Jhuma Gope

Effect of power on the growth of nanocrystalline silicon films

Nanocrystalline silicon thin films were grown using a gaseous mixture of silane, hydrogen and argon in a plasma-enhanced chemical vapor deposition system. These films were deposited away from the conventional low power regime normally used for the deposition of device quality hydrogenated amorphous silicon films. It was observed that, with the increase of applied power, there is a change in nanocrystalline phases which were embedded in the amorphous matrix of silicon. Atomic force microscopy micrographs show that these films contain nanocrystallite of 20–100 nm size. Laser Raman and photoluminescence peaks have been observed at 514 cm−1 and 2.18 eV, respectively, and particle sizes were estimated using the same as 8.24 nm and 3.26 nm, respectively. It has also been observed that nanocrystallites in these films enhanced the optical bandgap and electrical conductivity.

Influence of deposition temperature of thermal ALD deposited Al2O3 films on silicon surface passivation

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).

Effect of Hydrogen Content and Bonding Environment on Mechanical Properties of Hydrogenated Silicon Films Deposited by High-Frequency PECVD Process

The mechanical properties of hydrogenated silicon thin films deposited using high-frequency PECVD process were studied, which certainly have importance for optoelectronic devices particularly for getting stability and long operating lifetime in harsh conditions. Nanoindentation technique was used to measure the load versus displacement curves, hardness (H), elastic modulus (E), plastic resistance parameter (H/E), elastic recovery (ER), and plastic deformation energy (𝑈𝑟), while laser scanning stress measurement setup was used to measure the intrinsic stress of these films. The concentration of bonded hydrogen in these films was found in the range of 3.6 to 6.5 at. % which was estimated using integrated intensity of IR absorption peak near 640 cm−1. Dependence of mechanical properties of these films on hydrogen content and bonding environment has been investigated. The film containing minimum hydrogen content (3.6%) shows the maximum elastic recovery (52.76%) and minimum plastic deformation energy (3.95×10−10 J). Surface roughness measured by AFM was found to decrease with the increase in hydrogen content in the film. The dependency of stress on the plasma frequency and applied power has also been discussed.

Silicon Surface Passivation by Al2O3 film using Atomic Layer Deposition

Silicon surface passivation is studied using Al2O3 thin film deposited by thermal process using atomic layer deposition (ALD) method. Minority carrier lifetime measurements showed that the film passivate the silicon surface effectively. Capacitance–voltage measurement confirms the activation of negative fixed charges after sintering at 400 °C.