Honored recipients of annual doctoral theses award

“It motivates me for continuing working hard in future and it sets a good tradition of honor and encouragement”, says Muhammad Asad.

Utilizing graphene and spin transport properties

His thesis is about utilizing graphene for future radio-frequency (RF) applications by solving the challenges from the whole range of material synthesis, via nanodevice fabrication of RF transistors, characterization and integration of graphene field-effect transistors (FET) amplifier in RFIC circuits. The application areas of his work are in future high-frequency electronics, communication and sensor systems.

Dmitrii Khokhriakov’s research focuses on experimental studies of 2D materials and their heterostructures, and in particular spin transport properties. He developed large area graphene spin circuits to study the spin transport in more complicated devices than was done before, and ultimately managed to make the first prototype of a spin-based majority logic device working with pure spin currents at room temperature.

“Although this research is still on the fundamental side, it has perspective for applications in the electronics of the future”, he says. “Currently, the increase in performance of electronics comes from downscaling of transistors. However, this approach results in the growing role of quantum effects that pose such hurdles as increased leakage current and heating. An alternative way forward is to use the electron spin, for instance its magnetic properties, to improve the way we can store and process information. Hopefully, the work in my thesis adds a little brick to the edifice of spintronics, which may one day become an essential part of future computing devices.”

Career in industry

At the moment, both winners are continuing their careers in industry. Muhammad Asad is using his RF electronics related knowledge to develop new products and technologies, while Dmitrii Khokhriakov has recently accepted a job as an at Gothenburg-based Smoltek, a company that develops carbon nanotechnology for microelectronics.

“During my PhD, I really enjoyed working both in the cleanroom and in our electronics testing lab”, he says.

“For the next step in my career, I want to continue working with nanoelectronics R&D, but in a more industrial setting with a focus on the product.”

The prize money will be spent on two quite different things.

“I will probably save the money towards a nice summer vacation once the travel restrictions are lifted”, says Dmitrii Khokhriakov.

“I will buy a cricket bat, balls and bowling machine! Cricket is a sport not well-known in Sweden but that’s what I like the most”, says Muhammad Asad.

Mohammad Asad about his research and thesis

“In general, my thesis was about utilizing graphene for future radio-frequency (RF) applications by solving the challenges from the whole range of material synthesis, via nanodevice fabrication of RF transistors, characterization and integration of graphene FET amplifier in RFIC circuits. The focus was of the impact of graphene adjacent dielectrics on the RF performance of graphene FETs.

A great achievement was the experimental verification of a theoretical concept of improving the charge carrier velocity in graphene by utilizing the adjacent substrate materials with higher optical phonon (OP) energy. In this regard, graphene FETs was fabricated on a single crystal diamond (a beautiful combination of sp2 and sp3 carbon), a promising dielectric material has a highest OP energy and thermal conductivity similar to that of graphene. With this approach, a state-of-the-art high frequency graphene FETs was realized with record high fmax performance for 500 nm gate length. Furthermore, in this work, a fully integrated X and Ku band GFET IC amplifier with state-of-the-art performance was demonstrated.”

Read the thesis: “Impactof adjacent dielectrics on the high-frequency performance of graphenefield-effect transistors”

Dmitrii Khokhriakov about his research and thesis

“My research is focused on experimental studies of 2D materials and their heterostructures, and in particular on their spin transport properties. I developed large area graphene spin circuits to study the spin transport in more complicated devices than was done before. Ultimately, I managed to make the first prototype of a spin-based majority logic device working with pure spin currents at room temperature.

In addition, I have worked a lot with topological insulators, which are also part of 2D materials family. Their unique feature is the large spin-orbit coupling, which allows for active control over spin polarization that is not possible to achieve in graphene. The most important finding from these investigations was that when the graphene and a topological insulator are combined together, the resulting heterostructure allows gate-tunable conversion between charge and spin currents directly in graphene. This a highly desired functionality for the development of spin-based logic technologies.”