隨著半導體技術的進步，在不降低設備性能的情況下，還要同時提高矽基底積體電路的晶體密度是一項非常重大的挑戰。過渡金屬硫屬化物(TMCs)因為其直接能隙的半導體特性、強光吸收以及優異的載流子遷移率而成為最具潛力的材料之一。此外，TMCs中強相關的d軌道電子和強自旋軌道耦合產生的電性、機械性質以及光學特性，皆使得他們在基礎研究以及工業應用上擁有很大的吸引力。在TMCs當中，特別是二維過渡金屬二硫化物(TMDCs，MX2型)具有與維度縮放目的相匹配的原子級厚度，因此為奈米電子學和奈米光子學應用提供了新的可能性。
本研究我們分為兩個部分進行探討。第一個部分探討的是TMCs當中具有ABX3的鈣鈦礦結構的材料製造。我們嘗試通過優化的CVD製程硫化鋯酸鋇(BaZrO3, BZO)薄膜和鋯鈦酸鉛(PZT)薄膜，並利用X光繞射、拉曼光譜和光致發光(PL)光譜分別研究晶體結構、聲子振動和PL發光的演變。在BZO薄膜硫化的實驗中，我們確切觀察到了PL訊號的出現。而對於PZT薄膜，我們透過TEM的結果發現薄膜中幾乎沒有氧被硫取代。此外，在硫化過程當中，我們觀察到會有部分鉛離子從PZT薄膜游離出來情況出現。
在第二個部分，我們將前驅層WO3硫化後得到WS2薄膜，其中我們透過拉曼以及PL光譜首先驗證了薄膜的品質及特徵與文獻相符，之後我們將WS2薄膜轉移至鐵電PTO/STO(111)基板上，並定義一系列薄膜相對於基板[1-10]結晶方向的夾角角度。我們可以觀察到，隨著定義夾角角度的變化，WS2薄膜的PL峰值位置也會隨著改變，此外，在通過局部極化改變底層鐵電PTO的極化方向後，WS2薄膜的PL峰值會隨之移動甚至分裂，這些結果皆表明了，無論是通過改變轉角度還是屏蔽電荷擾動，WS2/PTO/STO(111)異質結構的能隙皆可以透過控制界面條件來達到任意調控。

With the progress and prosper of semiconductor technologies, it faces constant challenges to increase the transistor density in a silicon-based integrated circuit without degrading the performance of devices. Transition metal chalcogenides (TMCs) has emerged and become one of the most potential materials due to their direct band gap semiconducting character, strong light absorption and excellent carrier mobility. Besides, the strongly-correlated d-orbital electrons and strong spin-orbit coupling in TMCs give rise to their fascinating electronic, mechanical and optical properties, making them attractive for both fundamental research and industrial applications. Among these TMCs, in particular, two-dimensional (2D) transition metal dichalcogenides (TMDCs, MX2 type) have an atomic scale thickness matching the dimension scaling purposes and therefore provides new possibilities toward nanoelectronics and nanophotonics applications.
We divide our research topics into two sections. The first section is associated with the fabrication of TMCs with perovskite type ABX3 structure. We tried to sulfurize barium zirconate (BaZrO3, BZO) film and lead zirconate titanate (PZT) films by an optimized chemical vapor deposition procedure. A combination of X-ray diffraction, Raman spectroscopy and photoluminescence (PL) spectroscopy is adopted to investigate the evolution of crystal structure, optical phonon vibration, and PL emission, respectively. In the case of the post-sulfurized BZO films, an emergence of PL emission signal is observed. For the PZT films, the results from transmission electron microscopy (TEM) indicate little oxygen in the films was replaced by sulfur. Besides, certain amounts of lead ions are dissociated from the PZT films during the sulfurization process.
In the second section, we sulfurized the precursor WO3 ultrathin films to obtain single crystal WS2 films. The film quality and associated layer-dependent Raman and PL spectra were confirmed, whose characteristics were consistent with literatures. Afterwards, we transferred WS2 films onto ferroelectric PTO/STO (111) substrates with a series of well-defined angles with respect to the [11 ̅0] crystallographic direction of substrates. It could be observed that the position of PL peak of the transferred WS2 films shifts accordingly with the change of relative angles. In addition, the PL peak of WS2 films would shift and even split after the polarization direction of the underlying ferroelectric PTO was locally altered via electric poling procedures. These results indicate that the optical bandgap of WS2/PTO/STO (111) heterostructure can be arbitrary tuned by controlling the interfacial condition, either by twisted angles or by screen charge perturbations.

1. Comparotto, C., et al., Chalcogenide Perovskite BaZrS3: Thin Film Growth by Sputtering and Rapid Thermal Processing. ACS Applied Energy Materials, 2020. 3(3): p. 2762-2770.
2. Radisavljevic, B., et al., Single-layer MoS2 transistors. Nat Nanotechnol, 2011. 6(3): p. 147-150.
3. Magda, G.Z., et al., Exfoliation of large-area transition metal chalcogenide single layers. Sci Rep, 2015. 5: p. 14714.
4. Choi, W., et al., Recent development of two-dimensional transition metal dichalcogenides and their applications. Materials Today, 2017. 20(3): p. 116-130.
5. Kim, H., et al., Role of alkali metal promoter in enhancing lateral growth of monolayer transition metal dichalcogenides. Nanotechnology, 2017. 28(36): p. 36LT01.
6. Yang, P., et al., Batch production of 6-inch uniform monolayer molybdenum disulfide catalyzed by sodium in glass. Nat Commun, 2018. 9(1): p. 979.
7. Zhao, W., et al., Origin of indirect optical transitions in few-layer MoS2, WS2, and WSe2. Nano Lett, 2013. 13(11): p. 5627-34.
8. Amani, M., et al., Recombination Kinetics and Effects of Superacid Treatment in Sulfur- and Selenium-Based Transition Metal Dichalcogenides. Nano Lett, 2016. 16(4): p. 2786-91.
9. Izyumskaya, N., et al., Processing, Structure, Properties, and Applications of PZT Thin Films. Critical Reviews in Solid State and Materials Sciences, 2007. 32(3-4): p. 111-202.
10. Siddiqui, M., J.J. Mohamed, and Z.A. Ahmad, Structural, piezoelectric, and dielectric properties of PZT-based ceramics without excess lead oxide. Journal of the Australian Ceramic Society, 2019. 56(2): p. 371-377.
11. Park, S.-E., Shrout, T.R, Requirements of Piezoelectric Materials for Medical Ultrasound Transducers. 1996.
12. Tressler, J.F., Alkoy, S., Newnham, R.E., Piezoelectric Sensors and Sensor Materials. 1998.
13. Kenji Uchino, S.T., Piezoelectric ceramic actuators A review of machinery applications. 1996.
14. Vrejoiu, I., et al., Intrinsic Ferroelectric Properties of Strained Tetragonal PbZr0.2Ti0.8O3 Obtained on Layer–by–Layer Grown, Defect–Free Single–Crystalline Films. Advanced Materials, 2006. 18(13): p. 1657-1661.
15. Pandya, S., et al., Strain-induced growth instability and nanoscale surface patterning in perovskite thin films. Sci Rep, 2016. 6: p. 26075.
16. Marincel, D.M., et al., Domain pinning near a single-grain boundary in tetragonal and rhombohedral lead zirconate titanate films. Physical Review B, 2015. 91(13).
17. Pintilie, L., et al., Polarization induced self-doping in epitaxial Pb(Zr0.20Ti0.80)O3 thin films. Sci Rep, 2015. 5: p. 14974.
18. Swarnkar, A., et al., Are Chalcogenide Perovskites an Emerging Class of Semiconductors for Optoelectronic Properties and Solar Cell? Chemistry of Materials, 2019. 31(3): p. 565-575.
19. Gross, N., et al., Stability and Band-Gap Tuning of the Chalcogenide Perovskite BaZrS3 in Raman and Optical Investigations at High Pressures. Physical Review Applied, 2017. 8(4).
20. Perera, S., et al., Chalcogenide perovskites – an emerging class of ionic semiconductors. Nano Energy, 2016. 22: p. 129-135.
21. Klein, A., et al., Electronic band structure of single-crystal and single-layerWS2:Influence of interlayer van der Waals interactions. Physical Review B, 2001. 64(20).
22. Li, Y., et al., Accurate identification of layer number for few-layer WS2 and WSe2 via spectroscopic study. Nanotechnology, 2018. 29(12): p. 124001.
23. Gutierrez, H.R., et al., Extraordinary room-temperature photoluminescence in triangular WS2 monolayers. Nano Lett, 2013. 13(8): p. 3447-54.
24. Manzeli, S., et al., 2D transition metal dichalcogenides. Nature Reviews Materials, 2017. 2(8).
25. Zeng, H., et al., Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides. Sci Rep, 2013. 3: p. 1608.
26. Smith, H.M. and A.F. Turner, Vacuum Deposited Thin Films Using a Ruby Laser. Applied Optics, 1965. 4(1): p. 147-148.
27. Dijkkamp, D., et al., Preparation of Y‐Ba‐Cu oxide superconductor thin films using pulsed laser evaporation from highTcbulk material. Applied Physics Letters, 1987. 51(8): p. 619-621.
28. Pottathara, Y.B., et al., Synthesis and Processing of Emerging Two-Dimensional Nanomaterials, in Nanomaterials Synthesis. 2019. p. 1-25.
29. Somani, P.R., S.P. Somani, and M. Umeno, Planer nano-graphenes from camphor by CVD. Chemical Physics Letters, 2006. 430(1-3): p. 56-59.
30. Pollard, A.J., et al., Formation of Monolayer Graphene by Annealing Sacrificial Nickel Thin Films. J. Phys. Chem., 2009.
31. Liu, K.K., et al., Growth of large-area and highly crystalline MoS2 thin layers on insulating substrates. Nano Lett, 2012. 12(3): p. 1538-44.
32. Yang, X., et al., Structural phase transition of BaZrO3 under high pressure. Journal of Applied Physics, 2014. 115(12).
33. Bin Rafiq, M.K.S., et al., WS2: A New Window Layer Material for Solar Cell Application. Sci Rep, 2020. 10(1): p. 771.
34. Sebait, R., et al., Identifying Defect-Induced Trion in Monolayer WS2 via Carrier Screening Engineering. ACS Nano, 2021. 15(2): p. 2849-2857.
35. Zheng, S., et al., Coupling and Interlayer Exciton in Twist-Stacked WS2 Bilayers. Advanced Optical Materials, 2015. 3(11): p. 1600-1605.