Studies on grain boundaries in nanocrystalline silicon grown by hot-wire CVD

Abstract

The use of a tantalum wire in Hot-Wire Chemical Vapour Deposition has allowed the deposition of dense nanocrystalline silicon at low filament temperatures (1550ºC). A transition in crystalline preferential orientation from (220) to (111) was observed around 1700ºC. Transmission Electron Microscopy images, together with Secondary Ion Mass Spectrometry measurements, suggested that no oxidation occurred in material obtained at low filament temperature, due to the high density of the tissue surrounding grain boundaries.Greater amount of SiH 3 radicals formed at these temperatures seemed to be responsible of the higher density.

Reversibility of silicidation of Ta filaments in HWCVD of thin film silicon

“…Thus by using higher temperatures, the filament is less affected, especially at the "cold ends". It was found by several groups that a lower filament temperature is beneficial for the material quality [8,9]. However, under the conditions used in this study, high quality a-Si:H [4,5] and µc-Si:H [6] material are obtained at high deposition rates (1 nm/s and 0.2 nm/s respectively).…”

Control of doped layers in p–i–n microcrystalline solar cells fully deposited with HWCVD

“…Recently, dense c-Si:H has been obtained at low substrate temperatures (T s ~ 150-300ºC) using tantalum wires and low filament temperatures (T f ~ 1500-1700ºC) [4]. Efficiencies as high as 9% have been achieved in c-Si:H p-i-n solar cells with the active layer deposited by HWCVD in the above-mentioned range of deposition conditions [5].…”

Amorphous to nanocrystalline transition in HWCVD Si:H films by substrate temperature variation

“…2a, sample 36) for all the films show grains of average size 20 nm, separated from each others by thread like structures. These white thread like structures are identified as low density amorphous regions [7]. The high resolution TEM (HRTEM) images for films deposited at T s ≥ 200 o C show presence of nanocrystallites of silicon with lattice spacing ~0.3 nm randomly distributed in amorphous matrix (Fig.…”