Getting Integrated into the System

For the first couple months, I learned quite a bit about thermoelectrics and some experimental procedures. It was such a flood of information though, that a lot of it did not settle in. The last couple months (I am now in my fourth month of research with CEEM) I have really started understanding more of the details of what I have been researching. In addition to getting some of the experimental methods down, I have started understanding the bigger picture.

Recently I’ve been involved with researching the figure of merit of thermoelectric materials, which is basically just a measure of their efficiency. We have obtained data on important physical parameters, such as the carrier concentration, the mobility, the Hall coefficient, and the electrical conductivity. The figure of merit depends on all of these parameters in some shape or form, so I have been learning about the trends that certain semiconductor materials exhibit while varying temperature. We are interested in the efficiency at numerous different temperatures, although currently thermoelectrics are being looked into for higher temperatures. This is why we run our materials in both a low temperature setup (ranging from approximately 10-300K) and a high temperature setup (ranging from 300-750K). I have done quite a bit of data analysis on both low and high temperature measurements, and from this raw data I am getting a better idea of the physics behind semiconductors and thermoelectric research.

Ever since beginning research with CEEM, my opinion of research has changed drastically. I used to think it was somewhat important to my future, including building my resume and getting experience. Now I believe it is the best thing you can possibly do during your undergraduate education. Learning concepts in class and applying them to real world technology is such a massive bridge to cross, and personally, I believe that the vast majority of concepts and experience can be formulated from on the job training. While I still think forming a strong base in the classroom is important, my understanding for condensed matter physics and materials has risen exponentially since beginning this internship. If I had tried to take a theoretical approach to understanding the research being done with thermoelectrics before starting this internship, I would have had no idea where to begin. Seeing it actually done increasing my learning curve drastically, and now I can safely explain the general concepts behind the research being done here at UCSB on thermoelectrics.

A Remote Alternative Energy Source: Thermoelectrics

When it comes to alternative energy, most people can quickly name off a few, for example solar energy, nuclear fission, natural gas or hydroelectric power. Hardly ever will you hear someone name thermoelectrics, but honestly, it’s for a good reason. Thermoelectrics is still very much a developing field, and recent advances in the theory of thermoelectrics has led to a huge push to advance existing thermoelectric technology.

This quarter I was introduced to thermoelectrics, including its theory, applications, and the experimental procedures of testing thermoelectric devices. The lab I am working in is mostly concerned with maximizing what is called the figure of merit. The higher the figure of merit, the more efficient a thermoelectric material is for its two main applications: power generation and cooling.

Thermoelectrics are already have seen some applications to the real world, but the figure of merit is not high enough yet in order for thermoelectrics to be applied on a large scale. Luxury vehicles with seat warmers often have thermoelectrics. This is because when you apply a potential across some thermoelectric devices, they create a heat gradient. The cold end is used to cool seats very quickly. Unfortunately, little niche applications such as these are the only real benefits they have provided us in the real world. With a higher figure of merit though, power can be recaptured at high efficiency if there is a heat gradient across the thermoelectric material. Ideally, thermoelectrics could be placed in exhaust pipes to make cars more efficient or in power plants to salvage much of the lost energy to heat.

The lab I am working in tests the conductivity, carrier concentration, Seebeck coefficient, mobility as well as other parameters that influence the figure of merit. So far I have been introduced to the entire experimental process of creating a semiconductor wafer and measuring its hall coefficient through a Van Der Pauw machine. There are several different types of Van Der Pauw machines, mostly for different temperature ranges. Van Der Pauw machines work by applying a magnetic field across the material, creating what is called the Hall Effect. From the response in magnetic field, we can measure the Hall Coefficient, as well as many other properties of the semiconductor wafer.

I’m getting really excited to progress more. A lot of what I’ve been doing has been learning experimental procedures, and while I find that very interesting I can’t wait to master the techniques and start obtaining data on a regular basis. I have learned how to perform AFM (atomic force microscopy), measure Hall coefficients, analyze and understand the types of data I am getting, as well as fully prepare semiconductor samples to be measured. It is always a little rough when you start out learning new things, but I’m confident that in a few short weeks I will start actually being very productive for the lab I am working in.