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Electronic properties of clean and oxygen covered (100) cleaved surfaces of PbS
A58 Surface Science 92 (1980) 365 384 © North-Holland Publishing Company T H E I D E A L ( 1 1 1 ) , ( 1 1 0 ) A N D ( 1 0 0 ) S U R F A C E S O F Si, Ge A N D G a A s ; A COMPARISON OF THEIR ELECTRONIC STRUCTURE I. I V A N O V , A. M A Z U R a n d J. P O L L M A N N
Institute of Physics, University of Dortmund, D-4600 Dortmund 50, W. Germany Received 18 July 1979; accepted for publication 25 September 1979 In this paper we report all surface band structures and some layer densities of states for the ideal (111), (110) and (100) surfaces of Si, Ge and GaAs in comparison. The bulk materials are described by the best available empirical tight-binding Hamiltonians. The surface problem for semi-infinite solids is solved exactly using the Koster-Slater scattering-theoretic technique. The results for the different surfaces and the different materials are compared and characteristic properties stemming from particular surface geometries or varying ionicity are identified unambiguously. The calculations were carried out using first-nearest-neighbour as well as first- and second-nearest-neighbour bulk Hamiltonians. The sensitivity of the surface band structures with respect to the used bulk Hamiltonians is discussed. For some of the eleven different surfaces these are the f'trst surface band structure calculations on the basis of a realistic tight binding bulk description. Surface Science 92 (1980) 385-392 © North-Holland Publishing Company ELECTRONIC PROPERTIES OF CLEAN AND OXYGEN COVERED (100) CLEAVED SURFACES OF PbS Thomas GRANDKE * and Manuel CARDONA
Max-Planck-lnstitut fiir Festk6rperforschung, D-700 Stuttgart 80, Fed. Rep. Germany Received 23 July 1979; accepted for publication 20 September 1979 The position of the Fermi level at the (100) surface of n- and p-PbS is investigated by means of ultraviolet photoemission spectroscopy. Independently of the bulk carrier type the surface turns out to be nearly intrinsic, possibly slightly p-type, right after cleaving. This result is interpreted in terms of a reduced gap in the surface band structure. After a time of ~3 h an n-type layer is found at the surface, this probably being due to preferential evaporation of sulphur atoms. The loss of sulphur can be compensated by exposure to approximately 109 L of O2, thus shifting the Fermi level back to its original position. Nevertheless, the oxygen is also evaporated in vacuum, like the sulphur, after finishing the exposure experiment.
Surface Science 92 (1980) 393 399 © North-Holland Publishing Company A T O M I C M I G R A T I O N ON D I S O R D E R E D S U R F A C E S J. K L A F T E R a n d R. S I L B E Y
Department of Chemistry and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Received 15 August 1979; accepted for publication 4 October 1979 A model of atomic migration along disordered surfaces is presented. The disorder is assumed to give rise to a distribution of activation energies. The migration is assumed to be incoherent
Institute of Physics, University of Dortmund, D-4600 Dortmund 50, W. Germany Received 18 July 1979; accepted for publication 25 September 1979 In this paper we report all surface band structures and some layer densities of states for the ideal (111), (110) and (100) surfaces of Si, Ge and GaAs in comparison. The bulk materials are described by the best available empirical tight-binding Hamiltonians. The surface problem for semi-infinite solids is solved exactly using the Koster-Slater scattering-theoretic technique. The results for the different surfaces and the different materials are compared and characteristic properties stemming from particular surface geometries or varying ionicity are identified unambiguously. The calculations were carried out using first-nearest-neighbour as well as first- and second-nearest-neighbour bulk Hamiltonians. The sensitivity of the surface band structures with respect to the used bulk Hamiltonians is discussed. For some of the eleven different surfaces these are the f'trst surface band structure calculations on the basis of a realistic tight binding bulk description. Surface Science 92 (1980) 385-392 © North-Holland Publishing Company ELECTRONIC PROPERTIES OF CLEAN AND OXYGEN COVERED (100) CLEAVED SURFACES OF PbS Thomas GRANDKE * and Manuel CARDONA
Max-Planck-lnstitut fiir Festk6rperforschung, D-700 Stuttgart 80, Fed. Rep. Germany Received 23 July 1979; accepted for publication 20 September 1979 The position of the Fermi level at the (100) surface of n- and p-PbS is investigated by means of ultraviolet photoemission spectroscopy. Independently of the bulk carrier type the surface turns out to be nearly intrinsic, possibly slightly p-type, right after cleaving. This result is interpreted in terms of a reduced gap in the surface band structure. After a time of ~3 h an n-type layer is found at the surface, this probably being due to preferential evaporation of sulphur atoms. The loss of sulphur can be compensated by exposure to approximately 109 L of O2, thus shifting the Fermi level back to its original position. Nevertheless, the oxygen is also evaporated in vacuum, like the sulphur, after finishing the exposure experiment.
Surface Science 92 (1980) 393 399 © North-Holland Publishing Company A T O M I C M I G R A T I O N ON D I S O R D E R E D S U R F A C E S J. K L A F T E R a n d R. S I L B E Y
Department of Chemistry and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Received 15 August 1979; accepted for publication 4 October 1979 A model of atomic migration along disordered surfaces is presented. The disorder is assumed to give rise to a distribution of activation energies. The migration is assumed to be incoherent