Critical investigation on Cu-O bonding configuration variation in copper-oxide thin films for low-cost solar cell applications

The present work provides a detailed investigation on how Copper-Oxygen bonding configuration varies with the plasma processing parameters. XRD, FTIR, XPS and Raman spectroscopy is extensively used to identify and study the phases and phase changes in the films. The Copper-Oxygen bonding configuration was altered by varying the RF power and substrate temperature. We studied the combined effect of both RF power and substrate temperature on the Cu-O bonding configuration, which in turn affects the optical and electrical properties, which are essential to understand before the device fabrication. Films were deposited with 40, 60 and 80 W of RF power at the different growth temperatures such as RT(room temperature), 200 °C and 400 °C. Even the RT deposited films were found to be exhibiting the crystalline nature to the maximum extent. We observed a wide range of variation in the Cu-O bonding configurations with the RF power and growth temperature. Films deposited at 80 W are leaning towards Cu 2 O phase, whereas films deposited with 40 W is close to CuO phase. Also it is found that, for a fixed power, the films deposited at high substrate temperature are leaning towards Cu 2 O Phase. © 2019 Elsevier Lt

Titanium oxide adhesion layer for high temperature annealed Si/Si3N4/TiOx/Pt/LiCoO2 battery structures

This work describes the influence of a high annealing temperature of about 700C on the Si(substrate)/Si3N4/TiOx/Pt/LiCoO2 multilayer system for the fabrication of all-solid-state lithium ion thin film microbatteries. Such microbatteries typically utilize lithium cobalt oxide (LiCoO2) as cathode material with a platinum (Pt) current collector. Silicon nitride (Si3N4) is used to act as a barrier against Li diffusion into the substrate. For a good adherence between Si3N4 and Pt, commonly titanium (Ti) is used as intermediate layer. However, to achieve crystalline LiCoO2 the multilayer system has to be annealed at high temperature. This post-treatment initiates Ti diffusion into the Pt-collector and an oxidation to TiOx, leading to volume expansion and adhesion failures. To solve this adhesion problem, we introduce titanium oxide (TiOx) as an adhesion layer, avoiding the diffusion during the annealing process. LiCoO2, Pt and Si3N4 layers were deposited by magnetron sputtering and the TiOx layer by thermal oxidation of Ti layers deposited by e-beam technique. Asdeposited and annealed multilayer systems using various TiOx layer thicknesses were studied by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS). The results revealed that an annealing process at temperature of 700C leads to different interactions of Ti atoms between the layers, for various TiOx layer thicknesses (25–45 nm).This work was financially supported by FEDER/ COMPETE and FCT funds with the Projects PTDC/ EEA-ELC/114713/2009, PEst-C/QUI/UI0686/2013 and UID/EEA/04436/2013, first author scholarship SFRH/BPD/95905/2013 and second author scholarship SFRH/BD/78217/2011. This work was carried out with the support of the Karlsruhe Nano Micro Facility (KNMF, www.kit.edu/knmf), a Helmholtz Research Infrastructure at Karlsruhe Institute of Technology (KIT, www.kit.edu)