Optical image of a TDBG sample (IMAGE) ICFO-The Institute of Photonic Sciences Caption Optical image of a TDBG sample made into a Hall bar shape for precise measurement of electrical resistivity and photoconductivity. Credit ICFO Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. License CC BY-NC 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.