The reduction in physical size of the Non-volatile memory (NVM) demands the use of high-k dielectrics due to loss in charge trapping behavior. The large bandgap of Al2O3 (∼7.0 eV) proves it suitable for blocking and tunneling layer, while the high dielectric constant of HfO2 proves it suitable for charge trapping layer (CTL). In this paper, we propose the application of Al doped HfO2 used as CTL. The doping concentration has been varied by varying the number of sub-cycles (sequential cycles of HfO2, Al2O3) by ALD system. The optical energy bandgap of Al doped HfO2 observed to be increases from 4.91−5.20 eV as the Al incorporation content increases with 1:9−1:4 ALD sub-cycles. Oxygen vacancy defect in the thin film decreased to 17.87% for 1:4-Al doped HfO2 sample as verified from the XPS. The increase in Al incorporation leads to charge loss towards silicon substrate due to high bandgap energy. In addition, charge traps are not well performed due to reduction of internal defects in the film. After 10 years, the NVM device with Al doped HfO2 (1:9) CTL has improved charge retention characteristics by 14% as compared to a normal HfO2 charge trap layer NVM device.
We propose an ultrasonic motor of high torque with a new configuration for application in automobiles. The newly designed stator is a two sided vibrator consisting of a toothed metal disk with a piezoelectric ceramic ring bonded on both faces of the disk which generates a flexural traveling wave along the circumference of disk. In this configuration, the displacement on the surface of stator may not be confined. It also produces a large vibrating force and amplitude because the vibrator is sandwiched by two piezoelectric plates. It is possible to increase the torque by improving the vibration characteristics. We used the finite element method to compute the vibration mode of the motor of diameter 48 mm. A sixth mode was chosen as the operation mode with a resonance frequency of about 73 kHz. We fabricated a prototype according to this design and measured its performance. The performance measurement of the prototype motor showed that its stall torque was about 1.8 Nm and efficiency was 37% at 60% of the maximum torque. Compared to a conventional motor which employed a single sided piezoelectric vibrator of the same outer diameter, we obtained, with this prototype, a maximum torque of about twice as great. The motor may be useful to apply as an actuator in a mobile car.
The operation principle of travelling wave rotary type ultrasonic motor can be applied to fluidic transfer mechanism of micro-pump successfully. In this paper, we propose a novel type valveless micro-pump that uses extensional vibration mode of travelling wave as a volume transporting means. The proposed pump is consisted of coaxial cylindrical shells that joined piezoelectric ceramic ring and metal body respectively. To confirm the actuation mechanism of proposed pump model, a numerical simulation analysis on the proposed model was implemented. In accordance with the variation of exciting wave mode and pump body dimension, we analyzed the vibration displacement characteristics if proposed model, determined the optimal design condition, fabricated the prototype pump from the analysis results and evaluated its performance. The maximum flow rate was about 580[µl/min] and the highest back pressure was 0.85[kPa] at 120[V rms ] input voltage. We confirmed that peristaltic motion of piezoelectric actuator was able to be applied to the fluid transferring mechanism of valveless type micro pump effectively through this research.
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