Highly Reliable Carbon Nanotube Transistors with Patterned Gates and Molecular Gate Dielectric

Abstract

The prospect of realizing nanoscale transistors using individual semiconducting carbon nanotubes offers enormous potential, both as an alternative to silicon technology beyond conventional scaling limits and as a way to implement high-speed devices and circuits on flexible substrates. A significant challenge is the realization of low-voltage nanotube transistors with individually addressable gate electrodes that display large transconductance, steep subthreshold swing, and large on/off ratio. Their integration into circuits with large signal gain and good stability still needs to be demonstrated. Here, we demonstrate that these important goals can be achieved with the help of a bottom-gate device structure that combines patterned metal gates with a thin gate dielectric based on a molecular self-assembled monolayer. The obtained transistors operate with a gate-source voltage of 1 V and have a transconductance of 5 µS, a subthreshold swing of 68 mV/decade, and an on/off ratio of 10 7 . To verify the excellent operational and shelf life stability, we show that the device performance does not degrade during 10 000 switching cycles and during storage under ambient conditions for more than 300 days. We also demonstrate that the device structure allows the implementation of unipolar logic circuits with good switching characteristics.

Electrical Characteristics of Field‐Effect Transistors based on Chemically Synthesized Graphene Nanoribbons

“…SDS is a surfactant that is commonly used for the dispersion and deposition of carbon nanotubes. [ 18 ] The GNRs were located by atomic force microscopy (AFM) and their location on the substrate was referenced against an array of pre-patterned alignment markers. Due to the small GNR concentration, the dispersion stayed clear during the entire process.…”

Unique Role of Self‐Assembled Monolayers in Carbon Nanomaterial‐Based Field‐Effect Transistors

“…In some cases, to decrease the dielectric thickness, inorganic dielectric materials with larger permittivity (for example TiO x , AlO x and HfO x ) were used. Similarly, to passivate the hydroxyl groups on their surfaces, alkylphosphonic acids were usually used to form high‐quality SAMs 56. It should be mentioned that the substrates need to be pre‐activated in order to provide suitable reactive sites for the subsequent surface reactions.…”

“…However, their integration into electrical circuits with large signal gain and good stability still needs to be demonstrated. Weitz's group demonstrated that these important goals can be achieved with the help of a bottom‐gate device structure that combines patterned metal gates (20 nm thick layer of aluminum) with a thin gate dielectric (3.6 nm thick layer of aluminum oxide) based on a molecular self‐assembled monolayer (2.1 nm thick of n‐ octadecylphosphonic acid) ( Figure ) 56. The devices show excellent operational and shelf life stability performance without degradation during 10 000 switching cycles and during storage under ambient conditions for more than 300 days.…”

Logic Gates Based on Carbon Nanotube Field-Effect Transistors with SiNx Passivation Films

“…However, when a higher frequency was applied to the inverter, the wave shape was distorted. This phenomenon was affected by the parasitic capacitance of CNT-FETs, 22) because the inverter was fabricated on a Si substrate covered with a SiO 2 layer and was operated by a backgate. The capacitance degrades the performance of the inverter.…”