At real tellurium surfaces natural accumuIation layers exist which can be changed substantially by different etching processes. For pure samples this surface layer may mask the galvanomagnetic properties of the bulk completely. Employing a new etching process the influence of the surface can be reduced drastically, complete elimination is possible using a field effect arrangement. A comparison of the results obtained from samples with different degrees of accumulation at the surface allows a separation of the galvanomagnetic properties of the surface and the bulk.
Surface Shubnikov-de Haas oscillations were studied in (0001) and (11̄00) accumulation layers of pure tellurium single crystals in external electric fields up to 106 V/cm. Whereas in accumulation layers of purely chemical origin at most two electric subbands could be identified, up to four subbands have been detected with the application of additional electric surface fields. The energies of the subbands were derived from the data and compared with a theoretical model assuming an exponential surface potential. The agreement is reasonably good, having in mind the complicated valence band structure of tellurium. The effective mass mc of the surface holes was determined from the temperature dependence of the amplitude of the quantum oscillations. It was found that mc had increased with respect to the bulk values. The Dingle temperature varied between 3 and 6 K for different samples.
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