Low Frequency Noise Spectroscopy At Nanoscale Carbon Nanotube Materials And Devices PDF Download

This dissertation, "Electronic Characterization of Individual Single-walled Carbon Nanotubes" by Chi-yan, Wong, 王志仁, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled ELECTRONIC CHARACTERIZATION OF INDIVIDUAL SINGLE-WALLED CARBON NANOTUBES Submitted by Wong Chi Yan for the Degree of Master of Philosophy at The University of Hong Kong in September 2007 The outstanding properties of carbon nanotubes (CNTs) have attracted con- siderable research effort in the last decade. CNTs are quasi-one-dimensional materials which can be used to study fundamental quantum effects of one- dimensional systems. TherehasbeenagreatdealofinterestspecificallyinsemiconductingCNTs, which have shown to be promising candidates as the building blocks for the next-generation electronic applications. Carbon nanotube electronic devices have the potential to replace conventional silicon-based counterparts. How- ever, there are still obstacles that remain with regard to the scientific study or application oriented researches. For example, the growth orientation and the band gaps of individual CNTs are difficult to control. In addition, pronounced low-frequency current fluctuation, 1/f noise, exists. The measured noise levelisevencomparabletothesignallevelundersomecircumstances, therebylimit- ing the application of CNTs in low-signal electronics and the overall reliability of CNT based devices. In this thesis, single-walled CNTs (SWNTs) were chosen as a studying modelduetotheirsimplicityinnature. DifferentmethodsofindividualSWNT fieldeffecttransistor(FET)fabricationmethodswerecompared. Themethods included: (I) Directed growth of ultra long SWNTs on a wafer by CVD using ethanol, and (II) Dispersing the SWNTs fabricated by ordinary CVD, on the wafer with organic solvents. The noise behavior for both fabrication methods were characterized by DAQ and lock-in noise measurement methods. Thereafter, thebasicI-V measurementsoffabricatedSWNTFETdevices were also performed. The hysteresis effect and its time dependent measure- ments in FETs were illustrated. The measurements results suggested that the hysteresis effect in nanotube devices was attributed to the charge traps in the oxide layer of FETs. Finally, the 1/f noise of SWNT FETs was studied. It was shown that the 1/f noise arose from the carrier number fluctuations rather than mobility fluctuations, as a superposition of Lorentzian fluctuation spectra. The corre- -2 sponding Hooge constant was found to be gate dependent and about 10 in thelinearregime. Bycomparingwiththereportedsimulationresultofrandom telegraphsignal(RTS)noiseamplitudeinsubthresholdregime, itwasproposed that such Lorentzian fluctuation spectra were due to the RTS noise, arising from the gate potential fluctuations in the CNT, and the charge exchange be- tween CNT and oxide layer. These potential fluctuations were attributed to trapped charges in the oxide nearby which changed the number of carriers in the CNTs. DOI: 10.5353/th_b3955704 Subjects: Nanotubes Nanostructured materials - Electric properties Transistors