With molecular beam epitaxy and topotactic chemical reaction, we prepared NdFeAs(O,H) epitaxial thin films with various hydrogen concentrations on 5ยฐ vicinal-cut MgO substrates. By measuring the resistivities along the longitudinal and transversal directions, the ab-plane and the c-axis resistivities (๐ !" and ๐ # ) were obtained. The resistivity anisotropy ๐พ $ โก ๐ # /๐ !" of NdFeAs(O,H) with various hydrogen concentrations was compared with that of NdFeAs(O,F). At the H concentrations which led to superconducting transition temperatures Tc over 40 K, ๐พ $ recorded ~100-150 at 50 K. On the other hand, a low ๐พ $ value of 9 was observed with the mostly doped sample. The exponent ฮฒ of the ab-plane resistivity obtained by fitting a power law expression ๐ !" (๐) = ๐ % + ๐ด๐ & to the data was close to unity down to low temperature in the vicinity where the second antiferromagnetic phase locates, which may be related to the quantum critical point discussed at the over-doped side of the phase diagram.
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