本文探討以雙（叔丁基胺）雙（二甲基胺）鎢與硫化氫作為原子層沉積法之前驅物製備硫化鎢的可行性與其反應機構，進而發現該反應同時含有化學氣相沉積的成份特性。此外，生成之硫化鎢的物理與化學性質由高解析度穿透式電子顯微鏡、X光繞射與X光光電子能譜探究。經文獻回顧與數據分析，本文推定，硫化氫對鎢錯合物的硫化反應為速率決定步驟、配位基的移除由高溫反應過程中的分子脫附及與硫化氫的反應共同促成，且氧化反應與硫化反應共同競爭鎢錯合物前驅物。此反應機構能成功解釋何以反應由高溫降至低溫（由300至250°C）時，氧化鎢的生成量反而速增，而在較高溫反應時則可輕易得到高純度的硫化鎢。
原子層沉積製程文獻中以烷基胺金屬配位錯合物為前驅物製備金屬硫化物者甚少，乃因烷基胺與氮的高親和度使其易生成氮化物之故。烷基胺因此最常用在製備金屬氧化物與氮化物上。本研究展示，雙（叔丁基胺）雙（二甲基胺）鎢作為原子層沉積前驅物能合成高純度硫化鎢，氮汙染量甚低，其原因不僅出於烷基胺錯合物在高溫反應中的降解與脫附，也應歸功於硫化氫對烷基胺配位基的移除作用。因此雙（叔丁基胺）雙（二甲基胺）鎢乃為一合適之硫化鎢合成前驅物。本文在探討前驅物化學反應機制外，亦為原本為數不多的硫化鎢原子層沉積法拓展了新的合適前驅物選擇。

A mechanism of the formation of WS2 from sequential reaction of bis(tert-butylimino)bis(dimethylamino)tungsten (BTBMW) and H2S is proposed and attempted to justify by XPS and Raman scattering data. Three key features of the reactions are justified to be present and support the mechanism: sulfurization being the rate-limiting step, ligand removal facilitated by H2S and oxidation competition with sulfurization for BTBMW. Our model explains why purity of WS2 is highly dependent on the reaction temperature.
This study introduced a novel ALD method with CVD component to manufacture high purity, 2D-structured WS2 with bis(tert-butylimino)bis(dimethylamino)tungsten. This is peculiar, as metal alkylamides are used mostly for synthesis of nitrides and oxides due to the concern of nitrogen contamination. We demonstrated that little to no residue consisting of nitrogen was detected in the as-prepared WS2. Therefore, from an engineering perspective, a new option for synthesizing high purity WS2 films in an ALD-like feature is introduced. This method also benefits from its potential for depositing high aspect-ratio material in a highly thickness-controlled manner.

TABLE OF CONTENTS
LIST OF ABBREVIATIONS
1 Introduction ............................................................................................................................. 1
2 Literature Review .................................................................................................................... 4
2.1 ALD process and the search for a new WS2 precursor .................................................. 4
2.2 Metal alkylamides as ALD/CVD precursors ................................................................... 7
2.3 Decomposition mechanism of BTBTT and BTBDT / Adsorption of BTBMW
on Si(100) .................................................................................................................................. 9
2.4 Manufacture of WS2 via CVD/ALD................................................................................11
2.4.1 WO3 sulfurization ..................................................................................................11
2.4.2 Direct ALD process............................................................................................... 14
3 Experimental .......................................................................................................................... 17
3.1 Materials..................................................................................................................... 17
3.2 Standard atomic layer deposition ............................................................................ 17
3.3 Characterization methods......................................................................................... 20
4. Results and Discussion .............................................................................................................. 22
4.1 Chemistry of WS2 formation process in ALD ............................................................... 22
4.1.1 Proposed mechanism ............................................................................................ 22
4.1.2 ALD reaction product........................................................................................... 25
4.1.2.1 WS2: the dominant reaction product ....................................................... 25
4.1.2.2 Detailed XPS scan ...................................................................................... 26
4.1.2.3 EDXS purity examination ......................................................................... 29
4.1.3 Impurity elimination by desorption and sulfurization ...................................... 31
4.1.3.1 Species identification at lower temperature regime, 100°C, 125°C
and 200°C................................................................................................................ 31
4.1.3.2 Species identification at higher temperature regime, 250°C,
275°C and 300°C .................................................................................................... 32
4.1.3.3 XPS survey scans........................................................................................ 33
4.1.3.4 Ligand removal process ............................................................................. 35
4.1.3.5 Reduction of W(VI) amino complex ......................................................... 40
4.1.3.6 Sulfurization: the rate-limiting step ......................................................... 42
4.1.3.7 Oxidation and competition with sulfurization......................................... 43
4.1.3.7.1 Antagonism ...................................................................................... 43
4.1.3.7.2 H2O and WO3 in O 1s spectra ........................................................ 45
4.1.4 Raman spectroscopy ............................................................................................. 47
4.1.4.1 WS2 identification by Raman spectroscopy ............................................. 47
4.1.4.2 WS2 formation at 300°C ............................................................................ 48
4.1.4.3 Substrate specific area effect on the formation of WO3 ......................... 49
4.1.4.4 WO3 vibrational frequency suppression by moisture residue and
amorphous WO3 ..................................................................................................... 50
4.1.4.4.1 WS2 / f-CNTs / Al substrate system................................................ 51
4.1.4.4.2 WS2 / Si substrate system ............................................................... 55
4.1.4.5 Summary of Raman scattering analysis .................................................. 56
4.2 Development of a novel WS2 ALD method.................................................................... 57
4.2.1 ALD window.......................................................................................................... 57
4.2.2 Saturation .............................................................................................................. 59
4.3 Morphology of as-prepared WS2 / f-CNTs .................................................................... 62
4.3.1 HRTEM image of WS2 / f-CNTs.......................................................................... 62
4.3.1.1 50 ALD cycle .............................................................................................. 62
4.3.1.2 200 ALD cycle ............................................................................................ 64
4.3.1.3 350 cycle...................................................................................................... 68
4.3.2 Quantitative XRD analysis of WS2 / f-CNTs ...................................................... 73
4.4 Film growth and growth rate of WS2............................................................................. 77
4.4.1 Film growth rate ................................................................................................... 77
4.4.2 Dead layer.............................................................................................................. 79
4.4.3 AFM image ............................................................................................................ 81
5 Conclusion ................................................................................................................................... 83
Note ................................................................................................................................................. 85
REFERENCES .............................................................................................................................. 86

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