Scalable Complementary Logic Gates with Chemically Doped Semiconducting Carbon Nanotube Transistors

Abstract

Use of random network carbon nanotube (CNT) transistors and their applications to complementary logic gates have been limited by several factors such as control of CNT density, existence of metallic CNTs producing a poor yield of devices, absence of stable n-dopant and control of precise position of the dopant, and absence of a scalable and cost-effective fabrication process. Here, we report a scalable and cost-effective fabrication of complementary logic gates by precisely positioning an air-stable n-type dopant, viologen, by inkjet printing on a separated semiconducting CNTs network. The obtained CNT transistors showed a high yield of nearly 100% with an on/off ratio of greater than 10(3) in an optimized channel length (∼9 μm). The n-doped semiconducting carbon nanotube transistors showed a nearly symmetric behavior in the on/off current and threshold voltage with p-type transistors. CMOS inverter, NAND, and NOR logic gates were integrated on a HfO2/Si substrate using the n/p transistor arrays. The gain of inverter is extraordinarily high, which is around 45, and NAND and NOR logic gates revealed excellent output on and off voltages. These series of whole processes were conducted under ambient conditions, which can be used for large-area and flexible thin film technology.

Tuning the threshold voltage of carbon nanotube transistors by n-type molecular doping for robust and flexible complementary circuits

“…The inverter demonstrated a very high noise margin of 28 V at a supply voltage of 80 V (70% of 1/2V DD ) and a gain of 85 (Fig. 4C), values that were not achieved for previously reported SWNT CMOS inverters (14,30,32). Our obtained noise margin value indicates that even if the noise causes the input voltage shift of 28 V at each direction, the inverter can still produce the correct output signal.…”

“…The advantages of CMOS circuits compared with unipolar logic circuits include lower power consumption, simpler circuit design, higher noise margin, better tolerance to the spread of threshold voltages of the transistors, and consequently higher circuit yields (15-17). Several approaches have been reported to adjust the threshold voltage of SWNTs and enable n-type SWNT transistors, including the use of (i): low-work function metal as source/drain contacts (20-22), (ii) atomic layer deposited (ALD) high-κ oxide on the SWNTs (23), and (iii) chemical doping on either the contacts or the bulk of SWNTs (14,(24)(25)(26)(27)(28)(29)(30)(31)(32). However, the continuous and reliable tuning of the threshold voltage of SWNT TFTs has not been achieved, thereby hindering optimal SWNT circuit performance.…”

“…Solution-processed single-walled carbon nanotubes (SWNTs) are a promising candidate for flexible circuits due to their high charge carrier mobility (6), excellent flexibility/stretchability (7)(8)(9), and their compatibility with lowcost, large-area manufacturing processes, such as printing (1,10) of SWNTs. Their applications in thin-film transistors (TFTs) and integrated logic circuits (11)(12)(13)(14) have been demonstrated. However, to achieve robust digital circuits with high immunity against the influence of electronic noise in the system, it is important to be able to control the specific value of the threshold voltage of a transistor during the fabrication process (15,16).…”

High‐Throughput Fabrication of Flexible and Transparent All‐Carbon Nanotube Electronics

“…However, due to the lack of techniques that allow the deposition of liquid photoresists on an extremely large scale, CNT‐based electronic devices have been limited to the wafer‐scale12, 15, 16 or medium‐scale integration level 17, 18. Printing technology, such as inkjet printing,19, 20, 21, 22, 23, 24 screen printing,25, 26, 27, 28 and gravure printing,29, 30 in manufacturing electronics has drawn tremendous interest during the past few decades. Compared with traditional multi‐step photolithography, printing is a cost‐effective and scalable technology with high throughput and high compatibility to transferring and fabricating large‐scale nanocarbon electronics like the roll‐to‐roll printing technique,31, 32 which provides an important way to achieve the mass production of large‐scale flexible electronics at extremely low cost.…”

Polymer-sorted (6,5) single-walled carbon nanotubes for solution-processed low-voltage flexible microelectronics

“…These results compare favorably with previously reported unipolar inverters based on solutionprocessed mixed SWNTs using diode-load 8,27 and voltage bootstrapping circuitries, 28 although somewhat improved performances have been reported for inverters based on complementary-like architectures. 13,14,20,29 To further demonstrate the potential of the proposed technology, we fabricated polymer/(6,5) SWNTs transistors directly on free-standing flexible polyimide foils. The significantly higher hole mobility and on/off ratio of the transistor, as compared to devices fabricated on rigid substrates, are most likely attributed to improved substrate surface coverage with polymer/(6,5) SWNT due to different surface topography (Fig.…”