To improve the efficiency of nano-electronic device fabrication,a new method named floating electrical potential assembly is proposed to realize large-scale assembly of Cu/CuO nanowires.The simulation of floating electrical potential distribution on the micro-electrode chip is performed by COMSOL software,and the simulation result shows that the coupled electrical potential on the floating drain electrodes is very close to the original electrical potential applied on the gate electrode,which means that the method can provide di-electrophoresis(DEP)force for all the electrode pairs at one time,thus realizing large-scale assembly at one time.With Cu/CuO nanowires well dispersed and micro-electrode chip fabrication,nanowires assembly experiments are performed and the experimental results show that Cu/CuO nanowires are assembled at hundreds of micro-electrodes pairs at one time,and the success rate of nanowires assembly also reaches 90%.
The large-scale assembly and fabrication method for single-walled carbon nanotube(SWCNT) nano devices was implemented.Assembly of SWCNT field effect transistor(FET) was realized by floating potential dielectrophoresis approach.The simulation of floating potential distribution of the chip was performed by comsol multiphysics coupling software.Six hundred devices were assembled on the area of less than one square centimeter.The fabricated devices were characterized by atomic force microscopy and scanning electron microscopy.The experimental results showed that large-scale assembly had been realized,and the success rate of ideal assembly for SWCNT FET had been assessed.
A highly sensitive single-walled carbon nanotube(SWCNT)-based ammonia(NH3) gas detector is manufactured by orderly assembling SWCNT using the dielectrophoretical(DEP) technology.Atom force microscopy(AFM) and scanning electron microscopy(SEM) images revealed that SWCNTs were assembled between the microelectrodes.SWCNTs were affected by the electrophoretic force which was carried out by the related theoretical analysis in a nonuniform electric field.The SWCNT field effect transistors geometry was obtained.The electrical performance of NH3 gas sensor with the SWCNT field effect transistors geometry was tested before and after the adoption of NH3 at room temperature.Experimental results indicated that the efficient assembly of SWCNT was obtained by the applied alternating current voltage with frequency of 2 MHz and amplitude of 10 V.The SWCNTs-based gas sensor had high sensitivity to NH3,and the electrical conductance of NH3 gas sensor reduced two times after interaction with NH3.The SWCNTs surface gas molecules were removed by means of ultraviolet ray irradiation for 10 min.Hence,the fabricated NH3 gas sensor could be reversible.There is a clear evidence that the adsorption of NH3 on the SWCNT channel is easy to be realized.Our theoretical results are consistent with recent experiments.
Nowadays,one of the bottlenecks which hinder the development and application of carbon nanotube(CNT)nano device is that no pure semiconducting CNT(s-CNT)or metallic CNT(m-CNT)can be obtained,and for solving this problem scientists proposed some methods on preparation or separation,but all the results still should be detected and feedback to the process for further improving the preparation and separation methods.Thus,it is very important to measure and distinguish the electrical properties of CNT.For that,scientists proposed a method to measure CNT electrical properties based on DC electrostatic force microscope(EFM)mode,which distinguishes m-CNT from s-CNT according to different scan line shape to CNT with different electrical properties.But,we discovered that the probe lift-up height will seriously affect the shape of the scan line,which makes this method not reliable in distinguishing m-CNT from s-CNT.In this paper,the authors deeply researched the influence of probe lift-up height and also gave corresponding theoretical analysis and explanation,which will greatly improve the method of detecting CNT electrical properties by EFM.
Zengxu ZhaoXiaojun TianJie LiuZaili DongLianqing Liu
