Professor Wei Fei of Tsinghua University realized one-step preparation of 99.9999% semiconductor carbon nanotube array

Recently, Professor Wei Fei, Department of chemical engineering, Tsinghua University, published a paper entitled "rate selected growth of the culture semiconductor carbon nanotube arrays" (DOI: 10.1038 / s41467-019-12519-5) online on nature communications It is pointed out that the atomic assembly rate and band gap of CNTs are locked in each other during the growth process, and the exponential decay rate of the number of metal tubes with the length is higher than that of semiconductor tubes by an order of magnitude When the length reaches 154 mm, 99.9999% ultra long semiconductor tube array can be fabricated in one-step This method provides a new technical route for the preparation of perfect structure and high-purity semiconductor horizontal array, which is of great value for the controllable preparation of new generation carbon based electronic materials With the rapid development of information technology, semiconductor chip has become an important foundation of digital economy and national security In recent years, the Moore's law with silicon-based materials as the core is about to come to the end Among many alternative materials, carbon nanotubes become an ideal candidate material for the new generation of chip electronics with nanometer size and excellent electron hole mobility DARPA announced an investment of US $1.5 billion to promote the "electronic rejuvenation program" for the development of miniature, high-performance carbon nanotube chips Stanford University and Massachusetts Institute of technology have developed carbon nanotube computers and 16 bit microprocessors based on 14000 carbon nanotube transistors, fully demonstrating the development potential of carbon nanotubes in the post silicon era China has significant advantages in the field of engineering application of carbon nanotube electronic devices and materials preparation, especially in the field of undoped preparation of single carbon nanotube transistor and the field of minimum carbon nanotube devices In the field of large-scale preparation of carbon nanotubes, it has also taken the lead in batch preparation of the world's highest and kiloton production of agglomerated and vertical array carbon nanotubes, and has been widely used in the field of power batteries However, the structural defects and chirality control of CNTs are still the key problems that restrict the application of high performance carbon based chips For this reason, Professor Wei Fei's team focused on the research and development of ultra long carbon nanotubes with perfect structure for more than 10 years It was found that the structure consistency of ultra long carbon nanotubes on the decimeter scale length was consistent It was the first to prepare the world's longest 550 mm carbon nanotubes, and verified the Schulz Flory distribution law that the number of carbon nanotubes decreased exponentially with the length Further research shows that the number of metal and semiconductor tubes also meet the Schulz Flory distribution, but the half-life length of semiconductor tube is more than 10 times that of metal tube The results of Raman scattering, Rayleigh scattering and isotope labeling indicate that the difference of half-life length between metal and semiconductor tube is due to the growth rate of band gap locking To reduce the activation energy difference between diffusion and poisoning in heterogeneous catalysis and to increase the length of carbon nanotubes is the key to realize controllable fabrication of semiconductor tube arrays with narrow gap distribution According to this, the team designed a square laminar flow reactor, precisely controlled the air flow field and temperature field and optimized the structure of the constant temperature zone, reducing the catalyst deactivation probability to 1 / 10 billion, and successfully realized the large area growth of ultra long horizontal array carbon nanotubes on the surface of seven 4-inch silicon wafers, with the longest length of 650 mm and the conversion number of unit reaction site reaching 1.53 × 106 s-1 Using 154 m m carbon nanotube array as the channel material, the transistor device has a switch ratio of 108, a mobility of more than 4000 cm 2 / VS and a current density of 14a / m, which shows the excellent electrical properties of ultra long carbon nanotubes at the array level for the first time This method provides a new way for in-situ spontaneous purification of semiconductor materials and lays a solid foundation for the development of a new generation of high-performance carbon based integrated electronic devices This work is another innovative work of Professor Wei Fei's team after the realization of controllable preparation of half meter long carbon nanotubes and in-situ winding into large-area, single handed carbon nano pipeline clusters It provides a feasible route for the realization of the application of carbon nanotubes in high-end electronic products and flexible electronic devices, and promotes the development of national micro electronics industry The corresponding author of the article is Professor Wei Fei, the first author is Zhu Zhenxing, a 2015 level doctoral student in the Department of chemical engineering of Tsinghua University, Wei Nan, a postdoctoral student in the Department of Applied Physics of the University of Alto, Finland, Xu Jun, a professor in the Department of microelectronics of Tsinghua University, Cheng Weijun, a 2016 level doctoral student, Wang Yao, an associate professor in the Department of chemical engineering of Tsinghua University, Zhang rufan, Shen Boyuan, sun Shilei, Gao Junshen, a doctoral student With the work This research work is supported by national key basic research development plan, National Natural Science Foundation of China and Beijing Municipal Science and Technology Commission.