X-ray Photoelectron Spectroscopy (XPS) Depth Profiling for Evaluation of La2Zr2O7 Buffer Layer Capacity

Abstract

Lanthanum zirconate (LZO) films from water-based precursors were deposited on Ni-5%W tape by chemical solution deposition. The buffer capacity of these layers includes the prevention of Ni oxidation of the substrate and Ni penetration towards the YBCO film which is detrimental for the superconducting properties. X-ray Photoelectron Spectroscopy depth profiling was used to study the barrier efficiency before and after an additional oxygen annealing step, which simulates the thermal treatment for YBCO thin film synthesis. Measurements revealed that the thermal treatment in presence of oxygen could severely increase Ni diffusion. Nonetheless it was shown that from the water-based precursors’ buffer layers with sufficient barrier capacity towards Ni penetration could be synthesized if the layers meet a certain critical thickness and density.

MOD Derived Pyrochlore Films as Buffer Layer for All-Chemical YBCO Coated Conductors

“…After the annealing (see figure 4), the inter-diffusion region remains unaltered, while deep oxygen diffusion into the tape can be clearly seen. The presence of Ni at film surface cannot be detected, thus confirming that 120 nm thick LZO film acts effectively as Ni diffusion barrier, in agreement with the results obtained with similar techniques by other groups [22]. It is worth noting that Auger spectroscopy revealed the presence of residual carbon into the LZO film even after the annealing simulating YBCO deposition.…”

Aqueous Chemical Solution Deposition of Novel, Thick and Dense Lattice-Matched Single Buffer Layers Suitable for YBCO Coated Conductors: Preparation and Characterization

“…The capacity of the buffer layers to withstand nickel penetration can be evaluated by XPS depth profiling [26]. Figure 5 shows the result of 40 consecutive sputter cycles, each consisting of an elemental analysis of C, La, Ce, Zr, Ni, O after 50 s of Ar + ion bombardment for an as-deposited La 0.50 Ce 0.40 Zr 0.10 O y layer.…”

Effects of Varied Cleaning Methods on Ni-5% W Substrate for Dip-Coating of Water-based Buffer Layers: An X-ray Photoelectron Spectroscopy Study

“…In summary, the combination of chemical cleaning with etching for 15 min followed by thermal cleaning was chosen to be the best in terms of a reduced surface contamination, an undisturbed textured Ni surface and an improved wettability with a contact angle of 18° which is sufficient for dipcoating in an aqueous sol-gel system [17]. Such cleaned substrates are particularly suitable for water-based solutions, which have a high surface tension.…”

“…The chemical composition in terms of atom percentages of Ni and W and the contaminants including C and O quantified using XPS is presented. Previously, XPS has been used as an effective analytical tool for studying the buffer layer capacity [17]. The wetting property of the substrate after different cleaning methods has been pictured and presented.…”