx/CuxO co-modified ZnO NRs was 4.7 times as high as that of the ZnO NRs. The two materials show great potential for low-concentration nitrogen dioxide gas sensing application.

摘要---i
Abstract---iii
致謝---v
目錄---vi
圖目錄---xi
表目錄---xv
第一章 緒論---2
1.1 前言---2
1.2 研究動機---3
第二章 文獻回顧---6
2.1 氣體感測器---6
2.1.1 氣體感測器種類---6
2.1.2 金屬氧化物半導體氣體感測器---8
2.1.3 二維過渡金屬二硫族化合物氣體感測器---8
2.1.4 氣體感測器基本性質---9
2.2 金屬氧化物感測機制---10
2.2.1 氣體吸附反應---11
2.2.2 氣體脫附反應---13
2.2.3 氧化鋅與二氧化氮之吸附反應---15
2.3 影響靈敏度的因素---17
2.3.1 奈米材料影響表面接受功能、傳感功能---18
2.3.2 奈米複合材料影響表面接受功能、傳感功能---19
2.3.3 微結構、孔隙度影響通用因子---22
2.4 氧化鋅概論---22
2.4.1 氧化鋅晶體結構---22
2.4.2 氧化鋅n-type半導體特性---24
2.4.3 氧化鋅光學性質---25
2.4.4 氧化鋅奈米柱合成方法與機制---26
2.5 氧化鋅奈米複合材料之氣體感測應用---28
2.5.1 二硫化鉬修飾---28
2.5.2 銅氧化物修飾---30
2.6 修飾材料合成---30
2.6.1 磁控濺鍍法---31
2.6.2 光沉積法---31
第三章 實驗方法與儀器---35
3.1 感測材料及元件製作流程---35
3.1.1 基板電極製作---35
3.1.2 氧化鋅奈米柱合成---36
3.1.3 添加修飾材料---38
3.2 材料分析儀器---41
3.2.1 掃描式電子顯微鏡---41
3.2.2 能量色散X-射線光譜儀---41
3.2.3 X-射線光電子光譜儀---41
3.2.4 X-射線繞射分析儀---41
3.2.5 拉曼光譜儀---42
3.2.6 螢光光譜儀---42
3.3 氣體感測實驗---42
3.3.1 氣體感測系統架構---42
3.3.2 二氧化氮濃度計算---43
3.3.3 氣體感測實驗步驟---44
第四章 結果與討論---46
4.1 氧化鋅材料分析---46
4.1.1 表面形貌---46
4.1.2 晶體結構及分子結構---47
4.1.3 光致放光性質---48
4.2 濺鍍合成之硫化鉬修飾氧化鋅材料分析---48
4.2.1 表面形貌---48
4.2.2 元素組成---51
4.2.3 化學鍵結---51
4.2.4 晶體結構及分子結構---52
4.2.5 光致放光性質---53
4.3 光沉積法合成之硫化鉬修飾氧化鋅材料分析---55
4.3.1 表面形貌---55
4.3.2 元素組成---57
4.3.3 化學鍵結---57
4.3.4 晶體結構及分子結構---58
4.3.5 光致放光性質---59
4.4 光沉積法合成之硫化鉬/銅氧化物共修飾氧化鋅材料分析---60
4.4.1 表面形貌---60
4.4.2 元素組成---62
4.4.3 化學鍵結---62
4.4.4 晶體結構及分子結構---64
4.4.5 光致放光性質---65
4.5 二氧化氮氣體感測結果---66
4.5.1 氧化鋅氣體感測---67
4.5.2 濺鍍合成之硫化鉬修飾氧化鋅氣體感測---69
4.5.3 光沉積合成之硫化鉬、硫化鉬/銅氧化物共修飾氧化鋅氣體感測---71
4.5.4 靈敏度比較---74
第五章 結論---77
參考文獻---79

1. A. Hulanicki, S. Glab, and F. Ingman, “Chemical sensors: definitions and classification,” Pure and Applied Chemistry, 63(9), 1247-1250 (1991).

2. P. Srinivasan, M. Ezhilan, A. J. Kulandaisamy, K. J. Babu, and J. B. B. Rayappan, “Room temperature chemiresistive gas sensors: challenges and strategies—a mini review,” Journal of Materials Science: Materials in Electronics, 30(17), 15825-15847 (2019).

3. M. J. Tierney and H. O. L. Kim, “Electrochemical gas sensor with extremely fast response times,” Analytical Chemistry, 65(23), 3435-3440 (1993).

4. R. Bogue, “Detecting gases with light: a review of optical gas sensor technologies,” Sensor Review, 35(2), 133-140 (2015).

5. E. Lee, Y. S. Yoon, and D. J. Kim, “Two-dimensional transition metal dichalcogenides and metal oxide hybrids for gas sensing,” ACS Sensors, 3(10), 2045-2060 (2018).

6. L. Francioso, M. Russo, A. Taurino, and P. Siciliano, “Micrometric patterning process of sol–gel SnO2, In2O3 and WO3 thin film for gas sensing applications: towards silicon technology integration,” Sensors and Actuators B: Chemical, 119(1), 159-166 (2006).

7. L. C. Hsu, T. Ativanichayaphong, H. Cao, J. Sin, M. Graff, H. E. Stephanou, and J. C. Chiao, “Evaluation of commercial metal‐oxide based NO2 sensors,” Sensor Review, 27(2), 121-131 (2007).

8. S. Mahajan and S. Jagtap, “Metal-oxide semiconductors for carbon monoxide (CO) gas sensing: A review,” Applied Materials Today, 18, 100483 (2020).

9. A. Mirzaei, S. Leonardi, and G. Neri, “Detection of hazardous volatile organic compounds (VOCs) by metal oxide nanostructures-based gas sensors: A review,” Ceramics International, 42(14), 15119-15141 (2016).

10. C. S. Rout, M. Hegde, A. Govindaraj, and C. Rao, “Ammonia sensors based on metal oxide nanostructures,” Nanotechnology, 18(20), 205504 (2007).

11. R. Kumar, N. Goel, M. Hojamberdiev, and M. Kumar, “Transition metal dichalcogenides-based flexible gas sensors,” Sensors and Actuators A: Physical, 303, 111875 (2020).

12. N. Joshi, M. L. Braunger, F. M. Shimizu, A. Riul, and O. N. Oliveira, “Two-dimensional transition metal dichalcogenides for gas Sensing applications,” in Nanosensors for Environment, Food and Agriculture, Springer, 1, 131-155 (2020).

13. V. Bochenkov and G. Sergeev, “Sensitivity, selectivity, and stability of gas-sensitive metal-oxide nanostructures,” in Metal Oxide Nanostructures and Their Applications, American Scientific Publishers, 3, 31-52 (2010).

14. P. Karnati, S. Akbar, and P. A. Morris, “Conduction mechanisms in one dimensional core-shell nanostructures for gas sensing: A review,” Sensor and Actuator B: Chemical, 295, 127-143 (2019).

15. T. P. Mokoena, Z. P. Tshabalala, K. T. Hillie, H. C. Swart, and D. E. Motaung, “The blue luminescence of p-type NiO nanostructured material induced by defects: H2S gas sensing characteristics at a relatively low operating temperature,” Applied Surface Science, 525, 146002 (2020).

16. S. W. Fan, A. K. Srivastava, and V. P. Dravid, “UV-activated room-temperature gas sensing mechanism of polycrystalline ZnO,” Applied Physics Letters, 95(14), 142106 (2009).

17. Y. Liu, E. Koep, and M. Liu, “A highly sensitive and fast-responding SnO2 sensor fabricated by combustion chemical vapor deposition,” Chemistry of Materials, 17(15), 3997-4000 (2005).

18. C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. Aplin, J. Park, X. Bao, Y. H. Lo, and D. Wang, “ZnO nanowire UV photodetectors with high internal gain,” Nano Letters, 7(4), 1003-1009 (2007).

19. M. R. Islam, M. Rahman, S. Farhad, and J. Podder, “Structural, optical and photocatalysis properties of sol–gel deposited Al-doped ZnO thin films,” Surfaces and Interfaces, 16, 120-126 (2019).

20. J. Xuan, G. Zhao, M. Sun, F. Jia, X. Wang, T. Zhou, G. Yin, and B. Liu, “Low-temperature operating ZnO-based NO2 sensors: a review,” RSC Advances, 10(65), 39786-39807 (2020).

21. M. W. Ahn, K. S. Park, J. H. Heo, J. G. Park, D. W. Kim, K. J. Choi, J. H. Lee, and S. H. Hong, “Gas sensing properties of defect-controlled ZnO-nanowire gas sensor,” Applied Physics Letters, 93(26), 263103 (2008).

22. C. Zhang, X. Geng, J. Li, Y. Luo, and P. Lu, “Role of oxygen vacancy in tuning of optical, electrical and NO2 sensing properties of ZnO1-x coatings at room temperature,” Sensors and Actuators B: Chemical, 248, 886-893 (2017).

23. J. Zhang, Z. Qin, D. Zeng, and C. Xie, “Metal-oxide-semiconductor based gas sensors: screening, preparation, and integration,” Physical Chemistry Chemical Physics, 19(9), 6313-6329 (2017).

24. F. Lu, Y. Liu, M. Dong, and X. Wang, “Nanosized tin oxide as the novel material with simultaneous detection towards CO, H2 and CH4,” Sensors and Actuators B: Chemical, 66(1-3), 225-227 (2000).

25. A. Dey, “Semiconductor metal oxide gas sensors: A review,” Materials Science and Engineering: B, 229, 206-217 (2018).

26. D. Degler, U. Weimar, and N. Barsan, “Current understanding of the fundamental mechanisms of doped and loaded semiconducting metal-oxide-based gas sensing materials,” ACS Sensors, 4(9), 2228-2249 (2019).

27. L. Qian, K. Wang, Y. Li, H. Fang, Q. Lu, and X. Ma, “CO sensor based on Au-decorated SnO2 nanobelt,” Materials Chemistry and Physics, 100(1), 82-84 (2006).

28. S. A. Müller, D. Degler, C. Feldmann, M. Türk, R. Moos, K. Fink, F. Studt, D. Gerthsen, N. Bârsan, and J. D. Grunwaldt, “Exploiting synergies in catalysis and gas sensing using noble metal‐loaded oxide composites,” ChemCatChem, 10(5), 864-880 (2018).

29. J. Ma, Y. Ren, X. Zhou, L. Liu, Y. Zhu, X. Cheng, P. Xu, X. Li, Y. Deng, and D. Zhao, “Pt nanoparticles sensitized ordered mesoporous WO3 semiconductor: gas sensing performance and mechanism study,” Advanced Functional Materials, 28(6), 1705268 (2018).

30. X. Liu, Z. Chang, L. Luo, X. Lei, J. Liu, and X. Sun, “Sea urchin-like Ag-α-Fe2O3 nanocomposite microspheres: synthesis and gas sensing applications,” Journal of Materials Chemistry, 22(15), 7232-7238 (2012).

31. P. Rai, S. M. Majhi, Y. T. Yu, and J. H. Lee, “Noble metal@ metal oxide semiconductor core@ shell nano-architectures as a new platform for gas sensor applications,” RSC Advances, 5(93), 76229-76248 (2015).

32. A. V. Polotai, T. H. Jeong, G. Y. Yang, E. C. Dickey, C. A. Randall, P. Pinceloup, and A. S. Gurav, “Effect of Cr additions on the electrical properties of Ni-BaTiO3 ultra-thin multilayer capacitors,” Journal of Electroceramics, 23(1), 6-12 (2009).

33. H. Tian, H. Fan, G. Dong, L. Ma, and J. Ma, “NiO/ZnO p–n heterostructures and their gas sensing properties for reduced operating temperature,” RSC Advances, 6(110), 109091-109098 (2016).

34. Y. Liu, X. Zhang, B. Wu, H. Zhao, W. Zhang, C. Shan, J. Yang, and Q. Liu, “Preparation of ZnO/Co3O4 hollow microsphere by pollen‐biological template and its application in photocatalytic degradation,” ChemistrySelect, 4(43), 12445-12454 (2019).

35. M. E. Franke, T. J. Koplin, and U. Simon, “Metal and metal oxide nanoparticles in chemiresistors: does the nanoscale matter?,” Small, 2(1), 36-50 (2006).

36. A. Kolmakov and M. Moskovits, “Chemical sensing and catalysis by one-dimensional metal-oxide nanostructures,” Annual Review of Materials Research, 34, 151-180 (2004).

37. Y. Zhang, M. K. Ram, E. K. Stefanakos, and D. Y. Goswami, “Synthesis, characterization, and applications of ZnO nanowires,” Journal of Nanomaterials, 2012(20), 1-22 (2012).

38. Z. L. Wang, “Zinc oxide nanostructures: growth, properties and applications,” Journal of Physics: Condensed Matter, 16(25), R829 (2004).

39. M. J. Spencer and I. Yarovsky, “ZnO nanostructures for gas sensing: interaction of NO2, NO, O, and N with the ZnO (1010) surface,” The Journal of Physical Chemistry C, 114(24), 10881-10893 (2010).

40. M. Breedon, M. Spencer, and I. Yarovsky, “Adsorption of NO2 on oxygen deficient ZnO (2110) for gas sensing applications: a DFT study,” The Journal of Physical Chemistry C, 114(39), 16603-16610 (2010).

41. L. Schmidt-Mende and J. L. MacManus-Driscoll, “ZnO–nanostructures, defects, and devices,” Materials Today, 10(5), 40-48 (2007).

42. A. Janotti and C. G. Van de Walle, “Oxygen vacancies in ZnO,” Applied Physics Letters, 87(12), 122102 (2005).

43. K. Vanheusden, W. Warren, C. Seager, D. Tallant, J. Voigt, and B. Gnade, “Mechanisms behind green photoluminescence in ZnO phosphor powders,” Journal of Applied Physics, 79(10), 7983-7990 (1996).

44. C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” Journal of Applied Physics, 105(1), 013502 (2009).

45. S. Baruah and J. Dutta, “Hydrothermal growth of ZnO nanostructures,” Science and Technology of Advanced Materials, 10(1), 013001 (2009).

46. S. Xu and Z. L. Wang, “One-dimensional ZnO nanostructures: solution growth and functional properties,” Nano Research, 4(11), 1013-1098 (2011).

47. L. W. Ji, S. M. Peng, J. S. Wu, W. S. Shih, C. Z. Wu, and I. T. Tang, “Effect of seed layer on the growth of well-aligned ZnO nanowires,” Journal of Physics and Chemistry of Solids, 70(10), 1359-1362 (2009).

48. H. Ghayour, H. Rezaie, S. Mirdamadi, and A. Nourbakhsh, “The effect of seed layer thickness on alignment and morphology of ZnO nanorods,” Vacuum, 86(1), 101-105 (2011).
49. Z. He and W. Que, “Molybdenum disulfide nanomaterials: structures, properties, synthesis and recent progress on hydrogen evolution reaction,” Applied Materials Today, 3, 23-56 (2016).

50. L. P. Feng, J. Su, S. Chen, and Z.T. Liu, “First-principles investigations on vacancy formation and electronic structures of monolayer MoS2,” Materials Chemistry and Physics, 148(1-2), 5-9 (2014).

51. W. Zheng, Y. Xu, L. Zheng, C. Yang, N. Pinna, X. Liu, and J. Zhang, “MoS2 van der waals p–n junctions enabling highly selective room‐temperature NO2 sensor,” Advanced Functional Materials, 30(19), 2000435 (2020).

52. Y. H. Tan, K. Yu, J. Z. Li, H. Fu, and Z. Q. Zhu, “MoS2@ ZnO nano-heterojunctions with enhanced photocatalysis and field emission properties,” Journal of Applied Physics, 116(6), 064305 (2014).

53. Y. Han, D. Huang, Y. Ma, G. He, J. Hu, J. Zhang, N. Hu, Y. Su, Z. Zhou, and Y. Zhang, “Design of hetero-nanostructures on MoS2 nanosheets to boost NO2 room-temperature sensing,” ACS Applied Materials & Interfaces, 10(26), 22640-22649 (2018).

54. Z. Zang, “Efficiency enhancement of ZnO/Cu2O solar cells with well oriented and micrometer grain sized Cu2O films,” Applied Physics Letters, 112(4), 042106 (2018).


55. L. Y. Hong, H. W. Ke, C. E. Tsai, and H. N. Lin, “Low concentration NO gas sensing under ambient environment using Cu2O nanoparticle modified ZnO nanowires,” Materials Letters, 185(15), 243-246 (2016).

56. D. DeMeo, S. MacNaughton, S. Sonkusale, and T. Vandervelde, “Electrodeposited copper oxide and zinc oxide core-shell nanowire photovoltaic cells,” in Nanowires—Implementations and Applications, InTech, 141-156, (2011).


57. K. Bazaka, I. Levchenko, J. W. M. Lim, O. Baranov, C. Corbella, S. Xu, and M. Keidar, “MoS2-based nanostructures: synthesis and applications in medicine,” Journal of Physics D: Applied Physics, 52(18), 183001 (2019).

58. S. Jung, S. Jeon, and K. Yong, “Fabrication and characterization of flower-like CuO–ZnO heterostructure nanowire arrays by photochemical deposition,” Nanotechnology, 22(1), 015606 (2010).

59. M. A. Hossain, B. A. Merzougui, F. H. Alharbi, and N. Tabet, “Electrochemical deposition of bulk MoS2 thin films for photovoltaic applications,” Solar Energy Materials and Solar Cells, 186, 165-174 (2018).

60. S. Xie, Q. Zhang, G. Liu, and Y. Wang, “Photocatalytic and photoelectrocatalytic reduction of CO2 using heterogeneous catalysts with controlled nanostructures,” Chemical Communications, 52(1), 35-59 (2016).

61. S. Vempati, J. Mitra, and P. Dawson, “One-step synthesis of ZnO nanosheets: a blue-white fluorophore,” Nanoscale Research Letters, 7(1), 1-10 (2012).

62. A. Azarov, P. Rauwel, A. Hallén, E. Monakhov, and B. G. Svensson, “Extended defects in ZnO: Efficient sinks for point defects,” Applied Physics Letters, 110(2), 022103 (2017).

63. A. Levasseur, E. Schmidt, G. Meunier, D. Gonbeau, L. Benoist, and G. Pfister-Guillouzo, “New amorphous molybdenum oxysulfide thin films their characterization and their electrochemical properties,” Journal of Power Sources, 54(2), 352-355 (1995).

64. D. Merki, S. Fierro, H. Vrubel, and X. Hu, “Amorphous molybdenum sulfide films as catalysts for electrochemical hydrogen production in water,” Chemical Science, 2(7), 1262-1267 (2011).

65. S. J. Hibble and G. B. Wood, “Modeling the structure of amorphous MoS3: A neutron diffraction and reverse Monte Carlo study,” Journal of the American Chemical Society, 126(3), 959-965 (2004).