  Bi2Sr2Ca1Cu2O8+d (Bi-2212) thin films with thicknesses less than 50 nm (<20
unit cells) are grown by pulsed laser deposition (PLD) onto (001) LaAlO3 (LAO)
single crystal substrates. Phase-pure and smooth c-axis oriented Bi-2212 films
with optimal oxygen doping, critical temperature Tc0 up to 86 K, and critical
current density Jc(60 K) above 1 MA/cm2 are obtained for samples that are
annealed in situ at temperatures below 700 {\deg}C. At higher temperature
Bi-2212 films on LAO substrates partially decompose to non-superconducting
impurity phases, while films on MgO and SrTiO3 substrates are stable. The
broadening of Tc of the metal-to-superconductor resistive phase transition in
magnetic fields is much larger for thin films of Bi-2212 as compared to
YBa2Cu3O7. The magnetic field-induced suppression of Tc0 is stronger for
Bi-2212 films containing impurity phases as compared to the phase-pure Bi-2212
films. The degradation of LAO substrate crystals after several steps of
deposition and chemical removal of the Bi-2212 layer is investigated. New,
commercially prepared substrates provide Bi-2212 films with smallest surface
roughness (3 nm) and strong out-of-plane texture. However, thin films of almost
the same quality are obtained on re-used LAO substrates that are mechanically
polished after the chemical etching.
