Defence in the field of theoretical and computational physics, Noora Tuomisto, Lic.Sc.(Tech.)
Modeling increases understanding of how nanoelectronics components could work
Noora Tuomisto, Lic.Sc.(Tech.), will defend the dissertation "Modeling of tunneling through single, double and step barrier structures" on 15 June 2018 at 1 PM at the Aalto University School of Science, lecture hall M1, Otakaari 1, Espoo. In this thesis we have modeled quantum mechanically tunneling currents in nanoelectronic devices. With modeling we are able to explain experimental results and strive to develop more energy efficient, less space consuming and even completely new types of electronics devices.
As electronics components continue to decrease in size quantum mechanical effects start to play a bigger role in their operation. Even slight modifications in the atomistic structure can have huge effects on the current flow and operation of the devices. In this thesis we study so-called tunnel junctions which are already commonly used in electronics components such as USB-memory sticks. In future, completely new types of devices might also be constructed using tunnel junctions. Ferroelectric tunnel junctions, which have been modeled in this thesis, could be used, for example, in new types of computer memories.
Tunnel junctions consist of two electrodes with an extremely thin insulator in between. Traditionally current does not flow through insulators but in a tunnel junction current can pass through the thin insulating layer due to the quantum mechanical effect of tunneling. In this thesis we have developed two computer programs that give the current through different types of tunnel junctions as a function of the applied bias voltage. Quantum mechanical resonant tunneling can be seen in the calculated current-voltage curves as steep rises in current values and as large asymmetries in curves for opposite bias voltage directions. By comparing calculated and measured currents we can better understand which properties of the materials and the junctions affect the current flow the most. By modeling we can also predict what kind of structures would be most useful in applications. In addition, modeling increases understanding of the physical phenomena affecting the currents through nanometer scale layered structures.
Opponent: Professor Bernardo Barbiellini, Lappeenranta University of Technology, Finland
Custos: Professor Martti Puska, Aalto University School of Science, Department of Applied Physics
Electronic dissertatation: http://urn.fi/URN:ISBN:978-952-60-8038-3