| Citation | Distinguished for his outstanding contributions to electron microscopy of materials. In his early work he developed theories of inelastic scattering and absorption of electrons passing through materials, of channelling patterns, and of SEM image contrast. He used electron diffraction scattering factors from critical voltage experiments to obtain bonding charge density maps for several elemental structures, and electron energy loss spectroscopy to demonstrate covalent bonding in transition metal aluminides. In GeSi/Si heterostructures, he discovered a novel source of misfit dislocations. Since 2000 he has carried out extensive studies of InGaN quantum wells used in LEDs which are remarkable for emitting bright light in spite of high dislocation densities. Combining electron microscopy and uniquely 3-D atom probe studies (with Cerezo), he showed that indium is distributed randomly (not clustered as previously thought), and that steps observed at interfaces provide a mechanism for carrier trapping. This work represents a significant advance in understanding the properties of these important energy saving devices. Humphreys is recognised as a world leader in this field. His InGaN work has attracted much industrial interest, resulting in several collaborations with industry aimed at developing the technology. Humphreys has also done outstanding work in promoting science, particularly in schools. |