A phase stability diagram of the NdCeCuO (NCCO) films grown by in situ laser ablation in O2 is demonstrated. The superconducting NCCO films can be grown under the deposition conditions below and close to the CuO/Cu2O transition line without vacuum annealing. On post-deposition cooling in an oxygen pressure lower than the deposition pressure, the superconductivity of the in situ NCCO films can be significantly improved without vacuum annealing. This process may shorten the reduction step and mitigate the over-reduction of the superconducting films. A film grown at 680 °C in 300 mTorr and then cooled down in 0.5 mTorr shows Tc(onset) of 21 K and Tc(zero) of 18 K.

In situ growth of Ba1−xKxBiO3 (BKBO) films by laser ablation has been studied as a function of gas pressure and substrate temperature in O2, N2O, and N2O/O2 (1:1), respectively. The superconducting BKBO films can be grown at 410–500 °C in 15–60 mTorr of O2, at 390–510 °C in 20–2000 mTorr of N2O, and at 390–500 °C in 15–700 mTorr of N2O/O2 (1:1), respectively. Oxygen partial pressure plays an important role in controlling the doping of potassium into the BKBO phase during in situ deposition and hence the growth of the superconducting films. The optimum deposition pressures are 40 mTorr of O2, 30–50 mTorr of N2O, and 20–50 mTorr of N2O/O2 (1:1), under which not only the temperature range available for growing the superconducting films is wider but also the Tc’s of the as-grown films are higher. N2O used as an oxidation gas during growth is efficient in suppressing the crack formation in the BKBO films on cooling. The target composition also plays an important role in film growth. The optimal target composition studied is Ba:K:Bi=0.6:0.8:1.0.

The phase formation in BiSrCaCuO (BSCCO) films grown by in situ laser ablation has been studied as a function of excess concentrations of Ca and Cu in the target with oxidation gases such as O2 and N2O, gas pressures ranging from 0.02 to 10 Torr, and substrate temperatures ranging from 490 to 750 °C. A set of phase diagrams has been plotted illustrating O2 or N2O partial pressures vs substrate temperature, marking the stability fields and transitions among different phases of Bi2Sr2CuOx (2201), Bi2Sr2CaCu2Ox (2212), Bi2Sr2Ca2Cu3Ox (2223), and Bi2Sr2Ca3Cu4Ox (2234), amorphous products, and decomposition of the BSCCO films. In O2 and N2O, the first appearance of the 2212 phase is located at 510 °C/20 mTorr and 490 °C/100 mTorr, respectively. The BSCCO film decomposes at a high temperature that increases with increasing gas pressure. Higher gas pressures enhance the growth of the 2201 phase that may also be formed by cooling from partial film melting. Higher substrate temperature and gas pressure as well as the surplus of Ca and Cu in the target facilitate the growth of the 2223 and 2234 phases. The decomposition curve of the Ca and Cu enhanced BSCCO films is shown to be found at lower temperatures in comparison to the stability lines of the 2212 and 2223 phases; furthermore, its slope deviation occurs at 650–690 °C which is lower by as much as about 130 °C compared to that of stoichiometric superconductors. Nearly pure 2212, 2223, or 2234 films or a mixture of them can be grown within a temperature range of 575–690 °C at a pressure as high as 10 Torr, irrespective of the kind of oxidation gas.