Carbon Nanotubes and Spintronics - Properties and Applications

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Going beyond traditional electronics in the solid state, it is plausible to think that the next revolution in electronics would be molecular. Until now, the most encouraging candidate poised to transform next-generation electronics is carbon.

Typically, rolled up graphite sheets, known as carbon nanotubes, possess electronic properties that can be manipulated through their structural details—they can be semiconductors, conductors, and insulators.

Carbon Nanotube-Based Semiconductors and Their Associated Challenges

In 2001, IBM created the most rudimentary logic element, a NOT gate, from a single nanotube. Recently, IBM developed nanotube transistors that outclassed the best silicon devices currently in the market.

There are two major challenges to overcome for nanotube-based electronics. One of the challenges is connectability—it is one thing building a nanotube transistor, but it is very different to link up millions of them together. The second challenge is the ability to expand to mass production. Existing approaches to nanotube electronics are usually a single component at a time, which is not economical.

Molecular electronics (which, truly speaking, includes nanotubes) meet similar scaling challenges. However, there are a few probable solutions. One method to the quantum limit barriers in conventional silicon technology is to accept the quantum effects and design devices around them. Quantum spin devices and single-electron devices are under analysis in numerous labs.

Single-Electron Transistor

The single-electron transistor, developed keeping in mind a small number of electrons, is one such case of a nanotechnological method that merges a new scale factor with minimal power consumption. Room-temperature single-electron transistors made using conventional silicon chemistry have been established and quite a few other methods are being pursued.

The technology is hard to commercialize for several reasons, and estimates indicate it will take about a decade. Companies that are actively involved in this study include NEC, Hitachi, Toshiba, and NTT.

Recent Advances in Using Quantum Spin Effects

Latest progress in using quantum “spin” effects has led to efforts in spintronics. Spintronics depends on a feature of electronics called spin, and not on the movement of electrons themselves. Spin can hold state information quite like a charge does.

The above two quantum-based methods use inorganic assembled nanoscale devices. Regarded as an improvement over existing silicon manufacturing techniques, they will not, however, positively curb the growing cost of building fabrication facilities.

Properties of Spintronics

Magnetism is controlled by the direction of spin of electrons, and progressive research into the use of this property has resulted in the making up of the term “spintronics.” The read heads of disk drives already use electron spin through an effect known as giant magnetoresistance, as does MRAM, which has already witnessed limited commercial production.

Study of the Magnetic Recording

Recently, a study of the magnetic recording on a hard disk has shown that none of the important dimensions goes beyond 1 μm: media thickness, track width, bit length, and read head size are all measured in nanometers.

In the recent past, an effect known as ballistic magnetoresistance has been shown to have the potential to make read heads that can handle storage densities of 1 Tb/inch², which is 10 times the density expected in the next generation of hard drives. Commercial application of spintronics in electronics has a long way to go but the potential is still present.