Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Applied Physics | en_US |
| dc.contributor.advisor | Hao, Jianhua (AP) | en_US |
| dc.creator | Zhao, Yuqian | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13939 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Substrate and interface engineering for centimeter-sized wafer-scale growth of crystalline black phosphorus ultrathin films | en_US |
| dcterms.abstract | Since Novoselov et al. first successfully exfoliated graphene from bulk graphite using scotch tape in 2004, two-dimensional (2D) materials have emerged as a significant area of research, recognized for their vast potential applications across various fields, including flexible devices, sensors, and optics. Among these materials, 2D black phosphorus (BP) and its monolayer form, phosphorene, have attracted considerable attention as promising alternatives to graphene. 2D BP not only possesses a bandgap that lies between that of graphene (0 eV) and transition metal dichalcogenides (TMDs) (1.0 eV–2.0 eV), but also exhibits a tunable direct bandgap, exceptional carrier mobility, and a significant on/off ratio. These characteristics position BP as one of the most compelling research topics within the realm of 2D materials. For the successful commercialization of BP, it is essential to establish robust techniques for producing large-area 2D BP-based devices on various available substrates under easily controlled conditions for further investigation. | en_US |
| dcterms.abstract | In the first part of the thesis, we employed a piezoelectric actuator to conduct the interfacial biaxial strain engineering, allowing us to investigate the anisotropic Raman response of the ultrathin BP transferred onto an oxide dielectric substrate. Our findings revealed that three characteristic peaks exhibit a redshift when tensile strain is applied, while they display a blueshift under compressive strain. Notably, under a tensile strain of 0.2%, the B2g mode experiences a shift of -12.2 cm⁻¹/%. Conversely, when a compressive strain of -0.2% is applied, the Raman shift rate of the B2g mode can increase to as much as 15.3 cm⁻¹/%. Additionally, we calculated the Grüneisen parameters to explore the relationship between tensile or compressive strain and the phonon behavior of crystalline BP. The underlying physical mechanism responsible for the observed Raman response under strain is discussed, highlighting its connection to variations in bond angles and bond lengths within BP. Furthermore, modulation of biaxial strain may alter the anisotropic dispersion of BP, underscoring its substantial potential for innovative polarized light detection applications. | en_US |
| dcterms.abstract | Although exfoliation enables efficient separation of high-quality multilayer 2D BP from single-crystalline bulk sources, facilitating detailed investigations into their fundamental properties. However, this method is not ideal for large-scale production due to challenges in achieving precise control over both the thickness and lateral dimensions. Consequently, in the second part of the thesis, we developed a clean transfer strategy to produce centimeter-scale, high-quality few-layer BP films grown via precisely controlled pulsed laser deposition (PLD) on silicon substrates. | en_US |
| dcterms.abstract | Ethylene-vinyl acetate (EVA) polymer and ethylene glycol (EG) were selected as the adhesive layer and medium, respectively, to preserve the superior crystalline quality and properties of BP throughout the transfer process. Importantly, we successfully fabricated large-scale bottom-gate few-layer BP field-effect transistor (FET) arrays on SiO₂/Si substrates, demonstrating exceptional homogeneity. Our FET device arrays demonstrated exceptional electrical characteristics, featuring a high carrier mobility of 295 cm² V⁻¹ s⁻¹ and a significant current switching ratio of 3.6x10³, comparable to that of as-grown BP films on mica substrates. This work illustrates that the wet transfer method can effectively create scalable, high-crystallinity BP-based device arrays while maintaining excellent electrical performance, thus enabling more complex design possibilities for a wide range of applications. | en_US |
| dcterms.extent | xiii, 115 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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