Growth and Raman spectroscopy of ultrathin ZnO(0001) films on Ag(001)

The growth and vibrational properties of ultrathin ZnO(0001) films on Ag(001) were investigated by X-ray and ultraviolet photoemission spectroscopy (XPS/UPS), low-energy electron diffraction (LEED), and Raman spectroscopy. Our results indicate the formation of well-defined stoichiometry and crystalline phase similar to 5 ML thick ZnO (0001) films characterized by two domains rotated by 30 degrees. Further film analysis using Raman spectroscopy showed that the ultrathin films display substantial intensity enhancement of their Raman combination modes. Our findings suggest a significant role of the finite-size film electronic and structural properties on its vibrational properties. These observations may serve as a pathway toward further investigations dependent on film thickness and orientation. More important, the modification of the vibrational properties is expected to be relevant to understanding general phenomena in ZnO nanostructures (i.e. thin films, nanoparticles, nanorods).

Automated summary

The research discovered that ultrathin ZnO films on Ag substrates exhibit well-defined stoichiometry and crystal phases, with Raman spectroscopy showing a substantial enhancement of Raman combination modes. The electronic and structural properties of finite-size films play a significant role in their vibrational properties, providing clues for understanding ZnO nanostructures.