REAL-TIME SPECTROELLIPSOMETRY STUDY OF THE INTERACTION OF HYDROGEN WITH ZNO DURING ZNO A-SI1-XCXH INTERFACE FORMATION

Using real time spectroellipsometry (SE), we have studied the interfac ial interactions that occur when i- and p-type hydrogenated amorphous silicon-carbon alloys (a-Si1-xCx:H) are deposited from hydride-contain ing plasmas onto transparent, conducting films of ZnO. The SE spectra collected during the nucleation of a-Si1-xCx:H onto ZnO reveal a widen ing of the near-interface optical gap of ZnO by approximately 0.1 eV, an effect attributed to the penetration of atomic H from the plasma. T he SE data, along with ex situ secondary ion mass spectrometry, reveal that the H diffuses into ZnO to depths >200 angstrom. The defects tha t result from H incorporation in ZnO (e.g., O vacancies) lead to a shi ft in the near-interface Fermi level higher into the ZnO conduction ba nd and to an estimated enhancement in the electron concentration by ap proximately 10(20) CM-3.