在材料領域中，三維系統的單晶結構隨著技術的成熟，在保持晶格完整還能同時降低厚度，形成準二維系統(Quasi-two-dimensional system)已是一大趨勢，其中薄膜磊晶於控制厚度與成長單晶結構方面為優秀的製程技術，且透過脈衝雷射沉積法(Pulsed Laser Deposition)，製備材料快速之外，更能保有與原材料相同比例的薄膜。
鈦酸鍶(SrTiO3,STO)是鈣鈦礦結構中擁有順電性(Paraelectricity)的一種材料，雖然在低溫受量子漲落影響抑制了鐵電性(Ferroelectricity)，而展現量子順電性(Quantum Paraelectricity)，許多研究嘗試在室溫，透過對鈦酸鍶做化學，力學以及光學上的調控，使在低溫受限的鐵電性能在室溫下展現。
在此研究中，我們運用了脈衝雷射沉積法的技術成長薄膜，也運用濕式蝕刻的分離技術(Freestanding)，將薄膜轉移至其他基板上，和表面形成異質結構。在分離的前後，藉由原子力顯微鏡(Atomic Force Microscope)探測薄膜為平坦的表面，接著以國家同步輻射中心(NSRRC)提供的X射線分析(X-Ray Diffraction & X-Ray Linear Dichroism)，薄膜以層層磊晶的方式生長成單晶結構，最後以接觸式表面電位顯微鏡(contact-Kelvin Probe Force Microscope)，也成功量測到鐵電性可以靠轉移的方式於室溫下展現，驗證了先前的研究以及在此基礎上有所突破。

As the mature technology, the thickness of single crystal thin films in three-dimensional system can be reduced to become ultrathin films while remained the intriguing functionalities. These ultrathin material structures were called quasi-two-dimensional system. It is an excellent technique in terms of thickness control and growth of single crystal structure. Strontium titanate (SrTiO3, STO) is a paraelectric materials in perovskite structure. Although it is affected by quantum fluctuations at low temperatures to suppress ferroelectricity, it exhibits the quantum paraelectricity at ambient temperature. Many researchers have tried to perform chemical composition, mechanical, and optical adjustments to strontium titanate, so that the low-temperature limited ferroelectric properties can be displayed at room temperature. In this study, we use pulsed laser deposition technique to grow thin films, and also use wet etching separation technique (also called freestanding) to transfer the thin films to other substrates and to integrate heterogeneous structures. We use both the scanning probe microscope and X-ray analysis to carry out the ferroelectricity characterization in strontium titanate thin films at room temperature before and after freestanding and also verify the previous research and breakthroughs on this basis.

1 Khan, A. I. et al. Negative capacitance in a ferroelectric capacitor. Nature Materials 14, 182-186, doi:10.1038/nmat4148 (2015).
2 Peng, W. W. et al. Room-temperature soft mode and ferroelectric like polarization in SrTiO3 ultrathin films: Infrared and ab initio study. Sci Rep 7, 11, doi:10.1038/s41598-017-02113-4 (2017).
3 Jang, H. W. et al. Ferroelectricity in Strain-Free SrTiO3 Thin Films. Phys. Rev. Lett. 104, 4, doi:10.1103/PhysRevLett.104.197601 (2010).
4 Wadhawan, V. Introduction to ferroic materials. (CRC press, 2000).
5 Whangbo, M. H., Gordon, E. E., Bettis, J. L., Bussmann-Holder, A. & Kohler, J. Tolerance Factor and Cation-Anion Orbital Interactions Differentiating the Polar and Antiferrodistortive Structures of Perovskite Oxides ABO(3). Zeitschrift Fur Anorganische Und Allgemeine Chemie 641, 1043-1052, doi:10.1002/zaac.201500058 (2015).
6 Ahn, C. W. et al. A brief review on relaxor ferroelectrics and selected issues in lead-free relaxors. Journal of the Korean Physical Society 68, 1481-1494, doi:10.3938/jkps.68.1481 (2016).
7 Lee, D. et al. Emergence of room-temperature ferroelectricity at reduced dimensions. Science 349, 1314-1317, doi:10.1126/science.aaa6442 (2015).
8 Zhong, W. & Vanderbilt, D. Effect of quantum fluctuations on structural phase transitions in SrTiO3 and BaTiO3. Physical Review B 53, 5047-5050, doi:10.1103/PhysRevB.53.5047 (1996).
9 Ang, C. & Yu, Z. Dielectric relaxor and ferroelectric relaxor: Bi-doped paraelectric SrTiO3. Journal of Applied Physics 91, 1487-1494, doi:10.1063/1.1428799 (2002).
10 Koyama, Y. et al. Doping-induced ferroelectric phase transition in strontium titanate: Observation of birefringence and coherent phonons under ultraviolet illumination. Physical Review B 81, doi:10.1103/PhysRevB.81.024104 (2010).
11 Uesu, Y. et al. Polar order in quantum paraelectric (SrTiO3)-O-16 and (SrTiO3)-O-18 at low temperature. Journal of the Physical Society of Japan 73, 1139-1142, doi:10.1143/jpsj.73.1139 (2004).
12 Li, X. et al. Terahertz field-induced ferroelectricity in quantum paraelectric SrTiO3. Science 364, 1079-+, doi:10.1126/science.aaw4913 (2019).
13 Nova, T. F., Disa, A. S., Fechner, M. & Cavalleri, A. Metastable ferroelectricity in optically strained SrTiO3. Science 364, 1075-+, doi:10.1126/science.aaw4911 (2019).
14 Wordenweber, R., Schubert, J., Ehlig, T. & Hollmann, E. Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films. Journal of Applied Physics 113, 8, doi:10.1063/1.4802676 (2013).
15 Chen, C. T. et al. OUT-OF-PLANE ORBITAL CHARACTERS OF INTRINSIC AND DOPED HOLES IN LA2-XSRXCUO4. Phys. Rev. Lett. 68, 2543-2546, doi:10.1103/PhysRevLett.68.2543 (1992).
16 Haverkort, M. W. et al. Magnetic versus crystal-field linear dichroism in NiO thin films. Physical Review B 69, 4, doi:10.1103/PhysRevB.69.020408 (2004).
17 Balke, N. et al. Exploring Local Electrostatic Effects with Scanning Probe Microscopy: Implications for Piezoresponse Force Microscopy and Triboelectricity. Acs Nano 8, 10229-10236, doi:10.1021/nn505176a (2014).
18 Schlom, D. G. et al. Strain tuning of ferroelectric thin films. Ann. Rev. Mater. Res. 37, 589-626, doi:10.1146/annurev.matsci.37.061206.113016 (2007).