Absence of a Steady State in Hydrogen Diluted Silane Plasmas Due to Mass Dependent Gas Pumping Speeds and Its Consequences

Abstract

AbstractWe have investigated the cause for continued changes in the silane related species observed using mass spectroscopy during i-layer deposition process lasting several tens of minutes. Silane decomposition is found to influence the mass spectrometer filament and therefore, pressure changes were compared to ascertain differences in pumping speed using a rotary, mechanical pump. The cathode voltage was used as a measure of effective hydrogen to silane ratio in real time and deliberate tailoring of this ratio is seen to result in a discernible difference in the degradation of single junction amorphous silicon solar cells. Some obvious consequences of this subtle, pump-type dependent transient behavior are discussed.