Abstract
The utilisation of 2-D transition metal dichalcogenides (TMDs) holds the potential to improve the efficiency of gas-sensitive electronic devices due to their advantageous semiconductive properties, tunable transport characteristics, and heightened reactivity at active sites. As a member of transition metal dichalcogenides, monolayer Rhenium disulfide (ReS2) is expected to have the potential as a gas sensitive material. This thesis aims to examine the capability of ReS2 as a material for adsorption. The adsorption target gases are carbon monoxide (CO), carbon dioxide (CO2), hydrogen(H2), nitrogen dioxide (NO2) and nitrogen dioxide (NO). The methodology employed in this study is rooted in the application of first-principles calculations based on the density functional theory (DFT). In order to determine the most favourable adsorption configuration, we employ a systematic approach by utilizing multiple initial sites and diverse gas configurations as starting points for the optimisation process.Following the search for the most stable adsorption configuration of gas molecule, the adsorption characteristics of the gas molecules on the energetic favourable configurations are subject to in-depth examination. Our work shows that the adsorption of five gas molecules onto ReS2 results in a spontaneous process with a release of energy. Meanwhile, the charge transfer direction is from gases to ReS2, indicating gas molecules and ReS2 can be considered electron donor-acceptor pair. The outcomes of the analysis of adsorption energy and charge transfer suggest that ReS2 exhibits low sensitivity towards CO, CO2, and H2. Furthermore, the adsorption of these gases does not significantly impact the electronic structure of the ReS2 monolayer based on the analysis of band structure and density of states. In order to characterise its potential as a gas-sensing material, extra electric field is applied in CO and CO2 adsorption cases to investigate their adsorption properties on the ReS2 surface. It has been established that the presence of an electric field has a positive impact on the adsorption capacity of ReS2 for these two gaseous species. However, in order to achieve a substantial improvement in adsorption, it is imperative to apply a high-intensity electric field.
NO2 and NO adsorption on ReS2 show a large and complex interaction between gas molecules and material. ReS2 has more sensitivity to NO and NO2 than CO, CO2 and H2. The adsorption energy and charge transfer of NO2-ReS2 and NO-ReS2 adsorption systems are -0.512 eV and -0.434 eV, which are far more significant than CO-ReS2, CO2-ReS2 and H2-ReS2. The adsorption of nitrogen oxides has led to a significant alteration in the electronic configuration of ReS2. A significant degree of orbital hybridization between them and ReS2 is observed. Thus, ReS2 is an excellent material for NO2 detection and potential material for NO detection. If ReS2 is expected to enhance its adsorption properties towards other gases, its sensitivity and selectivity of ReS2 can be further improved through material modification techniques. This study can provide a basis for developing ReS2-based sensors in applications and experiments.
| Date of Award | Oct 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Kien Woh Kow (Supervisor) & Hainam Do (Supervisor) |