Explore The Influence Of Material Post-treatment Process On The Performance Of Carbon Tube Transistors

Carbon nanotubes are considered to be the most potential candidate to replace silicon as the semiconductor channel material of field effect transistors in the post-Moore era due to their unique structure and electronic properties.To obtain high-performance,low-power and high-quality nanoelectronic devices,the first prerequisite is to prepare high-purity semiconductor-type single-walled carbon nanotube thin films.At present,a series of studies have shown that the solution method can prepare the high purity semiconductor-type single-walled carbon nanotubes well,and high uniformity of the carbon nanotube thin films can be formed.However,the surface of the carbon nanotube thin films obtained has a large amount of organic polymer remaining,which enlarges the contact resistance of the device.As the size of the device decreases,the contact resistance between the carbon tube and the metal electrode is becoming more and more important.This paper starts research from here,and strives to effectively remove the polymer on the surface of the carbon nanotube films,reduce the contact resistance of the device and improve the performance of the device.The main research contents of this paper are as follows:1.The effects of different post-treatment processes on the performance of carbon nanotube transistors are explored andthe effects of different post-treatment processes on the removal of polymer on the surface of carbon nanotube thin films are evaluated for the first time,and a combined process of post-treatment of carbon nanotube materials is summarized,which provides guidance and basis for the selection of treatment process of carbon nanotube materials in the future.In this paper,different post-treatment processes are used to remove the polymer on the surface of carbon nanotube thin films,and then the carbon nanotube transistor devices are prepared on the surface of carbon nanotube thin films.Finally the performance of the corresponding devices is compared to characterize the effect of removing the polymer.The post-treatment process includes annealing,yttrium oxide coating-and-decoating and combination of-annealing and yttrium oxide coating-and-decoating.The experimental reSults show that based on the number of times of annealing process,it can be concluded that one time of annealing can basically achieve the effect of removing polymer on the surface of carbon nanotube thin films,and too many times of annealing may cause damage to the surface of the sample.Based on the number of times of yttrium oxide pickling process,it can be concluded that the number of times of yttrium oxide coating-and-decoating has a larger impact on the long channel device,that is,too many times of annealing will cause damage to the surface of the sample.As a result,defects are formed on the surface of the sample and the electrical performance of the device is decreased.Therefore,one time of yttrium oxide coating-and-decoating is more suitable for the experimental operation,which can reduce the experimental cost and achieve the experimental effect.Based on the process sequence of annealing+yttrium oxide coating-and-decoating,it can be concluded that the performance of the device under the process of annealing+yttrium oxide coating-and-decoating is significantly better than that under the process of yttrium oxide coating-and-decoating+annealing.The paper uses performance parameters Such as transfer curve and output curve to characterize the improvement effect of polymer removal on device performance.The experimental results show that the annealing+yttrium oxide coating-and-decoating process has the best improvement on the device performance,especially the gate control ability,including the maximum transconductance and the minimum subthreshold swing.At the same time,the device also has the maximum on-state current,the maximum saturation current and the minimum on-state resistance,which proves that the combination of annealing and yttrium oxide coating-and-decoating process has the best effect to remove the polymer on the surface of carbon nanotube thin films.2.The contact resistance Rc is used for the first time to judge the effect of polymer removal from the surface of carbon nanotube thin films on device contact improvement from the physical level.The contact resistance of the device directly reflects the contact between the metal electrode and carbon nanotubes.The smaller the contact resistance,the smaller the total resistance of the device and the lower the power consumption of the device.Aiming at the research of contact resistance,this paper analyzes the two main methods of extracting contact resistance,transfer length method and Y-function method.The contact resistance obtained by the transfer length method is the result of fitting the on state resistance and the corresponding channel length of a series of devices,and the calculation error is small.The contact resistance by Y-function method is calculated by extracting a series of parameters of a single device,which requires high quality of the device,and the result is accidental.By preparing multiple groups of transistors with successively reduced channel lengths,the paper uses the transfer length method to extract the contact resistance of the transistors based on different post-treatment methods.The results show that the contact resistance of the device with the combination of annealing and yttrium oxide coating-and-decoating process is about 3.61 KΩ,while that of the untreated device is 8.16 KQ.The results show that the annealing+yttrium oxide coating-and-decoating process has the best effect in removing the polymer on the surface of carbon nanotube thin films.3.By preparing different metal contact transistors,the universal applicability of the post-treatment combined process is verified.Through the design of carbon nanotube transistor devices with different contacts,the effects of different post-processing techniques on the performance of different contact devices are explored.Two kinds of contact devices,Pd metal and Ti metal,are fabricated.The ohmic contact between Pd metal and carbon nanotubes is formed,while the non ohmic contact between Ti metal and carbon nanotubes is formed.In this paper,the performance comparison of different contact devices under different post-treatment processes is completed.Compared with the Pd contact device,the polymer and other impurities on the surface of the carbon nanotubes in the Ti contact device are equivalent to the degenerate doping of the semiconductor carbon tube,which makes the Schottky barrier very thin and the carriers easier to tunnel through the barrier.Therefore,the polymer on the surface of the carbon nanotube thin films will improve the performance of the Ti contact device.The experimental results show that the Ti contact device has the minimum open current and the maximum contact resistance under the annealing + yttrium oxide coating-and-decoating process,while the Pd contact device has the maximum open current and the minimum contact resistance under the annealing+yttrium oxide coating-and-decoating process,whichproves the universality of the effect of different post-treatment processes.