Real-time spectroscopic ellipsometry and its application to the processing of yttrium barium copper oxide films by molecular beam epitaxy

The major issues which currently limit the use of YBCO in devices based on Josephson junction technology are related to the properties of the interfaces between YBCO and other materials. Specifically, oxygen deficiency at the interface severely degrades the properties of a junction. In this thesis, both ex situ and real-time spectroscopic ellipsometry (SE and RTSE) have been explored for use as tools to understand this effect.; Initially, the sensitivity of SE to the oxygen content in the near surface region of a YBCO film was studied. It was found that for atomically smooth c-axis oriented YBCO films, SE is sensitive to the oxygen concentration within one unit cell, even when the profile is graded. The sensitivity to small changes in the surface concentration of oxygen was also determined. This was done for both a- and c-axis oriented films that were exposed or buried under a normal metal layer.; SE was then used to determine the reference dielectric function data for five common YBCO substrate materials; {dollar}rm LaAlOsb3, NdGaOsb3, (LaAlOsb3)sb{lcub}0.3{rcub}{dollar}-(Sr{dollar}rmsb2AlTaOsb6)sb{lcub}0.7{rcub}, LaSrGaOsb4{dollar} and 9.5 mol% {dollar}rm Ysb2Osb3{dollar}-ZrO{dollar}sb2.{dollar} Also, data for one known reaction layer material, BaZrO{dollar}sb3,{dollar} was determined.; An RTSE was constructed for a molecular beam epitaxy (MBE) deposition system for observation of the processing of YBCO and one of its constituent oxides. The instrument was used to monitor the deposition of {dollar}rm Ysb2Osb3{dollar} on Si. The thickness derived from the RTSE measurement showed excellent agreement with the thickness determined by in situ flux measurements, as well as with Rutherford backscattering spectroscopy. From comparison of the cation incorporation vs. the arrival rate, a sticking coefficient of {dollar}approx{dollar}1.00 {dollar}pm{dollar} 0.07 was obtained for Y.; Finally, SE was used to study the diffusion of oxygen in YBCO. The activation energy {dollar}(Esb{lcub}a{rcub}){dollar} for the diffusion of oxygen in YBCO was found by heating an initially oxygen deficient film at various rates in a 10% O{dollar}sb3{dollar}/90% O{dollar}sb2{dollar} atmosphere and observing the temperature at which oxidation was completed. {dollar}Esb{lcub}a{rcub}{dollar} was between 0.43 and 0.52 eV. Last, the reactivity of ozone as compared to molecular oxygen was found to be at least 2000 times at 500{dollar}spcirc{dollar}C.