D B. Romero

Recovery of forming gas damaged Pb(Nb,Zr,Ti)O3 capacitors

We report on the recovery of fully integrated Pb(Nb, Zr, Ti)O3 ferroelectric capacitors damaged during forming gas (4% H2, balance N2) annealing. The capacitors were encapsulated using TiOx and SiO2 as interlevel dielectrics to prevent any loss of oxygen or lead. Hydrogen, however, diffused into the ferroelectric film leading to the loss of ferroelectricity. To recover the properties of the capacitor, the fully integrated structure was annealed in N2 ambient to drive the hydrogen out. Raman scattering experiments performed in the high frequency regime to detect the [OH−] stretching vibration mode confirmed the removal of hydrogen after annealing in N2. The ferroelectric properties, including polarization and resistivity of the capacitors, were restored to their initial values prior to damage. This shows that the process of hydrogen damage is reversible with the time to recovery being dependent on the amount of hydrogen in the forming gas.

Diagnostics of “colossal” magnetoresistance manganite films by Raman spectroscopy

Polarized Raman scattering by phonons is used to characterize thin films prepared by laser ablation of La1−xCaxMnO3 targets. It was found that, in the temperature range from 6 to 300 K, phonon spectra of La0.7Ca0.3MnO3 films exhibit observable differences from those in bulk materials (microcrystalline ceramics and single crystals). A significant difference was found in the spectra of “as-grown” films compared to those annealed in oxygen at 800 °C. The observed Raman peaks and their linewidths exhibit an irregular temperature dependence near Tc. A correlation of Raman data with magnetization of the sample was also found.