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Date: 08-04-14

Combination of graphene and silicon to drive the next wave in semiconductors

To jump off the wall, where the Silicon is hit by severe limitation in miniaturization using photolithography techniques, the semiconductor industry is pinning huge hope on new material Graphene, which holds the commercially and technically beneficial characteristics/properties.

The world's second biggest chip maker Samsung in partnership with Sungkyunkwan University, have developed a new synthesis method to speed the commercialization of graphene. This breakthrough is first such graphene synthesis in the world as claimed by Samsung.

The new method of growing large area, single crystal wafer scale graphene synthesizes large-area graphene into a single crystal on a semiconductor, maintaining its electric and mechanical properties. The new method repeatedly synthesizes single crystal graphene on the current semiconductor wafer scale.

Carbon material graphene can be built in atomic thickness (an atom or two atom thick graphene sheets can be prepared) but the challenge here is to make graphene work like electronic devices such as diode, transistor, MOSFET, and also wiring them as electronic circuits. There is some progress made recently in graphene based electronic devices & circuits.

To make devices out of graphene, the graphene material is deposited over another thin material, which can be insulator or even a semiconductor material such as SiC (Silicon Carbide). To form transistors scientists are trying out self-assembling-transistors made up of nanowires.

In the present Silicon MOSFETs, the gate is etched between drain and source. In case of graphene based transistors a solution of nanowires are poured over graphene & they are aligned to form transistor electronics by using different process than the present VLSI chip making technology.

But placing billions of nanowires over a space or few square centimeters is turning out to be very challenging, mainly ensuring reliability of the device. Another challenge is creating a graphene layer by using a process, which is suitable for volume manufacturing

Some of the recent achievements in building nanotech based electronics circuits based on graphene includes:

The researchers at UCLA were able to deposit nanowire on an atom scale graphene. The transistors built using graphene out perform silicon in frequency performance.
These graphene based transistor have the ability to operate in tera Hertz - frequency ranges.

The team at UCLA used dielectrophoresis assembly approach to precisely place nano-wire gate array on large area graphene layer created by chemical vapor deposition (CVD). The deposition has made on a glass substrate instead of semiconductor substrate. This helped the devices to operate at frequencies of 10GHz.
Due to the well-accepted thermal and & electron mobility properties of graphene, graphene is scientists favorite material.

Another set of researchers at IBM were able to build wafer-scale graphene IC smaller than pin head. The new IC consisting of graphene transistors and a pair of inductors are completely integrated on a silicon carbide (sic) wafer. IBM researchers claim they achieved this despite the poor adhesive quality of graphene with metals. To know more on this visit http://www-03.ibm.com/press/us/en/pressrelease/34726.wss

Material scientists at Rice University find a new way to control electronic properties of graphene alloy. Rice researchers were able to create intricate patterns of graphene that are separated by a similarly thin non conduct material made up of nitrogen and boron.

The carbon graphene is called black graphene & the graphene made of nitrogen & boron is called white graphene. Scientist Boris Yakobson and colleagues describe a discovery that could make it possible for nanoelectronic designers to use well-understood chemical procedures to precisely control the electronic properties of "alloys" that contain both white and black graphene.

The researcher claim they can precisely predict the electronic properties of the final product based solely upon the conditions - technically speaking, the so called 'chemical potential' during synthesis.

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