Patterning Gold Nanoparticles And Interfacial Seeded Growth For Their Application In Nanoscale Circuits

As the key component of information manufacturing,nanopatterning not only offers an ideal platform for investigating the novel properties of materials under the micro and nanoscale,but also constitutes the foundation of improving the integration of circuits and miniaturization of functional devices.The methods for nanopatterning mainly fall into two categories: top-down method and bottom-up method.The bottom-up method is receiving increasing attention because it is compatible with the mature synthesis of nanomaterials and is capable of assembling various functional nanoparticles for its application in nanoscale circuits,sensors and waveguide;on the other hand,the tiny size of nanomaterials indicates its huge potential in fabrication nanostructures with small feature size.However,there still remain several challenges in existing assembling techniques,for example,the requirement of templates which restricts the pattern shape,the unsatisfactory resolution of assembly and the uncontrollable interparticle gap.In order to address these challenges,the AFM nanoxerography is used to realize the assembly of gold nanoparticles with ultra-high resolution without requiring templates,and the interfacial seeded growth is conducted to reduce the interparticle distance,which hold potential in the field of nanoscale circuits.1.AFM nanoxerography is employed for the assembly of gold nanoparticles,which means we applied voltage onto the subsrate through the AFM tip,and then the charge pattern is generated and guided the particles to the predefined pattern.The advantage of this method lies in the ultrahigh resolution of nanoparticle pattern,which is resulted from the tiny size of the tip of 7 nm and the nanoparticle size of merely 5 nm.When the surface potential is 0.2 V,there are only two to three particle on each charge spot,which means the feature size is only about 10 nm.Another benefit of AFM nanoxerography is the high flexibility,because the spacing between adjacent spots and the particle number on each spot can be tuned by changing the pattern shape and the surface potential respectively.Based on the nanoparticle pattern,we achieved highly controllable seeded growth and monitored the growth process using SEM,AFM,Optical Microscopy and extinction spectra,which reveals the evolution of nanoparticle morphology with size from 5 nm to 60 nm.The increase of the particle size improves the scattering of nanoparticle by three orders of magnitude,which makes the patter after growth clearly visible under the 5X lens,and thus demonstrates significant potential in fabrication of anti-counterfeit patterns.2.The interfacial seeded growth based on nanoparticle arrays not only provides an ideal platform for monitoring the chemical reactions in situ,but also decreases the interparticle gap in the assemblies and optimize the properties of assemblies.In this work,we align the particles in the linear manner and conduct interfacial seeded growth to form closely packed particle arrays.The width of such arrays could be adjusted by surface potential,and when the surface potential is set as 0.2 V,the width of arrays only contains two to three particles,and the width after growth is merely 200 nm.Besides,we measure the current-voltage curve and obtained the conductivity of 17.5 S/m.In order to optimize the device for electrical measurement,we transferred the arrays from silicon to insulating substrate to remove the conductive contribution of silicon.In addition,the low-temperature sintering is used to promote the coalescence of particles to provide more paths for electron transport and improve the conductivity.