Carbon Nanotubes Related Devices and Applications Carbon nanotube is a magic material. The unique structure brings it amazing characteristics. Lots of people believe that the usage of carbon nanotube will bring technology revolution to the industry. In this presentation, we will focus on two stunning properties that related to our major. And use some real stories to help you understand how the carbon nanotubes will change the future of the semiconductor industry. Presented by: Peng Zhiyuan, Chen Jiadong April 30, 2014

Outline Who invented the carbon nanotube? What is a carbon nanotube? --unique structures and properties What are the applications --CNTFET and Heat dissipation

Major Contributors: Sumio Iijima A leading researcher at NEC Laboratories since the late 1980’s. Discovered carbon nanotubes in 1991 by demonstrating that the carbon fibers produced by a carbon arc were hollow.

Carbon nanotube structure Roll a graphene sheet in a certain direction: Armchair structure Zigzag structure Chiral structure conductor semiconductor semiconductor Armchair Zigzag Chiral

Chiral vector: Depending on their n,m values, nanotubes can be either electrically metallic or semiconductor. In general, an (n, m) SWNT will be metallic when n - m = 3q, where q = 0, 1, 2, 3, 4, 5……

The tube conducts at negative Vg and turns off with a positive Vg The tube conducts at negative Vg and turns off with a positive Vg. The resistance change between the on and off state is many orders of magnitude. This device behavior is analogous to a p-type metal–oxide–semiconductor field-effect transistor (MOSFET)

CNTFET Back Gate Top Gate

Why we need CNTFET? 22nm Physical limits force us to take action For the Microelectronic device the performance is controlled by the semiconductor material doping concentration. In nanometer scale ,corresponding statistical error could be as high as 10 percent or higher. Nanotube transistors can operate even without dopants and are less sensitive to differences in the channel length. A typical carbon nanotube’s diameter is between 1 ~ 2 nm.

Advantages Carbon nanotube structure is an ideal one-dimensional conductive path. Better control over channel formation High electron mobility High current density Small switch time

Invert GHz to THz

Heat dissipation One of the greatest challenges in semiconductor design is finding ways to move waste heat out of a structure and into whatever dissipation area is designed for it. 

One of the most significant problems facing modern CPUs is the efficient transmission of heat between the CPU cores and the heat sinks.  Traditional way

Moving heat more efficiently into the heatsink would reduce CPU core temps and allow for higher frequency operation. Why?

 Thermal Interface Material 

Same price, better performance

Thermal properties of CNT Nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction", but good insulators laterally to the tube axis. Measurements show that a SWNT has a room-temperature thermal conductivity along its axis of about 3500 W·m−1·K−1. compare this to copper, a metal well known for its good thermal conductivity, which transmits 385 W·m−1·K−1. A SWNT has a room-temperature thermal conductivity across its axis (in the radial direction) of about 1.52 W·m−1·K−1, which is about as thermally conductive as soil.

The Lawrence Berkeley National Lab (Berkeley Lab) team is working on a method that would ensure more of the nanotubes come into contact with the actual metal layer . The six-fold improvement --Using organic compounds --strong covalent bonds between the carbon nanotubes and the metal layer at the top of a chip. --thermal interface material can conduct heat 6x more effectively off the top of a chip

Same price, much better performance

Key concepts The structure of a nanotube strongly affects its electrical properties. Carbon nanotube structure is an ideal one-dimensional conductive path. SWNT and MWNT Ballistic conduction—thermal property Higher drive currents and higher transconductance than the Si MOSFETs.