Industrial Applications of Ultrafast Lasers II: Illustrative Examples

As a follow-up to Seminar I, I will discuss specific examples of fs UPS and photovoltage experiments on industrially relevant materials and stacks. Aside from single crystal Si wafers, virtually all materials found in MOS devices, photovoltaics, oxides, organic films (OLEDs, resists) and phase change materials, are polycrystalline or amorphous. Angle integrated UPS provides high count rates that increase sensitivity useful for identifying defect state densities in materials. Specific examples described in this seminar include the Pt/HfO2 /Si MOS stack, the thin film earth abundant photovoltaic Cu2 ZnSn(S,Se)4 -CZTS,Se and its interfaces with solution deposited CdS and high work function back contact MoO3 , the Al2 O3 tunnel barrier deposited on Al and Si, and the phase change material TiN/GeSbTe. In each of these cases, extracting the band bending in the underlying semiconductor provided fundamental information on device performance. An example of spectroscopy on the organic LED (OLED) AlQ3 will be given.