Nanoelectronics

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Nanoelectronics refer to the use of nanotechnology on electronic components, especially transistors. Although the term nanotechnology is generally defined as utilizing technology less than 100 nm in size, nanoelectronics often refer to transistor devices that are so small that inter-atomic interactions and quantum mechanical properties need to be studied extensively. As a result, present transistors do not fall under this category, even though these devices are manufactured with 45 nm, 32 nm, or 22 nm technology.

Nanoelectronics are sometimes considered as disruptive technology because present candidates are significantly different from traditional transistors. Some of these candidates include: hybrid molecular/semiconductor electronics, one dimensional nanotubes/nanowires, or advanced molecular electronics.

Fundamental concepts

In 1965 Gordon Moore observed that silicon transistors were undergoing a continual process of scaling downward, an observation which was later codified as Moore's law. Since his observation transistor minimum feature sizes have decreased from 10 micrometers to the 28-22 nm range in 2011. The field of nanoelectronics aims to enable the continued realization of this law by using new methods and materials to build electronic devices with feature sizes on the nanoscale.

The volume of an object decreases as the third power of its linear dimensions, but the surface area only decreases as its second power. This somewhat subtle and unavoidable principle has huge ramifications. For example the power of a drill (or any other machine) is proportional to the volume, while the friction of the drill's bearings and gears is proportional to their surface area. For a normal-sized drill, the power of the device is enough to handily overcome any friction. However, scaling its length down by a factor of 1000, for example, decreases its power by 1000³ (a factor of a billion) while reducing the friction by only 1000² (a factor of "only" a million). Proportionally it has 1000 times less power per unit friction than the original drill. If the original friction-to-power ratio was, say, 1%, that implies the smaller drill will have 10 times as much friction as power. The drill is useless.

For this reason, while super-miniature electronic integrated circuits are fully functional, the same technology cannot be used to make working mechanical devices beyond the scales where frictional forces start to exceed the available power. So even though you may see microphotographs of delicately etched silicon gears, such devices are currently little more than curiosities with limited real world applications, for example, in moving mirrors and shutters.^[1] Surface tension increases in much the same way, thus magnifying the tendency for very small objects to stick together. This could possibly make any kind of "micro factory" impractical: even if robotic arms and hands could be scaled down, anything they pick up will tend to be impossible to put down. The above being said, molecular evolution has resulted in working cilia, flagella, muscle fibers and rotary motors in aqueous environments, all on the nanoscale. These machines exploit the increased frictional forces found at the micro or nanoscale. Unlike a paddle or a propeller which depends on normal frictional forces (the frictional forces perpendicular to the surface) to achieve propulsion, cilia develop motion from the exaggerated drag or laminar forces (frictional forces parallel to the surface) present at micro and nano dimensions. To build meaningful "machines" at the nanoscale, the relevant forces need to be considered. We are faced with the development and design of intrinsically pertinent machines rather than the simple reproductions of macroscopic ones.

All scaling issues therefore need to be assessed thoroughly when evaluating nanotechnology for practical applications.

Approaches to nanoelectronics

Nanofabrication

Main articles: Nanocircuitry and nanolithography

For example, single electron transistors, which involve transistor operation based on a single electron. Nanoelectromechanical systems also fall under this category. Nanofabrication can be used to construct ultradense parallel arrays of nanowires, as an alternative to synthesizing nanowires individually.^[2][3]

Nanomaterials electronics

Besides being small and allowing more transistors to be packed into a single chip, the uniform and symmetrical structure of nanotubes allows a higher electron mobility (faster electron movement in the material), a higher dielectric constant (faster frequency), and a symmetrical electron/hole characteristic.^[4]

Also, nanoparticles can be used as quantum dots.

Molecular electronics

Main article: Molecular scale electronics

Single molecule devices are another possibility. These schemes would make heavy use of molecular self-assembly, designing the device components to construct a larger structure or even a complete system on their own. This can be very useful for reconfigurable computing, and may even completely replace present FPGA technology.

Molecular electronics ^[5] is a new technology which is still in its infancy, but also brings hope for truly atomic scale electronic systems in the future. One of the more promising applications of molecular electronics was proposed by the IBM researcher Ari Aviram and the theoretical chemist Mark Ratner in their 1974 and 1988 papers Molecules for Memory, Logic and Amplification, (see Unimolecular rectifier)^[6][7] . This is one of many possible ways in which a molecular level diode / transistor might be synthesized by organic chemistry. A model system was proposed with a spiro carbon structure giving a molecular diode about half a nanometre across which could be connected by polythiophene molecular wires. Theoretical calculations showed the design to be sound in principle and there is still hope that such a system can be made to work.

Other approaches

Nanoionics studies the transport of ions rather than electrons in nanoscale systems.

Nanophotonics studies the behavior of light on the nanoscale, and has the goal of developing devices that take advantage of this behavior.

Nanoelectronic devices

Radios

Nanoradios have been developed structured around carbon nanotubes.^[8]

Computers

Simulation result for formation of inversion channel (electron density) and attainment of threshold voltage (IV) in a nanowire MOSFET. Note that the threshold voltage for this device lies around 0.45V.

Nanoelectronics holds the promise of making computer processors more powerful than are possible with conventional semiconductor fabrication techniques. A number of approaches are currently being researched, including new forms of nanolithography, as well as the use of nanomaterials such as nanowires or small molecules in place of traditional CMOS components. Field effect transistors have been made using both semiconducting carbon nanotubes^[9] and with heterostructured semiconductor nanowires.^[10]

Energy production

Research is ongoing to use nanowires and other nanostructured materials with the hope to create cheaper and more efficient solar cells than are possible with conventional planar silicon solar cells.^[11] It is believed that the invention of more efficient solar energy would have a great effect on satisfying global energy needs.

There is also research into energy production for devices that would operate in vivo, called bio-nano generators. A bio-nano generator is a nanoscale electrochemical device, like a fuel cell or galvanic cell, but drawing power from blood glucose in a living body, much the same as how the body generates energy from food. To achieve the effect, an enzyme is used that is capable of stripping glucose of its electrons, freeing them for use in electrical devices. The average person's body could, theoretically, generate 100 watts of electricity (about 2000 food calories per day) using a bio-nano generator.^[12] However, this estimate is only true if all food was converted to electricity, and the human body needs some energy consistently, so possible power generated is likely much lower. The electricity generated by such a device could power devices embedded in the body (such as pacemakers), or sugar-fed nanorobots. Much of the research done on bio-nano generators is still experimental, with Panasonic's Nanotechnology Research Laboratory among those at the forefront.

Medical diagnostics

There is great interest in constructing nanoelectronic devices^[13][14][15] that could detect the concentrations of biomolecules in real time for use as medical diagnostics,^[16] thus falling into the category of nanomedicine.^[17] A parallel line of research seeks to create nanoelectronic devices which could interact with single cells for use in basic biological research.^[18] These devices are called nanosensors. Such miniaturization on nanoelectronics towards in vivo proteomic sensing should enable new approaches for health monitoring, surveillance, and defense technology.^[19][20][21]

Further reading

Bennett, Herbert S.; Andres, Howard; Pellegrino, Joan; Kwok, Winnie; Fabricius, Norbert; Chapin, J. Thomas (March–April 2009). "Priorities for Standards and Measurements to Accelerate Innovations in Nano-Electrotechnologies: Analysis of the NIST-Energetics-IEC TC 113 Survey". Journal of Research of the National Institutes of Standards and Technology 114 (2): 99–135. http://nvl.nist.gov/pub/nistpubs/jres/114/2/V114.N02.A03.pdf. 

Despotuli, Alexander; Andreeva, Alexandra (August- October 2009). "A Short Review on Deep-Sub-Voltage Nanoelectronics and Related Technologies". International Journal of Nanoscience (World Scientific Publishing Co.) 8 (4-5): 389–402. Bibcode 2009IJN....08..389D. doi:10.1142/S0219581X09006328. http://www.worldscinet.com/ijn/08/preserved-docs/0804n05/S0219581X09006328.pdf. 

• Online course on Fundamentals of Electronics by Supriyo Datta (2008)

References

1. ^ "MEMS Overview". http://mems.sandia.gov/tech-info/mems-overview.html. Retrieved 2009-06-06. 
2. ^ Melosh, N.; Boukai, Abram; Diana, Frederic; Gerardot, Brian; Badolato, Antonio; Petroff, Pierre & Heath, James R. (2003). "Ultrahigh density nanowire lattices and circuits". Science 300 (5616): 112–5. Bibcode 2003Sci...300..112M. doi:10.1126/science.1081940. PMID 12637672. http://www.sciencemag.org/cgi/content/abstract/300/5616/112. 
3. ^ Das, S.; Gates, A.J.; Abdu, H.A.; Rose, G.S.; Picconatto, C.A. & Ellenbogen, J.C. (2007). "Designs for Ultra-Tiny, Special-Purpose Nanoelectronic Circuits". IEEE Trans. on Circuits and Systems I 54: 11. doi:10.1109/TCSI.2007.907864. http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4383238. 
4. ^ Goicoechea, J.; Zamarreñoa, C.R.; Matiasa, I.R. & Arregui, F.J. (2007). "Minimizing the photobleaching of self-assembled multilayers for sensor applications". Sensors and Actuators B: Chemical 126 (1): 41–47. doi:10.1016/j.snb.2006.10.037. 
5. ^ Petty, M.C.; Bryce, M.R. & Bloor, D. (1995). An Introduction to Molecular Electronics. London: Edward Arnold. ISBN 0195211561. 
6. ^ Aviram, A.; Ratner, M. A. (1974). "Molecular Rectifier". Chemical Physics Letters 29: 277. Bibcode 1974CPL....29..277A. doi:10.1016/0009-2614(74)85031-1. 
7. ^ Aviram, A. (1988). "Molecules for memory, logic, and amplification". Journal of the American Chemical Society 110 (17): 5687–5692. doi:10.1021/ja00225a017. 
8. ^ Jensen, K.; Jensen, K.; Weldon, J.; Garcia, H. & Zettl A. (2007). "Nanotube Radio". Nano Lett. 7 (11): 3508–3511. Bibcode 2007NanoL...7.3508J. doi:10.1021/nl0721113. PMID 17973438. http://pubs.acs.org/doi/abs/10.1021/nl0721113. 
9. ^ Postma, Henk W. Ch.; Teepen, Tijs; Yao, Zhen; Grifoni, Milena & Dekker, Cees (2001). "Carbon nanotube single-electron transistors at room temperature". Science 293 (5527): 76–79. Bibcode 2001Sci...293...76P. doi:10.1126/science.1061797. PMID 11441175. http://www.sciencemag.org/cgi/content/abstract/293/5527/76. 
10. ^ Xiang, Jie; Lu, Wei; Hu, Yongjie; Wu, Yue; Yan; Hao & Lieber, Charles M. (2006). "Ge/Si nanowire heterostructures as highperformance field-effect transistors". Nature 441 (7092): 489–493. Bibcode 2006Natur.441..489X. doi:10.1038/nature04796. PMID 16724062. 
11. ^ Tian, Bozhi; Zheng, Xiaolin; Kempa, Thomas J.; Fang, Ying;Yu, Nanfang; Yu, Guihua; Huang, Jinlin & Lieber, Charles M. (2007). "Coaxial silicon nanowires as solar cells and nanoelectronic power sources". Nature 449 (7164): 885–889. Bibcode 2007Natur.449..885T. doi:10.1038/nature06181. PMID 17943126. http://www.nature.com/nature/journal/v449/n7164/abs/nature06181.html. 
12. ^ "Power from blood could lead to 'human batteries'". Sydney Morning Herald. August 4, 2003. http://www.smh.com.au/articles/2003/08/03/1059849278131.html. Retrieved 2008-10-08. 
13. ^ LaVan, D.A.; McGuire, Terry & Langer, Robert (2003). "Small-scale systems for in vivo drug delivery". Nat Biotechnol. 21 (10): 1184–1191. doi:10.1038/nbt876. PMID 14520404. 
14. ^ Grace, D. (2008). "Special Feature: Emerging Technologies". Medical Product Manufacturing News. 12: 22–23. http://www.mpmn-digital.com/mpmn/200803/?pg=24. 
15. ^ Saito, S. (1997). "Carbon Nanotubes for Next-Generation Electronics Devices". Science 278 (5335): 77–78. doi:10.1126/science.278.5335.77. 
16. ^ Cavalcanti, A.; Shirinzadeh, B.; Freitas Jr, Robert A. & Hogg, Tad (2008). "Nanorobot architecture for medical target identification". Nanotechnology 19 (1): 015103(15pp). Bibcode 2008Nanot..19a5103C. doi:10.1088/0957-4484/19/01/015103. http://www.iop.org/EJ/abstract/0957-4484/19/1/015103. 
17. ^ Cheng, Mark Ming-Cheng; Cuda, Giovanni; Bunimovich, Yuri L; Gaspari, Marco; Heath, James R; Hill, Haley D; Mirkin,Chad A; Nijdam, A Jasper; Terracciano, Rosa; Thundat, Thomas & Ferrari, Mauro (2006). "Nanotechnologies for biomolecular detection and medical diagnostics". Current Opinion in Chemical Biology 10 (1): 11–19. doi:10.1016/j.cbpa.2006.01.006. PMID 16418011. 
18. ^ Patolsky, F.; Timko, B.P.; Yu, G.; Fang, Y.; Greytak, A.B.; Zheng, G. & Lieber, C.M. (2006). "Detection, stimulation, and inhibition of neuronal signals with high-density nanowire transistor arrays". Science 313 (5790): 1100–1104. Bibcode 2006Sci...313.1100P. doi:10.1126/science.1128640. PMID 16931757. 
19. ^ Frist, W.H. (2005). "Health care in the 21st century". N. Engl. J. Med. 352 (3): 267–272. doi:10.1056/NEJMsa045011. PMID 15659726. http://content.nejm.org/cgi/content/full/352/3/267. 
20. ^ Cavalcanti, A.; Shirinzadeh, B.; Zhang, M. & Kretly, L.C. (2008). "Nanorobot Hardware Architecture for Medical Defense". Sensors 8 (5): 2932–2958. doi:10.3390/s8052932. http://www.mdpi.org/sensors/papers/s8052932.pdf. 
21. ^ Couvreur, P. & Vauthier, C. (2006). "Nanotechnology: intelligent design to treat complex disease". Pharm. Res. 23 (7): 1417–1450. doi:10.1007/s11095-006-0284-8. PMID 16779701. 

External references

• Virtual Institute of Spin Electronics
• Site on electronics of Single Walled Carbon nanotube at nanoscale - nanoelectronics
• Site on Nano Electronics and Advanced VLSI Research
• Website of the nanoelectronics unit of the European Commission, DG INFSO
• Nanoelectronics at UnderstandingNano Web site
• Nanoelectronics - PhysOrg