Al2O3 Interfacial Layer Research Articles

X-ray photoelectron spectroscopy study of Al/Ta2O5 and Ta2O5/Al buried interfaces

Buried interfaces of thin Al/Ta2O5 and Ta2O5/Al films were studied using the x-ray photoelectron spectroscopy technique. The peak decomposition technique was employed to identify the composition and chemical states at the interface region. It was observed that there is an “intermixing layer” at the Al/Ta2O5 interface, where Ta2O5 has been reduced to lower binding energy states due to the reaction of Al with Ta2O5 during deposition. On the other hand, the Ta2O5/Al interface is relatively stable, consisting of Ta2O5 and Al2O3 interfacial layers. Based on a uniform multilayer structure model, the thickness of the interfacial layers was estimated by using the relative photoelectron intensities.

Physical structure of Al-pSi metal-insulator semiconductor solar cells

Investigations have been made of Al-pSi metal-insulator semiconductor (MIS) cells fabricated by depositing Al films onto silicon substrates with thermally grown SiO2 surface films on the order of 18 Å thick. These studies have involved depth concentration profiling and ellipsometric measurements to understand the physical structure, electrical and optical characterization of aluminum films, and efforts to optimize an Al-Si cell with a SiO antireflection (AR) coating. Depth concentration profiles show that the correct physical model is not Al/SiO2/Si, but Al/Al2O3(Si)/Si with the Al2O3 interfacial layer being 15 Å thick. The Al film reduces the SiO2 to yield Al2O3+Si for an interfacial film. Investigations to optimize the Al-Si cell structure involved using optical constants measured for Al films to determine AR layer thicknesses, which maximize cell photocurrent for each Al film thickness. Analytical studies were also conducted concerning sheet resistance effects to determine the required grid design to maximize the fill factor. These analytical and experimental studies are used to project an ultimate, practical AM1 efficiency of 11–12% for Al-pSi MIS cells based on a continuous metal front layer and a silicon resistivity of 2–5 Ω cm.