Graphene And Flexible Electronics

•        Graphene is a two dimensional form of carbon which is one atom thick layer of graphite.
•       It is around 100 times stronger than steel and has a conductivity which is much better than   copper.
•        High charge carrier mobility – 10,000 cm square/Vs.
•        It is the strongest and thinnest material known to exist.
•        Due to its electronic properties, it absorbs 2.3% of light that passes through it.
•       Signal flowing through the devices made of graphene can flow with speeds greater than the speed of light.
•        High thermal conductivity, chips with better dissipating heat can be made.
•      Antennas, transistors, batteries and touch screens become more efficient and flexible when created by using Graphene.
•      It has a modulation depth of 64% with GHz bandwidth whereas silicon has a modulation depth of 46%.

       

        Energy band diagram for Semiconductor and Graphene

1.       In semiconductors, an electron bound to an atom can break free only if it gets enough energy from photon passing to jump the 'band gap'.
2.      But in graphene the gap is infinitesimal.Thus graphene electrons can move easily and very fast.

Graphene photo-detector

The principle of photodetectors includes:

(1) carrier generation by absorption of an incident photon in a semiconducting layer,

(2) carrier transport and multiplication if available,

(3) extraction of the photo-generated carriers as a junction or device current.

Due to its zero band gap nature, graphene will absorb photons of all frequencies from visible to infrared range.

• Region I is the metal controlled region, II is the transition region, and III is the graphene only region. 
• In Region I the work function is defined by metal electrode; Region III is a graphene-only segment. Region II is a transition between graphene and metal. 
• The graphene-metal interface was found to show increased under the local light illumination. A difference between the metal work function and the Fermi level of graphene Δφ creates a small local electric field.
• Due to the high carrier mobility in graphene, such a detector offers enormous operation speeds lying beyond the limits of state of the art silicon photonics devices. By stacking a few layers one could increase light absorption in graphene.

Comparison between Graphene and Silicon

Applications

Graphene's mechanical properties is applicable in making a new generation of composite materials, and along combined with its optical properties making flexible displays.