Some materials exhibit deterioration in photoconductivity upon exposure to illumination. One prominent example is hydrogenated amorphous silicon (a-Si:H) in which a metastable reduction in photoconductivity is observable (see Staebler–Wronski effect). Other materials that were reported to exhibit negative photoconductivity include ZnO nanowires, molybdenum disulfide, graphene, indium arsenide nanowires, decorated carbon nanotubes, and metal nanoparticles.