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Epitaxial Growth and Novel Physical Properties of Layered Thin Film Materials Containing Tetragonal Fete /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Epitaxial Growth and Novel Physical Properties of Layered Thin Film Materials Containing Tetragonal Fete // Zhihao He.
作者:	He, Zhihao,
面頁冊數:	1 electronic resource (140 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
Contained By:	Dissertations Abstracts International86-06B.
標題:	Crystal structure. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31810328
ISBN:	9798346823391

Epitaxial Growth and Novel Physical Properties of Layered Thin Film Materials Containing Tetragonal Fete /
He, Zhihao,

Epitaxial Growth and Novel Physical Properties of Layered Thin Film Materials Containing Tetragonal Fete /Zhihao He. - 1 electronic resource (140 pages)

Source: Dissertations Abstracts International, Volume: 86-06, Section: B.

FeTe, a simple Fe-based layered compound, does not exhibit bulk superconductivity even under a high pressure, in contrast to its superconducting cousin materials such as FeSe and FeS. However, our research group has made an intriguing discovery: induced two-dimensional (2D) superconductivity at the interface of topological insulator (TI)/FeTe heterostructures, including the Bi2Te3/FeTe and Sb2Te3/FeTe systems. The successful fabrication of these heterostructures can be attributed to their layered nature, despite the mismatch in crystal structure symmetry between the topological insulators (TIs) and the FeTe. A further investigation of the interface configurations between TIs and FeTe could yield valuable insights into the underlying mechanisms of the emergent 2D superconductivity in these systems. In this thesis study, three layered structures containing FeTe were fabricated. The first is a tetragonal FeTe phase comprising nanocrystals with their c-axes aligned (CAT-FeTe), with the in-plane orientations of these crystals occurring randomly; the second is a heterostructure comprising a FeTe/Bi-Te system, with the Bi-Te components including Bi4Te3, Bi6Te3, and Bi2Te3. The third structure is a heterostructure of FeTe/MnTe. MnTe refers to different phases of MnTe, including newly discovered layered MnTe (l-MnTe) and layered Mn4Te3 (l-Mn4Te3), distorted zinc-blende MnTe (dZB-MnTe), and wurtzite MnTe (WZ-MnTe).The first structure, designated c-axis-aligned nanocrystals tetragonal FeTe (CAT-FeTe), was directly grown on c-plane sapphire via molecular beam epitaxy, resulting in the emergence of a novel structural phase comprising c-axis-aligned nanocrystals. The reflection high-energy electron diffraction patterns (RHEED) display two sets of streaks simultaneously at all rotation angles of the sample. High-resolution X-ray diffraction (HRXRD) studies have confirmed that the nanocrystals are tetragonal FeTe, with their c-axes aligned to the growth direction. Atomic force microscopy (AFM) imaging reveals that further growth of these nanocrystals involves a cannibalism process, resulting in nanocrystal pillars with sizes of approximately 0.5 to 1 µm. The temperature-dependent resistance of these thin films displays an overall semiconducting behaviour, although there are instances where the resistance is non-measurable or exhibits jumps and falls, which can be attributed to the thermal responses of the nanocrystals during cooling and heating processes. This discovery offers a method for the formation of inhomogeneous heterostructures, such as those comprising Bi2Te3/FeTe and Sb2Te3/FeTe systems, with all possible twisted angles between the two components.The second structure is an FeTe/Bi-Te heterostructure system. The Bi-Te binary system, characterised by the homologous series of the (Bi2)m(Bi2Te3)n, has consistently attracted research interest due to its layered structures and potential in advanced materials applications. Despite extensive studies of Bi2Te3, exploration of other compounds has been constrained by synthesis challenges. The findings of our study demonstrate that the MBE growth of FeTe on Bi2Te3can transform the Bi2Te3layer into distinct Bi-Te phases, thereby forming corresponding FeTe/Bi-Te heterostructures through the manipulation of growth conditions. The combined analysis, utilising RHEED, HRXRD and cross-sectional high-resolution scanning transmission electron microscopy (HR-STEM), indicates that specific growth conditions employed for the growth of the FeTe layer can facilitate the extraction of Te from Bi2Te3, resulting in the formation of Bi4Te3 and Bi6Te3.

English

ISBN: 9798346823391Subjects--Topical Terms:

3561040
Crystal structure.

Epitaxial Growth and Novel Physical Properties of Layered Thin Film Materials Containing Tetragonal Fete /
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520 $a FeTe, a simple Fe-based layered compound, does not exhibit bulk superconductivity even under a high pressure, in contrast to its superconducting cousin materials such as FeSe and FeS. However, our research group has made an intriguing discovery: induced two-dimensional (2D) superconductivity at the interface of topological insulator (TI)/FeTe heterostructures, including the Bi2Te3/FeTe and Sb2Te3/FeTe systems. The successful fabrication of these heterostructures can be attributed to their layered nature, despite the mismatch in crystal structure symmetry between the topological insulators (TIs) and the FeTe. A further investigation of the interface configurations between TIs and FeTe could yield valuable insights into the underlying mechanisms of the emergent 2D superconductivity in these systems. In this thesis study, three layered structures containing FeTe were fabricated. The first is a tetragonal FeTe phase comprising nanocrystals with their c-axes aligned (CAT-FeTe), with the in-plane orientations of these crystals occurring randomly; the second is a heterostructure comprising a FeTe/Bi-Te system, with the Bi-Te components including Bi4Te3, Bi6Te3, and Bi2Te3. The third structure is a heterostructure of FeTe/MnTe. MnTe refers to different phases of MnTe, including newly discovered layered MnTe (l-MnTe) and layered Mn4Te3 (l-Mn4Te3), distorted zinc-blende MnTe (dZB-MnTe), and wurtzite MnTe (WZ-MnTe).The first structure, designated c-axis-aligned nanocrystals tetragonal FeTe (CAT-FeTe), was directly grown on c-plane sapphire via molecular beam epitaxy, resulting in the emergence of a novel structural phase comprising c-axis-aligned nanocrystals. The reflection high-energy electron diffraction patterns (RHEED) display two sets of streaks simultaneously at all rotation angles of the sample. High-resolution X-ray diffraction (HRXRD) studies have confirmed that the nanocrystals are tetragonal FeTe, with their c-axes aligned to the growth direction. Atomic force microscopy (AFM) imaging reveals that further growth of these nanocrystals involves a cannibalism process, resulting in nanocrystal pillars with sizes of approximately 0.5 to 1 µm. The temperature-dependent resistance of these thin films displays an overall semiconducting behaviour, although there are instances where the resistance is non-measurable or exhibits jumps and falls, which can be attributed to the thermal responses of the nanocrystals during cooling and heating processes. This discovery offers a method for the formation of inhomogeneous heterostructures, such as those comprising Bi2Te3/FeTe and Sb2Te3/FeTe systems, with all possible twisted angles between the two components.The second structure is an FeTe/Bi-Te heterostructure system. The Bi-Te binary system, characterised by the homologous series of the (Bi2)m(Bi2Te3)n, has consistently attracted research interest due to its layered structures and potential in advanced materials applications. Despite extensive studies of Bi2Te3, exploration of other compounds has been constrained by synthesis challenges. The findings of our study demonstrate that the MBE growth of FeTe on Bi2Te3can transform the Bi2Te3layer into distinct Bi-Te phases, thereby forming corresponding FeTe/Bi-Te heterostructures through the manipulation of growth conditions. The combined analysis, utilising RHEED, HRXRD and cross-sectional high-resolution scanning transmission electron microscopy (HR-STEM), indicates that specific growth conditions employed for the growth of the FeTe layer can facilitate the extraction of Te from Bi2Te3, resulting in the formation of Bi4Te3 and Bi6Te3.
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