High precision prediction of thin film composition by LIBS

The measurement of average composition or spatial elemental distribution in thin films of a few micrometer thickness is important for product evaluation or process monitoring in thin film product industry. This work reports that the average composition of thin solar cell films (~ 2 mm) could be predicted with high precision (<; 1% relative standard deviation) by laser induced breakdown spectroscopy (LIBS). The depthwise distribution of constituent elements could also be measured with a spatial resolution below 100 nm as was confirmed with secondary ion mass spectrometry. It is discussed that the high precision of LIBS with its intrinsic rapid, no sample preparation, in-air measurement capability provides a powerful technique for composition monitoring at manufacturing sites.