About Us

Established in 1933 by the Nobel Laureate C.V. Raman, the Department of Physics soon evolved into the leading centre in the country for advanced postgraduate education and cutting-edge research in physics. The largest number of Ph.D.s in physics in India -- 110 since 1998 -- come from this department. Graduates from the department have gone on to distinguished careers in science and occupy leading positions in research institutes in India and the world over. ...more

Research Highlights

Novel Route to Achieve Hierarchical Ordering of Colloidal Crystals

Colours are one of the most striking ways in which Nature showcases her beauty. Be it the vividly-patterned wings of the butterfly, the elegant feathers of the peacock or the myriad-coloured birds--they all enthral, mesmerize and charm each of us alike--from a child to an adult, a layman to a scientist, a writer to a poet.

However, unlike the colours due to dyes and pigments, most of the colours observed in living organisms are primarily due to underlying periodic structures. Nature remarkably self-assembles these structures from individual building blocks that could be as small as a millionth of a millimetre. Apart from their aesthetic appeal, realization of these structural colours has tremendous applications in our everyday life. Structural colours can have a significant impact on modern electronic gadgets such as smartphones and laptops. The display panel of the devices based on structural colours will use the ambient light itself to power themselves, which in turn can also solve the problems of poor visibility of screens in excess glare.

Over the last decades, scientists across the world are striving hard to realize structural colours in laboratory that can mimic the beautiful colours seen in nature. However, the major impediments in realizing them have been the low mobility of the building blocks, namely colloids and nanoparticles, on surfaces. Owing to their large size, these particles do not diffuse significant distances on the surfaces before meeting another one of their kind, so that they would grow further on. For any useful application, tuning of this separation between the growing centres is very crucial.

In a major breakthrough, scientists at the city's Jawaharlal Nehru Centre for Advanced Scientific Research and Indian Institute of Science have developed a new strategy wherein they can precisely control the spacing between these growing centres. They have taken recourse to soft-lithography to engineer surfaces with inhomogeneous yet periodic structures. With great ingenuity, they have been able to introduce attraction between the building blocks and the engineered surfaces that locomote the building blocks to the desired sites before the ensuing growth could begin. This technique gives a facile control over the growing structures and that too with much-needed simplicity in the growth techniques. These findings that will shortly appear in prestigious scientific journal "Proceedings of National Academy of Sciences, U.S.A. (2016)รข" aree expected to have a crucial impact on the photonics industry.

Chandan K. Mishra, A. K. Sood and Rajesh Ganapathy, Site-Specific Colloidal Crystal Nucleation by Template-enhanced Particle Transport, Proceedings of National Academy of Sciences (PNAS), U.S.A. vol 113 (43), 12094 (2016)"

http://www.thehindu.com/sci-tech/science/Bengaluru-researchers-mimic-nature-to-produce-richer-colour/article16896281.ece [www.thehindu.com]

Noisy contacts in graphene

Prof. Arindam Ghosh:

Researchers have shown that significant electrical noise is generated at the interface of metals and graphene, a single layer of carbon atoms. This may have major implications on the applicability of graphene in future electronic devices.
All miniature electronic devices like the transistors and the diodes are ultimately interfaced with a metal to form contacts. However, the contact region is usually disordered and can form a barrier for current flow, severely limiting the device performance. Contacts may also generate electrical noise, which is random fluctuation in the electrical resistance with time. Electrical noise is generally caused by impurities within or close to the material, and can make a device unreliable and unsuitable for high performance applications.
The effects of contacts in conventional devices have been well studied. However, until now it has not been very clear what is the dominant source of electrical noise in graphene devices, the contacts or graphene itself. Writing in Nature Communications P. Karnatak et. al. have shown that contacts not only present a large resistance to current flow but also add a significant amount of electrical noise in graphene transistors.
Contacts affect graphene more severely compared to conventional semiconductors, due to its single atomic thickness. Here, the metal atoms chemically modify graphene and leave it vulnerable to potential fluctuations nearby causing large noise. This research led by Prof. Arindam Ghosh, also shows that as the electrical quality of graphene improves, the relative effect of the contacts becomes stronger, presenting a challenge in creating high quality devices.
Currently, there is a great deal of research interest in materials that are made up of just one or few atomic layers. These materials are expected to allow further miniaturization of our electronic devices. A good understanding of the origin of noise and eventually minimizing it will be the key to designing future electronics from these ultimately thin materials.

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