From May 15th to July 15th 2023 I had the opportunity to do my second research stay at the University of Bremen in the Solid-State Materials group of Prof. Dr. Martin Eickhoff at the Institute of Solid State Physics (IFP). This time, thankfully funded by MAPEX. The aim of my visit was to follow up the cooperation work initiated in June 2022 through a research stay financed by the UNAM international mobility programme "Initiation into Research", carried out within the framework of the cooperation agreement between ENES Morelia and the Faculty 1 of the University of Bremen.

During my stay we focused on the fabrication of biosensors. More specifically,field-effect transistors modified with enzymes (EnFETs) through a functionalization process (silanization and immobilization of enzymes) on AlGaN/GaN an GaN/AlGaN/GaN substrates. The fabrication of the EnFETs was carried out with the aim to analyze and understand the conduction mechanisms occurring in these devices, and therefore, to be able to suggest a model that can be used in future to improve their architecture. For this purpose, in addition to the electrical characterization measurements of the EnFETs, both atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to calculate and analyze the thickness of the functionalization layer on the surface of the transistors.

This experience has allowed me to learn and carry out experimental processes for the fabrication of biosensors, as well as to understand the electrical characteristics of these devices. Thanks to the outstanding results obtained, it will be possible for me to conclude my thesis successfully; and moreover, to promote the institutional cooperation with a joint scientific contribution, e.i, a publication.

I would like to thank Prof. Dr. Martin Eickhoff for enabling, supporting and trusting the ideas discussed in this project. I thank Genrietta Steingelb for her patience and support to teach me the biosensor manufacturing process. I thank Alexander Hinz for his time, help and support in the laboratory as well as the rest of the members of the Solid-State Materials Group for their hospitality.

I deeply thank MAPEX and the International Office of the Univ. of Bremen for giving me the opportunity to carry out this research stay in order to conclude the cooperation work initiated in June 2022. All this experience has been highly enriching for my personal and academic development.

I’m also very grateful to Dr. Alejandra Castro-Carranza for her time, guidance and support for the preparation of this proposal and her connection with the Univ. of Bremen as Research Ambassador for Mexico. Particularly, for her recommendation of my profile to the IFP, thanks to which all of this has been possible.

Last but not least, I deeply thank Prof. Dr. Ju?rgen Gutowski for his guidance and advice during my research stay.