Dependence of ZnO:Al properties on the substrate to target position in RF sputtering

• Published in: Thin solid films 2008-08, Vol.516 (20), p.7094-7097
• Main Authors: Couzinié-Devy, F., Barreau, N., Kessler, J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed Matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Energy; Exact sciences and technology; Materials Science; Methods of deposition of films and coatings; film growth and epitaxy; Natural energy; Photovoltaic conversion; Physics; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Thin films; ZnO
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2007.12.053

Al doped ZnO (ZnO:Al) is commonly used as front contact in Cu(In,Ga)Se 2 based thin film solar cells, and for this application is often deposited by RF magnetron sputtering from a ceramic target. In the present study, we use a configuration in which the substrates are immobile under the sputter target and we find the ZnO:Al film properties to depend strongly on the substrate position relative to the target erosion area (or “racetrack”). The zone immediately under the racetrack has higher resistivity correlated to a lesser crystallinity. The differences between these zones (inside the racetrack, under the racetrack, outside the racetrack) are studied as a function of the substrate: bare soda-lime glass (SLG), (CBD)CdS coated SLG, undoped ZnO coated SLG. It is shown that the evolution of the ZnO:Al films non homogeneity is substrate dependent. The impact on complete CIGSe/CdS/ZnO/ZnO:Al devices is measured and show that the influence of the substrates has to be taking in account; the device prediction made from models using the ZnO:Al properties measured on bare glass are inaccurate.