Publicação
CVD Diamond membranes as photothermal sensors
| Resumo: | Diamond is widely recognized to have excellent properties, the main one being hardness. However, it also stands out for its biocompatibility, optical transparency, and chemical stability. Furthermore, the electrical properties can be easily adjusted with doping during manufacturing. This thesis focuses on the production of doped chemical vapor deposition (CVD) diamond and the study of the deposition parameters and the consequent growth of polycrystalline films. The technique used and discussed was Hot Filament Chemical Vapor Deposition (HFCVD) involving three phases: carburization, deposition, and cooling. In the deposition phase, the precursor gases of the doping elements are injected into the reactor. For boron-doped diamond (BDD) films was used boron oxide, B2O3, dissolved in ethanol, and tetraethyl orthosilicate (TEOS) for the silicon-doped films (SiDD). Initially, several samples were produced to optimize the deposition conditions of each film. Some of those were then used for the bilayers (formed by SiDD film and BDD film). For the diamond isolation, a 45 % HNO3/HF solution was used for the elimination of the silicon substrate in a controlled manner. The polycrystalline diamond films were characterized using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, 3D profilometry, and electrical measurements. Furthermore, the values of thermal sensitivity (β), temperature coefficient of resistance (TCR) and the Y parameters were determined. For the bilayer membranes, electrical measurements were performed in the presence and absence of illumination (source white LED) to determine their influence on the behavior. The 3D profilometry tests revealed consistency with the morphology of each film, with the lowest values for nanocrystalline (NCD) films and the highest for microcrystalline (MCD). The parameter that most affected grain size was the increase in CH4 flow under constant substrate temperature conditions. The incorporation of SiV- optical centers was evaluated through the intensity of the 2254 cm-1 peak in the Raman spectrum, as well as the documentation of presence of sp3 (at 1332 cm-1) and sp2 bonding (at 1350 cm-1 and 1540 cm-1). The development of doped diamond membranes was successful, however, no change in thermoelectric behavior was observed with the incidence of white light. Future work should focus on the production of films with lower boron doping to study the photothermal response of the bilayer membranes. |
|---|---|
| Autores principais: | Barreto, Eduarda Rodrigues |
| Assunto: | CVD Diamond HFCVD Boron doping SiV centers TEOS Bilayer |
| Ano: | 2025 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | Diamond is widely recognized to have excellent properties, the main one being hardness. However, it also stands out for its biocompatibility, optical transparency, and chemical stability. Furthermore, the electrical properties can be easily adjusted with doping during manufacturing. This thesis focuses on the production of doped chemical vapor deposition (CVD) diamond and the study of the deposition parameters and the consequent growth of polycrystalline films. The technique used and discussed was Hot Filament Chemical Vapor Deposition (HFCVD) involving three phases: carburization, deposition, and cooling. In the deposition phase, the precursor gases of the doping elements are injected into the reactor. For boron-doped diamond (BDD) films was used boron oxide, B2O3, dissolved in ethanol, and tetraethyl orthosilicate (TEOS) for the silicon-doped films (SiDD). Initially, several samples were produced to optimize the deposition conditions of each film. Some of those were then used for the bilayers (formed by SiDD film and BDD film). For the diamond isolation, a 45 % HNO3/HF solution was used for the elimination of the silicon substrate in a controlled manner. The polycrystalline diamond films were characterized using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, 3D profilometry, and electrical measurements. Furthermore, the values of thermal sensitivity (β), temperature coefficient of resistance (TCR) and the Y parameters were determined. For the bilayer membranes, electrical measurements were performed in the presence and absence of illumination (source white LED) to determine their influence on the behavior. The 3D profilometry tests revealed consistency with the morphology of each film, with the lowest values for nanocrystalline (NCD) films and the highest for microcrystalline (MCD). The parameter that most affected grain size was the increase in CH4 flow under constant substrate temperature conditions. The incorporation of SiV- optical centers was evaluated through the intensity of the 2254 cm-1 peak in the Raman spectrum, as well as the documentation of presence of sp3 (at 1332 cm-1) and sp2 bonding (at 1350 cm-1 and 1540 cm-1). The development of doped diamond membranes was successful, however, no change in thermoelectric behavior was observed with the incidence of white light. Future work should focus on the production of films with lower boron doping to study the photothermal response of the bilayer membranes. |
|---|