Electronics - Page 38

Researchers from Vanderbilt say they now understand for certain why graphene is so sensitive to its electrical environment. Solving this issue will allow to have better electron mobility in graphene at room-temperature, and come close to graphene's theoretical (but not practical) high electron mobility.

The problem is charged impurities on the surface of graphene. This was suspected before, but is now confirmed. Now the challenge will be to make graphene without those charged impurities.

Researchers from the Rensselaer Polytechnic Institute have discovered new graphene based materials that can be customized to produce specific band gap and magnetic properties (i.e. have tunable functionality in electronics). The materials may be used to enable new nanoelectronics, optics, and spintronics devices.

The researchers found out that graphitic nanoribbons can be segmented into several different surface structures called nanowiggles. Each of these structures produces highly different magnetic and conductive properties. This means that you can basically create a new graphene nanostructure that is customized for a specific task or device.

A research team from Chalmers University of Technology in Sweden developed a new subharmonic graphene FET mixer at microwave frequencies. This could pave the way for new opportunities in future electronics as it enables compact circuit technology, potential to reach high frequencies and integration with silicon technology.

A mixer combines two (or more) electronic signals into one or two composite output signals. The ability in graphene to switch between hole or electon carrier transport via the field effect requires a unique niche for graphene for rf ic applications. The researchers say this symmetrical electrical characteristic has enabled them to build a G-FET subharmonic resistive mixer using only one transistor.

IBM has managed to produce RF integrated circuits on an 8" graphene wafer. IBM says that this demonstration is a "major step in transitioning this promising material from a scientific curiosity into a real technology". The graphene was grown on copper foil from high-temperature vapor and later coated with the polymer PMMA.

These are RF devices - as it's still difficult to create logic using graphene (it has no natural bandgap), although some researchers are working towards methods to fix this issue.

Professor Kaustav Banerjee from the University of California, Santa Barbara (UCSB) has been named winner of the 2011 international research award by the Electrostatic Discharge Association (ESDA) - following his visionary proposal to investigate the electro-thermal behavior of graphene electronics. The award includes a cash prize of $10,000.

Intel reports that they have already carried out some high-current measurements on the graphene devices prepared by Professor Banerjee's team and were amazed at the current carrying capacity of a monolayer or bilayer of carbon atoms.

Researchers from Rice University and the Hong Kong Polytechnic University discovered that Graphene nanoribbons could stand tall on substrates and also form arcs. The contact between the graphene and substrate (which could be diamond and also nickel) is very light and so the graphene retains nearly all of its inherent electrical or magnetic properties. Using such a design can theoretically enable putting 100 trillion graphene-wall field-effect transistors (FETs) on a square-centimeter chip.

According to James Meindl (from the Georgia Institute of Technology) graphene will only become a viable alternative once CMOS semiconductor manufacturing will reach 7 nanometer - which will happen around 2024 (according to Moore's law).

Meindl believes that the most likely usages of graphene is switches - and he's working on 15 nanometer-wide ribbons that could rival silicon.

IBM researchers has fabricated a 2-GHz graphene frequency doubler RF circuit in a CMOS-compatible manufacturing process, on 8" wafers. To fabricate this the researchers inverted the usual manufacturing process and define gate structures first on silicon wafers and then transfer graphene layers fabricated using chemical vapor deposition to the silicon. After defining the areas of graphene IBM was able to attach source and drain contacts to the graphene to complete FET structures.

Inverted-T gate structure

The device itself, the frequency doubler, integrates multiple field effect transistors and radio frequency passives and demonstrated a conversion gain of approximately -25db (at 2 Ghz).

Researchers from Purdue University developed room temperature graphene inverters. They say that these new inverters could enable graphene transistors - which could be used in all sorts of digital applications.

The new inverters has a gain factor above one - an essential condition if you want to use these in transistors.

MIT announced the creation of the MIT/MTL Center for Graphene Devices and Systems (MIT-CG). This is an interdepartmental center which is part of the Microsystems Technology Laboratories (MTL) with an aim to bring together MIT researchers and industrial partners to advance the science and engineering of graphene-based technologies.

The MIT-CG will research the basic physical properties of graphene and will also explore advanced technologies and strategies that will lead to graphene-based materials, devices and systems for a variety of applications (including graphene-enabled systems for energy generation, smart fabrics and materials, radio-frequency communications, and sensing).