Energy conservation and delay minimization are the two major goals while designing ultra-low-power digital integrated circuits at lower technology nodes. Here, silicon based carbon nanotube field effect transistor (CNTFET) has been explored as a novel material for future electronics design applications (EDA). In this paper, two energy-efficient switching activity minimization techniques have been applied with proposed designs. First technique detects the completion of sensing stage operation known as transition completion detection (TCD) technique. TC signal generated from NAND operation of complementary outputs of sensing stage which minimizes glitches in the complementary outputs of the latch stage. Another clock gating mechanism applied at the latch stage to smoothen the output waveforms Q and . The proposed and existing designs simulated using 32nm CMOS and 32nm CNTFET technology, indicating that the CNTFET based design reduces power by 45% and 36% respectively in comparison with conventional CMOS. Proposed Low Power Sense Amplifier Flip Flop with transition control detection (TCD-LPSAFF) and Ultra Low Energy Sense Amplifier Flip Flop (ULESAFF) give optimum power delay product (PDP) which is 35.7x10-18 J and 29.6x10-18 J respectively. Also, the effect of process variation has been analyzed at specified corners (FF, TT and SS) in the temperature range of -40º C to 120º C. The performance of all designs has been validated by functionality testing with variation in diameter, number of tubes and pitch respectively.