The properties of ferroelectric films are known to degrade when subjected to hydrogen in forming gas anneals. Earlier studies have attributed this degradation to the loss of oxygen from these films during these anneals. In this study, we show that though oxygen is lost during forming gas annealing, hydrogen incorporation is the primary mechanism for the degradation of ferroelectric properties. Raman spectra obtained from the forming gas-annealed films show evidence of polar hydroxil [OH−] bonds in the films. The most probable site for hydrogen ions is discussed based on ionic radii, crystal structure, electrical properties, and Raman spectra. We propose that the hydrogen ion is bonded with one of the apical oxygen ions and prevents the Ti ion from switching. Pyroelectric measurements on forming gas-annealed capacitors confirm that the capacitors no longer possess spontaneous polarization.

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The polarized hyper-Raman spectra of a calcite crystal in different scattering geometries are obtained. Two silent A1u-vibrntions a t 227 and 1085 cm-l as well as infrared active vibrations are found. The upper branch of mixed A2,-poIaritons and their resonance with E,-vibrations is investigated. The calculation of mixed polariton dispersion curves is presented.IIonywm,r nonRpmooairnbre cnewrpbr r~n e p~~o w B~i~a~~~o~r s o r o paccemms K~M C T~J I J I~ 1 i ; l J l L L~I I T~~ npa paamiwmx reo3teTpmx p a c c e m m . Iipoixe nr~rr~rir xmtonmbrx ~o n e 6 arrrrii o6rrapyirccrm nnc JIMAEIH ,,wmhIx" &,-I;one6amii 227 rI 1085 em-'. HccneAosaiia ncpsrrris UCTBL cmmarnmx A g u -n~n~p~~~~~~~ II peaona~rc ~T E I X ~O~R~~T O E I O R c E,-Rone-lI1>HBCJClI ~laCrlC?T AI4CnepCr/IOIIHI~IX KpIiBLIX CRICUlaHIIbIX IIOJfHpEITOHOB. In trodnctionItecently the hyper-ltaman scattering in some crystals mas studied [l to 51. The interest in the hyper-ltainan scattering as an independent spectroscopic method has grown over the last few years becaiisc of the ability to allow the observation of silent modes which is inaccessible by other methods. Silent vibrations forbidden in the Itainan scattering and Ilt-absorption may be active in hyper-Raman spectra due to selection riilcs [GI. For example, two silent vibrations of B1,-sysmmetry at 113 and 406 cn1-I were observed in a rutile hyper-Itaman spectrum 143. Dipole vibrations arc always active in the hyper-Raman scattering. Therefore, the study of polaritons in both noncentrosymmetric and centrosymmetric crystals is possibleThe calcite vibration spectrum was carefully studied by different methods: 11%-absorption and reflection [8], Raman scattering [9], hyper-Raman scattering [3, 101 inelastic neutron scattering [11], theoretical calculations El1 to 131. A small part of the calcite hyper-Kaman spectrum in the frequency region below 300 cm-' was studied and only some IR-active modes were found [3, 101.In the present paper we study the hyper-Raman scattering by phonons and polaritons in a CaCO, centrosymmetric crystal. Some polarized spectra in the frequency region of fundamental calcite vibrations (0 to 1600 cm-l) were obtained and two silent modes were observed, Besides, the polariton hyper-Raman spectra associated with Kaman inactive mixed A*,-vibrations were studied.[5, 71. ExperimentalHyper-Raman spectra were excited by the polarized light of a YAG laser (mi = = 9396 cm-l) and were detected by a niultichannel photoelectric instrument described previously [14]. The power density of the exciting light did not exceed lo8 W/crna inside the crystal. I n the 90" and 180" hyper-Raman scattering geometries t,he laser 142092 Troitsk, Moscow Region, USSR.

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