One of the several promising new technologies for computing at nano-scale is quantum-dot cellular automata (QCA). In this paper, new designs for different QCA sequential circuits are presented. Using an efficient QCA D flip-flop (DFF) architecture, a 5-bit counter, a novel single edge generator (SEG) and a divide-by-2 counter are implemented. Also, some types of oscillators, a new edge-triggered K-pulse generator (KPG) and a negative pulse generator (NPG) are presented for implementation in QCA. The robust layouts of proposed circuits are designed, implemented and simulated using QCADesigner software without any wire crossing. The fault effects at the output of proposed DFF due to the missing cell defects are analyzed. Also, the robustness of the proposed QCA designs with respect to temperature variations is examined. The proposed designs are compared with the previous QCA works and conventional CMOS technology. The simulation results confirm that the novel QCA architectures work properly and can be simply used in designing of QCA sequential circuits.
