Gaseous pollution has become a global issue and its presence above certain limits is hazardous to human health and environment. Detection of such gases is an immediate need and researchers around the world are trying to solve this problem. Metal oxides are being used as sensing materials for a long time, but a high operating temperature limits applications in many areas. On the other hand, two-dimensional (2D) materials with high surface-to-volume ratio and chemical stability are promising candidates in the field of gas sensing. This includes monolayer transition metal dichalcogenides, such as MoS2 and WS2, which are direct band gap materials. While few layer transition metal dichalcogenides are indirect band gap materials, they are easier to synthesize than monolayers. Therefore, it is important to understand whether few layer transition metal dichalcogenides possess the same sensing behavior as the corresponding monolayers. For this reason the first part of this dissertation compares the sensing behavior of monolayer and few layer MoS2 and WS2. Two dimensional hexagonal boron nitride is a highly stable structural analogue of graphene. However, its insulating behavior with large band gap is not suitable for sensing. Recently, monolayer Si2BN has been proposed to exist. As the presence of Si makes this material reactive, the second part of this dissertation addresses its application as sensing material. In the _nal part of this dissertation, in search of a metal free, non-toxic, and earth abundant sensor material, further structural analogues of graphene are considered, namely monolayer C3N, monolayer C3Si, and monolayer C6BN. In particular, different theoretical approaches for studying the sensing performance of materials are compared to each other.

Depuis que les dimensions des nano-dispositifs ont atteint l’échelle nanométrique, la simulation quantique est devenue incontournable dans le domaine de la nanoélectronique. Parmi les différents phénomènes physiques, l’interaction électron-phonon représente un processus majeur limitant la mobilité des porteurs de charge à température ambiante. En combinant la théorie multibandes k.p avec le formalisme quantique des fonctions de Green hors-équilibre, nous avons étudié et comparé deux types de dispositifs double-grille dopés p: le transistor MOS «conventionnel» et celui dit «sans jonction». L’influence de l’orientation cristalline, du matériau semi-conducteur, de la longueur de grille et de l’épaisseur du substrat a été étudiée afin d’optimiser les performances de ces dispositifs aux dimensions ultimes. D’un point de vue plus fondamental, l’interaction avec les phonons est habituellement implémentée à partir de l’approche auto-cohérente de Born (SCBA). Nous avons exploré la validité des approches non auto-cohérentes numériquement moins coûteuse qui conservent le courant : Lowest Order Approximation (LOA). Une comparaison entre SCBA, LOA et son prolongement analytique (LOA+AC) en modèle multi-bande a été menée. / Device simulation has attracted large interest since the dimensions of electronic devices reached the nanoscale. Among the new physical phenomena observed we focus on interaction-induced effects. Particular emphasis is placed on electron-phonon interactions as it is one of the most important carrier mobility-limiting mechanisms in nanodevices. Using the k.p multiband theory combined with the Non-Equilibrium Green's Function formalism, we model 2 types of double-gate devices: p-type MOSFETs and junctionless p-type MOSFETs. The 2D architecture of the double-gate device enables us to investigate the influence of confinement in one direction, infinite propagation in the other direction and connection to semi-infinite reservoirs in the last one. Different crystallographic orientation, channel materials, gate lengths and channel widths are investigated. From a fundamental point of view, phonon scattering is usually implement via the so-called Self-Consistent Born Approximation (SCBA°. We explore the validity of a one shot current conserving method based on the Lowest Order Approximation (LOA). A comparison between SCBA, LOA and its analytic continuation (LOA+AC) in multiband models is discussed.