The era of electronics started much before it got its name as electronics. Earlier it was called Radio engineering. The “electronics” word came into vogue in late 1940 and became very prominent by late 1950’s.The electronics industry was revolutionised by the invention of first transistor in 1948 and silicon based semiconductor.
Now, it is more than seven decade that we are living with electronics hand in hand. Our reliance and dependency on this is increasing day by day and we have come to an era where without electronics we cannot survive.
For decades and decades together Silicon remained the only option for electronics.
And we have seen the performance of silicon based device in terms of speed, power consumption, size and cost has improved multi-fold. But recent development in material engineering has paved new ways to electronics. Nano technology is leading to a new space of miniaturization as well as cost competitiveness. These developments of material science can be marked as:
- 2-D electronics
- Organic Electronics
- Memristors
- Spintronics
- Molecular Electronics
2-D Electronics
In the year 2010, Nobel Prize for Physics has been awarded to Andre Geim and Konstantin Novoselov for the experiments carried out on Graphene.
Graphene is a structural variant of Carbon. Carbon atoms in Graphene forms a hexagonal two dimensional structure (Lattice) which is as thick as atomic layer and has a high electrical conductivity, hight thermal conductivity, high mechanical flexibility and probably highest mechanical strength ( Strongest material tested ever).Graphene is the beginning where concept of 2D electronics has started.
A two dimensional electronics or a two dimensional semiconductor is a type of semiconductor whose thickness is on atomic scale. Meaning there by in this semiconductor as the name signify, will have only two dimension length and breadth, third dimension of thickness will be almost missing ( to a scale of atomic width) and this semiconductor will be able to conduct more electricity and heat, will consume less power and exhibit more mechanical strength & stability.2D materials are incredibly thin and light weight and are stable at size below 10 nm ( 1 nm= 10-9 meter), the point at which traditional semiconductor material have the characteristic of failure means starts failing. Graphene is also highly transparent to the incident light and it absorbs only 2% of incident light upon it.
The Graphene poses some technical challenges while being used in digital electronics (because at atomic level it has lack of Band Gap).Going forward into the domain of material science, nano layers of materials of same group e.g. Si, Ge and Sn, exhibit similar properties of Graphene and has no lacking while being used in digital electronics. Meaning there by 2D electronics which got its origin in Graphene has moved into other materials viz. Silicine, Germanene, Phosphorene e.t.c. These materials have other additional properties like excellent magnetic properties, tuneable band gap, active optical properties and so on.
2D material viz Silicine, Germanene, Phosphorene and so on, have tremendous potential in the field of Optoelectronics such as Light Emitting Diodes (LED), Optical Signal Processor and solar Photo Voltaic panels. Owing to their light weight and flexibility they are suitable for flexible design of wearables and other flexible application.
2D materials can be used to produce a transistor equivalent to the size of molecule. Size and stability of these paves the way being used in computing.
Most promising application of 2D electronics is in Solar Energy industry, where any surface like paper, walls, window, glass of consumer durables and so on can be converted into solar cells.
2D electronics has its uses in supercapacitors, fuel cells and many more
Organic Electronics
In the year 2000, Nobel Prize in the chemistry was given (to Alan Heeger, Alan Macdiarmid and Shirakawa) for the development of “Conductive Polymers”. In common parlance they proved that plastic can conduct electricity. And this is the origin of “Organic Electronics”. Organic electronics materials are made out of organic molecules ( carbon based materials) or polymers by chemical synthesis. Organic Electronics materials also includes variety of dyes and many other organic molecules.
Organic materials are yet to compete in performance if compared with conventional inorganic conductors and semiconductors, but it comes with several advantage over the conventional one. It has very low material as well as production cost, has adaptivity of synthesis, is bio-compatible and mechanically flexible.
We already are familiar with our smart phone and TV with OLED i.e. Organic LED. But, the potential for future application stretch far beyond the visual effect owing to LED. Organic material has the possibility that we will be able to fold our smartphone or any other portable device like a paper. Health care system will see a new height with possibility that organic material has, where this can interact with our biological cell and sensory organs.
Health care system can respond to signal at cellular level in our body with the capability added by organic electronics. Owing to this possibility our artificial organs or limbs can be brought very near to natural one in terms of feeling and reaction. Artificial skin close to natural skin are not very far-off.
The organic electronics unleashes the possibility where solar cells will be printed over plastic sheets and can be folded like a map ready to install anywhere.
As the organic electronics material will be synthesised in the lab and will be bio de-gradable, hence it will have better sustainability cycle when compared to conventional one which has a dependency on mined material from the earth.
Memristors
Memristors word has been coined with two words, memory and resistors. Meaning there by, it is going to be a resistor with memory effect.
In theory, memristors was predicted as far as in 1971 (by Leon Chua) and was explained through some mathematical equation. The predication says that we are missing an electronics component like memristors. But any such device was physically produced in 2008 by Stanley Williams.
Memristors have properties that its resistance can be programmed and at the same time device will memorise its value.
Recent development in memristors has achieved very reliable stuff where it can be cycled more than 100 billions and can remain be stable more than 10 years.
We are very much familiar with RAM ( Random Access Memory) and Flash memory (e.g. Pen drives). In RAM, memory mobility is very high but the disadvantage is that it does not retain the data in power off mode. Flash drives retains the data in power-off condition but memory mobility is very slow. Memristors on the other hand combines the capability of both where it has very high mobility and also retains the data even in the power-off mode.
Memristors when compared with conventional solid state device requires less energy as well as has a faster speed of operation. At the same time memristors can accommodate double the data in same physical size of device compared to conventional semiconductor.
Not only that, our conventional semiconductors when exposed to radiation either loses the data or data is distorted, whereas memristors are immune to the such radiation.
In our conventional computing system, data is stored in a location(memory) and processed in other location (processor).The data traffic between these two location firstly redueces the speed of computation and at the same time consumes huge amount of energy. Memristors store and process the information in the same location. Due to this fact the challenge of speed as well as power consumption are taken care. Hence, the use of memristors in our conventional computing is paving a new way.
The property of memristors where it stores and process the information at the same location is similar to human brains building block “Neurons”. With this capability, there is a paradigm shift in computing called “Neuromorphic Computing”, which will mimic our internal neuron structure and energy efficient processing like our brain. This will lead to putting a brain to chip i.e. embedded artificial intelligence in the hardware, giving away to run the same on a separate software platform.
In the context of Artificial Intelligence(AI), “Neuromorphic Computing”, by memristors, will lead to new generation of chips which will be able to do the self-learning and interpretate the environment around it, without the help of coded software. Currently the Artificial Intelligence runs on cloud. With this Neuromorphic Computing, AI which is running in central servers on cloud will shift to chip i.e. Edge Computing.
In practical terms, an autonomous car require network connectivity (4G/5G) through which it sends the data collected through its sensors to its central server on the cloud for analysis. Central server does the data analysis and send the execution command back to the car. In this process latency is created and it is also very power consuming to handle such a huge data. With the advent of memristors, all computation can be done locally inside the brain of the car. This will take the AI to a different level.
Neuromorphic Computing will establish a new level in AI in Edge Computing, Robotics, IOT (Internet of Things),Machine Vision, Artificial Skin, sensory Organs and so on.
Spintronics
Spintronics is a word coined from Spin and Electronics.
The invention of this can be traced back to early 1988 , when a Giant Magnetoresistive Effect was discovered by Albert Fert in France and Peter Gruenberg in Germany.
Our Conventional electronics harness the property of charge on the electrons, whereas Spintronics harnesses the property of spinning of the electron.
Conventional electronics and semiconductor defines the state of a devive by zero and one state. For example, a capacitor is called on “one” state when it is fully charged and in “zero” state when fully discharged. This is way our data is stored on “0” and “1” format in our memory devices with the help of billions of capacitors.
Apart from the charge on the electron, every electron spins on its axis in two different direction i.e. “clock wise” and “counter-clockwise”. This motion is inherent to electrons and can be altered from one to another with some application. This spinning of electrons generates magnetic moment and can be altered with the application of external magnetic field.
Spintronics, uses this property of electrons where clock-wise rotating electrons are called in “0” state and counter-clockwise in “1” state.
In conventional way, charging and discharging of a capacitors is power consuming and in order to maintain the state of a capacitors in “1” state, it has be charged several times in a second, whereas spin of an electron is inherent and it does not require any power for maintain the same. The advantage of this is that it is non-volatile, means memory does not go-off when the power is shutdown compared to conventional charge based electronics.
Spintronics is the driving technology for next generation nano technology. It will enhance the memory capability and processing speed while reducing the power consumption.
Quantum-mechanical computing based on spintronics can achieve a speed unheard of with conventional electrical computing.
Spinning of electrons , which is the fundamental of spintronics, can be manged in several ways. Few of these examples are:
- By applying magnetic field.
- Stray electric and magnetic field.
- Electromagnetic wave e.g. circularly polarised light.
- A thermal gradient.
While, spintronics is a magnetic phenomenon of electrons, Ferro magnetic material started as a core to this and different devices like Giant-Magneto-Resistence, Tunneling-Magneto- Resistence, Magnetic-Tunnel-Junction are built around it.
Despite, paced advancement in ferrous material, semiconductor spintronics is also the part of focus to find a way to generate and controls of the spins of the electrons. The selection of material for semiconductor spintronics depends on the property of material exhibiting ferromagnetism at room temperature e.g. GaAs ( Gallium Arsenide) and InAs (Indium Arsenide).Spinning of electron can be easily controlled and managed in semiconductor and such devices can be easily integrated with present semiconductor architecture and technology. Based upon spintronics we have devices like spin-transitors, spin-LEDs, optical switches, memory devices and so on.
Because of unique science behind this technology , the operation of spintronics sensors and devices are more precise, reliable and repeatable. Compared to electromechanical sensors, spintronics sensors are immune to mechanical shock, vibration and temperature. Due to these very precise property , sensors are being used in Class I medical device hearing aids providing miniaturization ,stability and ease of operation with better sensitivity. Spintronics devices and sensors are also used in Class III devices like pacemaker and implants, where all the above property is key for its uses.
Spintronics devices are used to detect disease in human boady like cancers.The property, that the affected organ has different magnetic property then the normal one is being harnessed in this detection. And this uses is being used an a major game changer in the medical field. Electron transport in DNA is another field of great importance and research that is being carried out.
Spintronics devices are used in mass storage. The storage density i.e. amount of data stored in a physical area of a chip is much higher than conventional one for example it can store more that one trillion bits per square inch.
Another game changer of the future may be the spin based quantum computation in nano technology. Where the neuromorphic computing and Quantum Computing will take the front seat.
Molecular Electronics
The ultimate goal of electronics is miniaturization .Molecular electronics is that branch of electronics or for that matter research, where single molecule or bunch of molecule is treated as electronics building blocks. Whereas our conventional electronics are made out of bulk of materials. In single molecule electronics i.e. Molecular electronics, this bulk material is replaced with single molecule.
Molecular Electronics as a potential technology is basically a bottom-up approach where the smallest building unit, molecule , is being assembled to perform electronic operation whereas top-down approach is working to shrink macroscopic components and systems.
Origin of Molecular Electronics can be traced back to 1974 when Mark Ratner and Arieh Aviram published the study of electron transport through single molecule. Theire suggestion for an ad hoc calculation and a proposal that single molecule can be used as device has led to this branch of electronics.
Electron movement by a single molecule is at the centre of molecular electronics. This concept of electron movement through single molecule is described in two different ways.
The one way is movement of electron through single molecule described as electron transfer where as the other one is movement of current passing through single molecule.
In Molecular Electronics, the ultimate goal of miniaturization is achieved and due to this power consumption for its operation reduces drastically where as it sensitivity increases exponentially. Another major advantage of this molecular electronics is that some of the molecular system has tendency to self-assemble to a bigger functional block. In this phenomenon ,components of a system come together spontaneously due to some environmental factor to form a large functional unit.
The dimensionally small molecular circuit or electronic component has wide range and variety of electrical, mechanical, optical and thermal properties ,where each of these properties in singular as well as in combined state gives rise to countless new physical phenomenon.
Molecular Electronics , in principle offers following advantages over the conventional electronics:
- The reduced size of each building block i.e. molecule, will offer higher packing density of devices. This will subsequently reduce the cost & power and improve the efficiency & effectiveness.
- Molecular wire could reduce the transit time of a transistor , there by reduing the time of operation.
- Molecular Self-assembly can be used to modify the electronic behaviour of an electronics component providing both switching and sensing capability on a single molecular scale.
- Special properties of a molecule e.g. stable geometric structure could lead to new dimension in electronics which is otherwise not possible in conventional one.
- By intelligent choice of composition and geometry one can create variation in molecular transport, binding, optical and structural property.
On the other hand, molecules have obvious disadvantage of being unstable at high temperature. Moreover, fabrication of reliable molecular junction requires control of unprecedented level. Achieving the same not only difficult but slow and costly also.
Several molecular electronic solution have been developed e.g. molecular wire, single molecule transistor, rectifiers and so on. However, molecular electronics is still in infant stage of research and these devices are yet to come out of laboratory bed.
