| Popis: |
The potential for submillimeter-wave laser relative reflectivity measurements with an accuracy of better than 10 -4 (corresponding to a potential for relative measurements of surface resistivity with an accuracy better than 10 -2 Ohms per square) has been investigated. An experimental arrangement to minimize the effects of changes in laser output and detector drift to levels, necessary to obtain this accuracy has been demonstrated. This was accomplished by simultaneous measurement with a reference detector to reduce short-term fluctuations and rapid sampling to account for longer term drift. Systematic error due to reproducibility of alignment with sample changes limited the present preliminary results to an overall accuracy of approximately 10 -2 This achieved level of accuracy is sufficient for measurements of present state-of-the-art thin film high T c superconductors at 77 K, an example of which is presented here. |
