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Abstract Field effect passivation of crystalline silicon surface is controlled by tailoring the built-in charge in a bilayer dielectric system consisting of hafnium oxide (HfO 2) and aluminium oxide (Al 2 O 3). The effective surface recombination velocity (S eff, max) ~ 10 cm/s is achieved at intermediate bulk injection levels with thermal ALD deposited HfO 2 (top)/Al 2 O 3 (bottom) bilayer system on n-type silicon with individual layer thickness between 3 and 7 nm. The best realized S eff,max value is lower by a factor of ~ 2.5 with respect to the single Al 2 O 3 layer of similar thickness deposited under the same experimental conditions. The improved field effect passivation is quantified by enhanced effective charge density for the bilayer system in comparison with the corresponding value for single Al 2 O 3 layer. The introduction of extra trap centers at the interface of the bilayer system is primarily responsible for the enriched field effect passivation, however, the sequence of the dielectric layers is important. Highlights • Stack of Al 2 O 3 and HfO 2 enhances passivation of c-Si surface as compared to a single Al 2 O 3 layer. • Layers are deposited by thermal ALD with total physical thickness of ~ 10 nm. • The enhanced passivation by the bilayer stack is observed to be due to the enhanced trapped charge density. • Contribution of trapped charge density is evaluated using the method of bias-stress capacitance-voltage measurement. • The passivation performance of the stack is greatly affected by the sequence of the oxide layers. [ABSTRACT FROM AUTHOR]

The evidence of good quality silicon surface passivation using thermal ALD deposited Al doped zinc oxide (AZO) thin films is demonstrated. AZO films are prepared by introducing aluminium precursor in between zinc and oxygen precursors during the deposition. The formation of AZO is confirmed by ellipsometry, XRD and Hall measurements. Effective minority carrier lifetime (teff) greater than 1.5ms at intermediate bulk injection levels is realized for symmetrically passivated p-type silicon surfaces under optimised annealing conditions of temperature and time in hydrogen ambient. The best results are realised at 450°C annealing for > 15min. Such a layer may lead to implied open circuit voltage gain of 80mV. [ABSTRACT FROM AUTHOR]

The effect of deposition temperature (Tdep) and subsequent annealing time (tanl) of atomic layer deposited aluminum oxide (Al2O3) films on silicon surface passivation (in terms of surface recombination velocity, SRV) is investigated. The pristine samples (as-deposited) show presence of positive fixed charges, QF. The interface defect density (Dit) decreases with increase in Tdep which further decreases with tanl up to 100s. An effective surface passivation (SRV<8 cm/s) is realized for Tdep ≥ 200 °C. The present investigation suggests that low thermal budget processing provides the same quality of passivation as realized by high thermal budget process (tanl between 10 to 30 min). [ABSTRACT FROM AUTHOR]

One two months old calf was presented with history of abnormal growth with profuse continuous lachrimation from both eyes since birth. On examination, it was diagnosed as bilateral ocular dermoid and advised surgical correction. Dermoids were excised carefully by superficial lamellar keratectomy. The patient recovered uneventfully and showed no reocurrence. [ABSTRACT FROM AUTHOR]

Hafnium oxide (HfO 2 ) is a potential material for equivalent oxide thickness (EOT) scaling in microelectronics; however, its surface passivation properties particularly on silicon are not well explored. This paper reports investigation on passivation properties of thermally deposited thin HfO 2 films by atomic layer deposition system (ALD) on silicon surface. As-deposited pristine film (∼8 nm) shows better passivation with <100 cm/s surface recombination velocity (SRV) vis-à-vis thicker films. Further improvement in passivation quality is achieved with annealing at 400 °C for 10 min where the SRV reduces to ∼20 cm/s. Conductance measurements show that the interface defect density ( D it ) increases with film thickness whereas its value decreases after annealing. XRR data corroborate with the observations made by FTIR and SRV data. [ABSTRACT FROM AUTHOR]