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@InProceedings{PirralhoPPSOFRA:2017:AnPhBi,
               author = "Pirralho, Marilia Jesus P{\'a}scao and Peres, Marcelos Lima and 
                         Pena, Fernando Silva and Soares, Demetrio A. W. and Okazaki, 
                         Anderson K. and Fornari, Celso Israel and Rappl, Paulo Henrique de 
                         Oliveira and Abramof, Eduardo",
          affiliation = "{} and {} and {} and {} and {} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas 
                         Espaciais (INPE)} and {Instituto Nacional de Pesquisas Espaciais 
                         (INPE)}",
                title = "Anomalous photoconductivity in Bi2Te3 topological insulator 
                         films",
            booktitle = "Resumos...",
                 year = "2017",
         organization = "Brazilian Workshop on Semiconductor Physics, 18. (BWSP)",
             abstract = "Topological insulators represent a new state of quantum matter 
                         that have an insulating bulk band gap but present metallic surface 
                         states. The surface states are topologically protected against 
                         non-magnetic impurities and it is possible the existence of a pure 
                         spin polarized current [1]. Three dimensional topological 
                         insulator as Bi2Te3 has attracted attention due to its topological 
                         properties and its potential application for development of 
                         spintronic devices [2]. In literature there is little or no 
                         information about photoconductivity in topological insulators, in 
                         particular in Bi2Te3. Photoconductivity measurements represent a 
                         powerful tool to probe the presence of defect states within be 
                         band structure and transport via more than one conduction channel. 
                         In this work we investigated the photoconductive properties of 
                         Bi2Te3 epitaxial layers in the temperature range of 77 to 300K. 
                         Unexpectedly, our measurements indicated that samples present 
                         negative photoconductivity, where the conductivity reduces under 
                         illumination, in the whole range of temperatures. In addition, 
                         these measurements revealed the presence of persistent 
                         photoconductivity effect for low temperatures, 77K-170K, which may 
                         be associated to the existence of a defect level within the band 
                         gap. From the photoconductivity decay curves, when light is 
                         removed, we could extract recombination times as a function of 
                         temperature and hence extract the energy associated to the traps 
                         located in band gap[3]. This study will reveal the effect of 
                         disorder in the photoconductivity properties in Bi2Te3 films and 
                         the role of surface states in the negative photoconductivity 
                         effect. Acknowledgments: The authors would like to acknowledge 
                         CAPES and FAPEMIG for support. References: [1] P. Dziawa, et al, 
                         Nature Materials 11, 1023 (2012); [2] Y. L. Chen, et al. Science 
                         325, 178 (2009); [3] J.A.Hagmann, X.Liu, M.Dobrowolska and 
                         J.K.Furdyna. Journal of Applied Physics, 113: 17C724., 2013.",
  conference-location = "Maresias, SP",
      conference-year = "14-18 ago.",
             language = "en",
           targetfile = "abramof_anomalous.pdf",
        urlaccessdate = "04 dez. 2020"
}


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