Strain modulation on 2D materials and their heterostructures
Han, Jinkun (2020-03-19)
Strain modulation on 2D materials and their heterostructures
(19.03.2020)
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
suljettu
Julkaisun pysyvä osoite on:
https://urn.fi/URN:NBN:fi-fe202003309778
https://urn.fi/URN:NBN:fi-fe202003309778
Tiivistelmä
Strain modulation is a direct and effective method to tune the lattice structure of the 2D materials. Studying the band structure, photoluminescence (PL) and other physical properties of 2D materials under strain is important for the application of 2D materials in emerging wearable and flexible devices field. In this thesis, we first study uniaxial strain modulation to the electronic band structure of mono-layer WSe2 and graphene/ WSe2 van der Waals heterostructure. We found that neutral exciton (A) and trion (A+) PL of mono-layer WSe2 red-shifted with 25 meV/% strain and 33 meV/%, while A and A+ PL of graphene/WSe2 heterostructure red-shifted with 23 meV/ %, 28meV/% during strain on process. During strain release process, A and A+ PL of mono-layer WSe2 and graphene/WSe2 heterostructure are blue shifted by 20 meV/%, 27 meV/%, 22 meV/%, 28 meV/% respectively.
From optical images during strain on and release process, we found that the mono-layer WSe2 and 1L graphene/WSe2 heterostructure had the best stretchability and recoverability compared to bilayer and multilayer materials. From the intensity and the change of PL peak energy during the strain on and release process to the mono-layer WSe2 and 1L graphene/WSe2 heterostructure we also have a conclusion that the interface contacts of 1L WSe2/PET and graphene/WSe2 are improved and the residual strain is released during the strain on process. Also the unintentional doping of the impurities and defects introduced during fabrication process are reduced.
There are very few systematic study of the properties of 2D materials modulated by biaxial strain, hence the design and fabrication of a biaxial strain stage is of great significance to study energy gap modulation of properties of 2D materials with biaxial strain.
From optical images during strain on and release process, we found that the mono-layer WSe2 and 1L graphene/WSe2 heterostructure had the best stretchability and recoverability compared to bilayer and multilayer materials. From the intensity and the change of PL peak energy during the strain on and release process to the mono-layer WSe2 and 1L graphene/WSe2 heterostructure we also have a conclusion that the interface contacts of 1L WSe2/PET and graphene/WSe2 are improved and the residual strain is released during the strain on process. Also the unintentional doping of the impurities and defects introduced during fabrication process are reduced.
There are very few systematic study of the properties of 2D materials modulated by biaxial strain, hence the design and fabrication of a biaxial strain stage is of great significance to study energy gap modulation of properties of 2D materials with biaxial strain.