Nanoscale depth-resolved cathodoluminescence spectroscopy of ZnO surfaces and metal interfaces

The electronic properties of ZnO surfaces and interfaces has until recently been relatively unexplored. We have used a complement of ultrahigh vacuum scanning electron microscope (SEM)-based, depth-resolved cathodoluminescence spectroscopy (DRCLS), temperature-dependent charge transport, trap spectroscopy, and surface science techniques to probe the electronic and chemical properties of clean surfaces and interfaces on a nanometer scale. DRCLS reveals remarkable nanoscale correlations of native point defect distributions with surface and sub-surface defects calibrated with capacitance trap spectroscopies, atomic force microscopy, and Kelvin probe force microscopy. The measurement of these near-surface states associated with native point defects in the ZnO bulk and those induced by interface chemical bonding is a powerful extension of cathodoluminescence spectroscopy that provides a guide to understanding and controlling ZnO electronic contacts.