Speaker: Dávid Beke (HUN-REN Wigner RCP SZFI)
Title: Nanostructured Photon Emitters: From Silicon Carbide Nanoparticles to Tunable Spinel Scintillators
Date: Tuesday, 29 October 2024, 10:00
Place: KFKI Campus, Bldg. 1, 2nd floor, Conference Room
Abstract:
Nanostructured Photon Emitters: From Silicon Carbide Nanoparticles to Tunable Spinel Scintillators
In this seminar, I present the culmination of my 13 years of research at the Wigner Research Centre for Physics, with a focus on the last 9 years following my PhD, along with my future research plans. Under the supervision of Adam Gali and with the support of numerous researchers within the institute, I have investigated the synthesis and optical properties of silicon carbide (SiC) nanostructures, with the aim of understanding their emission characteristics and shifting the emission towards the red and infrared regions for potential applications.
These SiC nanostructures, particularly ultrasmall nanoparticles, are predominantly fabricated through stain etching, which involves HF and HNO3 at elevated temperatures. While SiC exists in over 250 polytypes, only cubic SiC can be etched using this method. Our research into the reaction mechanism has led us to describe a process that reveals simultaneous electron and hole injection, which accounts for the observed polytype selectivity. We have termed this process "No-Photon Exciton Generation Chemistry – NPEGEC" for SiC etching. This understanding enabled us to control nanoparticle size and describe their optical properties as a function of size and surface characteristics. Despite this control, even the largest SiC nanoparticles emit green to yellow light due to their intrinsic band gap.
As our research progressed, we shifted focus towards quantum emitters in solid-state systems. Color centers, typically point defects within a crystal structure, enable sub-bandgap emission with additional features. In my presentation, I will demonstrate the purely chemical synthesis of silicon vacancies and divacancies in SiC particles, including nanoparticles, without the involvement of high-energy particle interactions, a rare and significant achievement in the field.
Finally, I will introduce my current research enthusiasm: spinel scintillator nanostructures, whose optical properties can be tuned across the emission wavelength and decay time. I am confident that these materials not only offer exciting prospects for fundamental research but also hold immediate potential for real-world applications.
