Surface and Near Surface Area Density of States for Magnetron-Sputtered ZnO and Al-ZnO: A MIES, UPS, and VBXPS Study Investigating Ultrahigh Vacuum Sputter Cleaning and UV Oxygen Plasma

The impact of nonsolvent-based cleaning methods on zinc oxide and aluminum-doped zinc oxide was investigated across a range of doping concentrations up to 25% aluminum. A combination of electron spectroscopic techniques was utilized in order to characterize the electronic states present on the surface and to discern the differences between the near surface area and outermost layer valence band states. Understanding the differences between the near surface area and outermost layer of an interface is crucial when optimizing devices for charge transfer. The techniques were valence band X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and metastable-induced electron spectroscopy. The band gap was also measured via ultraviolet/visible spectroscopy.