Dependencies of microstructure and stress on the thickness of GdBa2Cu3O7 − δ thin films fabricated by RF sputtering

Abstract

GdBa2Cu3O7 − δ (GdBCO) films with different thicknesses from 200 to 2,100 nm are deposited on CeO2/yttria-stabilized zirconia (YSZ)/CeO2-buffered Ni-W substrates by radio-frequency magnetron sputtering. Both the X-ray diffraction and scanning electron microscopy analyses reveal that the a-axis grains appear at the upper layers of the films when the thickness reaches to 1,030 nm. The X-ray photoelectron spectroscopy measurement implies that the oxygen content is insufficient in upper layers beyond 1,030 nm for a thicker film. The Williamson-Hall method is used to observe the variation of film stress with increasing thickness of our films. It is found that the highest residual stresses exist in the thinnest film, while the lowest residual stresses exist in the 1,030-nm-thick film. With further increasing film thickness, the film residual stresses increase again. However, the critical current (Ic) of the GdBCO film first shows a nearly linear increase and then shows a more slowly enhancing to a final stagnation as film thickness increases from 200 to 1,030 nm and then to 2,100 nm. It is concluded that the roughness and stress are not the main reasons which cause the slow or no increase in Ic. Also, the thickness dependency of GdBa2Cu3O7 − δ films on the Ic is attributed to three main factors: a-axis grains, gaps between a-axis grains, and oxygen deficiency for the upper layers of a thick film.

Epitaxial superconducting GdBa2Cu3O7−δ /Gd2O3 nanocomposite thin films from advanced low-fluorine solutions

“…simultaneous deposition and growth. The properties of the thin films synthesized by sputtering [23][24][25][26], PLD [27] or MOCVD [28] have confirmed the results obtained in the case of single crystals and bulk samples. However, in the search for a scalable and low-cost technique for the preparation of coated conductors, some researchers have focused on chemical solution deposition (CSD) as an attractive option for thin film growth [29][30][31].…”

“…The results shown in figure 5 provide clues to discern the origin of the problem. Under the currently used nucleation and growth conditions [25][26][27], the GdBCO phase nucleates at temperatures in the range of 710 °C-725 °C, but at these temperatures the heterogeneous nucleation of GdBCO leads to multiple nuclei orientations oriented perpendicular to the substrate interface (c-axis, a-b plane and maybe even <103> axes) because we are in the region of high supersaturation conditions [31,58]. We observe that the (103) peak is the first observed when temperature is increased (between 710 °C and 725 °C), thus suggesting that homogeneous nucleation, leading to randomly oriented grains, occurs before the c-axis oriented epitaxial grains ((00 l) peaks appear between 750 °C and 790 °C).…”

Large critical current densities and pinning forces in CSD-grown superconducting GdBa2Cu3O7−x-BaHfO3nanocomposite films

“…This higher T c value by roughly 3 K is linked with a shift of the irreversibility line towards higher B and T, which leads to an improvement of the in-field properties of GdBCO with respect to YBCO. In the past, GdBCO thin films were mainly prepared by in situ methods (where in situ refers to the crystallization of the superconducting phase): sputtering, pulsed laser deposition (PLD) or metalorganic chemical vapor deposition (MOCVD) [18][19][20][21][22]. However, in the search for a scalable and low-cost technique for the preparation of CCs, some researchers have focused on the chemical solution deposition (CSD) as an attractive option for thin film growth [23][24][25][26].…”

Study of Microstructure and Mechanical Properties of Electrodeposited Cu on Silicon Heterojunction Solar Cells

“…Residual stress, interfacial reactions, film thickness, and film microstructure influence materials system's adhesion behavior [21][22][23][24]. Usually, these factors are often interconnected and challenging to decouple.…”