Stress Dependence of Optically Active Diamagnetic Point Defects in Silicon Oxynitride

Abstract

The cathodoluminescence (CL) spectrum arising from diamagnetic point defects of silicon oxynitride lattice was analyzed to extract quantitative information on local stress fields stored on the surface of a silicon nitride polycrystal. A calibration procedure was preliminarily made to obtain a relationship between CL spectral shift and applied stress, according to the piezo-spectroscopic effect. In this calibration procedure, we used the uniaxial stress field developed in a rectangular bar loaded in a four-point flexural jig. Stress dependence was clearly detected for the most intense spectral band of a doublet arising from diamagnetic ([triple bond]Si-Si[triple bond]) defects, which was located at around 340 nm. The shallow nature of the electron probe enabled the characterization of surface stress fields with sub-micrometer-order spatial resolution. As applications of the PS technique, the CL emission from [triple bond]Si-Si[triple bond] defects was used as a stress probe for visualizing the residual stress fields stored at grain-boundary regions and at the tip of a surface crack propagated in polycrystalline silicon nitride.

Oxygen Hole States in Zirconia Lattices: Quantitative Aspects of Their Cathodoluminescence Emission

“…In other words, the vacancy sites can be employed, upon preliminary quantitative calibrations, as "stress sensors" in both crystalline and amorphous lattices. [8][9][10]12 However, many basic aspects of the CL emission from oxide materials yet remain to be clarified, which confines CL spectroscopy to somewhat incomplete outputs and limits its potential efficacy both in material physics and in applicative engineering research.…”

“…In all these cases, anion order is expected to have a strong influence on physical properties, especially when these are sensitive to local disorder and distortions . In this context, cathodoluminescence spectroscopy (CL) has already been phenomenologically applied to a number of advanced topics and appears to possess a potential to unfold several fundamental issues to them related. − Besides its uniqueness as a direct means of visualizing oxygen vacancy concentration in the very neighborhood of oxide surfaces, CL is also capable of providing mechanical stress information by exploiting a piezo-spectroscopic effect on the light emission from oxygen vacancy sites. In other words, the vacancy sites can be employed, upon preliminary quantitative calibrations, as “stress sensors” in both crystalline and amorphous lattices. − , However, many basic aspects of the CL emission from oxide materials yet remain to be clarified, which confines CL spectroscopy to somewhat incomplete outputs and limits its potential efficacy both in material physics and in applicative engineering research.…”

Off-Stoichiometry Spectroscopic Investigations of Pure Amorphous Silica and N-Doped Silica Thin Films

“…Compared to pure SiO 2 , the complex network of bonds induced by nitrogen can lead to the formation of different kinds of defects, where the silicon atoms should be randomly coordinated by a different number of nitrogen and oxygen atoms. The degradation of the SiO x N y structure, caused by annealing in air, leads to the formation of nitrogen-related defects, such as Si 2 N• and NOSi•, which, in turn, affect both red and blue bands in the CL spectrum. , A possible qualitative explanation for the shift of the temperature threshold, T c , toward lower temperatures with increasing N content could be that the oxynitride structure formed during film deposition begins to undergo breaking of N-related dangling bonds at an increasingly lower temperature, thus forming a higher density of defects for each fraction of N leaving the system as compared to an undoped structure. Indeed, the NBOHC red band, related to SiO•, is emitted from the Si 2 N• complex and from other subcoordinated forms of it, which, in turn, originate from the breaking of a Si–N bond.…”

“…However, while ODC sites reach a saturated concentration and eventually annihilate upon interaction with the oxygen from the atmosphere at above 1000 °C, NBOHC (and POR) formation shows no maximum and proves continuously enhanced in the studied interval of temperature. Defect structures in silicon oxynitride glasses have not been so far the subject of extended spectroscopic CL investigations, even if, in the literature, topical reports appeared of some characteristic features. , It is expected that the introduction of nitrogen in the silica matrix gives rise to a rather complex network of defects. For different nitrogen concentrations, CL spectra exhibit important modifications depending on annealing temperature as well as on dopant concentration, showing that the presence of nitrogen in the amorphous network significantly affects the behavior of defects in the matrix.…”