Feature 1● － Professor Hideo Hosono and His Approach to Material Research
Striving for Research on Essential for Life
Professor Hideo Hosono of the Tokyo Institute of Technology, a power hitter in materials science, has hammered his fourth home run into the stand it seems. His most recent achievement is a new ammonia synthesis process using C12A7 (12CaO‧7Al2O3) as a catalyst. The well-known conventional Haber-Bosch process (developed in 1903) enables us to synthesize ammonia from nitrogen gas in the atmosphere as a raw material. Nitrogen fertilizer produced from the synthesized ammonia has greatly contributed to global food supply and prosperity. However, this method, a landmark in human history, might eventually be replaced by the “Hosono Process.” Whether a hundred years of history will actually take this turn depends on future trends and developments. But Professor Hosono is confident that his process is highly likely to provide superior conversion efficiency.
(Interview and article: Yoshiyuki Matsuo)
Interviewer: Professor Hosono, you discovered and invented the transparent oxide semiconductor, IGZO. Sharp Corporation has been running an extensive advertising campaign for it. However, I believe you first licensed use of the technology to Samsung. Is that right?
Hosono: Sharp Corporation, one of the licensees of IGZO, has registered its name as an authorized trademark. I doubt if it is allowed to trademark a name that has long been used in the academic society. Apart from that, this technology has already been the basis of other business, and among companies and related organizations tremendous battles are being fought over patents and other matters. Some newspapers reported that a patent for the groundbreaking semiconductor had already been granted to Samsung, but these articles were not reporting the truth. We were in a dispute over an IGZO patent in South Korea at that time. We won the trial and accordingly formally licensed Samsung to use the technology. We only granted general licensing rights that were not constrained by anybody, and by chance, we made our first contract with Samsung. The contract was not made prior to contracts with any other companies, as was suggested. We have already licensed LG, Japanese companies including Sharp, and Chinese companies.
IGZO development has finally reached production level. I think that even researchers working in development in the electronics industry never imagined that a transparent semiconductor made of an oxide could be made practical. At an international conference in 1995, we reported the concept and concrete examples of the material design of transparent amorphous oxides with high electron mobility. Subsequently, we created high-performance transparent thin-film transistors (TFTs) in 2003 (crystalline IGZO) and 2004 (amorphous). Things rapidly advanced after that.
Interviewer: IGZO is a technology that is used in the displays of devices such as smartphones and liquid-crystal TVs, so I’m sure that it will have widespread applications in many areas.
Hosono: Around 1995, amorphous silicon occupied the mainstream of research. Most energy in the field was directed at research on this semiconducting material. I was interested in creating an original semiconducting material and gave a presentation on oxides at an international conference on amorphous semiconductors. After that the presentation, some expert of amorphous silicon said to me thatthis is not your place because this is asemiconductor conference but no glass.
Around that time, someone asked me what my dream was, and I answered that it was to kick amorphous silicon out from the world. These days, I don’t say that. The age in which the most energy in the field was directed at research on amorphous materials has almost gone at least in research.
Interviewer: What theme have you selected for FIRST (Funding Program for World-Leading Innovative R&D on Science and Technology)?
Hosono: We are concentrating mainly on superconductor. As part of our research theme, “Exploration of new superconductors and their related functional materials and superconducting wires for industrial application,” we are also engaged in research in scientifically relevant areas, i.e., electro-active materials, other than superconductivity. One such area is the ammonia synthesis catalyst, which is the most easily understood of our research targets. The FIRST research funds were reduced from an initially planned 9 billion yen to 3 billion yen when the administration changed to DPJ. At the same time, the new administration requested that we resubmit the research proposal. Subsequently, the response to the new proposal was that since the research on the catalyst was not relevant to the research on superconductivity, this theme should be removed. In spite of that, I encouraged the relevant researchers around me, saying that I would take responsibility, and we proceeded the research as originally planned. Finally, in the third year of the research, the FIRST interim report evaluated our research as deserving special consideration, in particular for catalyst for ammonia synthesis. Research can be like that. It will not always go the way evaluators speculate. What is important is for us to achieve results.
Interviewer: The development of the ammonia catalyst seems to be an ambitious attempt to replace the conventional Haber-Bosch process.
Hosono: The Haber-Bosch process is a truly breakthrough technology. When it was developed, the possibility of synthesizing ammonia from nitrogen and hydrogen was not clear, even in thermodynamic argument. Despite this, the process achieved the synthesis. However, we expect our approach would be more efficient than the Haber-Bosch process. The method uses a cement material called C12A7. When electrons are injected into C12A7, the material actually becomes a transparent metal and exhibits superconductivity at a low temperature, and it gives catalytic activity. A research paper was published from our group at the end of August reporting that the catalyst also enables carbon dioxide gas to be decomposed near room temperature.
We aimed to examine this material from the initial stages of FIRST. At that time, we had just discovered an iron-based superconductor, and the discovery fired a boom of research on such materials all over the world. However, Prof.Kazuhito Hashimoto of the University of Tokyo, who is now a member of the Council for Science and Technology Policy, advised me not to concentrate only on superconductivity. He told me that I should carry out research on various materials with the potential for applications. I had originally intended to do just that, and Dr.Koichi Kitazawa, the directorof the Japan Science and Technology Agency (JST) at that time, advised me to do what I wanted to do. With such a wide entry point, various types of research could be possible.
We discovered the iron-based superconductor as a byproduct in research of transparent oxide semiconductors. I intended to try to discover a method of catalysis based on C12A7 in turn under the banner of the iron-based superconductor research.
Interviewer: So, your true goal was different from that of the banner.
Hosono: This is why we included the term, “related functional materials,” in our theme, “Exploration of new superconductors and their related functional materials.” Generally, it is not easy to find a groundbreaking superconducting material even if you intend to. In particular, it is extremely difficult to find a superconducting material with a high transition temperature (Tc) which should be recorded in the history.
It took 20 years from the discovery of a high Tc copper-oxide superconductor to the discovery of an iron-based superconductor. The copper-based superconductor was also discovered by chance, not intentionally. The very researcher who discovered the superconductor had no choice but to concentrate the research. However, the researcher cannot die a heroic death from just doing the research.
Interviewer: So, you provided that extra something to avoid risk.
Hosono: That’s right. We chose the phrase “Super plus alpha” to represent our project. The “super” refers to superconductivity. Including that extra something, or the “plus alpha,” is essential. The goal of research on materials often changes rapidly from the intended goal. I believe that the scope of the research should not be focused on too narrow an area.
Interviewer: That’s clearly a policy based on the philosophy of a top scientist such as you.
Hosono: There are things we do not discuss even in the laboratory. When the researcher can explain the details of the research to others, it is already almost at its final stage. Obtaining sufficient results supports the hypothesis of the research in a convincing manner. However, at the initial stage, it is not easy to talk about the hypothesis with persuasion . In a sense, it is meaningless to talk about it. At any rate, we do everything that we need to do until we know we have done more or less enough. We collect experimental evidence regarding the hypothesis, and when we can sketch the overall story of the hypothesis, the research is almost complete.
Interviewer: From the standpoint of funding sponsors, researchers who obtain authoritative results in the way you do are reliable.
Hosono: I prepared the proposal document properly, so that it would not provoke a negative response from the reviewers. However, we never reveal everything about our research in the document. I keep my trump card concealed.
Interviewer: There is always something from the magician’s pockets of Professor Hosono. To change the subject, it seems the research proposals of European and American research organizations are written precisely.
Hosono: Still, I don’t know whether the proposals are kept strictly secret. Key research projects in Japan, such as the Exploratory Research for Advanced Technology (ERATO) projects of the JST, have been completed successfully, because the research has been left to the research leaderentrusted with it. I believe that the policy of “we trust you, so carry out your research freely within the your responsibility” has worked well. The opposite system is a review committee system. Rarely does a proposal convince all the committee members. Rather, for almost all such proposals, the result of it may be obvious even from the outset.
Interviewer: Research journals, such as Nature and Science, are edited by severe peer review. As a result, it seems that the results of groundbreaking research rarely appear in the journals.
Hosono: It does seem that such research results are not often published these days. Research papers on fashionable subjects frequently appear in the pages of journals. Researchers are so eager to follow trends that the research has become inflexible in a sense.
Interviewer: A typical example is genome research. The US and the UK have put an enormous amount of money into bio-related research, but there have been no great scientific findings. I suppose that a contributing factor to this lack of success is the review process. The review process for research proposals is too strict.
Hosono: Nevertheless, we have no choice but to use the review process when selecting 90% of research projects. I think that about 10% of research projects should be selected by simply entrusting them to researchers with talent and achievement. ERATO project adopts the official project after the leader’s surname and entrusted the projects to a project leader. The results of research basically differ depending on who is doing the research; research is all about people. Although Tora-san (the protagonist of a popular Japanese cinema series) might declare, “That's too fatalistic.”
The possibility that challenging basic research will be successfully completed is not so high, even if it has been nominally successful. Thinking about this, I calculated the amount of money that I have so far received for research as the representative. To my surprise, the total amount of money has reached the amount needed to build a large bridge.
Interviewer: Are you saying that a five hundred meter bridge could be built with the total funds a researcher receives for science research?
Hosono: I received 1.8 billion yen for an ERATO project, 1 billion yen for further research under SORST (Solution-oriented Research for Science and Technology), and 3.2 billion yen for a FIRST project. The research projects for which I have been working as the representative have received 6 billion yen (60 million dollar) in total. I once attended a lecture given by a civil engineering researcher. The lecturer said that the construction of a certain bridge cost 6 billion yen. Have I achieved results that are more valuable than a large bridge? I’m strongly aware of the burden of responsibility in using taxpayers’ money. I have to achieve results that recompense them.
Interviewer: I think that the development of IGZO has returned well above the 6 billion yen investment. Considering the innovation related to IGZO, the profits will reach an amount 100 times or 1000 times more than 6 billion yen, because the size of the global market for displays may have grown in scale to the order of 10 trillion yen per year.
Hosono: To be honest, now I feel better. The other day, someone from the JST told me that my project has no debt to pay, if it were in business.
Interviewer: Construction of an accelerator costs tens of billions or hundreds of billions of yen.
Hosono: Accelerators are not used for research on materials but for research on the truth of the natural world.
Interviewer: I’m personally very happy to know that only 50 cents per Japanese citizen have resulted in these wonderful achievements.
Hosono: The most famous invention achieved by Tokyo Institute of Technology is ferrite, which was invented in the 1930s. However, after 1945, there weren’t any great inventions comparable to ferrite.
Interviewer: Ferrite is still a product at TDK Corporation, isn’t it?
Hosono: Yes. We have to contribute to new inventions and discoveries that can play a role as banners for the university. We need to aim to carry out research that ties in with the identities of students and young researchers. I’m not saying this because I received 6 billion yen for our research, but I greatly feel responsible for that.
Since the thin-film transistor based on IGZO (crystal and amorphous) is our first creation, we would like to patent the result in a socially visible form. We would not lose in court by default. We would like to record in a visible form the entire history of the material, from our research on the material to its commercialization and our dispute in court over its patent. I believe that the record will serve as a reference for future researchers to understand where they might fail.
Interviewer: In what process and how was the ammonia synthesis catalyst created?
Hosono: I have been interested in ammonia synthesis since I was a young major in chemistry. Several years ago, when we were well on the way to putting IGZO into practical use, I had an opportunity to talk to Dr.Kenji Nomura, a collaborator who was scouted by a US company. At that time, an academic society had requested to write an article about transparent displays. Then, Dr. Nomura asked me what purpose transparent displays would serve. After seriously reconsidering it, we finally realized that it was just simply interesting.
I concluded that it would serve to realize a “Better life.” However, I have not been engaged in science in order to realize a “Better life.” I have been engaged in science in order to create materials “Essential for life.” This is just the work that I want to do. I want to do work that is essential to human life. I have always longed to do such work. While I was asking myself what that meant, it finally occurred to me that ammonia synthesis has been done using the same catalyst for 100 years. That changed everything. Ammonia as a fertilizer has served to support the increasing population. The Haber-Bosch process is an invaluable ammonia synthesis process in that it has helped humanity. However, 100 years have passed since it was developed. It’s about time that a new method was discovered. At that time, nobody was engaged in new research, and some researchers around us were experts on catalysts. So, we decided to do the research ourselves.
Of course, we also expected to be successful to some extent. It is difficult to synthesize ammonia, because atmospheric nitrogen molecules are formed by a triple bond between nitrogen atoms. Ammonia synthesis requires the triple bond to be dissociated. However, once the triple bond is dissociated, ammonia can be easily produced. So, how can we disscociate the triple bond? A nitrogen molecule has triple bonding. If an electron is injected onto each of the three corresponding antibonding orbitals one by one, the triple bonding must dissociate one after another. To achieve the process, we have only to use a material that will powerfully donate its electrons to nitrogen molecules. This way, the triple bonding of nitrogen molecules is dissociated. It is as simple as the methods that we learn in high-school science classes.
Examples of these materials are alkaline metals. Alkaline metals are elements that are easily ionized and that readily donate their electrons. However, they react with nitrogen to form a stable compound. We need a material to act as a catalyst; it must cut the triple bond of nitrogen molecules and then return to its original state. For this purpose, the material should possess two characteristics: it should readily donate its electrons to nitrogen molecules, and at the same time, it should be chemically stable. Therefore, our goal was to find a chemically stable material that releases electrons very easily.
Interviewer: That sounds like a contradiction.
Hosono: These two characteristics generally conflict. However, the electride that is produced by doping electrons into C12A7, which we have been working on, fulfills the requirements. We reported this fact in a research paper several years ago, and were looking for appropriate applications of this unique property. Against this backdrop, we decided to use this material to develop a new ammonia synthesis process. When I visited Michikazu Hara (a professor in the Materials and Structures Laboratory, Tokyo Institute of Technology), an expert on catalysts, he said to me, “Are you really going to do a new ammonia synthesis process? They say that if you poke your nose into that, you’ll be cursed.” According to him, ammonia synthesis is the highest peak in the field of catalytic chemistry, and consequently, many researchers have failed attempting to reach the goal of a new synthesis process. As a result, all researchers back away from it nowadays and no one dare to tackle the issue. But he said that he had himself been fascinated with ammonia synthesis and so he entered the field.
Interviewer: He could not abandon his dream completely even after having built his career.
Hosono: He asked me whether I was serious about it. When I answered that I was serious, he replied, “Okay, let’s do it together.” It was just before FIRST started.
Interviewer: As your story suggests, the outcome is not included in the list of the achievements that had been accomplished before FIRST.
Hosono: No, it isn’t. We developed a method for large-quantity synthesis of an electride that is stable in an ambient atmosphere and we subsequently continued our research for a long time. The most important thing about a catalyst is its outermost surface. The performance of the catalyst varies depending on its surface structure. Accordingly, we explored the conditions that allow the surface of a catalyst to take a structure similar to that of bulks. We carried out the basic research properly. Since we had figured out the conditions that allow the structure of atoms to appear on the surface, we believed that we would surely be able to apply the conditions to catalysts.
This is because catalysts that do not deliver sufficient performance have a surface that is not appropriate to catalysis. Generally, that their surface is different from that of bulks is given as a reason for their poor performance. Accordingly, for the first three years, we carefully examined the surface by using scanning tunneling microscope(STM). We collected sufficient information to confirm that we were going in the right direction. So, we cut off our escape route and applied ourselves to the exploration as if we were prepared to die. About a year and a half after we started the exploration, we finally discovered the conditions.
Interviewer: In the research process, you identified each of the conditions that precisely determine the surface structure.
Hosono: We published the report on the surface in 2011. So, our research on the surface started around 2009.
Interviewer: What state leads to the surface structure not being precisely determined?
Hosono: C12A7 has a cage-like structure. Electrons are present in the cage. When the surface of C12A7 is ruptured, the cage structure is destroyed. The electrons then escape from the cage, and the outermost surface of the material becomes an insulator. Consequently, although the bulk material possesses electrons, the surface of the destroyed cage is locally in a state in which electrons are exhausted. Needless to say, catalytic activity is also lost in the process. Since C12A7 in this state does not function as a catalyst, it is heated to an appropriate temperature for cage healing. The annealing allows the destroyed cage to recover to the same state as that of the inside of the material. However, in the initial stages of the research, we originally did not know whether the conditions inducing this phenomenon were actually present or not. We just looked for the conditions. This exploratory work was very unglamorous.
After the conditions for precisely rearranging the surface were determined, we also found that electrons come to the outermost surface.
STM observation on surface is generally only carried out when examining materials that develop clear cleavage, such as graphite. Materials that do not have cleavage nature, such as C12A7, are not studied in surface science. Young researchers in my laboratory said to me, “Professor Hosono, it is unreasonable. It is impossible to observe C12A7 with an STM, because it cannot be cleavaged.” I also thought to myself “Is that right? Damn!” But it was after I had submitted the research theme. However, since we could not back out of the research, we decided to direct our energies toward advancing as far as possible. Dr.Yoshitake Toda (a present research assistant professor) put his energies into the research for three years, which resulted in us being able to clearly observe the surface of C12A7 with an STM.
This is a model of C12A7. Electrons can be present inside this cage. When this single crystal is ruptured in an ultra-high vacuum, the cages on the surface are destroyed and electrons cannot be present. As a result, the surface becomes an insulator. When the crystal is heated again, the surface of the cages recovers from the destruction and electrons can enter the outermost surface leading to metallic nature. This process suggested that if nitrogen molecules came close to the basket, electrons would be donated to them. We were looking for this state.
Interviewer: You used an STM to observe the state.
Hosono: We did. Finally, we understood that haste makes waste. For five to six years before that, we were doing the research without using an STM, so that some reactions worked well, but others did not. After we started to use an STM, it took us three years to be able to observe the surface with an STM. Students also put their energy into the research. Finally, the use of an STM enabled us to observe the surface, and all obstacles were eliminated. In truth, we obtained good data in the first observation with the aid of the STM.
In spite of the successful results, when we submitted the research paper on ammonia synthesis, the reviewers could not understand the detail and they rejected the paper.
Interviewer: Even experts could not understand the importance of such a groundbreaking discovery.
Hosono: The research paper on iron-based superconductors was also rejected at first. In truth, the premise for its mechanism was in part insufficiently described in the paper. The insufficiency might have led to a misunderstanding. We corrected the problems pointed out, obtained the required data again, and redid the paper.
Interviewer: Nevertheless, it was a completely new field and so requires an effort to convince fundamentally.
Hosono: That’s right. It was necessary to obtain data again from a different viewpoint to convince the reviewers. Finally, when we managed to get them to understand the results, they changed their attitude toward the paper completely, saying that it was more groundbreaking than any other paper. They even wrote a NEWS & VIEWS article on our paper. It was a very dramatic change. In a sense, there were some compelling reasons. At first, they did not understand what we meant; they thought that the catalyst was the same as conventional alumina and they were questioning exactly how it was different from a conventional catalyst. It would have been easier to convince the reviewers if we had had an opportunity to have half an hour or so to explain the mechanism on a blackboard in front of them. Since paper reviews are carried out by anonymous reviewers though, it takes a long time for both sides to understand each other.
Interviewer: I felt the same way when I met you previously. It seems that you have a unique philosophy on chemistry. I believe that your chemistry is based on a different philosophy from that of ordinary chemists and material scientists.
Hosono: On the contrary, I think that my approach to material research is similar to that of other researchers. I don’t use mysterious methods. I always choose an orthodox approach.
C12A7 may appear to be complicated. However, when you break it down into elements, you will find it to be unexpectedly simple. This material allows an electric current to pass through, because some electrons in a cage constituting the crystal structure of this material can transfer from the basket to the adjacent cage by the tunneling effect. The electric current occurs only because of quantum tunneling through the thin cage wall. Some researchers believe that the tunneling effect is a special phenomenon that does not occur in cement-like materials. This is not true. The tunneling effect is a common phenomenon that occurs in various places.
Interviewer: So, the effect takes place in cements.
Hosono: If you control the conditions suitably. It does not choose a place to occur. This fact suggests that it is essential to devise an appropriate approach to induce a physical phenomenon in a specific material. A material is a stage on which physical properties and principles can play suitable roles. All you have to do is find the most suitable material that can be a platform to realize your concept.
Interviewer: What conditions are required for materials to be accepted by society?
Hosono: First, materials must be able to deliver excellent performance. However, materials are not only accepted for their excellent performance. They are also required to be unique.
Other cases are those in which there is no other choice but to accept the material. Our IGZO is a typical example of such a material. Other researchers basically did not want to use IGZO. They believed that semiconductors should be based on silicon, so they avoided using dirty materials such as oxides. Nevertheless, IGZO was accepted. This is simply because when they checked its performance, from the outset, IGZO was 20 times better than amorphous silicon. Consequently, they had no choice but to use it, regardless of whether the oxide-based material was good or not. In addition, since the material can be easily produced in a simple process, it instantly found widespread applications.
I belong to the world of academia. Accordingly, I find the greatest value in the cultivation of a new academic discipline. Specifically, a new academic discipline is developed, new functions are brought about, and new applications are found. I believe that these three factors are all essential for advances in materials science.
In my superconductivity project, I did not include a physicist as a core member. This was intentional. Superconductivity is a research area in the field of condensed-matter physics. However, if a physicist had played a main role, the entire research would have been carried out from the viewpoint of the physicist. Consequently, our goal of creating a new material might not have been accomplished. I was afraid that such a situation might occur.
Of course, we sufficiently consulted physicists, but we decided that the actual research would be carried out only by chemistry researchers. Our research was the world’s first superconductivity project led by researchers in solid-state chemistry. I wanted to accomplish such a project.
Interviewer: Professor Hosono, have you ever had a situation for which you had no ideas?
Hosono: Normally, I don’t have many ideas. An idea occurs to me only occasionally. I sometimes rethink an idea that occurs to me in the middle of the night, only to find it is unusable in the morning. I rarely get good ideas. Dr.Shinji Murai, a former professor at Osaka University, once ingeniously expressed research in alaboratory of university: the steady state of a laboratory is one in which nothing that we do goes well. What an insightful view! No other expression has ever exactly described my opinion in the way that one does. When work always proceeds smoothly, it is not groundbreaking. Then it is simply a state in which you are doing the work in the expected way.
Interviewer: This is only my personal opinion, but when we consider the rarely reported groundbreaking research results, we find that in the last dozen years or so, most of the new discoveries have been made in Japan, particularly in the field of engineering applications.
Hosono: You are probably right about that. They say that Japan has been outstripped by China, but Japan is still continuing to make groundbreaking achievements. Almost all of new superconductorshave been reported by Japanese researchers, and China is playing a role in improving those materials. It seems one reason for this is that China is particularly good at making improvements.
A Chinese acquaintance of mine said that I would never be successful in China. According to this acquaintance, the reason is that I tend to contradict the authorities and try to overturn convention. In China, researchers must respect the authorities. They have to follow the authorities when writing research papers in order to achieve a successful career. It seems that almost all the research papers published in China are written in such a manner. Most of these papers are based on the policies of the top researchers in European and American laboratories and concern improving previous research achievements. The situation looks almost the same in Korea. They carry out research based on the achievements of world-class authorities. On the other hand, I think Japanese researchers, and European and American researchers, direct their energies toward overturning conventional approaches.
Interviewer: That is one of the pleasures of working in the fields of science and technology.
Hosono: From the viewpoint of the history of science, the system is based on freedom. It seems to me that the fact that groundbreaking scientific achievements are possible has something to do with our social system. Which is preferable for innovation, a social system that requires researchers to please the authorities or a social system that allows researchers to try to overturn previous authority? I believe that new things are created in the process of trying to overturn previous authority. In that sense, China has not yet made any groundbreaking achievements in the area of materials science. In contrast, China has the energy to rapidly improve the performance of things created in Japan, Europe, and the US. China is far ahead of other countries in terms of its potential for improving things.
In the 1980s, when we experienced trade friction between Japan and the US over semiconductors, people said that the Europeans plant the seeds, the Americans grow the seeds, and the Japanese reap the harvest. Some even described the actions of the Japanese as “gleaning.”
Interviewer: Japan surely has the potential to revive what others have discarded.
Hosono: Now that twenty or thirty years have passed since the trade friction over semiconductors, Japan has grown to be a country that can actually plant seeds. We should not forget this.
Interviewer: Thank you very much, Professor Hosono.