Three demonstration samples of intrinsic hydrogenated amorphous silicon (a-Si:H) films were deposited using hot wire-chemical vapour deposition (HW-CVD) technique. The optical parameters and the thickness were determined from the extremes of the interference fringes of transmission spectrum in the range of 400-2500 nm using the envelope method. The calculated values of the refractive index (n) were fitted using the two-term Cauchy dispersion relation and the static refractive index values (n 0 ) obtained were 2.799, 2.629 and 3.043 which were in the range of the reported values. The calculated thicknesses for all samples were cross-checked with Taly-Step profilometer and found to be almost equal. Detailed analysis was carried out to obtain the optical band gap (E g ) using Tauc's method and the estimated values were 1.99, 2.01 and 1.75 eV. The optical band gap values were correlated with the hydrogen content (C H ) in the samples calculated from Fourier transform infrared (FTIR) analysis. An attempt was made to apply Wemple-DiDomenico single-effective oscillator model to the a-Si:H samples to calculate the optical parameters. The optical band gap obtained by Tauc's method and the static refractive index calculated from Cauchy fitting are in good agreement with those obtained by the single-effective oscillator model. The real and the imaginary parts of dielectric constant (ε r , ε i ), and the optical conductivity (σ ) were also calculated.
There are limited studies on COVID vaccine confidence at the household level in urban slums, which are at high risk of COVID-19 transmission due to overcrowding and poor living conditions. The objective was to understand the reasons influencing COVID-19 vaccine confidence, in terms of barriers and enablers faced by communities in urban slums and informal settlements in four major metro cities in India. A mixed method approach was adopted, where in field studies were conducted during April–May 2021. First, a survey of at least 50 subjects was conducted among residents of informal urban settlements who had not taken any dose of the COVID-19 vaccine in Mumbai, Bengaluru, Kolkata and Delhi; second, a short interview with five subjects who had taken at least one dose of the vaccine in each of the four cities to understand the factors that contributed to positive behaviour and, finally, an in-depth interview of at least 3 key informants in each city to ascertain the vaccination pattern in the communities. The reasons were grouped under contextual, individual/group and vaccine/vaccination specific issues. The most frequent reason (27.7%) was the uncertainty of getting the vaccine. The findings show the need for increasing effectiveness of awareness campaigns, accessibility and the convenience of vaccination, especially among vulnerable groups, to increase the uptake.
Cadmium sulfide (CdS) nanoparticles were synthesized by simple and low cost homemade hot injection method at low process temperature using different sulphur sources. The effects of sulphur concentration on the structural, morphological, and optoelectronic properties of synthesized CdS films were studied using a range of characterization techniques: X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and UV-Visible spectroscopy. The XRD studies revealed the formation of hexagonal type CdS nanoparticles. The varying morphology dependence on the sulphur source was ascertained from FESEM analysis. The longitudinal optical (LO) phonon vibrational modes of CdS were assigned in Raman spectra at 300 and 600 cm-1. The band gap of the CdS particles was estimated to be 2.30 eV from Tauc's plots. Consistent with the experimental results, our first-principles DFT calculations predict the band gap of CdS nanoparticles to increase with decreasing S concentration: Cd 52 S 52 (2.38 eV) Cd 52 S 51 (2.52 eV) and Cd 52 S 50 (2.65 eV), with both the valence and conduction band edges demonstrated to be dominated by S-p states.
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