College of Engineering News • Iowa State University

Q & A with Jiahao Chen, a Molecular Electronics Researcher

Jiahao Chen, PhD

Tell us about yourself and your background.Jiahao Chen, PhD

I am originally from the east coast of China near Shanghai. In 2012, I earned my undergraduate degree in materials science with a specialty in ceramics from Tongji University in Shanghai. Later that year, I came to Iowa State University and started working with Professor Kristen Constant. Under Professor Constant’s guidance, I earned my M.S. in materials science and engineering. I wanted to pursue my Ph.D. so I joined Professor Martin Thuo’s research group. Professor Thuo highlighted the topic of molecular electronics in a conversation as we were discussing my research direction, and it seemed like a new research area that was interesting to me. I’ve always been a fan of electronics, so I started pursuing molecular electronics research. I helped Professor Thuo set up his lab and was the only graduate student working on this research in the beginning. Now there are more people in our group working on molecular electronics. In July 2017, I earned my doctorate in materials science and engineering.

What is the focus of your research?

This new century is all about silicon. We are in a silicon age. Everything seems to be made of silicon including our phones, our computers, and many other electronics. It is a very traditional inorganic semiconductor. One of the applications of my research focuses on trying to use a single molecule to replace those silicones or other inorganic semiconductors to work as electronic devices. In other words, we integrate the organic molecules into electronic devices, trying to replace the inorganic materials with organic molecules.

What’s the problem?

Today, the challenge with inorganic semiconductors (silicon) is the lack of the ability to scale down, meaning we cannot easily reduce the size of materials (the small features of the semiconductor device) without creating defects. We are reaching the limit of the size. Other scientists are trying to find different materials to use, but our group is trying to use molecules because they are incredibly small and easy to make. If we can pack the molecules, then we can make an electronic device with a multitude of molecules. To put it into perspective, one molecule in length is approximately 2-3 nanometers or 1/500,000,000 of a meter. Currently, we are focusing on using molecules with a simple structure to build devices, but in the future, we hope to engineer molecules so we can create more diverse and functional devices that can be used in many applications beyond the traditional electronic devices, such as medical devices and cybersecurity.

What’s the benefit?

The benefit of using organic molecules instead of the traditional inorganic semiconductors is that you can change the molecules easily for certain needs. We can simply synthesize the organic molecules with more control. Once we have the molecules of interests, we pack them on a substrate, forming a 2-dimensional organic material. Inorganic materials require several steps to change their properties, including doping and annealing. In this way, changing the properties of the organic material is easier than processing the inorganic material.

In electronic devices, we need an electrical signal. The electrical signal is the movement of the electrical charge. The mechanism of the electrical charge is different in inorganic materials and organic molecules. In the organic molecules that we are using, there is a quantum phenomenon associated with the charge transport. In the everyday electronic devices we use now, there is a classical electrical conduction, which means there is some energy loss and heat is created. In quantum tunneling, there is no energy loss, and it will not create heat.

You will notice that some electronic devices that we use get very hot and slow down over time, which is not beneficial for the devices. For example, the more you use your computer or cell phone, it gets slower because it creates heat and small amounts of the device fail to perform properly. This process is known as electromigration. When we use molecular electronics, heat creation will not happen.

What does a typical day in your lab look like?

Our lab is on the third floor of Gilman Hall, and we have two undergraduate students helping with the research. I teach them how to perform the experiments and analyze the data, and I also serve as a mentor.

In our lab, we pack molecules on gold or silver substrate. We have learned from the challenges we experienced before which is understanding how the molecules are packed on the surface. People assume that they are packed in a very ordered way, but they are not. We have to address that issue before we move to building molecular electronics. We have to understand the molecule first. Therefore, the research before my published work was mostly on understanding the molecules. I’ve submitted two papers about molecular electronics that are under review now, and I am also preparing another paper.

Doing the experiment is not really the most important thing. Collecting the data and doing the experiments are only a small portion of my research. The most important part is analyzing the data. Molecules and the devices are so small; therefore, variations and perturbations need to be considered. We have to use statistics to help us understand the measurements. From the statistics, we can get some understanding of what is going on within the molecular electronic device.

Why is your research group unique?

In Iowa, we are the only group researching molecular electronics. The field of molecular electronics is not a broad topic to research, unlike other areas of materials, such as graphene. There are only a few groups working on this type of research.

Many other groups in chemistry are working on molecular assemblies. That is the platform that we use in molecular electronics, but there are no groups in Iowa that are trying to use these molecules to make an electrical device. Now we are engineering the molecules to see how we can alter the material, electrical, and device properties.

What does collaboration in your research group look like?

When we are in collaboration with another group, we are mostly transparent with one another so we share ideas and data. In this way, we can analyze the data better. Two heads are better than one. We may even write the stories together or proofread each other’s papers.

We have many collaborations in our group. We are collaborating closely with a group from Boston University. The Boston University group helps us with optical characterization of the molecules, and our group works on the electronic measurements. We also have collaborations in multiple departments at Iowa State and with groups from China and Korea.

Sometimes it can be a challenge to work across different groups and departments because we all speak our own “academic language.” We look at the same issue, but we look at it from different angles. We use different perspectives. It is challenging but also interesting because you can have more ideas to explain what is happening. Others may see something you have never seen. That gives new perspectives and insight into what we are looking at. To me, it is a good opportunity to learn something new.

What is your plan for the future?

I would like to have a future in academia. At the end of December, I will be going to Northwestern University to continue my research as a postdoctoral researcher and will most likely be focusing on energy-related materials.

I have been at Iowa State since 2012 and enjoyed these years in Ames. Iowa is such a wonderful place with beautiful people and scenes. I had two excellent supervisors throughout the past five years and gained many friends. Thanks to their guidance and help, my experience at Iowa State has been joyful and productive. The memory of classes, professors, staff, and friends will long be fresh.