Fig. 2: Evidence of bulk photoresponse.
a, b SEM images and measured photovoltage of three devices with different degrees of asymmetry. When the lengths of horizontal arms (Lh) decrease from device C to A, the photoresponse decreases and vanishes eventually due to the absence of broken symmetry. c, d SEM images and measured photovoltage of five devices with different numbers of nanoantennas, where the nanoantennas closest to the contact electrodes are removed gradually from Device D′ to A′. Device E′ has the same number of nanoantennas as device D′, but the orientation of nanoantennas is reversed. The photovoltages is only dependent on the number of nanoantennas but insensitive to their position. The non-zero photoresponse of device A′ could be due to non-uniform illumination, fabrication imperfections or nonlocal photoresponse from neighboring devices. Error bars are smaller than the size of markers. Dashed lines are guides to the eye.
