Cobalt Doping of Semiconducting Boron Carbide Using Cobaltocene

The decomposition of cobaltocene and metacarborane (closo-1,7-dicarbadecaborane) under low energy electron irradiation at about 200 K results in a material with the Fermi level closer to the valence band than the material resulting from the decomposition of metacarborane alone. This indicates that cobaltocene provides a relatively p-type dopant as seen in ultraviolet photoemission spectroscopy/inverse photoemission spectroscopy. Upon warming to room temperature, however, the Fermi level shifts towards the conduction band, suggesting an n-type dopant. This temperature dependent surface photovoltage effect is not compelling evidence for the majority carrier type but does suggest an increase in the carrier concentration in semiconducting boron carbides with cobaltocene fragment doping. Using cobaltocene to introduce dopants into a orthocarborane (closo-1,2- dicarbadecaborane) derived film, deposited by plasma enhanced chemical vapor deposition, a semiconducting boron carbide homojunction diode has been fabricated. This diode has potential applications in neutron detection, direct neutron power conversion, and as a dilute magnetic semiconductor.