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Negative atomic hydrogen ion (H$^{-}$) densities were measured in a pulsedlow-pressure E-mode inductively-coupled radio-frequency (rf) driven plasma inhydrogen by means of laser photodetachment and a Langmuir probe. Thisinvestigation focuses on the influence of different metallic surface materialson the volume production of H$^{-}$ ions. The H$^{-}$ density was measuredabove a thin disc of either tungsten, stainless steel, copper, aluminium, ormolybdenum placed onto the lower grounded electrode of the plasma device as afunction of gas pressure and applied rf power. For copper, aluminium, andmolybdenum the H$^{-}$ density was found to be quite insensitive to pressureand rf power, with values ranging between 3.6x10$^{14}$ to 5.8x10$^{14}$m$^{-3}$. For stainless steel and tungsten, the H$^{-}$ dependency was found tobe complex, apart from the case of a similar linear increase from 2.9x10$^{14}$to 1.1x10$^{15}$ m$^{-3}$ with rf power at a pressure of 25 Pa. Two-photonabsorption laser induced fluorescence was used to measure the atomic hydrogendensities and phase resolved optical emission spectroscopy was used toinvestigate whether the plasma dynamics were surface dependent. An explanationfor the observed differences between the two sets of investigated materials isgiven in terms of surface reaction mechanisms for the creation of vibrationallyexcited hydrogen molecules.

Influence of surface materials on the volume production of negative ions in a radio-frequency driven hydrogen plasma