  Negative atomic hydrogen ion (H$^{-}$) densities were measured in a pulsed
low-pressure E-mode inductively-coupled radio-frequency (rf) driven plasma in
hydrogen by means of laser photodetachment and a Langmuir probe. This
investigation focuses on the influence of different metallic surface materials
on the volume production of H$^{-}$ ions. The H$^{-}$ density was measured
above a thin disc of either tungsten, stainless steel, copper, aluminium, or
molybdenum placed onto the lower grounded electrode of the plasma device as a
function of gas pressure and applied rf power. For copper, aluminium, and
molybdenum the H$^{-}$ density was found to be quite insensitive to pressure
and 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 to
be 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-photon
absorption laser induced fluorescence was used to measure the atomic hydrogen
densities and phase resolved optical emission spectroscopy was used to
investigate whether the plasma dynamics were surface dependent. An explanation
for the observed differences between the two sets of investigated materials is
given in terms of surface reaction mechanisms for the creation of vibrationally
excited hydrogen molecules.
