Molecule-sized transistors

Another area of research is the construction of molecule-sized transistors made from graphene or carbon nanotubes and other materials. These technologies, when fully developed, will completely change the nature of computing by enabling the construction of a quantum computer, a device that could carry out in seconds calculations that existing computers would require possibly billions of years to complete. 

One of the most promising bottom-up approaches in nanoelectronics is to assemble 7i-conjugated molecules to build nano-sized electronic and opto-electronic devices in the 5-100 nm length scale. This field of research, called supramolecular electronics, bridges the gap between molecular electronics and bulk plastic electronics. In this contest, the design and preparation of nanowires are of considerable interest for the development of nano-electronic devices such as nanosized transistors, sensors, logic gates, LEDs, and photovoltaic devices. 

Another example is a Pentium 4 chip. Forty-two million transistors are arranged on a few cm2 of substrate. Replacing these transistors by organic molecules opens new promises. In particular, an organic molecule that bears source, drain and gate functionality would be 1-3 nm in size. In other words,... 

Nano-technology will play a prominent role in the future synthesis of molecular thin films and devices. Nano-technology is defined as the study and manufacture of structures and devices with dimensions about the size of a molecule. Nano-scale physics and chemistry might lead directly to the smallest and fastest transistors and the strongest and lightest materials ever made [2], Likewise, bio-catalysts such as proteins will be increasingly used to facilitate relevant chemical reactions at ambient conditions. Natural macromolecules will be explored to provide selectivity similar to inorganic chemicals such as zeolites. 

Jackel, F. et al.. Prototypical single-molecule chemical-field-effect transistor with nanometer-sized gates, Phys. Rev. Lett. 92, 188303, 2004. 

In the future scientists may be able to produce transistors and other electronic components consisting of individual molecules, dramatically increasing the speed and reducing the size of computers a computer corresponding to the laptops we now carry around suddenly fits inside a wristwatch . 

While not completely accurate, the PFEO model provides an estimate of the first level excitation energy and explains the trend in HOMO-LUMO gap. As the molecule increases in size the HOMO-LUMO gap decreases in magnitude and it becomes easier to generate an excited state. Technologically this has some ramifications for example, hexacene s very small HOMO-LUMO gap makes its electrons easy to excite. The material is easily oxidized in air and unsuitable for air stable transistors. The HOMO and LUMO surfaces for pentacene are shown in Fig. 2.8. It is clear that the wavefunction indeed travels around the perimeter of the molecule and this distance is a significant determiner of the electronic properties of the material. 

This size reduction is analogous to a continuous decrease in the dimensions of species accessible for studies and applications. Not only that small is beautifiil, but also it enforces progress and provides a new dimension to science and technology. Chemists are finally able to work with single molecule and atoms, yet not billions of them at a time. Nano has become a buzzword of the new century. New nano journals and nano letters and nano webpages have been emerging. We are constantly reading about nano wires, sensors, transistors, and nanocomputers. 

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