Search results for "Feen"
showing 3 items of 53 documents
Time-dependent quantum transport in nanosystems : a nonequilibrium Green's function approach
2016
A time-dependent extension to the Landauer–Büttiker approach to study transient quantum transport in arbitrary junctions composed of leads and conducting devices is developed. The nonequilibrium Green’s function approach is employed for describing the charge and heat transport dynamics. The importance of the developed method is that it provides a closed formula for the time-dependent density matrix in both electronic and phononic systems. In the electronic case the nonequilibrium conditions are due to a switch-on of a bias voltage in the leads or a perturbation in the junction whereas in the phononic case the central region of interest is coupled to reservoirs of di erent temperatures. In b…
Modeling the mechanical behavior of carbon nanostructures
2016
Low-dimensional nanostructures are expected to have vast number of applications in the future. Particularly large amount of research has been invested in the atomthick carbon membrane called graphene, which has become popular due to its unique electronic and mechanical properties. This thesis presents studies of the mechanical and electromechanical properties of several different types of graphene nanostructures. In addition, short detours are performed in order to study the elasticity of gold nanostructures and topology effects in graphene nanoribbons. The research is performed by using several different simulation methods. In simulations the system parameters and environment can be chosen…
Typpiseostettu grafeeni
2017
Tässä Pro Gradu -tutkielmassa perehdytään typpiseostetun grafeenin rakenteeseen, ominaisuuksiin, karakterisointiin, valmistukseen ja sovelluksiin. Valtaosa typpiseostetun grafeenin ominaisuuksista pohjautuu puhtaaseen grafeeniin, joten myös sitä käsitellään samalla. Typpi voi sitoutua grafeenihilaan eri tavoilla, joten mahdolliset konfiguraatiot ja niiden vaikutus rakenteeseen ja grafeenin ominaisuuksiin käydään läpi. Spektroskopia ja karakterisointi -kappaleessa keskitytään eniten puhtaan ja typpiseostetun grafeenin ramanspektroskopiaan ja röntgensädefluoresenssispektroskopiaan (XPS). Valmistuskeinot-kappaleessa kerrotaan lyhyesti grafeenin yleisimmistä synteesimenetelmistä ja käydään läpi…