INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
PAC and PALS study in the HfO2+SiO2 system
C. Y. CHAIN; L. C. DAMONTE; S. FERRARI; E. L. MUÑOZ; A. F. PASQUEVICH; C. RODRIGUEZ TORRES
Buenos Aires, Argentina
Simposio; XV International Symposium on metastable, amorphous and Nanostructured Materials.; 2008
A high-k HfO2/SiO2 gate stack is taking the place of SiO2 as a gate dielectric in field effect transistors. This make very important to study the solid state chemical interaction between both oxides. Before beginning with a study of the reactions between both oxides at the interface of thin films, we initiated Perturbed Angular Correlations (PAC) and Positron Lifetime studies (PALS) of the solid state reactions using samples prepared mixing the oxides by ball milling. Sample preparation include pilling and annealing at different temperatures. The PAC technique requires the use of specials radioactive isotopes. In this case the probe 181Ta was used. This isotope results from the beta-decay of 181Hf. This isotope was introduce in the samples using HfO2 , where the 180Hf was activated by thermal neutron capture at the CNEA reactor. On the other hand, the PALS measurements were carried out using 22Na as source of positrons and non active samples. Equal molar amounts of the oxides were milled during 2, 4 and 8 hours. The samples were pilled under a pressure of 6 kN/m2. Room temperature PAC and PALS measurements were made after annealing under air at several temperatures. The results are compared with microstructure data existent in the literature of nanocrystalline ZrSiO4, synthesized by ball-milling and high-temperature annealing.