Illustration (IMAGE) Bielefeld University Caption When a control voltage is applied to graphene, the frequency conversion of the current can be controlled. Credit Image: Juniks, Dresden, CC-BY Usage Restrictions The image may only be used with appropriate caption or credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.