Institute of High Pressure Physics

A public defense of the doctoral dissertation of Manasa, MSc, will be held on 20 August 2025 (Wednesday) at 01:00 p.m. in the seminar room of the Institute of High Pressure Physics, Polish Academy of Sciences, in Warsaw, 29/37 Sokołowska St.

Dissertation title: „Physical properties optimization of iron-based superconductors by high-pressure growth technique”

Full text of the announcement

The dissertation and reviews are available here

Researchers from our Institute used advanced ab initio simulations to unravel how atoms bond in key semiconductor materials like BN, AlN, GaN, InN, and graphene. The calculations confirmed that the valence band of GaN is divided into two separate subbands. The upper subband of GaN is composed of gallium sp and nitrogen p orbitals, while the lower subband consists of metal d and nitrogen s orbitals. Calculation of overlap integrals allowed to determine the bond order in tetrahedrally coordinated semiconductors. According to these results, bonding occurs between resonant p-states of nitrogen and sp³-hybridized metal orbitals in tetrahedral nitrides, allowing tetrahedral symmetry to be maintained. A similar resonant bonding mechanism is observed in hexagonal BN, where the p orbitals of nitrogen create three resonant states necessary for maintaining the planar symmetry of the lattice. BN bonding differs from that in graphene, where carbon states are fully sp²-hybridized. Additionally, π-type bonds in graphene have no ionic contributions, which leads to the formation of Dirac states with linear dispersion close to the K point, closing the band gap

Understanding these nuanced bonding mechanisms refines our fundamental picture of how these semiconductors and 2D materials behave and could directly impact the design of next-generation optoelectronic devices.

The publication is available in Open Access: Ab Initio Elucidation of the Nature of the Bonding of Tetrahedral Nitrides (BN, AlN, GaN, and InN), Hexagonal BN, and Graphene Paweł Strąk, Konrad Sakowski, Pawel Kempisty, Izabella Grzegory, Agata Kaminska, Stanislaw Krukowski. Materials 2025, 18, 2875.

Figure: The electronic properties of bulk wurtzite gallium nitride (GaN). The panels represent, from the leftmost: band diagram, projected density of states (PDOS) of the Ga (left) and N (right) atoms.

The International Conference on Nitride Semiconductors ICNS-15 has just finished with a great success. ICNS-15 was held in Malmö in Sweden from July 6-11, 2025. The conference featured 881 scientific papers, 57 of which were presented by polish researchers. Our team - 21 people from the Institute of High Pressure Physics - presented 33 scientific papers.

We had a Plenary Speaker – prof. Michał Boćkowski, and three invited talks – Dr Anna Kafar, Prof. Paweł Kempisty and Prof. Henryk Turski. Our employees delivered also 7 contributed talks (oral presentations) and 22 poster presentations. Prof. Michał Boćkowski was a panelist in the Rump session "kV Nitride Power Devices: Challenges and Technologies”. We also served as moderators of the individual sessions.

The list of the all presentations by Institute's employees is available at the link.

Researchers from the Institute of High Pressure Physics were actively involved in the organization and had numerous scientific contributions. The ICSN-15 conference was chaired by Vanya Darakchieva, Lars Samuelson and Piotr Perlin. Prof. Tadek Suski was the Honorary Chair. Prof. Izabella Grzegory was among the Program Co-chairs, supporting Åsa Haglund, the Program Chair. Dr Anna Kafar was a panelist in “Women in Nitrides - diversity and inclusion” event.

Special congratulations to the young scientists on their Awards! Muhammed Aktas from the Optoelectronic Devices Laboratory NL15 received the award for the best poster presentation “Low-Temperature Characteristics of PolarizationDoped Nitride Emitters”. Congratulations!