US, Chinese researchers transform graphene into semiconductor

WASHINGTON - US and Chinese researchers used a laser technique to transform graphene, a super thin material that is at least 100 times stronger than steel, into a semiconductor that may replace silicon on a computer chip in the future.

Graphene, the best known conductor of heat and electricity, would need to carry an electric current that switches on and off to express 0 and 1 that a computer uses for processing information.

Researchers from the Purdue University, the University of Michigan and the Huazhong University of Science and Technology used a technique called "laser shock imprinting" to permanently stress graphene into having a structure that allows the flow of switching electric current, according to the study published in the latest journal Advanced Material.

Electrons jump across this structure called "band gap" to become conductor, but graphene doesn't naturally have a band gap.

The researchers used a laser to create shock wave impulses that penetrated an underlying sheet of graphene. The laser shock stretches the graphene onto a permanent, trench-like mold.

Hence, they widened the band gap in graphene to a record 2.1 electronvolts. Previously, scientists achieved 0.5 electronvolts, barely reaching the benchmark to make graphene a semiconductor like silicon.

"This is the first time that an effort has achieved such high band gaps without affecting graphene itself, such as through chemical doping," said the paper's corresponding author Gary Cheng, professor of industrial engineering at Purdue University.

It is still far from making graphene into a semiconducting device, but the technique provided more possibilities in taking advantage of the material's optical, magnetic and thermal properties, according to Cheng.