Chapter 152 Topological Semimetals

Chen Yuanguang did not correct the other party's statement about the photosensitivity of silicon wafers. The photolithography machine first acts on the photoresist, and then prints the pattern on the silicon wafer through an etching process.

After all, the other party is just the person in charge, and what he needs to do is to explain clearly why topological semimetals can become a way forward.

"Topological semimetals describe a class of substances, just as iron compounds include a variety of compounds containing the element iron. Different topological semimetals, like different iron compounds, will exhibit different properties.

What we need to find is a topological semimetal that can show photosensitivity.

Scientists have always placed high hopes on topological semimetals, believing that this material will replace silicon wafers and become the basis of future chip technology. This is because topological semimetals can exhibit a very special property: a wide spectrum effect.

The zero-bandgap structure in semimetals can absorb excitation photons of various energies. It is sensitive to the polarization of the laser, and the root of its linear polarization resolution comes from the anisotropy of the lattice. This leads to many topological semimetal materials having a significant photoelectric response mechanism that is sensitive to linear polarization, thereby producing a photocurrent response with significant anisotropy.

For example, the chirality of the Weyl cone makes it easy for electrons in semimetals to interact with the spin angular momentum of photons during transitions, forming a unique selection rule and generating circularly polarized resolved photocurrents. Another example is that the photocurrent response of some semimetals is enhanced by the huge Berry curvature near the Weyl point of the Weyl semimetal.

Lin Jia was bewildered. What was this? She had done some homework yesterday after listening to Chen Yuanguang's talk on topological semimetals, but she found that the homework seemed to be of no use at all.

Although Zhao Pu is a PhD in engineering, there is still a gap between PhDs. The gap between his PhD and Chen Yuanguang's is much greater than the gap between a second-tier university and Peking University or Tsinghua University.

Not to mention topological semimetals, which have never been understood before. This is a field that combines materials science, optics and condensed matter physics, and is considered a very cutting-edge field.

Zhao Pu was so confused that he couldn't even understand the principles behind it. It felt like he was listening to a foreign language.

"Dr. Chen, I have absolutely no idea what you are talking about.

But I guess, you mean that topological semimetals are sensitive to light, so photolithography machines can act on them, right?" Zhao Pu said with a wry smile.

Chen Yuanguang nodded: "Yes, I have discovered a material that is more sensitive to light than any topological semimetal discovered before, and is also more stable in terms of light sensitivity.

This is a very difficult property to find, because semimetal is in a state between metal and insulator, which means it is unstable. If you use its light-sensitive properties to draw pictures, it is difficult for the expected pattern to appear stably on it.

If we use a metaphor to describe it, you can think of it as rice paper, any bit of ink will create a large area on it, while the silicon wafer is A4 paper, ink printed on it will be very stable.

That’s right, it’s rice paper!”

Chen Yuanguang felt that he had finally found a suitable metaphor that would allow the two people in front of him to understand what he wanted to express.

“Xuan paper is thin, while A4 paper is thick, so writing on Xuan paper is unstable, while pictures or words written on A4 paper are very stable.

Now I have found a new material that is as thin as rice paper and as stable as A4 paper.

This also explains the question you just raised, that is, this material can be industrialized on a large scale.

Of course it also has some problems, but I have thought of solutions to these problems.

The biggest problem is that we need to modify the light source. We need to modify the light source of the lithography machine. Previously, the light source of the lithography machine acted on the photoresist, but we need polarized light.

In addition, we need to develop a large-scale process for topological semimetals.”

Chen Yuanguang's answer solved two problems. One is that topological semimetals will show photosensitivity to polarized light, so it can be used with a photolithography machine.

However, the light source needs to be modified.

The second is that this is industrial production technology.

"In addition, if we only solve the production end, we also need the design end, we need chip design, because we can make the chip bigger and use the transistors used in the 7nm process on a larger silicon wafer using 28nm.

Since I don't know much about chip design, I think this will still require a redesign of the chip.

Especially when it comes to completely new processes.”

After listening to this, Zhao Pu knew that given Chen Yuanguang's character, if he said that, it meant that he was absolutely sure of success.

"I will help you contact Yanjing and prepare experts to do the demonstration. After the demonstration, if it is feasible, we will select from these domestic enterprises and research institutions.

We have made this our top priority in recent years.”

For China, the chip issue is of vital importance. This can be felt from the large integrated circuit industry fund and the support for semiconductor manufacturers such as Huawei, SMIC, and Huahong.

Syngenta cannot go public through IPO with a fundraising scale of 70 billion RMB. Syngenta is backed by state-owned enterprises, and Huahong raised 20 billion RMB. After raising funds, it can put the money in the bank to earn interest.

Chip companies are now like our own children, and this is reflected in everything from policies to financial support.

For example, the lithography factory plan was hyped up by self-media bloggers but then nothing happened. Why? Because this technical route has not been proven to be feasible.

In other words, by following the route of lithography machines and feeling your way across the river, you will know what difficulties you will encounter and how to overcome them, and the input-output ratio will be relatively clear.

As for the photolithography factory, how to calculate the input-output ratio? This is a big project. If the money is invested but the results are not achieved in the end, who will be responsible? Who will sign? Who will approve the money? No one dares to make the final decision.

After the development of room-temperature superconductivity, Shuimu University took advantage of the cutting-edge technology and forced its way into the project.

It is said that the original success rate was only 50%, but with the development of room-temperature superconductors, the success rate has risen to 70%, which is also related to encouraging innovation.

It took a lot of effort for Shuimu University.

Zhao Pu had the keen insight to realize that Chen Yuanguang's plan was based on the transformation of the existing foundation, which meant that it would only cost a small amount of money to verify whether it was feasible.

Compared with the photolithography plant, the difficulty of transforming the light source is much smaller. Even the plan of the photolithography plant will be allowed, not to mention the plan of transforming the photolithography machine of Chen Yuanguang, who has room-temperature superconducting in front.

"Mr. Li, is this achieved through a magnetic doping strategy or using compatible sputtering support?" Lai Jiachen is a professor at Shenhai Jiaotong University who is engaged in topological semimetal research and is one of the young talents in this field.

He holds a Ph.D. from the University of Minnesota. He thought this was just a routine business trip, but what he saw reshaped his perspectives.

Is China's technology so advanced?
In his laboratory in Mianyang, he saw a topological semimetal that was both photosensitivity and stability. What's even more amazing is that this thing was in the form of a thin film.

"Sorry, I don't know either. I'm just an administrative staff member. I'm here to help you with your work and life in Mianyang. Although I also have a master's degree in materials science, that stuff is too high-end and it's beyond my ability to know." The man he called Mr. Li said indifferently.

He was responsible for receiving the three professors, and he was already very familiar with this set of rhetoric. When these people arrived and saw the material, they were all shocked. They had to find out which group made it, what process was used, and how it was made to maintain a balance between stability and photosensitivity.

Every time he heard this question, he wanted to roll his eyes. If he could figure it out, he would have chosen to pursue a doctorate instead of running off to Sichuan Province to become a selected student after graduating with a master's degree.

Combining these two properties with the thin film form, Lai Jiachen easily thought that this thing could be used in chip manufacturing. In fact, people have always placed high hopes on topological semimetals because they value its potential in chips.

Lai Jiachen graduated from the University of Minnesota, which has a very strong group in the field of topological semimetals. He did his doctorate and postdoctoral work in that group.

Because some of his fellow students from his doctoral period are still doing their postdoctoral studies there, and some have stayed in Minnesota, and he has many acquaintances in that group. He knows that they have recently made good results in topological semimetals and have produced a topological semimetal film with ultra-low energy consumption.

The paper was published in the journal Nature Communications, but the topological semimetal he saw in the Mianyang laboratory was ten years ahead of what they had made, and ten years was a conservative estimate.

All the way home from this trip, Lai Jiachen was still wondering how this thing was made, what the process was, and which group in the country was so awesome.

Lai Jiachen has always believed that the reason he was able to teach at Jiaotong University and be selected as one of the Thousand Young Talents in China is because China lacks talent in the promising emerging field of topological semimetals.

Now I realize that something is not right. China is so advanced in the field of topological semimetals. A postdoctoral fellow of his level will never be able to get an associate professor position at Shenhai Jiaotong University. The best he can get is a young teacher position with a promotion or leave policy.

“Professor Lai, if you are willing to participate in this project, please sign these documents. We will coordinate with Shenhai Jiaotong University to allow you to participate in the project.

If you don't want to, you just need to sign a confidentiality agreement and then you can go back. Tell me the time and I will help you book the ticket." The staff member surnamed Li said politely.

Lai Jiachen asked curiously: "Do I just need to sign a confidentiality agreement?
According to this visit, you are so secretive that you can't even reveal who made it. We don't know the process and parameters, and we have to test it ourselves. If it weren't for the Arabic numerals on it, I would have thought the country had dug up an alien spaceship and this was material picked up from an alien spaceship."

The staff member surnamed Li still maintained a polite smile and said, “Professor Lai, we didn’t expect to keep it confidential at all.

You should know that this will be used on chips. Mr. Zhao explained to you when he came here before that this is a large project that requires the cooperation of tens of thousands of engineers upstream and downstream, including chip design, laser production, optical lenses, etc., and at least dozens of suppliers. It is impossible to keep it confidential.

Of course, this does not mean that signing a confidentiality agreement is just a formality. Once we discover that you have leaked information, we will have a basis for subsequent accountability. "

Lai Jiachen continued to ask: "You really don't mean to force me?"

The staff member surnamed Li smiled bitterly and said, "Professor Lai, of course not. If I meant to force you, I wouldn't be talking to you.

This project involves a long period of time and requires a lot of coordination and cooperation. We don’t need one or two people, but hundreds of people. We don’t want to force anyone.”

Lai Jiachen asked again: "Is it true that you just said that the establishment will be retained?"

Staff member Li said: "Of course it is true. This is a project led by the national level. You will have to return to your original unit after the subsequent project is completed. I will not agree to it even if you want to stay here."

He thought to himself, unless you can become the project leader, but this is obviously impossible.

The organization did not force the transfer, but discussed that a group of people were needed to participate in the mass production of topological semimetals. Because this is a completely cutting-edge emerging field, no one knows how to do it, so it's like starting from scratch.

Lai Jiachen thought that this was actually a jump from academia to industry.

He was still very interested in being able to retain his position, as it meant there was no risk. If the project failed, he would just go back to Jiaotong University to teach.

Moreover, such opportunities are extremely rare. When Fairchild started in Silicon Valley, it was also a group of researchers who jumped from academia to industry and finally made epoch-making achievements. Intel, AMD, and Texas Instruments were all born in that PC wave.

Lai Jiachen believes that this new material has this potential, and experience is very important. As an associate professor at Jiaotong University, the research funding is only a few million yuan a year, and he has to compete with others for equipment.

Working here, you can use any equipment for projects worth billions of dollars, and the direction you are working in is the most cutting-edge, ten years ahead of American. Once industrialization is successful, you can jump into the industry and earn a million dollars a year.

He tested the material himself. As an expert in the field, he was well aware of its potential for application in the chip field.

Lai Jiachen thought for a long time but could not think of a reason to refuse. The only reason was his wife. His wife worked in Shenhai and it was impossible for her to come to Mianyang.

This is a problem, but the other party has said before that he can go back home for one month's vacation every year, and his wife can also come over. It is very convenient to have a direct flight to the airport.

Thinking of this, Lai Jiachen agreed directly: "I choose to stay. When do we start working?"

Staff member Li was not at all surprised that Lai Jiachen stayed. For these professors, seeing these materials was no different from seeing beautiful women; they were completely unable to resist the temptation.

"As for work, we'll start after we settle down. We'll assign you tasks then, so just wait for the arrangements."

Lai Jiachen continued: "Now you can tell me who developed this material, right? I have too many questions I want to discuss with him."

"It's the one you guessed, Professor Lai. I'm telling you in advance. It doesn't violate discipline. You can see him if you stay here for a few days."

　. . . 10,000 failed today, more will be added tomorrow

　　
　
(End of this chapter)