Delocalized Nature of theEδ′Center in Amorphous Silicon Dioxide

Abstract

We report an experimental study by electron paramagnetic resonance (EPR) of E(')(delta) point defect induced by gamma-ray irradiation in amorphous SiO2. We obtained an estimation of the intensity of the 10 mT doublet characterizing the EPR spectrum of such a defect arising from hyperfine interaction of the unpaired electron with a 29Si (I=1/2) nucleus. Moreover, determining the intensity ratio between this hyperfine doublet and the main resonance line of E(')(delta) center, we pointed out that the unpaired electron wave function of this center is actually delocalized over four nearly equivalent silicon atoms.

Si29Hyperfine Structure of theE′αCenter in Amorphous Silicon Dioxide

“…After irradiation of the materials considered, E' δ and E' γ centers are induced, but virtually no EPR signal due to E' α centers is detected [7][8][9]. As discussed extensively in our previous works [7][8][9], upon thermal treatment at T>500 K the EPR signal of E' γ and E' δ centers increases as a consequence of a hole transfer process form the [AlO 4 ] 0 centers to the sites precursors of the E' centers.…”

“…As discussed extensively in our previous works [7][8][9], upon thermal treatment at T>500 K the EPR signal of E' γ and E' δ centers increases as a consequence of a hole transfer process form the [AlO 4 ] 0 centers to the sites precursors of the E' centers. After prolonged thermal treatments, a third contribution to the EPR spectrum becomes evident, suggesting that E' α centers are also induced in the same materials by hole transfer [16].…”

“…The E' δ center is characterized by a nearly symmetric EPR main resonance with g∼2.002 and a 29 Si hyperfine doublet split by ∼10 mT [1][2][3][6][7][8][9]. Since its first observation [6] the microscopic model of this point defect has been largely debated [9].…”

“…Since its first observation [6] the microscopic model of this point defect has been largely debated [9]. However, a recent experimental investigation [7] has pointed out that the unpaired electron wave function of this defect is delocalized over four nearly equivalent Si atoms, supporting a microscopic model of the E' δ center consisting in an unpaired electron delocalized over a pair of nearby oxygen vacancies or over a 5-Si cluster in aSiO 2 [7][8][9].…”

Application of Maximum Entropy Method to Semiconductor Engineering

“…The t l = 0 sample without the carbon contamination shows no 1.1 eV peak, while 0.8 and 1.3 eV peaks are clearly present, which indicates that the 1.1 eV peak originates from the carbon, while the others are intrinsic SiO 2 traps. From [30,31], the A and C peaks can be E δ -and E γ -centers (oxygen deficiency), respectively. This A and C peak intensity becomes less for longer t l , which implies that the oxygen deficiencies are passivated by the carbon.…”