Ezio Zanghellini

Formation of Silicon Structures by Plasma‐Activated Wafer Bonding

A room temperature wafer bonding process based on oxygen plasma treatment or argon plasma treatment has been studied for surfaces of silicon, silicon dioxide, and crystalline quartz. The surface energy of the bonded samples was observed at different storage times. Atomic force microscope measurements, multiple internal reflection infrared spectroscopy, electrical characterization, secondary ion mass spectroscopy, and post‐processing steps were performed to evaluate the plasma‐treated surfaces and the formed bonded interfaces. Electrical measurements were used to investigate the usefulness of plasma‐bonded interfaces for electronic devices. The bonded interfaces exhibit high surface energies, comparable to what can be achieved with annealing steps in the range of 600–800°C using normal wet chemical activation before bonding. The high mechanical stability obtained after bonding at room temperature is explained by an increased dynamic in water removal from the bonded interface allowing covalent bonds to be formed.

Microscopic structure of tin-borate and tin-boratephosphate glasses

The structure of tin-borate and tin-boratephosphate glasses has been examined with diffuse reflectance infrared (DR-IR) and Raman spectroscopy. The basic network structure for these glasses is described as well as the positioning of tin in the network. Data suggests that the amount of phosphate present in the glass regulate the glass forming properties of tin. With borate as the dominating glass forming oxide, SnO acts like a glass former, but with increasing amount of phosphate SnO instead tends to behave as a network modifier.

Structural investigation of the Li+ ion insertion/extraction mechanism in Sn-based composite oxide glasses

The effect of lithium insertion for two Sn-based composite oxide glasses, Sn2BPO6 and Sn2P2O7, was examined during the first electrochemical discharge/charge cycle. Electrodes based on these glasses were analysed with micro-Raman spectroscopy at different steps during the cycle. In-situ X-ray diffraction has been used to confirm the amorphous state during the lithium insertion and extraction process. No alloy formation between Li and Sn could be discerned throughout the first cycle. It was found that when lithium enters the electrode, a reaction at the surface of the glass particles takes place resulting in Li3PO4, Li2O and SnO2 formation. The charge compensation mechanism is thought to be the reduction of Sn2+ to Sn. The formation of Li3PO4 is found to be irreversible and is as such partly responsible for the large observed capacity loss during the first cycle.

Two-component heat diffusion observed in LaMnO3 and La0.7Ca0.3MnO3

We investigate the low-temperature electron, lattice, and spin dynamics of LaMnO3 (LMO) and La0.7Ca0.3MnO3 (LCMO) by resonant pump-probe reflectance spectroscopy. Probing the high-spin d-d transition as a function of time delay and probe energy, we compare the responses of the Mott insulator and the double-exchange metal to the photoexcitation. Attempts have previously been made to describe the sub-picosecond dynamics of CMR manganites in terms of a phenomenological three temperature model describing the energy transfer between the electron, lattice and spin subsystems followed by a comparatively slow exponential decay back to the ground state. However, conflicting results have been reported. Here we first show clear evidence of an additional component in the long term relaxation due to film-to-substrate heat diffusion and then develop a modified three temperature model that gives a consistent account for this feature. We confirm our interpretation by using it to deduce the bandgap in LMO. In addition we also model the non-thermal sub-picosecond dynamics, giving a full account of all observed transient features both in the insulating LMO and the metallic LCMO.

Carbon Dioxide Capture from Ambient Air Using Amine-Grafted Mesoporous Adsorbents

Anthropogenic emissions of carbon dioxide (CO2) have been identified as a major contributor to climate change. An attractive approach to tackle the increasing levels of CO2 in the atmosphere is direct extraction via absorption of CO2 from ambient air, to be subsequently desorbed and processed under controlled conditions. The feasibility of this approach depends on the sorbent material that should combine a long lifetime with nontoxicity, high selectivity for CO2, and favorable thermodynamic cycling properties. Adsorbents based on pore-expanded mesoporous silica grafted with amines have previously been found to combine high CO2 adsorption capacity at low partial pressures with operational stability under highly defined laboratory conditions. Here we examine the real potential and functionality of these materials by using more realistic conditions using both pure CO2, synthetic air, and, most importantly, ambient air. Through a combination of thermogravimetric analysis and Fourier transform infrared (TGA-FTIR) spectroscopy we address the primary functionality and by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy the observed degradation of the material on a molecular level.

The effect of lithium insertion on the structure of tin oxide-based glasses

Two different SnO-based glasses, Sn2B3O6.5 and Sn2B2AlO6.5, have been examd. with FT-IR and Raman spectroscopy at different stages during the first electrochemical cycle. Some disruption of the connection between borate units in the network occurred during cycling. There was also an irreversible formation of Li3BO3 that can be related to the large capacity loss.

Ultrasonic and hypersonic behaviours of borate glasses

Comparative measurements of Brillouin light scattering and ultrasound in (K2O)0.04(B2O3)0.96 and (Ag2O)0.14(B2O3)0.86 borate glasses as a function of temperature between 1.5 and 300 K reveal that distinct mechanisms regulate the temperature behaviours of the acoustic attenuation. In the MHz range the attenuation and the sound velocity are mainly governed by (i) quantum-mechanical tunnelling below 20 K, (ii) thermally activated relaxations between 20 and 200 K and (iii) vibrational inharmonicity at even higher temperatures. In the GHz range and in the temperature interval between 77 and 300 K, additional contributions besides the relaxation process must be taken into consideration to account for the hypersonic attenuation.