https://jjcit.org/paper/122 10.5455/jjcit.71-1598791557 Mutaz Al-Tarawneh,Ziyad A. Altarawneh QCA,Asynchronous circuits,C-Element,Robustness,Structural defects 5 6509 2010 30-Aug.-2020 14-Oct.-2020 5-Nov.-2020 The continuous market demands for high-performance and energy-efficient computing systems have steered the computational paradigm and technologies towards nano-scale quantum dot cellular automata (QCA). This paper presents novel simple and complex QCA-based C-element structures. The proposed structures were thoroughly analyzed based on key design parameters, such as area, energy dissipation and robustness against structural defects. Simulation results demonstrate that the proposed simple structures have achieved up to 56% and 66% improvement in area and energy dissipation, respectively. On the other hand, the complex structures have shown a profound immunity against structural defects and achieved up to 143% improvement as compared to the simple structures. The proposed C-element structures can be considered as viable blocks for asynchronous designs.