000142931 001__ 142931
000142931 005__ 20190717172518.0
000142931 0247_ $$2doi$$a10.5075/epfl-thesis-4605
000142931 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis4605-2
000142931 02471 $$2nebis$$a5940883
000142931 037__ $$aTHESIS
000142931 041__ $$aeng
000142931 088__ $$a4605
000142931 245__ $$bdesign, characterization and application$$aA nano-tensile testing system for studying nanostructures inside an electron microscope
000142931 269__ $$a2010
000142931 260__ $$bEPFL$$c2010$$aLausanne
000142931 300__ $$a152
000142931 336__ $$aTheses
000142931 520__ $$aMechanical properties of nanostructures could be remarkably different from their bulk counterparts owing to scale effects, which have attracted considerable research interest in recent years. However, nanomechanics studies are hindered by the difficulties of conducting well-instrumented mechanical testing. The objective of this thesis is to develop a novel tensile stage that can be used to probe mechanical properties of universal one-dimensional (1D) nanostructures, like nanowires and nanotubes, inside a scanning/transmission electron microscope (SEM/TEM). The main challenges of performing tensile tests at the nanoscale are: (1) specimen alignment and fixation on the tensile stage; (2) application and measurement of tensile force with nano-Newton resolution; (3) measurement of specimen elongation with nanometer resolution. Previous studies have shown that micro-electromechanical system (MEMS) technology combined with advanced microscopy (e.g. SEM and TEM) provides promising perspectives to address these challenges. Two types of nano-tensile stages, fabricated in a silicon on insulator (SOI) wafer, were developed in this thesis, which consisted of a comb-drive actuator and either a differential capacitive force sensor or a double clamped beam force sensor. The optimized comb-drive actuators could output an in-plane force of about 210 µN at a drive voltage of 120 V, and the force sensors achieved resolutions of better than 50 nN. Individual 1D nanostructures were placed on the MEMS device by in-situ nanomanipulations and fixed at their two ends via focused electron beam induced deposition (FEBID). A strategy of modifying device topography, e.g. in the form of trenches or pillars, was proposed to facilitate the specimen preparation by in-situ manipulation that could achieve a high yield of about 80%. The mechanical testing function of the developed micro devices was demonstrated by tensile tests on individual Co and Si nanowires (NWs) inside an SEM. The average apparent Young's modulus, tensile strength and fracture strain of the electrochemically deposited Co NWs were measured to be (75.3±14.6) GPa, (1.6±0.4) GPa and (2.2±0.6) %, respectively. The measured Young's modulus is significantly lower than that of Co in the bulk form (209 GPa), which is likely caused by structural defects (e.g. pores) and surface effects (e.g. surface contaminations and surface oxide layers). The phosphorous-doped SiNWs grown bottom up by the vapor-liquid-solid (VLS) technique showed an average Young's modulus of (170.0±2.4) GPa and a tensile strength larger than 8.3 GPa. This finding confirms that materials strength increases as their sizes scale down. The top down electroless chemically etched Si <100> NWs show a tensile strength of 5.4 GPa. The developed MEMS devices and experimental techniques enable an alternative way of in-situ nanomechanical characterization based on electron microscopy. The design methodology and learning presented in this thesis would be useful to develop nano-tensile stages of other configurations with more advanced functions.
000142931 6531_ $$ananomechanics
000142931 6531_ $$aMEMS
000142931 6531_ $$atensile test
000142931 6531_ $$ananostructure
000142931 6531_ $$acomb drive
000142931 6531_ $$acapacitive sensor
000142931 6531_ $$ain-situ
000142931 6531_ $$aelectron microscope
000142931 6531_ $$anano-mécanique
000142931 6531_ $$aMEMS
000142931 6531_ $$aessai de traction
000142931 6531_ $$astructures nanométriques
000142931 6531_ $$aactuateur combiné
000142931 6531_ $$acapteur capacitif
000142931 6531_ $$ain-situ
000142931 6531_ $$amicroscope électronique
000142931 700__ $$aZhang, Dongfeng
000142931 720_2 $$aClavel, Reymond$$edir.$$g104789$$0242132
000142931 720_2 $$aMichler, Johann$$edir.
000142931 8564_ $$zTexte intégral / Full text$$yTexte intégral / Full text$$uhttps://infoscience.epfl.ch/record/142931/files/EPFL_TH4605.pdf$$s10608281
000142931 909C0 $$pLSRO$$0252016
000142931 909CO $$pSTI$$pthesis$$pthesis-bn2018$$pDOI$$ooai:infoscience.tind.io:142931$$qDOI2$$qGLOBAL_SET
000142931 918__ $$dEDPR$$cIMT$$aSTI
000142931 919__ $$aLSRO2
000142931 920__ $$b2010
000142931 970__ $$a4605/THESES
000142931 973__ $$sPUBLISHED$$aEPFL
000142931 980__ $$aTHESIS