Molecules adsorbed on two-dimensional (2D) materials can show interesting physical and chemical properties. This thesis presents scanning probe microscopy (SPM) investigation of emerging 2D materials, molecular nanostructures on 2D substrates at the nanometer scale, and biophysical processes on the biological membrane. Two main techniques of nano-probing are used: scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The study particularly emphasizes on self-assembled molecules on flat 2D materials and quasi-1D wrinkles. First, we report the preparation of novel 1D C60 nanostructures on rippled graphene. Through careful control of the subtle balance between the linear periodic potential of rippled graphene and the C60 surface mobility, we demonstrate that C60 molecules can be arranged into a 1D C60 chain structure of two to three molecules in width. At a higher annealing temperature, the 1D chain structure transitions to a more closely packed, quasi-1D hexagonal stripe structure. The experimental realization of 1D C60 structures on graphene is, to our knowledge, the first in the field. It could pave the way for fabricating new C60/graphene hybrid structures for future applications in electronics, spintronic and quantum information. Second, we report a study on nano-morphology of potential operative donors (e.g., C60) and acceptors (e.g., perylenetetracarboxylic dianhydride, aka. PTCDA) on wrinkled graphene supported by copper foils. We realize sub-monolayer C60 and PTCDA on quasi-1D and quasi-2D real periodic wrinkled graphene, by carefully controlling the deposition parameters of both molecules. Our successful realization of acceptor-donor binary nanostructures on wrinkled graphene could have important implications in future development of organic solar cells. Third, we report an STM and spectroscopy study on atomically thin transition-metal dichalcogenides (TMDCs) material. TMDCs are emerging 2D materials recently due to their intriguing physical properties and potential applications. In particular, our study focuses on molybdenum disulfide (MoS2) mono- to few-layers and pyramid nanostructures synthesized through chemical vapor deposition. On the few-layered MoS2 nanoplatelets grown on gallium nitride (GaN) and pyramid nanostructures on highly oriented pyrolytic graphite (HOPG), we observe an intriguing curved region near the edge terminals. The measured band gap in these curved regions is consistent with the direct band gap in MoS2 monolayers. The curved features near the edge terminals and the associated electronic properties may contribute to understanding catalytic behaviors of MoS2 nanostructures and have potential applications in future electronic devices and catalysts based on MoS2 nanostructures. Finally, we report a liquid-cell AFM study on the endosomal protein sorting process on the biological lipid membrane. The sorting mechanism relies on complex forming between Tom1 and the cargo sorting protein, Toll interacting protein (Tollip). The induced conformational change in Tollip triggers its dissociation from the lipid membrane and commitment to cargo trafficking. This collaborative study aims at characterizing the dynamic interaction between Tollip and the lipid membrane. To study this process we develop the liquid mode of AFM. We successfully demonstrate that Tollip is localized to the lipid membrane via association with PtdIns3P (PI(3)P), a major phospholipid in the cell membrane involved in protein trafficking. / Ph. D.

Les oscillateurs de référence de haute pureté sont actuellement utilisés dans un grand nombre d’applications allant du contrôle de fréquence aux horloges pour les radars, les GPS et l’espace... Les tendances actuelles dans ce domaine requièrent des architectures miniaturisées avec la génération de signaux directement dans la gamme de fréquences d’intérêt, autour de quelques GHz. Récemment, de nouvelles architectures basées sur les principes de l’optomécanique ont vu le jour dans ce but. De tels oscillateurs optomécanique génèrent non seulement des signaux hyperfréquences directement dans la gamme de fréquences GHz avec éventuellement un faible bruit de phase, mais permettent également un degré élevé d'intégration sur puce. Ce travail de thèse s'inscrit dans cette démarche. L’oscillateur optomécanique étudié se compose de cavités à cristaux photoniques suspendues couplées à des guides d’ondes silicium sur isolant intégrés dans une architecture tridimensionnelle. Ces cavités abritent des modes optiques fortement confinés autour de 1550nm et des modes mécaniques dans le GHz. De plus, ces structures présentent un recouvrement spatial entre phonon et photon élevé. Il en résulte un couplage optomécanique amélioré. Cette force de couplage optomécanique améliorée est ici sondée optiquement sur des structures à cristaux photoniques de conception optimisée. Ces cavités sont réalisées dans des matériaux semi-conducteurs III-V dont la piézoélectricité nous permet d'intégrer des outils supplémentaires pour sonder et contrôler les vibrations mécaniques via un pilotage capacitif, piézoélectrique ou acoustique. Ce contrôle total des modes mécaniques et de l’interaction optomécanique ouvre la voie à la mise en œuvre de circuits intégrés pour le verrouillage par injection et des boucles de rétroaction permettant de réduire le bruit de phase de l’oscillateur. / High purity reference oscillators are currently used in a wide variety of frequency control and timing applications including radar, GPS, space... Current trends in such fields call for miniaturized architectures with direct signal generation in the frequency range of interest, around few GHz. Recently, novel optomechanically-enhanced architectures have emerged with this purpose. Such optomechanically-driven oscillators not only generate microwave signals directly in the GHz frequency range with possibly low phase noise but also are amenable to a high degree of integration on single chip settings. This PhD work falls within this scope. The optomechanically-driven oscillator under study consists of suspended photonic crystal cavities coupled to integrated silicon-on-insulator waveguides in a three-dimensional architecture. These cavities harbor highly-confined optical modes around 1,55 µm and mechanical modes in the GHz and most importantly, feature a high phonon-photon spatial overlap, all resulting in an enhanced optomechanical coupling. This enhanced optomechanical coupling strength is here probed optically on photonic crystal structures with optimized design. These cavities are hosted in III-V semiconductor materials whose piezoelectricity enable us to integrate additional tools for probing and controlling mechanical vibrations via capacitive, piezoelectric or acoustic driving. This full control over the mechanical modes and optomechanical interaction, paves the way towards the implementation of integrated injection locking circuits of feedback loops for reducing the phase noise of the oscillator.

Nanotechnology offers great promise for the development of nanodevices. Hence it becomes important to study the mechanical behavior of nanostructures for their use in such systems. MEMS (Micro ElectroMechanical Systems) provide an effective and precise method for testing nanostructures. Consequently this study focuses on the development of a MEMS thermal nanotensile tester to investigate the mechanical behavior of one-dimensional nanostructures. Extensive characterization of these MEMS devices (structural, electrical and thermal behavior) was performed using experimental as well as finite element methods. Tensile testing of nanostructures requires manipulation of individual nanostructures on the MEMS device. The study involves the development of an efficient methodology for the manipulation of nanowires and nanobeams for nanoscale testing. Furthermore, two different sensing schemes for the developed devices, namely capacitive and resistive, have been extensively investigated and the advantages and various issues related to both have been discussed. Nanocrystalline (nc) Ni nanobeams (typical dimensions of 500 nm x 200 nm x 20 µm) have been tested to failure using the MEMS devices. Improvements in the design for the MEMS nanotensile tester have been suggested to significantly enhance the device performance and to resolve the various issues involved with nano scale tests. Differential capacitive sensing for stress-strain measurements has been suggested to improve the accuracy of strain measurements.