Brief History of Nanorevolution

At the turn of twenty-first century, we entered nanoworld. These days, if you try to run a simple Web search with the keyword "nano," thousands and thousands of references will come out: nanoparticles, nanowires, nanostructures, nanocomposite materials, nanoprobe microscopy, nanoelectronics, nanotechnology, and so on. The list could be endless.

When did this scientific nanorevolution actually happen? Perhaps, it was in the mid-1980s, when scanning tunneling microscopy was invented. Specialists in electron microscopy may strongly object to this fact by claiming decades of experience in observing features with nearly atomic resolution and later advances in electron-beam lithography. We should not omit molecular beam epitaxy, the revolutionary technology of the 1980s, which allows producing layered structures with the thickness of each layer in the nanometer range. Colloid chemists would listen to that with a wry smile, and say that in the 1960s and 1970s, they made Langmuir-Blodgett (LB) films with extremely high periodicity in nanometer scale. From this point of view, the nanorevolution was originated from the works of Irving Langmuir and Katherine Blodgett [1, 2] in 1930s, or from later works of Mann and Kuhn [3-5], Aviram and Ratner [6], and Carter [7], which declared ideas of molecular electronics in the 1970s. What is the point of such imaginary arguments? All parties were right. We cannot imagine modern nanotechnology without any of the above-mentioned contributions. The fact is that we are in the nanoworld now, and the words with prefix "nano-" suddenly have become everyday reality. Perhaps it is not that important how it happened (since it has become history already). However, we should realize the reason why it happened.

A driving force of the nanorevolution is a continuous progress in microelectronics towards increasing the integration level of integrated circuits (IC), and thus the reduction in the size of active elements of ICs. This is well illustrated by Moore's law [8] in Figure 1.1.

It was monitored during the last four decades that the size of active elements (e.g., transistors) reduces by a factor of two every 18 months. Of course, there were some deviations from this law, and the graph in Figure 1.1 requires some kind of error bars. However, a thick trend line, which may cover error margins, demonstrates the above behavior clearly. What is behind Moore's law? It is not just physics, microelectronic engineering, and technology alone, all of which have a spontaneous character of development. I believe that Moore's law is a free market

10 2,000 250,000 4 million ~40 million transistors transistors transistors transistors transistors per sq cm per sq cm per sq cm per sq cm per sq cm

10 2,000 250,000 4 million ~40 million transistors transistors transistors transistors transistors per sq cm per sq cm per sq cm per sq cm per sq cm

Year

Figure 1.1 Moore's law. (From: [8]. © 1996 MITRE Corporation. Reprinted with permission.)

Year

Figure 1.1 Moore's law. (From: [8]. © 1996 MITRE Corporation. Reprinted with permission.)

economy law, which reflects the growing public demand in microelectronic devices, and the competition between microelectronic companies.

Let's leave the economic aspects of Moore's law to economists, and start discussing physics. As one can see, the critical line of one micron was crossed in the 1990s, which means we entered the nanoelectronics era at that time. Electron beam lithography had started to overtake the conventional UV photolithography, which cannot provide submicron resolution. Smart technological approaches in microelectronics, such as VMOS, DMOS, and vertical CMOS transistors, also allowed the ability to meet the demands of the steadily growing market of personal computers. What is next? Can we further scale down the existing electron devices, based mostly on the field effect in semiconductors? The answer is no, because of obvious physical limitations of semiconductor microelectronics.

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