Post by williamplayer on Apr 23, 2014 12:01:36 GMT
High Quality Graphene Wafers Fabricated Using Beetle Tech
Many beetles, like ladybugs, have the ability to stick to things as they walk underwater. They can do this by trapping tiny bubbles within hair-like structures on their feet. Researchers at the National University of Singapore have used a similar bubble trick to develop a way to make high quality graphene films. Their new technique is the first which can accomplish both the growth and transfer steps of graphene onto a silicon wafer.
The researchers are calling their process face-to-face transfer. It differs from the standard dry or wet methods which transfer films in a roll-to-roll fashion. Although stardard methods can grow sheets up to 30 inches in length, they also create many defects. These defects — cracks, folds, and wrinkles — are unavoidable when CVD-grown graphene is transferred from its underlying copper substrate. Ideally, one wants to grow the graphene right on top of a silicon chip, or whatever substrate will be the end product.
In the face-to-face method, the silicon dioxide top layer of a piece of silicon is first bombarded with a nitrogen plasma. This creates a silicon oxy-nitride surface that can trap bubbles that form later during the CVD (chemical vapor deposition) process. As the copper layer that was spun on before the CVD step is later etched away, the graphene is held in place by those bubbles that take up positions to form “capillary bridges,” like those on the setae (bristles or ridges) of some beetles and frogs.
After they fabricated long (up to 1 meter), thin ribbons of graphene, the researchers were able to take images of the process using atomic force microscopy. They also tested the electrical properties of their product using standard four-probe resistivity measurements. To do this they first had to metalize 50nm spots of nickel to act as electrodes. Conductivity was in the range of 4,000 S/cm (compare the conductivity of copper, a bit higher at 6,000 S/cm). Importantly, they were also able to demonstrate uninterrupted electrical continuity of ribbons with length-width ratios of up to 105.
Read Full Article: www.extremetech.com/extreme/172707-high-quality-graphene-chips-fabricated-using-beetle-tech
Read Nature Article: www.nature.com/nature/journal/v505/n7482/full/nature12763.html
Many beetles, like ladybugs, have the ability to stick to things as they walk underwater. They can do this by trapping tiny bubbles within hair-like structures on their feet. Researchers at the National University of Singapore have used a similar bubble trick to develop a way to make high quality graphene films. Their new technique is the first which can accomplish both the growth and transfer steps of graphene onto a silicon wafer.
The researchers are calling their process face-to-face transfer. It differs from the standard dry or wet methods which transfer films in a roll-to-roll fashion. Although stardard methods can grow sheets up to 30 inches in length, they also create many defects. These defects — cracks, folds, and wrinkles — are unavoidable when CVD-grown graphene is transferred from its underlying copper substrate. Ideally, one wants to grow the graphene right on top of a silicon chip, or whatever substrate will be the end product.
In the face-to-face method, the silicon dioxide top layer of a piece of silicon is first bombarded with a nitrogen plasma. This creates a silicon oxy-nitride surface that can trap bubbles that form later during the CVD (chemical vapor deposition) process. As the copper layer that was spun on before the CVD step is later etched away, the graphene is held in place by those bubbles that take up positions to form “capillary bridges,” like those on the setae (bristles or ridges) of some beetles and frogs.
After they fabricated long (up to 1 meter), thin ribbons of graphene, the researchers were able to take images of the process using atomic force microscopy. They also tested the electrical properties of their product using standard four-probe resistivity measurements. To do this they first had to metalize 50nm spots of nickel to act as electrodes. Conductivity was in the range of 4,000 S/cm (compare the conductivity of copper, a bit higher at 6,000 S/cm). Importantly, they were also able to demonstrate uninterrupted electrical continuity of ribbons with length-width ratios of up to 105.
Read Full Article: www.extremetech.com/extreme/172707-high-quality-graphene-chips-fabricated-using-beetle-tech
Read Nature Article: www.nature.com/nature/journal/v505/n7482/full/nature12763.html