Speaker
Description
Defects at internal interfaces pose a major concern for layered heterostructures. For example, in a MOSFET the defects at the SiO2/Si interface can introduce charge traps, which can degrade the electronic performance of the device. The defects in Metal-Oxide-Silicon (MOS) systems were extensively researched using depth-resolved beam-based positron-annihilation techniques. Unfortunately, the investigation of interfaces with a thickness of less than 5 nm is not a trivial task. This is due to the small extent of the interface compared to the implantation profile of monoenergetic positrons provided by large-scale facilities such as NEPOMUC or ELBE. In the past, efforts were made to manipulate the positron diffusion by applying an external electric field to various layered systems. The electric field leads to the drift of thermalized positrons towards the interfaces.
In this work, we present a positron drift experiment on a MOS system biased from -30 V (accumulation) to +30 V (depletion) investigated by electric field-assisted Positron-Annihilation Lifetime Spectroscopy (PALS). The results show, that the in-situ application of a sample bias, which is also available at the PLEPS, is a promising addition to the common positron annihilation methods to investigate ultra-thin structures such as interfaces.
