Using tailored voltage waveforms (TVWs) to excite a low pressure, low-temperature plasma discharge, we compare the behavior of three gas mixtures, namely Ar, O 2 and SF 6 /O 2 mixtures, the last of which is currently used for the plasma-texturing of silicon wafers for photovoltaics. The primary goal of using TVWs is to control the ion bombardment energy at the surface of the wafer, and this control is demonstrated through retarding field energy analyzer (RFEA) measurements. However, the complicated electrical response of the plasma to such waveforms makes the ab initio prediction of the ion energy difficult, although by using said RFEA measurements, we show that it can be done approximately by using measured electrical data. In addition, we utilize the response of the plasma to mirror-image 'sawtooth' waveforms as a predictor of the dominant electron heating mode (α or drift-ambipolar, DA). At equivalent pressures and coupled powers, the Ar and O 2 mixtures always display behavior associated with electropositive plasmas (a solely α heating mode). However, with the addition of SF 6 to an O 2 gas flow, a transition can be observed towards a behavior associated with a more electronegative plasma (i.e. a dominant DA heating mode). This crossover in the dominant heating mode is observed through the relative self-bias voltage for each type of sawtooth waveform, and is therefore a useful predictor of the dominant electron heating mode in low pressure, cold plasma discharges.

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Using a plasma to generate a surface texture with feature sizes on the order of tens to hundreds of nanometers (“nanotexturing”) is a promising technique being considered to improve efficiency in thin, high-efficiency crystalline silicon solar cells. This study investigates the evolution of the optical properties of silicon samples with various initial surface finishes (from mirror polish to various states of micron-scale roughness) during a plasma nanotexturing process. It is shown that during said process, the appearance and growth of nanocone-like structures are essentially independent of the initial surface finish, as quantified by the auto-correlation function of the surface morphology. During the first stage of the process (2 min to 15 min etching), the reflectance and light-trapping abilities of the nanotextured surfaces are strongly influenced by the initial surface roughness; however, the differences tend to diminish as the nanostructures become larger. For the longest etching times (15 min or more), the effective reflectance is less than 5 % and a strong anisotropic scattering behavior is also observed for all samples, leading to very elevated levels of light-trapping.

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