RESUMO
Gravitational waves are detected using resonant optical cavity interferometers. The mirror coatings' inherent thermal noise and photon scattering limit sensitivity. Crystals within the reflective coating may be responsible for either or both noise sources. In this study, we explored crystallization reduction in zirconia through nano-layering with silica. We used X-ray diffraction (XRD) to monitor crystal growth between successive annealing cycles. We observed crystal formation at higher temperatures in thinner zirconia layers, indicating that silica is a successful inhibitor of crystal growth. However, the thinnest barriers break down at high temperatures, thus allowing crystal growth beyond each nano-layer. In addition, in samples with thicker zirconia layers, we observe that crystallization saturates with a significant portion of amorphous material remaining.
RESUMO
Among all transition metal oxides, titanium dioxide (TiO2) is one of the most intensively investigated materials due to its large range of applications, both in the amorphous and crystalline forms. We have produced amorphous TiO2 thin films by means of room temperature ion-plasma assisted e-beam deposition, and we have heat-treated the samples to study the onset of crystallization. Herein, we have detailed the earliest stage and the evolution of crystallization, as a function of both the annealing temperature, in the range 250-1000 °C, and the TiO2 thickness, varying between 5 and 200 nm. We have explored the structural and morphological properties of the as grown and heat-treated samples with Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometry, and Raman spectroscopy. We have observed an increasing crystallization onset temperature as the film thickness is reduced, as well as remarkable differences in the crystallization evolution, depending on the film thickness. Moreover, we have shown a strong cross-talking among the complementary techniques used displaying that also surface imaging can provide distinctive information on material crystallization. Finally, we have also explored the phonon lifetime as a function of the TiO2 thickness and annealing temperature, both ultimately affecting the degree of crystallinity.
RESUMO
The controlled synthesis of high-quality nitrogen (N) doped single layer graphene on the Ru(0001) surface has been achieved using the N-containing sole precursor azafullerence (C59NH). The synthesis process and doping properties have been investigated on the atomic scale by combining scanning tunneling microscopy and X-ray photoelectron spectroscopy measurements. We find for the first time that the concentration of N-related defects on the N-doped graphene/Ru(0001) surface is tunable by adjusting the dosage of sole precursor and the number of growth cycles. Two primary types of N-related defects have been observed. The predominant bonding configuration of N atoms in the obtained graphene layer is pyridinic N. Our findings indicate that the synthesis from heteroatom-containing sole precursors is a very promising approach for the preparation of doped graphene materials with controlled doping properties.
