Electronic devices based on molecular building blocks have attracted increasing interest because they may provide solutions for keeping track of Moore’s law. Since molecular structures are not limited by lithography resolution, they could allow a further reduction of the chip size compared to patter...
Electronic devices based on molecular building blocks have attracted increasing interest because they may provide solutions for keeping track of Moore’s law. Since molecular structures are not limited by lithography resolution, they could allow a further reduction of the chip size compared to patterned devices. Among the various molecular switching units suggested or tested to date, single-walled carbon nanotube(SWNT) is an exemplary case due to its excellent electronic properties, which include an exceptional current-carrying capacity and a high mobility. Several research groups have reported the successful fabrications of SWNT based diodes, logic gates, and chemical or biological sensors. Nevertheless, a few key technological issues still remain challenging, for example, the fabrication of n-type SWNT-field effect transistors (FETs) is necessary for the complementary logic circuits. SWNT-FET, without a special treatment, normally tends to show p-type behavior, which is attributed to either Fermi-level alignment at the contact or hole doping in the channel by environmental oxygen species, including water vapors and oxygen molecules. The existing strategies for fabricating n-type SWNT-FETs can be classified into two categories. In the first approach, electron dopants such as alkali metals or polymers are employed to generate electron carriers in the body of the SWNTs. The second approach entails engineering the contact barrier to achieve a lower Schottky barrier for electron transport into the conduction bands of the SWNTs. Nevertheless, in practice, electron dopants are vulnerable to oxidation and the work function of the metal surface is likely to increase upon oxidation under ambient air. Therefore, irrespective of the method used (channel doping or the contact barrier engineering), achieving long-term stability of n-type operation under ambient conditions remains a great challenge. Shim et al. demonstrated that polyethyleneimine-coated SWNTs could lead to air-stable n-type transistor operations and Zhang et al. achieved the same objective by following the second route. They reported the fabrication of the SWNT complementary devices and showed that Sc contacted SWNT-FETs appear to exhibit a long-term air stable n-type behavior without passivation. Accordingly, in this work we fabricated more stable n-type SWNT-FETs to controllable of electrical conduction property of the CNT channel used “contact barrier effect” and “channel dopping effect”.
Electronic devices based on molecular building blocks have attracted increasing interest because they may provide solutions for keeping track of Moore’s law. Since molecular structures are not limited by lithography resolution, they could allow a further reduction of the chip size compared to patterned devices. Among the various molecular switching units suggested or tested to date, single-walled carbon nanotube(SWNT) is an exemplary case due to its excellent electronic properties, which include an exceptional current-carrying capacity and a high mobility. Several research groups have reported the successful fabrications of SWNT based diodes, logic gates, and chemical or biological sensors. Nevertheless, a few key technological issues still remain challenging, for example, the fabrication of n-type SWNT-field effect transistors (FETs) is necessary for the complementary logic circuits. SWNT-FET, without a special treatment, normally tends to show p-type behavior, which is attributed to either Fermi-level alignment at the contact or hole doping in the channel by environmental oxygen species, including water vapors and oxygen molecules. The existing strategies for fabricating n-type SWNT-FETs can be classified into two categories. In the first approach, electron dopants such as alkali metals or polymers are employed to generate electron carriers in the body of the SWNTs. The second approach entails engineering the contact barrier to achieve a lower Schottky barrier for electron transport into the conduction bands of the SWNTs. Nevertheless, in practice, electron dopants are vulnerable to oxidation and the work function of the metal surface is likely to increase upon oxidation under ambient air. Therefore, irrespective of the method used (channel doping or the contact barrier engineering), achieving long-term stability of n-type operation under ambient conditions remains a great challenge. Shim et al. demonstrated that polyethyleneimine-coated SWNTs could lead to air-stable n-type transistor operations and Zhang et al. achieved the same objective by following the second route. They reported the fabrication of the SWNT complementary devices and showed that Sc contacted SWNT-FETs appear to exhibit a long-term air stable n-type behavior without passivation. Accordingly, in this work we fabricated more stable n-type SWNT-FETs to controllable of electrical conduction property of the CNT channel used “contact barrier effect” and “channel dopping effect”.
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