Studies On The Devices Of Suspended Single-Walled Carbon Nanotube And Related Properties

Single-walled carbon nanotubes(SWNTs)have some intriguing physical properties,providing great potential application in electronics.In this thesis,we have investigated the novel suspended SWNT devices and its properties.At first,we fabricated the individual suspended SWNT field effect transistors and investigated their performance.Then we proposed a novel technique to fabricate suspended SWNT devices which was based on the motion of the liquid silver.We also measured the transport properties in suspended SWNTs.At last,we fabricated suspended and aligned SWNT networks,and studied its Raman spectra.There are three main topics in this thesis,as listed below:Firstly,we report an effective technique of fabricating ultraclean individual suspended single-walled carbon nanotube(SWNT)transistors.The surface tension of molten silver is utilized to suspend an individual SWNT between a pair of Pd electrodes during annealing treatment.This approach avoids the usage and the residues of organic resist attached to SWNTs,resulting ultraclean SWNT devices.And the resistance per micrometer of suspended SWNTs is found to be smaller than that of non-suspended SWNTs,indicating the effect of the substrate on the electrical properties of SWNTs.The ON-state resistance(~50 k?),mobility of 8,600 cm~2/(V·s)and large on/off ratio(~10~5)of semiconducting suspended SWNT devices indicate its advantages and potential applications.Secondly,we demonstrate an effective,fast,and wafer-scale technique to fabricate suspended SWNT arrays,which is based on a dynamic motion of silver liquid to suspend and align the SWNTs between the prefabricated palladium electrodes in high temperature annealing treatment.At the beginning,some amount of SWNTs with random orientations are deposited onto the silver film,under which there are patterned palladium electrodes.When the temperature is raised above the melting point of silver film,the silver film will become silver liquid particles and move toward the palladium electrodes.During this process,the SWNTs become suspended,aligned,and strained between the palladium electrodes.Under the optimal conditions,almost all SWNTs become suspended,and these SWNT array devices have extremely low contact resistance.Then the suspended SWNT array transistors are fabricated by selective etching of metallic SWNTs using electrical breakdown,revealing a promising industrial applications.Thirdly,we fabricated suspended and aligned SWNT networks,through adjusting the shape and layout of palladium metal.The SWNTs are aligned in eight directions:up,down,left,right,upper right,lower right,upper left,and lower left.The Raman spectra of the SWNTs network were measured,and the downshift of the G+band indicates that,for the suspended SWNTs,the uniaxial strain is around 0.13%.This technique could be extended to two-dimensional material systems and open the pathway toward better optoelectronic and nanoelectromechanical systems.