The 'flicker noise' in graphene, which could potentially limit some of its applications, is down to some imperfections at the atomic level, a study has found. Graphene, which is essentially made of thin sheets of carbon, is a wonder material bursting upon the world of materials. It comes with some hard-to-believe properties: it's incredibly strong, allows heat and electricity to move freely through it, and is almost transparent.
The researchers found that a particular manufacturing method introduced some defects, which led to the flicker noise. The study was carried out by a team of Indo-Japanese researchers.
“Flicker noise is undesirable for most of the practical applications envisioned for graphene. For example, if graphene is to be used as an ultra-sensitive gas sensor which measures the tiny changes in graphene resistance on adsorption of gas molecules, Noise arising from random resistance fluctuations can pose severe limitations on the sensitivity of detection”, explained Anindita Sahoo, a member of the group which carried out the study.
“It can also impact other prospective graphene applications as transparent electrodes in solar cells, optoelectronic devices, interconnects in electronic devices and ultra-fast transistors for communication applications”, she added.
Extracted from graphite, a material from which pencil leads are made, graphene is the thinnest material possible: it's nothing but a one-atom-thick sheet of carbon atoms, with atoms arranged like a honeycomb. Quite naturally, scientists are busy finding ways to leverage these properties since graphene's first development in 2003.
Graphene or graphene-based materials have found themselves handy in sesnors, siren technology, security packaging, CPU cooling in computers, stronger and durable tennis rockets, and wheels for racing bicycles. However, producing industrial grade graphene in large scales remains a bit tricky.
Chemical Vapor Deposition (CVD) is one of the methods to produce high quality graphene at industrial scales. In CVD, Graphene is grown on the surface of metals like copper or nickel. It is essentially a chemical process happening at very high temperatures. Graphene can also be extracted from graphene oxide.
During the study, the team discovered that the flicker noise is because of undesirable changes in the arrangement of atoms in graphene. The team also studied the nature of defects introduced by both different graphene-manufacturing processes.
“By studying the nature of defects in these kinds of devices we can improve the device properties”, says Anindita. Clearly, understanding the basic physics is crucial to leverage the excellent properties of the wonder material, graphene.
Prof Arindam Ghosh.
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Vidya Kochat, Anindita Sahoo, Atindra Nath Pal, Sneha Eashwer, and Arindam Ghosh are at the Department of Physics, Indian Institute of Science. Gopalakrishnan Ramalingam, Arjun Sampathkumar, and Srinivasan Raghavan are at the Materials Research Centre, Indian Institute of Science. Ryugu Tero, Tran Viet Thu, Sanjeev Kaushal, Hiroshi Okada, and Adarsh Sandhu are associated with the Toyohashi University of Technology, Toyohashi, Japan,