Electrical properties of black phosphorus single crystals prepared by the bismuth-flux method

Systematic measurement of the electrical transport phenomena of black phosphorus grown by the all-closed bismuth- flux method has been performed in the range from room temperature down to 0.5 K for the electrical resistivity and down to 1.5 K for the Hall effect and the magnetoresistance effect. These samples exhibited p-type conduction with two types of acceptors, of which activation energies were 26.1 meV and 11.8 meV, respectively. The effective concentrations of acceptors were typically 1.36 x 10¹⁵ cm^-3 for the deeper level and 0.44 x 10¹⁵ cm^-3 for the shallower level. The maximum of the Hall mobility was found to be 2 x 10⁴ cm²/Vs around 20 K. A new observation of n-type conduction below about 7 K for some of these samples suggested the existence of a surface inversion layer as a channel of electron conduction.