Increasing the Strain Resistance of Si/SiO2 Interfaces for Flexible Electronics.

Understanding the changes that occur in the micro-mechanical properties of semiconductor materials is of utmost importance for the design of new flexible electronic devices, especially to control the properties of newly designed materials. In this work, we present the design, fabrication, and application of a novel tensile-testing device coupled to FTIR measurements that enables in situ atomic investigations of samples under uniaxial tensile load. The device allows for mechanical studies of rectangular samples with dimensions of 30 mm × 10 mm × 0.5 mm. By recording the alternation in dipole moments, the investigation of fracture mechanisms becomes feasible. Our results show that thermally treated SiO2 on silicon wafers has a higher strain resistance and breaking force than the SiO2 native oxide. The FTIR spectra of the samples during the unloading step indicate that for the native oxide sample, the fracture happened following the propagation of cracks from the surface into the silicon wafer. On the contrary, for the thermally treated samples, the crack growth starts from the deepest region of the oxide and propagates along the interface due to the change in the interface properties and redistribution of the applied stress. Finally, density functional theory calculations of model surfaces were conducted in order to unravel the differences in optic and electronic properties of the interfaces with and without applied stress.

Formation and Stability of Nontoxic Perovskite Precursor.

Strontium, calcium, and magnesium silicate hydrate phases are synthesized by the reaction between silica and solution of metal hydroxides. The kinetics of the reaction is recorded using a quartz crystal microbalance (QCM), continuously monitoring the change in frequency and dissipation energy. Based on QCM results, it is shown that properties of solutions like the pH-value or the type of ions play a pivotal function on the rate-determining stage of the reaction, the thickness of the diffuse layer, the formation of carbonates, as well as the kinetics of the formed phases. Further properties of the reaction products are investigated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and infrared spectroscopy (IR). With the help of thermogravimetric analysis (TGA) and temperature-dependent X-ray diffraction (XRD), we investigate how our synthesized phases can be turned into MSiO3 structures. Finally, the Goldschmidt rules for perovskites structures show that this might be an attractive way for new and nontoxic phases in the future.