Defect level distributions and atomic relaxations induced by charge trapping in amorphous silica

Abstract

We compute the distribution of electronic levels of native defects in amorphous silica from total energy differences of charge-state density functional theory calculations over an ensemble of atomic structures. The predicted distributions reproduce results from trap spectroscopy by charge injection experiments, validating the calculations. Furthermore, our study characterizes the experimentally inaccessible contributions of individual defect types to the overall distribution. Computed electron and hole trapping levels provide insight into the positive charge buildup in bulk silica observed in negative-bias-temperature-instability, an important degradation mechanism of metal-oxide-semiconductor devices.

Magnetic stability of oxygen defects on the SiO2 surface

“…Our calculations of the formation energies of the charged and neutral ODCs are in agreement with previous calculations, showing that the neutral ODC is thermodynamically more stable. 16,17,20 However, some calculations of the formation energy of E defects set the Fermi Energy 2.25-3.3eV above the VBM 63,64 (much closer to the VBM than to the center of the gap). On the (100) surface, if the Fermi energy is taken to be ∼2 eV above the VBM or lower, the 1+ PC configuration is more stable than the NOV.…”

“…13,14 First-principles calculations have enabled the assignment of atomistic defect structures to the measured electron paramagnetic resonance (EPR) and optical signatures of a wide variety of E centers and ODCs in silica and α-quartz. [15][16][17] Calculations of the EPR of E centers remains an active field. 18 Most calculations have focused on bulk silica, but similar defects exist on silica and α-quartz surfaces.…”

Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy

“…a silicon dangling bond. The electronic structure of the dangling bonds associated with oxygen vacancies have been calculated by several groups [28,37]. In this work, the E' γ center is taken as a prototypical paramagnetic defect for the simulations of the proposed single electron spin detection method.…”

Model form uncertainty versus intrinsic atomic variability in amorphous silicon oxides and nitrides

“…Computational techniques have become a useful and cost-effective way to predict the materials properties of a wide range of materials; in particular, multiscale approaches have been recently used to predict ensembles of low energy a-SiO 2 [6,18] and a-Si 3 N 4 [10,19] structures and their properties. At the heart of these predictions is density functional theory (DFT) [20], a quantum mechanical based technique that provides a good balance between accuracy and computational efficiency for a large variety of ground state properties of condensed matter systems [9].…”

“…Realizing the full potential of these techniques requires rigorous uncertainty quantification in the predictions that would enable simulation data-informed decision-making; see, for example, [2][3][4]. In this paper we quantify uncertainties and variability in first-principles calculations using density functional theory; this is important because this technique is often used as the foundation of multiscale materials modeling efforts [5,6]. In general, uncertainties in the predictions of a simulation arise either from known variability in an input quantity (aleatoric uncertainty) or due to a lack of knowledge (epistemic uncertainty) [7].…”