Rare earth elements play an increasingly important role in modern technology. Their unique magnetic and electronic properties make them essential components of wind turbines, smartphones, LEDs, and many other semiconductor devices. Among them, ytterbium has attracted growing interest in the field of optoelectronics. Several studies have shown that inserting thin layers of ytterbium oxide into semiconductor devices—such as solar cells, LEDs, or photodiodes—can improve their performance. These thin films help optimize how energy moves between different layers of a device, making the overall system more efficient.
However, despite these promising results, relatively little research has focused on how to precisely control the properties of ytterbium oxide itself.
Enter Dr. Guillermo Lozano Onrubia, a recent PhD graduate here at the Department of Chemistry who recently completed his degree as a graduate student with Professor Gilbert C. Walker and the Laboratory for Advanced Nanoscience at Surfaces and BioInterfaces (LANSBI).
Onrubia was born in Spain but moved shortly after to Austria. "I spent my youth travelling from one country to another, adapting to new languages, cultures and school syllabi. My passion for the natural sciences was probably awakened by my older brother, who always solved any questions I might have had, and by my interest to find solutions to tackle climate change."
At the age of 17, Onrubia moved to Heidelberg to study Chemistry. "After pursuing my B.Sc. and M.Sc., I decided that it was about time to cross the Atlantic and learn about a new culture, people and scientific fields. Toronto ended up being the best option: a highly multicultural city with a world-renowned university. During my 4.5 years of PhD, I’ve had the privilege of meeting my fellow students, who always provided me with the opportunity to learn about their research fields, and with whom I had the chance of playing seasons within the intramural football team, as well as mentors, who guided me throughout my studies to reach my goal."
"At U of T, my goal was to work on the development of a microscopy technique to investigate the electrical properties of rare earth metal oxides at a lateral resolution of just a few nanometers. It was also here that I realized that the solutions required to tackle climate change are not purely technical, which is why I decided to depart from academia and focus for my next step on strategy consulting with the new goal of learning more about the business world and learn how to solve some of the most pressing issues from a novel angle."
Onrubia's PhD research set out to explore ways to tune the electrical properties of thin films of ytterbium oxide and understand how these changes affect semiconductor devices. To do this, he first built a one-of-a-kind microscope called a pulsed-force Kelvin Probe Force Microscope (PF-KPFM). This instrument can measure electrical properties at extremely small scales, with a spatial resolution of about 10–15 nanometers. This level of detail is essential to determine whether the electrical behavior of these films is uniform or varies across their surface.
"Using this technique, we investigated two strategies to tune the electrical properties of ytterbium oxide: adjusting the thickness of the films and applying thermal annealing treatments. Our results show that both approaches can significantly influence the material’s behavior and can help improve the performance of devices such as OLEDs and photodiodes. More importantly, the PF-KPFM measurements revealed that the electrical properties change at the boundaries between microscopic grains in the material. These variations may influence how electrical charges move through a device, offering new insights into how these systems operate."
This work highlights the growing importance of rare-earth materials in modern electronics and shows how carefully engineering their properties at the nanoscale could help improve the next generation of optoelectronic technologies.
Onrubia was an active member of the U of T community during his time at U of T, becoming a member of Climate Positive Energy (now the Lawson Climate Institute). "As someone who is passionate about the fight against climate change and the support of the energy transition, I deeply enjoyed being part of the U of T community, including the Green Chemistry Initiative for a few years. Towards the end, I even had the pleasure of co-founding Student Energy UofT, a student-run club aimed towards providing students the tools to learn more about the energy transition. One of the most fun experiences during my time as co-president was to found SJET, the Student Journal on the Energy Transition."
He also noted that as someone who had just arrived to Canada for his studies, the main challenge at first was the isolation that accompanies such a change. "Luckily, the people I met from the very beginning both within as well as outside of the department were amazing, allowing me to build a new home."
"Failing is part of life, and it plays a major role during anyone’s time as a graduate student," he said, speaking of his journey through graduate school. "I remember at the beginning of the PhD feeling mentally blocked, not even daring to conduct an experiment out of fear of breaking something or getting irreproducible results. It took me a while to be aware of this blockade. As the saying goes: “Perfection is the enemy of progress”. Try things out, fail and learn."
As for what's next now that he's finished his degree, Onrubia said: "I am currently taking some time off before I start my new job in management consulting."