Research On Bending Properties Of Silver Nanowires Oriented Towards Controllable Two-Dimensional Manipulation

As a new one-dimensional nanomaterial with high aspect ratio,nanowires are possessed of more excellent mechanical properties than macroscopic materials.As one of the semiconductor nanowires,silver nanowires have excellent electrical conductivity,thermal conductivity and nano-optical properties,and are widely utilized in the fields of microelectronics,aerospace and biomedicine.Nanomanipulation is the controllable movement of nanomaterials through various devices or technologies.Thereinto the nanomanipulation of silver nanowires has great potential for application in ultra-high sensitive electrothermal sensors and battery technology,such as assembling nanowire sensors or assembling a silver nanowire array by silver nanowire manipulation to significantly improve battery performance.In this paper,based on the tapping mode and contact mode of atomic force microscope(AFM),the effects of bending manipulation on the deformation of silver nanowires were investigated and the effects of manipulating speed and manipulating position on the twodimensional lateral manipulation of silver nanowires were systematically studied.In-depth analysis of the structural bending deformation and damage of silver nanowires was carried out by scanning electron microscope.The adhesion between the silver nanowires and the silicon substrate was investigated by utilizing high resolution transmission electron microscope.Finally,based on the observed manipulating speed and position parameters,an attempt was made to assemble a simple two-dimensional structure with silver nanowires.The main research contents in this paper are as follows:(1)The effect of bending angle on the deformation and damage of silver nanowire structure was investigatedCombined with tapping mode and contact mode of AFM,the silver nanowires are bending-manipulated on silicon substrate to form different bending angles.AFM and scanning electron microscope(SEM)were utilized to characterize the bent part.When the bending angle reached 80°,the curved portion of the silver nanowire begins to appear damaged;as the bending angle increased,the silver nanowire eventually was broken from the bent part.(2)The mechanical properties of silver nanowires were investigatedThe nanoindentation experiments were performed on a silver nanowire and a silver substrate with AFM under the same parameter conditions(indentation depth 20 nm,press-in time 5 s),respectively.Comparing the indentation morphology and the force-displacement curve of silver nanowires and silver substrate,it is concluded that cracks appear on the surface of the silver nanowire,and the silver substrate forms protrusion structure on both sides of the indentation due to better ductility;the slope of the force-displacement curve indicates that the silver substrate is possessed of relatively high system stiffness.(3)The effects of manipulating speed and manipulating position on the lateral twodimensional manipulation of nanowires were analyzedThe middle manipulation and end manipulation of single silver nanowires were carried out under three speed conditions by the AFM.The morphology of silver nanowires before and after manipulation was compared and the lateral force changes during the manipulation were analyzed.The conclusion was drawn: lateral force curve at 0.1 ?m/s is more stable,and the silver nanowire structure showed no obvious damage.In addition,the cutting of silver nanowires can be achieved with a middle manipulation at 10 ?m/s.(4)The adhesion mechanism between silver nanowires and silicon substrate were elaboratedComparing the self-weight,lateral force of the silver nanowire and the vertical load of the tip,it is concluded that the self-weight of the silver nanowire is much smaller than the lateral force and the vertical load of the tip;the interaction between the silver nanowires and the silicon substrate is a key factor affecting manipulation.Characterization and compositional analysis of the structure between silver nanowires and silicon substrate were performed using high resolution transmission electron microscope.The results show that there is a non-uniform interfacial film between the silicon substrate and the silver nanowire,which is mainly composed of four components: Ag,Si,C and O.During the lateral two-dimensional manipulation,the interfacial film is destroyed by the lateral force;after that,the silver nanowires begin to move against the static friction under the action of the lateral force.In this paper,the bending characteristics of silver nanowires oriented towards controllable two-dimensional manipulation are studied.The influence of bending angle on the deformation of silver nanowires during lateral two-dimensional manipulation is investigated,and the optimal operating parameters(manipulating speed and manipulating position)are explored.The adhesion mechanism of silver nanowires to silicon substrates was investigated.On this basis,an attempt the assembly for assembling simple two-dimensional structures with silver nanowires was made.This paper further enriches the research on material structure deformation and substrate adhesion in the two-dimensional manipulation process,which is of great significance for realizing the controllable manipulation of silver nanowires,and promotes the application process of silver nanowires.