On October 8th, Professor Wei Fei's team from the Department of Chemical Engineering of Tsinghua University's paper entitled "Rate Selected Growth of the Ultrapure Semiconducting Carbon Nanotube Arrays" was published in Nature-Communications. Nature Communications).
The research in this paper indicates that the atomic assembly rate of carbon nanotubes during their growth process is locked to their band gap. The exponential decay rate of the number of metal tubes with length is orders of magnitude higher than that of semiconductor tubes. After the length reaches 154 mm, ultra-long semiconductors can be achieved. One-step preparation of tube arrays, this method provides a new technical route for the worldwide difficult problem of preparing perfectly structured, high-purity semiconductor tube horizontal arrays, and has important value for the controllable preparation of new-generation carbon-based electronic materials.
With the rapid development of information technology, semiconductor chips have become an important foundation for the digital economy and national security. In recent years, Moore's Law with silicon-based materials as its core has been declared invalid. Among many alternative materials, carbon nanotubes have become an ideal candidate for the new generation of chip electronics due to their nanometer size and excellent electron hole high mobility. The U.S. Defense Advanced Research Projects Agency announced a $ 1.5 billion investment to advance the "Electronic Revival Plan" for the development of miniaturized, high-performance carbon nanotube chips. Stanford University and the Massachusetts Institute of Technology have successively developed a carbon nanotube computer and a 16-bit microprocessor based on 14,000 carbon nanotube transistors, which fully demonstrated the development potential of carbon nanotubes in the post-silicon era.
China has significant advantages in the engineering application field of carbon nanotube electronic devices and materials preparation, especially in the field of non-doped preparation of single carbon nanotube transistors and the smallest carbon nanotube devices. In the field of carbon nanotube macro preparation, it has also taken the lead in batch production of the world's highest, kiloton-class production of aggregated and vertically arrayed carbon nanotubes, and has been applied on a large scale in the field of power batteries. However, the structural defects and control of chiral structure of carbon nanotubes are still the key issues restricting the application of high-performance carbon-based chips.
Rate-selective growth of high-purity semiconductor carbon nanotube arrays
To this end, Professor Wei Fei's team has focused on the research and development of perfect ultra-long carbon nanotubes for more than 10 years, and found that the structural consistency of ultra-long carbon nanotubes on the decimeter level is the first to produce the world's longest 550 mm carbon nanotubes The Schulz-Flory distribution law that the number of carbon nanotubes decreases exponentially with length is verified. Further research found that the number of metal and semiconductor tubes also met the Schulz-Flory distribution, but the half-life length of the semiconductor tube was more than 10 times that of the metal tube. Raman scattering, Rayleigh scattering optical characterization, and isotope-labeled growth rate tests show that the difference in the half-life lengths of metal and semiconductor tubes stems from the growth rate of locked carbon band gaps. Narrowing the difference in activation energies between heterogeneous catalysis diffusion and poisoning processes in order to increase the length of carbon nanotubes is the key to the controllable preparation of semiconductor tube arrays with narrow band gap distribution. Based on this, the team designed a laminar flow square reactor to precisely control the gas and temperature fields and optimize the structure of the constant temperature zone, reducing the probability of catalyst deactivation to one in 10 billion, and successfully achieved the ultra-long horizontal array of carbon nanotubes in 7 A large area of the surface of a 4-inch silicon wafer grows with a longest length of 650mm, and the number of conversions per unit reaction site reaches 1.53 × 106 s-1, which is hundreds of millions of times the general industrial response. A transistor device made using a carbon nanotube array at 154mm as a channel material, with a switching ratio of 108, a mobility of more than 4000cm2 / Vs, and a current density of 14 μA / μm, for the first time demonstrated the excellent electrical performance of ultra-long carbon nanotubes at the array level . This method of controlling the preparation of high-purity semiconductor tubes by using the band-gap locking growth speed provides a new route 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 following the realization of controllable preparation of half-meter-long carbon nanotubes and winding in situ into large-area, uni-handed carbon nano-tube clusters. The application of products and flexible electronic devices has provided a feasible route to promote the development of the national microelectronics industry.
Corresponding authors are Professor Wei Fei, and the first author is Zhu Zhenxing, a 2015 PhD student in the Department of Chemical Engineering at Tsinghua University; Wei Nan, a postdoctoral fellow in Applied Physics at Aalto University, Professor Xu Jun, Department of Microelectronics, Tsinghua University; Associate Professor Wang Yi from the Department of Chemical Engineering of the University, Assistant Professor Zhang Rufan, PhD students Shen Boyuan, Sun Silei, Gao Jun participated in the work. This research work was supported by projects such as the National Key Basic Research and Development Plan, the National Natural Science Foundation of China, and the Beijing Municipal Science and Technology Commission.