Defects in thin film silicon at the transition from amorphous to microcrystalline structure

Abstract

Defects in thin film silicon with different structure all the way from amorphous to microcrystalline were investigated by electron spin resonance with emphasis on amorphous material prepared close to the transition to crystalline growth. Electron beam irradiation and stepwise annealing is used for reversible variation of the defect density over three orders of magnitude. The electron irradiation enhances mainly the native paramagnetic defects. Additional resonances are found as satellites to the central line, which anneal rapidly at temperatures below 100 °C. These features are most pronounced for the amorphous material prepared close to the transition to crystalline growth. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrical detection of electron spin resonance in microcrystalline silicon pin solar cells

“…One can clearly observe the quenching contribution at t = 4 µs which can easily be fitted separately. From this analysis we find g db = 2.0045(5) which slightly differs from g e as it was found for samples A and C. Within the experimental uncertainty this agrees with the g values reported for Si dangling bonds in µc-Si:H (g = 2.0042-2.0058 depending on the deposition conditions) [5,45]. Note that despite of the difference between g db and g e , the temporal evolution of the quenching signal ( figure 8) is reflected by the line at g e = 2.0049 (deduced from the enhancing signal found in samples A and C, cf.…”

Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon

“…The measured g value is the zero crossing of the first derivative of the ESR line in the investigated material attributed to dangling bonds in intrinsic TFS. It was already found earlier 10,28,29 that the g values of the resonance in thinfilm silicon not only changes considerably between a-Si: H and c-Si: H ͑from g = 2.0054 to g = 2.0048͒ but also shows a small but distinct and reproducible variation within the Raman-amorphous region ͑SC=8...30%͒. The observed continuous variation of the g value indicates a change in the defect structure or defect energy already within the Ramanamorphous material and not surprisingly when going from fully amorphous to highly crystalline material.…”

“…This helped to keep a very high density of generated defects by preventing annealing at ambient. 15,[28][29][30][31] While in previous work we were mainly concerned with the effects of electron bombardment on the spin properties in the thin-film silicon materials, in the present report we focus on the interaction between the generated defects and the electronic transport and recombination in the material.…”

“…For variation in the defect density, we apply the defect creation by highenergy electron bombardment and subsequent annealing of the defects. 15,[28][29][30][31] This approach has been successfully applied to a-Si: H and related alloys in the past for reversible variation in the defects over several orders of magnitude. [32][33][34][35][36][37][38][39][40] Alternatively also keV electron bombardment for defect production has been reported in the literature.…”

“…28,29 Both tubes and substrate samples were handled, transported, and stored in liquid nitrogen ͑LN 2 ͒. Exposure time to ambient during installation of the samples to the ESR spectrometer or CPM setup was typically 1-3 min.…”