**5. Conclusions**

As exemplified by graphene and Bi2Te3, the presence of defects and dopants imparts the host material with new micro/quantum states or energy configurations that can strongly influence optical, electronic, and thermal properties. In addition to the above properties, S and F dopants are being explored to make graphene magnetic [10, 52–55], while N dopants are expected to provide much higher enhancements in quantum capacitance without compromising electrical conductivity [28]. Similar to Bi2Te3, defects in other layered systems such as SnSe and TaSe2 could be engineered to achieve better thermoelectric performance [56–62]. Although this chapter presented only some examples of defects in 2D materials, the same concepts also hold true for other 2D materials such as MoS2, WS2, and BN. Indeed, some properties (e.g., lumi‐ nescence and catalytic activity) of these materials can be tuned using defects [63–68]. As the design and development of new 2D materials are costly, complex, and limited due to the relatively poor air stability of many materials (e.g., silicene and phosphorene), the realization of desired properties and functionalities through control of defects (e.g., vacancies, dopants) in 2D materials is necessary. Though there is only one way for a given material to be defectfree, there are many possibilities for materials to be imperfect. The global scientific endeavors on understanding defects, such as the efforts presented in this chapter, provide a glimpse of the enormous potential of defects warranting further interdisciplinary research efforts.
