Technique, electrochemical Hall-effect measurements

At the end of the discussion of electrochemical measurement techniques, let us, however, briefly mention that there are other techniques that are not exclusively electrochemical in nature but related to the above methods such as thermoelectric measurements and Hall-effect measurements. Both techniques are extremely helpful in combination with conductivity experiments as they then allow the splitting of the conductivities into carrier concentration and mobilities. The first method relies on the emf formed as a sheer consequence of temperature differences (crosseffects in the thermal and chemical flux-force relations), while the second technique refers to concentration changes upon application of magnetic fields. Both techniques are particularly worked out for electronic carriers but are more tricky and much less straightforward for ionic carriers. For more details the reader is referred to Ref.16 301 302... 

M-S is an electrochemical impedance spectroscopy (EIS) technique [10-12] that can be difficult to perform and interpret if the system is not ideal. When the measurement is successful, it is able to determine both the fb and the free charge carrier density (donors or acceptors, A/Dopant) of the photoelectrode. Efb, along with the band gap (Eg) and the A dopant. can be used to determine the band structure of a photoelectrode and if it possesses the proper alignment with respect to the water splitting potentials (see chapter Introduction ). The A dopant also plays a role in the bulk and surface semiconductor properties such as the width of the depletion layer and rate of recombination. The conductivity type is also revealed by M-S analysis. The M-S plot will possess a negative slope for p-type materials and a positive slope for n-type materials (positive slope). In the case that the M-S measurement is not successful, then other techniques such as Hall Effect can still yield conductivity and A dopant for materials which can be deposited onto non-conductive substrates such as quartz. 

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