Banca de DEFESA: John Fredy Ricardo Marroquin

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : John Fredy Ricardo Marroquin
DATE: 18/07/2024
TIME: 09:00
LOCAL: Remoto Teams
TITLE:

Thin Films of Van der Waals Materials and GaAsBi Alloys: Synthesis, Characterization, Application and Effect of Ionizing Radiation.

KEY WORDS:

Automatic Mechanical Exfoliation (AME), thin films, van der Waals materials (vdW), Hydrogen Evolution Reaction, semiconductor, GaAsBi.

PAGES: 165
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

In recent years, the demand for materials with specific and advanced properties has grown exponentially, driven by the rapid evolution of science and technology. Highperformance materials are crucial for a wide range of applications, from electronics and energy to the environment. Among the diverse materials that have attracted significant attention, van der Waals (vdW) materials and III-V semiconductors, such as GaAsBi, stand out. Since the emergence of graphene, thin films based on van der Waals (vdWs) materials have gained prominence due to their wide range of applications in areas such as nanoelectronics, catalysis, sensors, and transducers. However, there is a limitation in the available techniques for the deposition of thin films of these materials over large areas. This work presents two innovative approaches for the deposition and improvement of films, offering superior or comparable electrical, optical, and structural properties to existing sophisticated techniques. In the first approach, we introduce Automated Mechanical Exfoliation (AME), an innovative technique for the deposition of thin films of vdW materials. AME stands out for providing high control over the uniformity of the films, in addition to being accessible, fast, and low-cost. This technique allows the deposition of vdW thin films on large-area substrates without damaging their surfaces, promoting high-quality interfaces and enabling various applications. The versatility of AME has been successfully demonstrated through the deposition of thin films of various vdWs. To evaluate the characteristics of the deposited films, advanced techniques such as X-ray diffraction, Raman spectroscopy, optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used. The results confirmed the high crystalline quality, uniform morphology, and controllable thickness of the films. Exploring the potential of these vdW thin films, promising applications in two distinct areas were demonstrated. Firstly, the films were used as efficient electrodes for the Hydrogen Evolution Reaction (HER), showing great potential for the production of clean energy. In addition, vdW thin films were deposited on YIG magnetic thin films, enabling the study of spin pumping in vdWs materials. Through these spintronic devices, it was also possible to show the quality of the interface of the films deposited by AME, since the injection of spins into the vdWs materials is only possible when there is a great quality in the interface property between the 2D material and the ferromagnetic film. In the second approach, this work explores the engineering of gamma-radiationinduced defects as a tool to create materials with innovative characteristics. TMD thin films produced by AME were exposed to gamma radiation and subsequently employed as large-area catalytically active electrodes, increasing catalytic efficiency by up to 1000%. In addition, based on a comprehensive characterization, the effect of gamma radiation on the electrical, structural, and optical properties of bismuth-doped gallium arsenide (GaAsBi) alloys grown by MBE on GaAs (1 0 0) substrates was studied, revealing a significant improvement in optical and electrical properties. With this, for the first time, the use of GaAsBi as gamma radiation sensors was proposed. In summary, this work presents two innovative approaches that contribute significantly to the development of high-performance materials with promising characteristics for various technological applications. AME stands out as an efficient and accessible deposition technique, while gamma-radiation-induced defect engineering opens up new possibilities for the creation of materials with improved properties

COMMITTEE MEMBERS:
Externo à Instituição - KLEBER GONÇALVES BEZERRA ALVES - UFPE
Externo à Instituição - ERALCI MOREIRA THERÉZIO - UFMT
Presidente - 1999840 - JORLANDIO FRANCISCO FELIX
Interno - 1547480 - JOSE ANTONIO HUAMANI COAQUIRA
Interna - 1218750 - LUANA CRISTINA WOUK