New Material: As Thin As Hair, Semiconductor Fiber Can "Weave" Cloth

In a green field, two researchers from Nanyang Technological University in Singapore showed a piece of white cloth 13.5 meters long, 0.6 meters wide and 1 mm thick. This plain looking cloth is actually not ordinary. It is a piece of photoelectric sensing cloth, which is "woven" from fiber materials as thin as hair. Hats and clothes made of the cloth are expected to replace smart devices such as mobile phones, tablet computers and smart watches.

On February 1, the international joint team led by Wei Lei, a professor of Nanyang Technological University, published a paper in Nature, introducing how this cloth "woven" with super long continuous high-quality silicon germanium fiber material came out.

Look for "flexible" materials

Making brittle materials soft and even able to weave clothes is one of the research directions of Wei Lei's team.

"Today's mobile phones, computers, smart watches and other devices can not be made without silicon materials. Before silicon materials were favored, germanium was a classic material used to make the first transistor in history." Wang Zhixun, the co first author of the paper and a postdoctoral researcher at Nanyang Technological University, introduced that these two materials have rich natural reserves and excellent electrical performance, But they are brittle materials that are "better broken than destroyed", and chips made of them are very easy to break.

It has been found that although inorganic semiconductor materials represented by silicon and germanium have become indispensable key materials for chip manufacturing, the intrinsic brittleness of these semiconductors has brought challenges to material scientists under the new trend of flexibility in the electronic industry.

In order to make these semiconductor materials "flexible, flexible and easy to use", in recent years, the international academic community has proposed some solutions to reduce dimensions.

Wang Zhe, a professor of Jilin University who participated in the research, explained that reducing dimensions means using silicon "points" (zero dimensional nano silicon) with extremely small three-dimensional dimensions, which can be considered as zero dimensional morphology, distributed on flexible substrates in the form of arrays, forming a soft and hard cross-linked network to achieve the flexibility of brittle and hard materials; Or reduce the thickness of the wafer and passivate the mechanical damage, so as to obtain a silicon film with planar (two-dimensional nano silicon) morphology that can be bent.

"At present, there are relatively few academic studies on one-dimensional (one-dimensional nano silicon) semiconductor fibers, mainly because of the extremely difficult preparation." Wei Lei said that the key challenge is how to continuously manufacture crack free semiconductor fibers with considerable length in large scale and high output.

Woven photoelectric sensor cloth comes out

Although scientists have found the micro pull-down method and other crystal growth methods starting from the melt, the preparation of semiconductor fibers still faces some major problems.

Wang Zhixun introduced that the fused core hot drawing method is a method of manufacturing multi material fibers by slightly modifying the method of producing glass fibers. This method has the characteristics of low cost, high speed, long fiber, etc. Its fiber drawing speed can reach tens of meters or even hundreds of meters per minute, and the drawing length of a single fiber can reach kilometers. However, semiconductor fibers produced by fused core hot drawing often have defects such as uneven shape, frequent core fracture, etc., which limit their practical application.

"To solve the production problem of semiconductor fiber, the hot core drawing method is a potential method, but it needs to fundamentally understand the defect generation mechanism and solve the problem from the source." Zhang Qichong, a researcher at the Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences, who participated in the research, told the China Science Daily that team members combined their own background advantages, Breaking through the traditional thinking, starting from basic science and combining with experimental verification, the different physical and chemical processes in the fused core hot drawing method are summarized in stages, and the key fluid and solid mechanics problems in fiber preparation are clarified.

From the establishment of the theoretical model to the successful drawing of the semiconductor fiber, the international joint team verified the systematic law of the fused core hot drawing method, and demonstrated the daily application of the braided photoelectric sensor cloth based on the semiconductor fiber. "This kind of sensing cloth can be sewn into a hat, a garment, or attached to a complex shaped surface in the form of a single fiber (one-dimensional nano silicon) to achieve a variety of practical applications in extreme environments such as continuous environmental light monitoring, indoor optical communication, health management and even deep-sea wireless communication." Chen Ming, associate researcher of the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences, who participated in the research, said.

"Hair" has great potential

Silicon and germanium are mature and widely used representative materials in the electronic industry. The semiconductor fiber made of them has an important advantage - it can be compatible with the existing technology.

Zhang Qichong said that photoelectric sensing is only a small part of the application of this silicon germanium fiber material, which has a broader application prospect. In the future, solar cells, temperature pressure and other signal sensing, data storage, and even integrated circuits and microprocessors may all be integrated into this "hair" and woven into daily clothes to improve people's quality of life.

"Now, we have realized the large-scale production of high-quality silicon and germanium semiconductor fiber materials in the laboratory, but we still face challenges to achieve a wider application." Wei Lei introduced that from the fiber morphology, the current shape is single, and different devices may need different shapes or fibers with certain internal structures in practical applications; From the perspective of materials themselves, it is necessary to further explore the fibrosis preparation of the third and fourth generation semiconductor materials.

Zhang Qichong revealed that in the future, the joint research team will further study multi-functional fiber materials to jointly solve the problems in production and preparation, so that people can carry intelligent devices like wearing close fitting clothes.