Free electrons and defects in microcrystalline silicon studied by electron spin resonance

Finger, F.; Malten, C.; Hapke, P.; Carius, R.; Flückiger, R.; Wagner, H.

doi:10.1080/09500839408240982

Cited by 62 publications

(26 citation statements)

References 13 publications

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“…Originally, this line was ascribed to free electrons in the conduction band, since its zero-crossing g value is almost the same as that for conduction electrons in crystalline silicon. 1 In addition, for n-doped c-Si:H at low temperatures a resonance with the same g value as the LESR signal has been observed. 9,18 Finally, the same broadening in the line shape has been observed with increasing temperature as that found for conduction electrons in crystalline silicon.…”

Section: -13mentioning

confidence: 82%

“…Systematic studies of the paramagnetic centers in c-Si:H were first presented in 1994. 1 Since the majority of the defects have g values near to that of free electrons, where g ϭ2.0023, a unique interpretation of the different centers is difficult and remains controversial. In this work, we provide additional interpretations for some of the ESR signals previously observed in c-Si:H.…”

Section: Introductionmentioning

confidence: 99%

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ESR observations of paramagnetic centers in intrinsic hydrogenated microcrystalline silicon

et al. 2002

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Paramagnetic centers in hydrogenated microcrystalline silicon, c-Si:H have been studied using dark and light-induced electron-spin resonance ͑ESR͒. In dark ESR measurements only one center is observed. The g values obtained empirically from powder-pattern line-shape simulations are g ʈ ϭ2.0096 and g Ќ ϭ2.0031. We suggest that this center may be due to defects in the crystalline phase. During illumination at low temperatures, an additional ESR signal appears. This signal is best described by two powder patterns indicating the presence of two centers. One center is asymmetric (g ʈ ϭ1.999, g Ќ ϭ1.996), while the other is characterized by large, unresolved broadening such that unique g values cannot be obtained. The average g value for this center is 1.998. The light-induced signal, which we interpret as coming from carriers trapped in the band tails at the crystalline grain boundaries, remains for at least several minutes after the light is turned off. Although the time scales of the decay curves are very different for two samples prepared by different techniques, both decays can be fitted using the assumption of recombination due to distant pairs of electrons and holes trapped in localized band-tail states.

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Section: -13mentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

ESR observations of paramagnetic centers in intrinsic hydrogenated microcrystalline silicon

et al. 2002

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“…The latter resonance is attributed to Si dangling-bond ͑DB͒ states. [5][6][7][8] The resonance at gϭ2.0043 cannot be unambiguously identified. From its resonance parameters it is probably related to dangling-bond states in Si-rich Si-O layers, 9,10 as a strong oxygen take up has been observed in secondary ion mass spectroscopy ͑SIMS͒ measurements on c-Si:H films, 11 and an increase of a signal at gϭ2.0044 in c-Si:H samples that were exposed to air for several weeks has been reported.…”

Section: Introductionmentioning

confidence: 99%

Electron spin resonance investigation of electronic states in hydrogenated microcrystalline silicon

et al. 1999

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Phosphorus-doped microcrystalline silicon with high-crystalline volume fraction was prepared by very highfrequency plasma enhanced chemical vapor deposition. The material is studied by electron spin resonance and transport measurements as a function of doping and temperature. In all samples a resonance at gϭ1.998 is found with spin densities very similar to the phosphorus dopant density and also the carrier density at high doping levels. This resonance is related to doping-induced excess electrons. Its spin density is largely temperature independent, and the corresponding electrons occupy dopant or conduction band tail states at low temperatures, while they are excited into the conduction band at high T. This gradual transition is accompanied by changes in linewidth, g value and spin-lattice relaxation time. Hyperfine interaction with P nuclei is only observed for intermediate doping levels and has very small intensity. From the value of the hyperfine splitting, the effective Bohr radius of the impurity wave function is estimated to 12 Å. Transport at low temperatures (TϽ20 K) proceeds via hopping between donor states and/or conduction-band tail states. A thermal activation energy of 3.5 meV and similar localization lengths as from the hyperfine data are found for this process. At temperatures above 20 K electronic transport is governed by a wide distribution of activation energies.

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“…10,11 Several possibilities for the microscopic origin of the CE center have been discussed in literature: (a) free electrons in the conduction band (CE resonance), 10 (b) interface defects at the boundary of amorphous and crystalline phases, 15 (c) electrons confined to an inversion layer at the boundary of amorphous and crystalline phases of the material (Ref. 16) and (d) localized states due to internal twin grain boundaries inside of crystalline columns (Refs.…”

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confidence: 99%

“…[10][11][12][13] This renders electron paramagnetic resonance (EPR) the method of choice to unravel the microscopic defect structure and shed light on the influence of defect centers on charge-carrier transport mechanisms. In particular, hyperfine interactions (HFI) between the unpaired electron spin and nuclear spins in its vicinity constitute ultra sensitive probes of the defect wave function and the material composition in the vicinity of the defect.…”

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confidence: 99%

Electrical detection of electron-spin-echo envelope modulations in thin-film silicon solar cells

et al. 2011

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Electrically detected electron-spin-echo envelope modulations (ED-ESEEM) were employed to detect hyperfine interactions between nuclear spins and paramagnetic sites, determining spin-dependent transport processes in multilayer thin-film microcrystalline silicon solar cells. Electrical detection in combination with a modified Hahn-echo sequence was used to measure echo modulations induced by 29 Si, 31 P, and 1 H nuclei weakly coupled to electron spins of paramagnetic sites in the amorphous and microcrystalline solar cell layers. In the case of CE centers in the μc-Si:H i-layer, the absence of 1 H ESEEM modulations indicates that the adjacencies of CE centers are depleted from hydrogen atoms. On the basis of this result, we discuss several models for the microscopic origin of the CE center and conclusively assign those centers to coherent twin boundaries inside of crystalline grains in μc-Si:H.

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Free electrons and defects in microcrystalline silicon studied by electron spin resonance

Cited by 62 publications

References 13 publications

ESR observations of paramagnetic centers in intrinsic hydrogenated microcrystalline silicon

ESR observations of paramagnetic centers in intrinsic hydrogenated microcrystalline silicon

Electron spin resonance investigation of electronic states in hydrogenated microcrystalline silicon

Electrical detection of electron-spin-echo envelope modulations in thin-film silicon solar cells

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