A study on the effects of gas composition and biased substrate towards the quality of CVD grown graphene /
Since its discovery in 2004, graphene has been tipped as the material that can boost the development of various applications. Among the methods developed to produce graphene in large-scale is chemical vapor deposition (CVD). CVD is viewed as the most cost-efficient method besides having the potentia...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur :
Kulliyyah of Engineering, International Islamic University Malaysia,
2019
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| Subjects: | |
| Online Access: | http://studentrepo.iium.edu.my/handle/123456789/4904 |
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| Summary: | Since its discovery in 2004, graphene has been tipped as the material that can boost the development of various applications. Among the methods developed to produce graphene in large-scale is chemical vapor deposition (CVD). CVD is viewed as the most cost-efficient method besides having the potential to synthesize high-quality graphene. Despite this potential, it requires great control in various aspects including the precise tuning of the gas composition. Throughout the years, consensus is due on the effects of the gas compositions used (CH4, H2, Ar) towards graphene growth. Using poly-crystalline Cu as substrate, this study aims at solving this issue by fine-tuning the H2 and CH4 composition at different stages of graphene growth. Prior to that, the effects of different H2 and Ar concentration during annealing towards the crystallinity of the Cu substrate are also explored. Next, a three-electrodes probe is devised to evaluate the electrical properties of different gas compositions during graphene growth. Lastly, a novel, biased-substrate method in graphene fabrication is performed with the aim to achieve better control of gas composition, leading to a more predictable graphene growth. X-ray diffraction results suggest that the lattice parameter, a of Cu annealed in H2 is susceptible to an increase of 0.55%. It is also discovered through Raman spectroscopy that 0% H2 concentration during annealing leads to the best graphene quality while during growth step, the CH4/H2 concentration ratio should be kept at equal or lower than 1. As predicted, the lowest CH4 concentration (10% of total concentration) during growth results in the lowest graphene thickness value. Linear voltammetry test on the graphene growth gas composition displays the significant role CH4 plays on the conductivity of the reactant gases compared to H2 and Ar. The biased- substrate treatment resulted in a marked increase of the I2D/IG ratio of the graphene with the value of 0.69 compared to 0.52 for the un-biased substrate. Transmission electron microscopy (TEM) results for the biased substrate-grown graphene suggest the presence of graphene/graphite with traces of sp3 carbon bonds that can be explained through the effects of the polarity and degree of the applied potential. |
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| Physical Description: | xv, 124 leaves : colour illustrations ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 113-124). |