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@MastersThesis{Okazaki:2015:EsFiFi,
               author = "Okazaki, Anderson Kenji",
                title = "Estudo de filmes finos de PbTe:CaF2 crescidos por epitaxia de 
                         feixe molecular",
               school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
                 year = "2015",
              address = "S{\~a}o Jos{\'e} dos Campos",
                month = "2015-02-25",
             keywords = "telureto de chumbo, fluoreto de c{\'a}lcio, epitaxia por feixe 
                         molecular, lead telluride, calcium fluoride, molecular beam 
                         epitaxy.",
             abstract = "Este trabalho tem como objetivo investigar as propriedades 
                         estruturais e el{\'e}tricas de filmes de PbTe dopados com 
                         CaF\$_{2}\$. Com esse prop{\'o}sito, filmes de 
                         PbTe:CaF\$_{2}\$ foram crescidos pela t{\'e}cnica de epitaxia 
                         de feixe molecular sobre substrato cristalino de BaF\$_{2}\$ 
                         (111), com a temperatura da fonte de CaF\$_{2}\$ variando entre 
                         500\$^{}\$C e 1250\$^{}\$C. A espessura dos filmes crescidos 
                         variou de 1,8 a 3,5 \$\mu\$m, e filmes com espessura acima de 
                         2,4 \$\mu\$m apresentaram uma diminui{\c{c}}{\~a}o na 
                         densidade de defeitos em sua superf{\'{\i}}cie. Nas amostras com 
                         oferta de CaF\$_{2}\$. abaixo de 1010\$^{}\$C, as imagens de 
                         difra{\c{c}}{\~a}o de el{\'e}trons de alta energia medidas 
                         \emph{in situ} exibiram um padr{\~a}o caracter{\'{\i}}stico de 
                         uma superf{\'{\i}}cie plana com degraus. Para temperaturas 
                         maiores da fonte de CaF\$_{2}\$., os padr{\~o}es revelaram que 
                         a deposi{\c{c}}{\~a}o ocorreu em ilhas. A presen{\c{c}}a de 
                         pequenos aglomerados observados nas imagens de microscopia de 
                         for{\c{c}}a at{\^o}mica corrobora com este resultado. Uma 
                         n{\'{\i}}tida fase de condensados de CaF\$_{2}\$. foi 
                         observada nas varreduras \$\omega\$-2\$\Theta\$ das 
                         an{\'a}lises de difra{\c{c}}{\~a}o de raios-x para as amostras 
                         que continham estas ilhas. Nas amostras com oferta de dopante 
                         abaixo de 900\$^{}\$C, os valores da largura {\`a} meia altura 
                         do pico de Bragg (222) do PbTe ficaram pr{\'o}ximos a 
                         103\${{"}}\$, valor similar ao da amostra de refer{\^e}ncia sem 
                         dopante, mostrando que a presen{\c{c}}a do fluoreto n{\~a}o 
                         afetou significativamente a qualidade cristalina dos filmes. O 
                         par{\^a}metro de rede manteve-se muito pr{\'o}ximo ao valor 
                         tabelado do PbTe volum{\'e}trico (6,462 A), revelando que a 
                         oferta de CaF\$_{2}\$., n{\~a}o causou uma tens{\~a}o 
                         significativa nos filmes. A energia de gap {\`a} temperatura 
                         ambiente tamb{\'e}m se manteve pr{\'o}xima ao valor tabelado 
                         para o PbTe (0,32 eV), mostrando que a adi{\c{c}}{\~a}o do 
                         dopante n{\~a}o causou a forma{\c{c}}{\~a}o de uma nova liga. A 
                         concentra{\c{c}}{\~a}o de portadores dos filmes de 
                         PbTe:CaF\$_{2}\$. flutuou entre 1,5 10\$^{17}\$ e 3,6 
                         10\$^{17}\$ cm\$^{-3}\$ a 77 K, n{\~a}o exibindo um 
                         comportamento sistem{\'a}tico {\`a} medida que a oferta do 
                         fluoreto aumentava. Os resultados das medidas el{\'e}tricas 
                         mostraram que a oferta de CaF\$_{2}\$. durante o crescimento 
                         n{\~a}o produziu um efeito de dopagem extr{\'{\i}}nseca para o 
                         PbTe. ABSTRACT: This work aims to investigate the structural and 
                         electrical properties of PbTe films doped with CaF\$_{2}\$. For 
                         this purpose, PbTe:CaF\$_{2}\$. films were grown by molecular 
                         beam epitaxy on (111) BaF\$_{2}\$. crystalline substrates, with 
                         the CaF\$_{2}\$. source temperature varying between 
                         500\$^{}\$C and 1250\$^{}\$C. The thickness of the grown 
                         films ranged from 1.8 to 3.5 \$\mu\$m and films thicker than 
                         2.4 \$\mu\$m presented a lower surface defect density. For 
                         samples grown with a CaF\$_{2}\$. source temperature lower than 
                         1010\$^{}\$C, the high energy electron diffraction images 
                         measured \emph{in situ} exhibited a pattern characteristic of a 
                         flat surface with steps. For higher CaF2 source temperature, the 
                         patterns revealed that the deposition occurred in islands. The 
                         presence of small agglomerates observed in the atomic force 
                         microscopy images corroborates with this result. An evident phase 
                         of CaF\$_{2}\$. condensates in the samples that presented these 
                         islands was observed in the \$\mu\$-2\$\theta\$ scans of the 
                         x-ray diffraction analysis. For the samples with a dopant offer 
                         lower than 900\$^{}\$C, the values of the full width at half 
                         maximum of the (222) PbTe Bragg peak stayed near to 
                         103\${{"}}\$, a value similar to the one of the undoped 
                         reference sample, what demonstrates that the presence of the 
                         fluoride did not affect significantly the crystalline quality of 
                         the PbTe films. The lattice parameter of the grown films remained 
                         very close to the tabulated value of the bulk PbTe (6.462 A), 
                         revealing that the CaF\$_{2}\$. offer did not cause a 
                         significant stress in the films. The energy gap at room 
                         temperature also remained close to the tabulated value of PbTe 
                         (0.32 eV), showing that the CaF\$_{2}\$. addition did not form a 
                         new alloy. The carrier concentration of the PbTe:CaF2 films 
                         fluctuated between 1.5 10\$^{17}\$and 3.6 10\$^{17}\$ 
                         cm\$^{-3}\$ at 77 K, and did not exhibit a systematic behavior 
                         as the fluoride offer raised. The electrical measurement results 
                         showed that the CaF\$_{2}\$. offer during growth did not produce 
                         an extrinsic doping effect on PbTe.",
            committee = "Rappl, Paulo Henrique de Oliveira (presidente/orientador) and 
                         Abramof, Eduardo (orientador) and An, Chen Ying and Peres, 
                         Marcelos Lima",
           copyholder = "SID/SCD",
         englishtitle = "Study of PbTe:CaF2 thin films grown by molecular beam epitaxy",
             language = "pt",
                pages = "124",
                  ibi = "8JMKD3MGP3W34P/3HU459L",
                  url = "http://urlib.net/rep/8JMKD3MGP3W34P/3HU459L",
           targetfile = "publicacao.pdf",
        urlaccessdate = "26 nov. 2020"
}


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