Nano electronic and photonic devices

MN are currently working on a number of areas in nanoelectronics:

 

QWIPs

Novel electronic nanodevices

Recently, new effects on the nanometre scale, such as electron wave behaviour and ballistic electron transport, have allowed us to design semiconductor devices that are based on completely new working principles. For instance, whereas only semiconductor physicists can explain the working principle of a conventional diode, a layman can understand how two of our "nano-diodes", ballistic rectifier and self-switching diode, operate. These devices are planar, meaning that the electrodes are placed side by side rather than placed in parallel on different layers like in a traditional transistor. The simplicity enables a dramatic reduction of parasitic capacitance and hence a very high operation speed. Such devices have been the subject of a University spin-out company for commercialisation www.nanoeprint.com. They have recently been demonstrated to operate at frequencies up to 2.5 THz (2,500 GHz), which is the highest speed in electronic nanodevices to date. Possible applications include very high speed computation, security or medical imaging, and future wide-bandwidth communications.

Nanolithography

Nanolithography

Atomic force microscope (AFM) is now a standard imaging tool in laboratories but has displayed limited capability of nanolithography. We discover that an internal tensile strain exists in a conducting polymer film, and the physical effect is utilized to achieve highly tunable and high-throughput nanolithography. Trenches with widths spanning nearly two orders of magnitude from 40 nm to 2.3 micron are easily fabricated. The approach is also excellent for pattern transfer to inorganic semiconductors, such as GaAs and silicon. Furthermore, a lithography speed of 0.5 mm/ s is achieved, which is a few orders of magnitude higher than other known methods of AFM-based nanolithography. A number of novel electronic nanodevices and even molecular electronics can be realised.

 

Flexible transistors

Three scientists had been awarded the Nobel Prize in Chemistry in year 2000 for their development of the electrically conductive polymers. Since plastics have been manufactured at very low cost, flexible, and over large area, it is obvious that plastic semiconductors will have extremely attractive advantages over traditional rigid and expensive semiconductors, such as silicon and GaAs. It has been envisaged that applications of plastic electronics will lead to major revolutions in our daily life. For instance, one can imagine (and actually can expect, too,) electronic newspapers that can be updated at train station, TV screens as part of wall paper, and intelligent post stamps, etc. Since the development of the first conducting polymer, research in this field has grow dramatically, leading to better control of the synthesis and development of new materials with a wide range of properties suitable for different types of applications. In fact, the progresses in organic nano-electronics in the research group have led to recent formation of a spin-out company, www.nanoeprint.com. Typical organic transistors are very slow, operating at 100 KHz or below, because the much slower charge carrier transport speed in organic semiconductors as compared with silicon. We have significantly enhanced the speed by optimising the device architecture, including using nanotechnology. In our recent experiments, 20 MHz speed has already been realised, making it promising for real applications.  

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