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Synthesis of graphene by chemical vapor deposition and its application in electronics and sensing.

机译：化学气相沉积法合成石墨烯及其在电子学和传感领域的应用。

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摘要

Graphene, a single atomic layer of hexagonally packed carbon atoms, has drawn significant attention with its outstanding electrical, optical, and chemical properties. Various promising applications based on graphene have been demonstrated, such as in electronics, optoelectronics, and chemical/bio sensing. To realize the promise, it is critical to synthesize large-scale, high quality graphene films transferable onto arbitrary substrates. In this dissertation, chemical vapor deposition (CVD) synthesis of graphene films and grains on Cu substrates is studied, and the applications of graphene as transparent electrodes and gas sensor are demonstrated.;The effects of Cu surface conditions and CVD parameters such as growth temperature and CH4 concentration on the nucleation density, grain size, and surface coverage of graphene are discussed. On the basis of the results, a two-step ambient pressure CVD technique is developed to synthesize large-scale uniform single-layer graphene films with grain sizes up to hundreds of square micrometers. The growth mechanism of CVD graphene on Cu is also discussed, and a growth model is proposed. Moreover, graphene grains (either isolated grains or several merged grains) formed during the early stage of CVD growth on Cu are studied. Individual graphene grains typically have a hexagonal shape and are single crystals. The grains show no definite epitaxial relationship with the underlying Cu substrate, and can grow continuously across Cu grain boundaries without any apparent shape distortion, indicating weak graphene-Cu interactions. Edges of these grains are found to be predominantly parallel to zigzag directions. Grain boundaries in graphene are characterized and found to impede electrical transport. An effective approach is proposed to control nucleation of CVD graphene by locally providing high concentrations of carbon, opening a route towards scalable fabrication of single crystal graphene devices without grain boundaries. Finally, graphene films (up to 4 layers) are transferred on cover glass flips for the measurements of optical transmittance and sheet resistance. The transferred graphene films show high electrical conductivity and high optical transmittance that make them suitable as transparent electrodes. Hydrogen sensors are also demonstrated on Pd-decorated graphene films. The sensors show high sensitivity, fast response and recovery, and can be used with multiple cycles.
机译：石墨烯是六方堆积的碳原子的单原子层，因其出色的电，光和化学性能而备受关注。已经证明了基于石墨烯的各种有前途的应用，例如在电子，光电和化学/生物传感方面。为了实现这一承诺，合成可转移到任意基板上的大规模，高质量的石墨烯薄膜至关重要。本文研究了铜衬底上石墨烯薄膜和晶粒的化学气相沉积（CVD）合成方法，并论证了石墨烯作为透明电极和气体传感器的应用。铜表面条件和生长温度等CVD参数的影响讨论了CH4浓度对石墨烯的成核密度，晶粒尺寸和表面覆盖率的影响。根据这些结果，开发了一种两步式常压CVD技术，以合成晶粒尺寸高达数百平方微米的大规模均匀单层石墨烯薄膜。还讨论了CVD石墨烯在Cu上的生长机理，并提出了生长模型。此外，还研究了在CVD上在Cu上生长的早期阶段形成的石墨烯晶粒（孤立晶粒或几个合并晶粒）。各个石墨烯晶粒通常具有六边形形状，并且是单晶。晶粒与下面的Cu衬底之间没有明确的外延关系，并且可以跨Cu晶粒边界连续生长而没有任何明显的形状变形，表明石墨烯与Cu之间的相互作用较弱。发现这些晶粒的边缘主要平行于之字形方向。表征并发现石墨烯中的晶界阻碍了电传输。提出了一种有效的方法，该方法通过局部提供高浓度的碳来控制CVD石墨烯的成核作用，从而开辟了可扩展制造无晶界的单晶石墨烯器件的途径。最后，将石墨烯薄膜（最多4层）转移到盖玻片上，以测量光透射率和薄层电阻。转移的石墨烯薄膜显示出高电导率和高透光率，使其适合用作透明电极。氢气传感器也已在装饰钯的石墨烯薄膜上得到证实。传感器显示出高灵敏度，快速响应和恢复能力，并且可以多次使用。

著录项

  • 作者

    Wu, Wei.;

  • 作者单位

    University of Houston.;

  • 授予单位 University of Houston.;
  • 学科 Engineering Electronics and Electrical.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 112 p.
  • 总页数 112
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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