Topographical development and misfit relief in laser-ablated heteroepitaxial YBa2Cu3O7−δ thin films

Strong pinning linear defects formed at the coherent growth transition of pulsed-laser-depositedYBa2Cu3Dam1, Huijbregtse2, Rector3 2002Phys. Rev. B

“…4 -6 Up to now, it was assumed that relaxation takes place by the introduction of misfit dislocations. 7 Yeadon et al 8 estimated a ͑thermo-dynamic͒ critical layer thickness between 8 and 21 mm. This calculation is based on equating the strain energy to the energy of misfit relieving edge dislocations.…”

“…However, misfit dislocations do not form spontaneously. Most probably, dislocation half-loops 8,9 have to nucleate at the film surface. The half-loop expands towards the interface where it forms a misfit dislocation and two threading dislocations ending at the film surface.…”

Effect of growth defects on microwave properties in epitaxial Ba0.5Sr0.5TiO3thin films grown on (001) MgO by pulsed laser deposition

“…The average spacing of the TD segments in our films is less than 50 nm. This small distance between the TDs will 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 [25]: when the coplanar half loops have opposite b they will constrict and annihilate, leaving two half-loops shrinking towards the substrate interface and film surface; when, two TDs have opposite b components parallel to ±[001] but a different component in the plane they will form two half loops and a constriction segment with a smaller b. Under such circumstances, TDs formed with other values of b are also common because of the strong interaction.…”

On the growth mechanisms of thin films produced by pulsed laser deposition

“…3) 2D (mesa type) and 3D (spiral type) features exist [9,10], which means that the net result of the retention of impinging species is non random. The impingement itself, is random, therefore certain locations on the surface of the growing film are more likely than others to retain adatoms.…”

“…It is concluded by Dam et al [11] that the dislocations are formed as a result of the merging of misaligned growth fronts, when overgrowing precipitates. 6) The incidence of 2D and 3D growth features is altered by the deposition conditions [10,11] which means that although underlying features can affect subsequent layers the extent to which they do so is moderated by the growth conditions . .…”