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8th World Conference on Photovoltaic Energy Conversion; 423-427, We report on the Scanning Tunneling Spectroscopy (STS) study of quantum dot sized SiGe alloy nanocrystals (NCs) to explore its bandgap energies. These alloy NCs have been prepared in a multichamber very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) reactor using a capacitively-coupled plasma technique. The STS study yielded a density of states (DOS) spectrum of NCs in which the conduction band (CB) and valance band (VB) edges were located, in addition, even midgap defect states in the forbidden region in some of the NC samples. The measured bandgap of SiGe alloy NCs in different samples reveals Ge content dependence. Though there was no dopant introduced intentionally during the growth, a shallow p-type nature of alloy NCs has been observed in all the samples even which may be attributed to charged grain boundary defects in high Ge content alloy NCs. The high bandgap value of NCs compared to bulk alloy indicates quantum confinement in the SiGe alloy NCs.

8th World Conference on Photovoltaic Energy Conversion; 133-137, The study aims to develop a suitable TCO via different modes of the ALD process for c-Si based passivating contact solar cells (PCS) and we have proposed a new type of deposition scheme. This TCO deposition, along with other layers (passivation and electron/hole transport layers) can be deposited in a single ALD run, which helps to fabricate a complete PCS device without exposing the device outside of the vacuum chamber. ZnO:Al (AZO) films on the glass/c-Si substrates from thermal (TH) ALD and plasma enhanced (PE) ALD processes were deposited at different temperatures (100-250 °C), and the growth per cycle (GPC) of these layers were calculated from spectroscopic ellipsometry and X-ray reflectometry. The GPC of films deposited by PE ALD at 200 C is measured to be 1.45±0.1 Å for Al2O3 and 1.78±0.2 Å for ZnO films; similarly for the TH ALD deposited films, a GPC of 1.00±0.1 Å and 1.20±0.1 Å, respectively. The (1: n) (Al2O3: ZnO) pulse ratio was used for the film deposition and optimized GPC of Al2O3 and ZnO was used to deposit about 200 nm AZO films for different Al concentrations (0.5 to 5 at %). The (1:21) (Al - 2%) ratio provides an optimum film property for the PE ALD process, and the same ratio was tried with TH ALD, where the film properties were significantly enhanced. Further, a new mode of deposition named “DTH” (DEZ-TMA-H2O) was explored, and an additional decrease in the film resistivity was observed. We have altered the sequence step of precursor dose and co-reactant in this mode. Compared to the conventional TH and PE ALD technique, the DTH mode of deposition proves to be the best fit for the TCO application here. A 200nm AZO film deposited by DTH ALD has a minimum resistivity in the range of 1.91×10-3 Ω-cm and high transparency of more than 85% in the visible region. DTH approach in the ALD proves to be an innovative deposition technique for developing films with enhanced quality, indicating the potential use in PCS device applications.