Analysis and Characterization of Thin Films: A Tutorial

The characterization of thin films used in photovoltaic applications is discussed in terms of the strengths and limitations of selected compositional, electrical, structural and chemical analysis techniques. The purpose is to provide a fundamental understanding of the methods to enhance the interpretation of results. The emphasis is the principles of surface analytical techniques, including scanning Auger electron spectroscopy, X-ray photoelectron spectroscopy and secondary ion mass spectrometry (SIMS). The information these methods convey, the ranges, resolutions and accuracies involved and the limitations are discussed specifically for thin film photovoltaic measurement applications. Problems associated with technique-generated artifacts, data misinterpretation, damage, experimental conditions, materials constraints, and surfaces are evaluated, with relevant examples provided from current technologies. Discussions cover electron and ion beam effects on analyses, depth-profiling, quantification, and elemental and chemical mapping. Finally, recent and evolving characterization techniques will be introduced. These include volume-indexed chemical mapping techniques for the unambiguous spatial resolution of impurities at device interfaces, and scanning tunneling microscopy, which provides real-time, atomic-level and spectroscopic imaging of processes at surfaces and interfaces in electronic materials and devices.