Spectroscopic features of dimer and dangling bond<i>E</i>′ centres in amorphous silica

Mukhopadhyay, Sanghamitra; Sushko, Peter V.; Mashkov, V. A.; Shluger, Alexander L.

doi:10.1088/0953-8984/17/8/009

Cited by 14 publications

(12 citation statements)

References 33 publications

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“…Moreover, if we restrict the average to the lowest-energy configurations, i.e., d SiSi 2.9Å, the g principal values will be ∼400 ppm larger: g 1 = 2.0023, g 2 = 2.0027, and g 3 = 2.0033, with a std of 400 ppm. The former average g values are compatible with the results of previous investigations where a hybrid functional (Becke threeparameter Lee-Yang-Parr) and localized basis sets were used but only a few dimer configurations were analyzed [28,32]. It is also worth noting that simply averaging g values over the investigated configurations, as done in Table II, does not properly convey the most relevant information of Fig.…”

Section: E δ Vs Si 2 Dimerssupporting

confidence: 83%

“…It is supposed to arise either from an interaction of an unpaired electron in a sp 3 -like orbital delocalized over four or five nearby 29 Si, or from an ionized single oxygen vacancy with the unpaired electron shared nearly equally by the two neighboring Si atoms (Si 2 dimer center). Though several theoretical works [17,26,32,33] support the Si 2 dimer hypothesis, they do not explain the intensity ratio between the main EPR resonance line and the 10 mT hyperfine doublet that seems to be better explained by assuming an E center involving at least four Si atoms [31,34]. Richard et al [35] have shown that for a positively charged oxygen vacancy, the dimer configuration appears to be the lowestenergy configuration with an 80% probability, in agreement with previous theoretical investigations [29].…”

Section: Introductionmentioning

confidence: 68%

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EPR parameters ofE′centers inv−SiO2from first-principles calculations

et al. 2014

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A first-principles investigation of E centers in vitreous silica (v-SiO 2 ) based on calculations of the electron paramagnetic resonance (EPR) parameters is presented. The EPR parameters are obtained by exploiting the gauge including projector augmented wave method as implemented in the QUANTUM-ESPRESSO package. First, we analyze the EPR parameters of a large number of Si 2 dimers. The g tensor of the Si 2 dimers is shown to possess an average rhombic symmetry and larger g principal values with respect to those observed, e.g., for the E γ center in silica. Furthermore, the g principal values clearly show a linear trend with the Si-Si dimer length. Our results suggest that the Si 2 dimers could correspond to an unidentified paramagnetic center, though occasionally the calculated g principal values of the Si 2 dimer might be compatible with those found experimentally for the E δ center. Next, we generate nondimer configurations by a procedure involving structural relaxations in the subsequent positively charged states. In particular, puckered, unpuckered, doubly puckered, and forward-oriented configurations are generated. The distributions of the calculated EPR parameters of the puckered and unpuckered configurations further support the assignment of the E γ center to an unpaired spin localized at a threefold coordinated silicon dangling bond. Moreover, by analyzing Fermi contacts and g tensors of the puckered and forward-oriented configurations, we suggest the assignment of the E α center to the latter type of configurations. This work also suggests that the differences in the EPR parameters of E α and E γ centers mainly arise from the strained geometry of the silicon dangling bond. In the forward-oriented configurations, one Si-O bond is about 0.2Å longer than the remaining two, whereas in the silicon dangling bond of the puckered and unpuckered configurations, all three bonds have a length of ∼1.6Å each.

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Section: E δ Vs Si 2 Dimerssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 68%

EPR parameters ofE′centers inv−SiO2from first-principles calculations

et al. 2014

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“…The property of having two stable configurations is also referred to as 'bi-stability' and maybe linked to some unexpected behavior of defects in microelectronic transistors. As such, it was the subject of intensive discussions but has been confirmed by several independent groups [49][50][51][52][53][54][55]. Looking from a device perspective, it has been shown that the oxygen vacancy easily reacts with a hydrogen and forms a defect called hydrogen bridge [7,56], which has a defect level within the SiO 2 bandgap.…”

mentioning

confidence: 93%

“…For instance, the P b center has been intensively examined [45] and its reactions with atomic and molecular hydrogen considered in [46,47]. Furthermore, the positively charged oxygen vacancy in SiO 2 was found to be stable in two configurations where one of them could be related to the E center [48][49][50]. The property of having two stable configurations is also referred to as 'bi-stability' and maybe linked to some unexpected behavior of defects in microelectronic transistors.…”

mentioning

confidence: 99%

Identification of oxide defects in semiconductor devices: A systematic approach linking DFT to rate equations and experimental evidence

Goes

Wimmer

El-Sayed

et al. 2018

Microelectronics Reliability

121

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It is well-established that oxide defects adversely affect functionality and reliability of a wide range of microelectronic devices. In semiconductor-insulator systems, insulator defects can capture or emit charge carriers from/to the semiconductor. These defects feature several stable configurations, which may have profound implications for the rates of the charge capture and emission processes. Recently, these complex capture/emission events have been investigated experimentally in considerable detail in Si/SiO2 devices, but their theoretical understanding still remains vague. In this paper we discuss in detail how the capture/emission processes can be simulated using the theoretical methods developed for calculating rates of charge transfer reactions between molecules and in electro-chemistry. By employing this theoretical framework we link the atomistic defect configurations to known trapping model parameters (e.g. trap levels) as well as measured capture/emission times in Si/SiO2 devices. Using density functional theory (DFT) calculations, we investigate possible atomistic configurations for various defects in amorphous (a)-SiO2 implicated in being involved in the degradation of microelectronic devices. These include the oxygen vacancy and hydrogen bridge as well as the recently proposed hydroxyl E center. In order to capture the effects of statistical defect-to-defect variations that are inevitably present in amorphous insulators, we analyze a large ensemble of defects both experimentally and theoretically. This large-scale investigation allows us to prioritize the candidates from our defect list based on their trap parameter distributions. For example, we can rule out the E center as a possible candidate. In addition, we establish realistic ranges for the trap parameters, which are useful for model calibration and increase the credibility of simulation results by avoiding artificial solutions. Furthermore, we address the effect of nuclear tunneling, which is involved according to the theory of charge transfer reactions. Based on our DFT results, we demonstrate the impact of nuclear tunneling on the capture/emission process, including their temperature and field dependence, and also give estimates for this effect in Si/SiO2 devices.

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“…[15][16][17][18] Since its first observation, the microscopic model for the E δ center has been hotly disputed. [18][19][20] At variance to the other E centers, the E α center possesses an orthorhombic g matrix. The generally recognized experimental hyperfine splittings for E γ , E α and E δ are 42, 49 and 10 mT, respectively.…”

Section: Introductionmentioning

confidence: 99%

First principles study of oxygen vacancy defects in amorphous SiO2

2017

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The oxygen vacancy defects of amorphous SiO2 (a-SiO2) in different charge states are investigated by the periodic density functional theory. Five types of the positively charged configurations are obtained including the dimer, forward-oriented, puckered 4×, 5× and back-projected unpuckered configurations. The energy, geometry structure, spin density, Bader charge and Fermi contact are concerned for these systems. These defects can be regarded as the potential microscopic structures for the corresponding centers including Eα′, Eγ′ and Eδ′ in the electron paramagnetic resonance (EPR) experiments. Then, the charge-state transitions of these defects are investigated by intentionally adding one electron to the positively charged systems. For the dimer, puckered 4× and back-projected unpuckered configurations, all of the corresponding neutral species maintain their initial types of geometry structures. For the forward-oriented configurations, the corresponding neutral species transform into the structures of the divalent Si atom. The puckered 5× configurations have the most abundant neutral species: some of them could maintain its style of the puckered 5× configurations, and some collapse to the neutral dimer or forward-oriented configurations. The dimer configurations have the lowest thermodynamic charge-state levels, and the puckered 4× configurations have the highest thermodynamic charge-state levels among the five types of configurations. This work is of benefit to identifying and controlling the oxygen defects in a-SiO2.

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Spectroscopic features of dimer and dangling bondE′ centres in amorphous silica

Cited by 14 publications

References 33 publications

EPR parameters ofE′centers inv−SiO2from first-principles calculations

EPR parameters ofE′centers inv−SiO2from first-principles calculations

Identification of oxide defects in semiconductor devices: A systematic approach linking DFT to rate equations and experimental evidence

First principles study of oxygen vacancy defects in amorphous SiO2

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