Research On Implantable And Biodegradable Low Voltage Transistors

Nowadays,implantable and biodegradable devices have gained more and more attention in medical electronics area.The MEMS devices which have integrated the transistors and sensors are thought to be one the most possible solution.However,the operation voltage of biodegradable report currently is too high to be applied in medical electronics.In this paper,we have investigated the low voltage biodegradable transistors and have successfully fabricated two kinds of biodegradable transistors.The main achievements are as follows:First,we have investigated the electric double layer effect of the sodium alginate?SA?film,which provide a solid theory to our follow discussions.We found that the frequency dependent specific capacitances of the SA membrane can be divided into two regions:in the low frequency region?below 100Hz?,the maximal capacitance is about 2?F/cm² was measured,which is equivalent to a 5nm thick SiO2 film.This huge capacitance is attributed to an electric double layer formed at the interface between the AZO and SA film;In the high frequency region?up 100Hz?,the proton in the SA film cannot response to the electric filed,so the capacitance decays exponentially.Second,we have successfully fabricated a kind of biodegradable transistors based on SA film and AZO?ZnO:Al?.The average mobility and subthreshold slope and on-off ratio are:6.19 cm² V^-1 s^-1,94 mv/decade and 10⁶ respectively for 30 transistors.These results show that the proposed transistors can work at an operation voltage as low as 1V and show high quality at the same time.Based on the achievements mentioned above,we have proposed a kind of low cost biodegradable transistors.Both the fabrication process and the structure of the biodegradable transistor are very simple.The free-standing sodium alginate?SA?membrane is used as both a substrate and the dielectric layer for the transistors.The source/drain electrodes and the channel region are made of one single patterned AZO thin film.The average mobility and subthreshold slope and on-off ratio are:4.15 cm² V^-1s^-1,94 mv/decade and 10⁶ respectively for 20 transistors.