Substrate and thickness influence on YBa$$_2$$Cu$$_3$$O$$_{7-\delta }$$ thin films grown by PLD deposition

Strain effect on the high T c superconductor YBa2Cu3O7: an ab initio study comparing bulk and monolayer models

“…However, the behavior of the Raman modes differs between a strained and an oxygen-deficient sample. The presence of strain without apparent oxygen deficiency has been observed in [23,35]. Furthermore, the frequency shifts observed in [35] for an YBCO sample on SrLaAlO 4 with a tensile strain in c axis are in agreement with the shifts observed in this work, while the frequency shifts expected in the case of oxygen deficiency are not observed.…”

“…The presence of strain without apparent oxygen deficiency has been observed in [23,35]. Furthermore, the frequency shifts observed in [35] for an YBCO sample on SrLaAlO 4 with a tensile strain in c axis are in agreement with the shifts observed in this work, while the frequency shifts expected in the case of oxygen deficiency are not observed. It should be noted that in the studies presented in [28,31], despite being based on first principles calculations, the method for imposing strain and optimizing the cell is different, and the strain values studied are very large (4.5% and 6.0%).…”

“…In section 3.2.1, we mention that the off-resonant Raman spectrum simulation presents a similar shape to experimental measurements [23,35,50,76,77] and previous theoretical reports [78][79][80].…”

“…In these cases it is correct to consider that the oxygen level remains fixed, and that the only effect on T c is due to strain. This type of linear relation between T c and c axis strain was also proposed in [23] and applied again in [35], deduced through a quantum phase fluctuations model, and applied to the study of YBCO with different strain levels in conventional substrates. As already mentioned, the Raman frequency shifts observed are in agreement with the results of this work.…”

“…Furthermore, the last one plays a role regulating the critical current and enhancing the vortex pinning process [28,32]. Therefore, in an experimental study (and also in theoretical calculations), oxygen deficiency and the presence of a compressive in-plane strain can have similar effects on the c axis (c axis enlargement) [25,33,34] and electronic properties [28,31]; knowing how the Raman modes shift under strain would allow us to discern between the presence of these two effects, as we have tried in previous works [23,35]. Furthermore, this study could be applied more directly in the analysis of YBCO samples grown on piezoelectric substrates, because strain and microstructure effects (like oxygen vacancies) can be uncoupled.…”