Natee Johnson, Mechanical Engineering
X-Ray Study of Nano-Scale Superlattice Materials
Faculty Mentor: Dr. Fow-Sen Choa
Nano-scale supperlattice (SL) based devices, such as quantum cascade lasers QCLs, have recently become very important due to their capability to identify toxic and explosive chemicals. In manufacturing these Mid-IR photonic devices, atomic-level scanning tunneling microscopes (STM) and transmission electron microscopes (TEM) have been used to characterize the growth quality of superlattice wafers. However, these methods yield observations that are localized and cannot view the entire structure and even now we have not been able to correlate these measured crystal lattice images with device performance. The x-ray scanning technique has greater likelihood of success given that it can observe not only the localized but also the entire superlattice structure. By extracting special features and key parameters in x-ray diffraction patterns, the epitaxial quality of QCL superlattices can be evaluated and correlated to the performance of fabricated QCL devices. We can then differentiate and classify different grades of wafers before starting device fabrication and testing. In this work, we use X-ray diffraction techniques and Fourier analysis as tools to study and compare grown SL wafer quality. The aim is to provide immediate feedback to QCL growers in order to improve their successive growth runs without waiting 3-4 weeks for device processing and testing, given that poor wafers will be immediately eliminated, and performance for all other wafers can be anticipated prior to fabrication.
1. How did you find your mentor for this project?
In class, one of my engineering professors offered to help interested students apply for the award and have him as a mentor on projects he was prepared to move forward.
2. How did you know this was the project you wanted to do?
It was outside of my current field of study, but I knew that it would strengthen my skill set and knowledge of this area in preparation for graduate school studies.
3. Is this your first independent research project?
No, I’ve completed several other research internships during my summers where I was given something to investigate and was able to take the research as far as I could.
4. Do you get course credit for this work?
Yes, I asked my professor if he could register me for an independent study so that the credit would show on my transcript and I would have time in my schedule allotted specifically for research.
5. How much time do you put into it?
The project is not in full blossom at the moment because I am participating in another program for the summer. I anticipate putting in at least 10 hours a week during the semester, but realistically, it will be whatever is demanded to complete the work in a timely fashion.
6. How did you hear about the Undergraduate Research Award program?
I had seen advertisements for it on myUMBC and around campus. I also have friends that participate who told me about it.
7. What academic background did you have before you started?
I started in the second semester of my fourth year. I am a mechanical engineering student, but the focus of my study is materials science under the mentorship of a Computer Science and Electrical Engineering professor. I have taken material science courses and circuits, but the advanced courses that will help me with this work will be taken in the semesters to come.
8. Was the application difficult to do?
No, I feel the application process was great because it helped me attain a greater understanding of the project and practice communicating the idea to others. The questions were excellent, straightforward, and not overly demanding.
9. How much did your mentor help you with this?
My mentor helped a significant amount because he formulated the idea and helped me groom it into a proposal. I don’t believe I would have been as successful without his patience and superior understanding of the material.
10. What is your advice to other students about getting involved in research?
I would encourage involvement in research because it is a great way to sharpen your critical thinking skills, as well as see coursework as a means to expand knowledge and not solely validate oneself with high scores. It’s also great for getting to know professors and vice versa. At some point, everyone will need letters of recommendation and having extensively worked with a professor beyond the classroom is a wonderful way to strengthen it. Also, keep an open mind. Many opportunities are overlooked because the right buzzwords were not attached. Do yourself the service of really looking into something you think you aren’t interested in, if only to confirm that you aren’t, but possibly to discover a perspective you may not have otherwise considered.
11. What are your career goals?
Ultimately, I would like to be a professor and really have a hand in education of young people in STEM fields. Prior to that, I would love to travel the world to learn other cultures and languages and somehow incorporate that into my teaching experiences.
12. What has been the hardest part about your research?
The hardest thing is trying not to learn everything at once, meaning keeping a healthy pace when taking on a new topic. It can be frustrating, but an even stride is more fruitful than a rushed one. It’s also difficult to accept the fact that “science” is a living thing that requires time like anything else. Rushing through experiments and simulations isn’t possible if you actually want to conduct them well.
13. What was the most unexpected thing?
Setbacks are always unexpected. If that weren’t the case, we would never have them. Things break, ideas don’t work, people really can forget to move the decimal point, and technology isn’t flawless. Given than, the most important thing is to stay flexible and encouraged. It’s a great quality to be resourceful and it really helps when things don’t go as expected.
14. How does your research relate to your work in other classes?It’s an interesting place for me to be in when I say to myself “I wish I took Orgo Chem.” (I would never wish that for myself without just cause.) The very basics of what you learn in class are the foundation of research. A lot of times you’re taking fundamental concepts and trying to create new ones. I say with bitter sweetness that I have used all my classes in the course of my research. The bitter part is that I wish I would have known that before I took the class. All the classes, from chemistry to statistics, psychology to phys ed, have helped in some way. Either in performing molar conversions, analyzing data, dealing with people, or simply maintaining one’s health as to remain a functional member of the team, I have called upon lessons from these courses.