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Electronic Properties of Materials (EPM)

The research of the EPM group aims at understanding the properties of materials and nanostructures including the associated physical phenomena using state-of-the-art electronic structure calculations.
Junction Fig

A wide range of different materials from semiconductors and insulators for electronics devices to novel materials for energy harvesting and storage are in focus. We have also long traditions in developing and implementing electronic structure methods needed in modelling materials and nanostructures.

Group leader professor Martti Puska

Group leader

Martti Puska

Research

Our main tools are the various computer codes for the electronic structure, based mainly on the density-functional theory (DFT), including first-principles molecular dynamics, quantum transport, time-dependent extensions to treat excited states, and modern functionals to treat the van der Waals interactions and to improve the descriptions of the energy band gaps and band alignment. The first-principles results for crucial parameters are also the basis for modelling the properties and phenomena associated with longer length and time scales. Examples include the lattice kinetic Monte Carlo (LKMC) simulations and various tight-binding schemes.

Our research takes place in a close connection with experimental groups. Moreover, in order to be on the leading edge in applying electronic structure methods, it is important also to participate in developing theories, methods and computer implementations. This also requires collaboration with experts in numerical mathematics and in computer architecture.

Nanoplasmonics

Plasmonics is a research field that studies collective excitations of free delocalized electrons, known as plasmons. In nanoplasmonics, the focus is on nanometer-scale systems, such as metal nanoparticles. In our group, we use time-dependent density-functional theory (TDDFT) to deepen quantum-mechanical first-principles understanding on plasmonic excitations. Our research includes method development, technologically relevant plasmonic systems as well as fundamental quantum aspects of plasmonic resonances.

Electron tunnelling

In electronic tunnel junctions, current flows from one electrode to the other across a thin insulating barrier. This quantum mechanical effect of tunnelling is the basic feature underlying many solid-state nanoelectronic devices such as resonant tunnelling transistors, magnetic tunnel junctions, SQUIDs, qubits, energy storage devices and sensors. In our group, we use density functional theory (DFT) to study the atomic structure at the electrode-barrier interface and how they affect the shape and dimensions of the tunnel barrier. We also study electron transport across tunnel junctions and explore the effects of different single and double barrier structures on the tunnelling current.

Electronic transport in carbon nanotube thin films

Exceptionally good electrical conductivity and high mechanical strength of carbon nanotubes could be utilized in various future applications. In particular, carbon nanotube thin films are flexible and conductive materials that are suited to be used as transparent electrodes. The conductivity of the thin film is mainly determined by the resistances of the nanotube junctions. To enhance the film conductivity, the nanotubes can be doped and they can also be linked with transition metal atoms or by organic or inorganic molecules. We study the electronic transport properties of these kinds of systems using the Green's function method combined with the density functional theory.

Charge transfer at hybrid molecular-semiconductor interfaces

The objective of this project is the understanding of the physical factors influencing the excited state charge transfer at the hybrid molecular – semiconductor interfaces. A particular attention is paid to the optimization of the semiconductor structure, anchoring form and dye sensitizer with the aim to achieve the required electron injection efficiency. For this purpose, the interfacial charge transfer process is simulated at the atomistic level applying Real-Time Time-Dependent Density Functional Theory (RT-TDDFT) and Ehrenfest Dynamics (ED) approaches.

Charged defects in 2D materials

Calculations of charged defects in 2D materials with the supercell approach suffer from a strong and anisotropic spurious electrostatic interactions between the charge and its periodic images. We have developed an a posteriori method for correcting the energies. The applicability of the method was demonstrated in the case of substitutional and adatom defects at monolayers of BN and MoS2.

Thin-film solar cells

A new European research project that goes by the name Sharc25 is setting out to make an extremely efficient thin-film solar cell for the next generation of more cost-effective solar modules. Its objective is to achieve up to 25 percent efficiency in thin-film solar cells made by the co-evaporation of copper indium gallium (di)selenide, or CIGS for short. Our task in this project is to model the properties of intrinsic point defects (vacancies, interstitials, antisites, and their complexes) and impurities in CuInSe2 (CIS) and CuGaSe2 (CGS) to understanding evolution of microstructures during the manufacture and use of solar cells.

Latest publications

Centre of Excellence in Quantum Technology, QTF, Electronic Properties of Materials, Department of Applied Physics

Linear growth of self-assembled alternating oligopeptide nanotubes with self-locking building blocks

Publishing year: 2019 MOLECULAR SIMULATION
Electronic Properties of Materials, Department of Applied Physics

Erratum: Charged Point Defects in the Flatland: Accurate Formation Energy Calculations in Two-Dimensional Materials [Phys. Rev. X 4, 031044 (2014)]

Publishing year: 2018
Department of Applied Physics, Electronic Properties of Materials

Metallic Twin Boundaries Boost the Hydrogen Evolution Reaction on the Basal Plane of Molybdenum Selenotellurides

Publishing year: 2018 Advanced Energy Materials
Department of Applied Physics, Electronic Properties of Materials

Stability of Cu-precipitates in Al-Cu alloys

Publishing year: 2018 Applied Sciences (Switzerland)
Electronic Properties of Materials, Department of Applied Physics

Structural details of Al/Al2O3 junctions and their role in the formation of electron tunnel barriers

Publishing year: 2018 Physical Review B
Department of Applied Physics, Electronic Properties of Materials

Post-Synthesis Modifications of Two-Dimensional MoSe<sub>2</sub> or MoTe<sub>2</sub> by Incorporation of Excess Metal Atoms into the Crystal Structure

Publishing year: 2018 ACS Nano
Electronic Properties of Materials, Department of Applied Physics, Centre of Excellence in Computational Nanoscience, COMP

Hydrogen-assisted post-growth substitution of tellurium into molybdenum disulfide monolayers with tunable compositions

Publishing year: 2018 Nanotechnology
Department of Applied Physics, Electronic Properties of Materials

Photoluminescence Study of B-Trions in MoS<sub>2</sub> Monolayers with High Density of Defects

Publishing year: 2018 Physica Status Solidi (B) Basic Research
Electronic Properties of Materials, Department of Applied Physics

Revealing the Atomic Defects of WS<sub>2</sub> Governing Its Distinct Optical Emissions

Publishing year: 2018 Advanced Functional Materials
Department of Applied Physics, Electronic Properties of Materials

Modeling of tunneling through single, double and step barrier structures

Publishing year: 2018
More information on our research in the Research database.
Research database

Research group members

Kevin Conley

Department of Applied Physics
Postdoctoral Researcher

Seyed Hashemi Petrudi

Department of Applied Physics
Doctoral Candidate
Ville Havu

Ville Havu

Department of Applied Physics
Senior University Lecturer

Rina Ibragimova

Department of Applied Physics
Doctoral Candidate
Karthikeyan Jeyakumar

Karthikeyan Jeyakumar

Department of Applied Physics
Postdoctoral Researcher

Hannu-Pekka Komsa

Department of Applied Physics
Academy Research Fellow
Maria Malitckaya

Maria Malitckaya

Department of Applied Physics
Doctoral Candidate
Martti Puska

Martti Puska

Department of Applied Physics
Professor
Petri Salo

Petri Salo

Department of Applied Physics
Senior University Lecturer
Emppu Salonen

Emppu Salonen

Department of Applied Physics
University Lecturer