Caracterização da composição, estrutura e propriedades termoelétricas dos filmes de InxGa1-xSb depositados por magnetron sputtering e modificados por irradiação iônica

InxGa1-xSb (x = 0.5, 0.6, 0.8 and 1) films were deposited by radio frequency magnetron sputtering onto SiO2/Si substrates at 420 °C and the compositional, structural and thermoelectric characterizations of the films were performed for different In/Ga ratio concentrations before and after ion irradiation at different fluences. Rutherford backscattering spectrometry (RBS) and particle-induced x-ray emission (PIXE) were employed in the analysis of the relative atomic concentration of the films. The structure of the films was characterized by grazing incidence x-ray diffraction (GIXRD) and extended x-ray absorption fine structure (EXAFS) analyses, whereas scanning electron microscopy (SEM) provided information about the morphology of the films. The thermoelectric properties of the films were measured with the aid of an equipment specially developed for this purpose. GIXRD showed the formation of polycrystalline zincblende structure in as-deposited films with the lattice parameter changing linearly with composition x as predicted by Vegard`s law. EXAFS evidenced that the lattice mismatch in ternary compounds is accommodated favorably through bond bending over bond stretching. Regarding the thermoelectric properties, it was observed that In0.8Ga0.2Sb films exhibited the highest ZT value (0.53 at 450 K) among the films investigated here. Upon ion irradiation with 16 MeV Au+7 ions with ion fluences ranging from 1 × 1013 cm−2 to 5 × 1014 cm−2 , InxGa1-xSb films presented a pronounced continuous-to-porous transformation and a bond length conservation with no loss of material or sputtering induced by the ion irradiation process. InxGa1-xSb compounds, however, exhibited a nonlinear stoichiometry-dependent porosity. Through GIXRD analysis, it was verified that it is easier to amorphize the ternary compound than its binary counterpart InSb. InxGa1-xSb nanofoams also showed to be remarkably stable under annealing in vacuum at 200 °C, with very small changes in atomic concentration induced by thermal annealing. Concerning the thermoelectric properties (ZT parameter), its value substantially decreased after ion irradiation. These results show that InxGa1-xSb films deposited by magnetron sputtering have potential application in gas sensor devices.Filmes de InxGa1-xSb (x = 0,5, 0,6, 0,8 e 1) foram depositados por magnetron sputtering em regime de radiofrequência sobre substratos de SiO2/Si, a 420 °C, e as caracterizações composicional, estrutural e termoelétrica dos filmes foram realizadas para diferentes taxas de In/Ga concentrações antes e depois da irradiação com íons em diferentes fluências. Espectrometria de retroespalhamento Rutherford (RBS) e emissão de raios-x induzida por partículas (PIXE) foram empregadas na análise da concentração atômica relativa dos filmes. A estrutura dos filmes foi caracterizada por difração de raios-x de incidência rasante (GIXRD) e estrutura fina de absorção de raios-x estendida (EXAFS), enquanto a microscopia eletrônica de varredura (MEV) forneceu informações sobre a morfologia dos filmes. As propriedades termoelétricas dos filmes foram medidas com o auxílio de um equipamento especialmente desenvolvido para este fim. GIXRD mostrou a formação de estrutura de zincoblenda policristalina nos filmes depositados com o parâmetro de rede mudando linearmente com a composição x, conforme previsto pela lei de Vegard. EXAFS evidenciou que o descasamento de rede em compostos ternários é acomodado favoravelmente através da flexão da ligação sobre o alongamento da ligação. Com relação às propriedades termoelétricas, observou-se que os filmes de In0.8Ga0.2Sb apresentaram o maior valor de ZT (0.53 a 450 K) entre os filmes aqui investigados. Após irradiação de íons com íons Au+7 de 16 MeV com fluências de íons variando de 1 × 1013 cm−2 a 5 × 1014 cm−2 , os filmes de InxGa1-xSb apresentaram uma pronunciada transformação da forma contínua à porosa e a conservação do comprimento de ligação sem perda de material ou pulverização induzida pelo processo de irradiação de íons. Os compostos InxGa1- xSb, no entanto, exibem uma porosidade dependente da estequiometria não linear. Através da análise GIXRD, verificou-se que é mais fácil amorfizar o composto ternário do que o seu homólogo binário InSb. As nanoespumas InxGa1-xSb também mostraram ser notavelmente estáveis sob recozimento a vácuo em temperatura de 200 °C, com mudanças muito pequenas na concentração atômica induzidas pelo recozimento térmico. Com relação às propriedades termoelétricas (parâmetro ZT), seu valor diminuiu substancialmente após a irradiação iônica. Esses resultados mostram que os filmes de InxGa1-xSb depositados por magnetron sputtering têm potencial aplicação em dispositivos sensores de gás

Estudo das propriedades eletrônicas e estruturais de filmes de In(0.5-x)AlxSb0.5 depositados por magnetron sputtering e irradiados por feixes de íons

Filmes de In(0.5-x)AlxSb0.5 foram depositados sobre substratos de SiO2/Si, a 420°C, por co-sputtering dos alvos de InSb, Al e Sb e as suas propriedades estruturais foram investigadas com o auxílio das técnicas de Grazing incidence X-ray diffraction (GIXRD) e Rutherford backscattering spectrometry (RBS). Filmes com quatro concentrações relativas de Al (0 %,9%,15% e 18%) foram irradiados com íons de Au+6 de 14 MeV de energia e fluências no intervalo 1x1013 - 2x1014 cm-2. Para todos os filmes de In(0.5-x)AlxSb0.5, o espectro de GIXRD mostrou a formação de um composto policristalino com estrutura zincblende, de forma que, quanto maior a concentração de Al nesta liga, menor o respectivo parâmetro de rede. Quando irradiados, observou-se que é mais fácil amorfizar o composto ternário (In(0.5-x)AlxSb0.5) que os seus membros binários InSb e AlSb, sendo que neste último não foi observado nenhuma evidência de amorfização no seu padrão de difração. Além disso, por meio da microscopia eletrônica de varredura (MEV), verificou-se que essa liga ternária torna-se porosa, a partir de uma certa fluência, para todas as concentrações de Al (exceção de AlSb), de modo que a porosidade dos filmes de In(0.5-x)AlxSb0.5 diminui, para uma mesma fluência (1x1014 cm-2), segundo a concentração relativa de Al aumenta. Em relação às propriedades eletrônicas dos filmes, mostrou-se, através da técnica de X-ray photoelectron spectroscopy (XPS), tanto nos filmes não irradiados como nos irradiados, que não havia ligação Al-Sb e que tinha maior quantidade relativa de oxigênio nas amostras irradiadas frente as não irradiadas.In(0.5-x)AlxSb0.5 films were deposited on SiO2/Si substrates, at 420°C, by co-sputtering of the InSb, Al and Sb targets and their structural properties were investigated by Grazing incidence X-ray diffraction (GIXRD) and Rutherford backscattering spectrometry (RBS). Films with four relative Al concentrations (0%, 9%, 15% and 18%) were irradiated with Au+ 6 ions of 14 MeV of energy and fluences in the interval 1x1013 - 2x1014 cm-2. For all In(0.5-x)AlxSb0.5 films, the GIDXRD diffractograms showed the formation of a polycrystalline compound with zincblende phase, so that the higher the Al concentration in this alloy, the lower the respective lattice parameter. When irradiated, it was found that it is easier to amorphise the ternary compound (In(0.5-x)AlxSb0.5) than its binary InSb and AlSb, and in the latter, no evidence of amorphization was observed in its diffraction pattern. Furthermore, by scanning electron microscopy (SEM), it was found that this ternary alloy becomes porous, after irradiation with sufficient fluence, for all concentrations of Al (except AlSb), so that the porosity of the In(0.5-x)AlxSb0.5 films decreases, for the same fluence (1x1014 cm-2), as the relative Al concentration increases. In relation to the electronic properties of the films, X-ray photoelectron spectroscopy (XPS) showed that there was no Al-Sb binding at the surface and that there was a greater relative amount of oxygen in the irradiated than non-irradiated samples

Ion implantation in β-Ga2O3 : Physics and technology

Gallium oxide, and in particular its thermodynamically stable β-Ga2O3 phase, is within the most exciting materials in research and technology nowadays due to its unique properties. The very high breakdown electric field and the figure of merit rivaled only by diamond have tremendous potential for the next generation “green” electronics enabling efficient distribution, use, and conversion of electrical energy. Ion implantation is a traditional technological method used in these fields, and its well-known advantages can contribute greatly to the rapid development of physics and technology of Ga2O3-based materials and devices. Here, the status of ion implantation in β-Ga2O3 nowadays is reviewed. Attention is mainly paid to the results of experimental study of damage under ion irradiation and the properties of Ga2O3 layers doped by ion implantation. The results of ab initio theoretical calculations of the impurities and defect parameters are briefly presented, and the physical principles of a number of analytical methods used to study implanted gallium oxide layers are highlighted. The use of ion implantation in the development of Ga2O3-based devices, such as metal oxide field-effect transistors, Schottky barrier diodes, and solar-blind UV detectors, is described together with systematical analysis of the achieved values of their characteristics. Finally, the most important challenges to be overcome in this field of science and technology are discussed

Caracterização de dielétricos depositados por “atomic layer deposition’’ usando estrutura MOS

Capacitores MOS com camadas dielétricas de Al2O3, HfO2, TiO2, fabricadas usando a técnica de deposição por camada atômica (ALD) e de SiO2, fabricadas por oxidação térmica. Medidas de I - V e C - V foram utilizadas para obter a constante dielétrica, espessura efetiva do óxido (EOT), tensão e campo de ruptura dielétrica, corrente de fuga e qualidade de interface. Os resultados mostram a presença de filmes com constantes dielétricas de 4,69 e 6,46 para os dielétricos de Al2O3 e HfO2, nesta ordem. A constate dielétrica para TiO2 não foi possível de ser calculada. Adicionalmente, correntes de fuga de 5 pA e 50 pA em -5 V para Al2O3 e HfO2, respectivamente, foram medidas. Entre os dielétricos high-k fabricados, o Al2O3 apresentou as melhores propriedades elétricas, tais como menor densidade de cargas aprisionadas ( ), maior valor de tensão de ruptura dielétrica (22,47 V) e campo elétrico de ruptura (10,40 MV/cm). O Al2O3 torna-se, então, um viável substituto para o problema da elevada corrente de tunelamento em filmes finos de SiO2, em transistores MOS, através da troca destes filmes por camadas mais espessas de Al2O3 de mesma capacitância, no entanto, resultando em diminuição na corrente de tunelamento.MOS capacitors with dielectric layers of Al2O3, HfO2, TiO2, made using atomic layer deposition (ALD) and SiO2, made by thermal oxidation. I - V and C - V measurements were used to obtain the dielectric constant, effective oxide thickness (EOT), voltage and dielectric rupture field, leakage current and interface quality. The results show the presence of films with dielectric constants of 4,69 and 6,46 for the dielectric of Al2O3 and HfO2, in this order. The dielectric constant for TiO2 could not be calculated. In addition, leakage currents of 5 pA and 50 pA in -5 V for Al2O3 and HfO2, respectively, were measured. Among the high-k dielectrics manufactured, Al2O3 presented the best electrical properties, such as lower density of entrapped loads ( ), higher dielectric rupture voltage (22,47 V) and electric field rupture (10,40 MV/ cm). Al2O3 then becomes a viable substitute for the problem of the high tunneling current in SiO2 thin films in MOS transistors, by changing these films by thicker Al2O3 layers of the same capacitance, however, resulting in a decrease In the tunneling stream

Investigação dos parâmetros ideais para fabricação de filmes de In(x) Al(1-x) Sb por sputtering

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Caracterização de dielétricos depositados por “atomic layer deposition’’ usando estrutura MOS

Capacitores MOS com camadas dielétricas de Al2O3, HfO2, TiO2, fabricadas usando a técnica de deposição por camada atômica (ALD) e de SiO2, fabricadas por oxidação térmica. Medidas de I - V e C - V foram utilizadas para obter a constante dielétrica, espessura efetiva do óxido (EOT), tensão e campo de ruptura dielétrica, corrente de fuga e qualidade de interface. Os resultados mostram a presença de filmes com constantes dielétricas de 4,69 e 6,46 para os dielétricos de Al2O3 e HfO2, nesta ordem. A constate dielétrica para TiO2 não foi possível de ser calculada. Adicionalmente, correntes de fuga de 5 pA e 50 pA em -5 V para Al2O3 e HfO2, respectivamente, foram medidas. Entre os dielétricos high-k fabricados, o Al2O3 apresentou as melhores propriedades elétricas, tais como menor densidade de cargas aprisionadas ( ), maior valor de tensão de ruptura dielétrica (22,47 V) e campo elétrico de ruptura (10,40 MV/cm). O Al2O3 torna-se, então, um viável substituto para o problema da elevada corrente de tunelamento em filmes finos de SiO2, em transistores MOS, através da troca destes filmes por camadas mais espessas de Al2O3 de mesma capacitância, no entanto, resultando em diminuição na corrente de tunelamento.MOS capacitors with dielectric layers of Al2O3, HfO2, TiO2, made using atomic layer deposition (ALD) and SiO2, made by thermal oxidation. I - V and C - V measurements were used to obtain the dielectric constant, effective oxide thickness (EOT), voltage and dielectric rupture field, leakage current and interface quality. The results show the presence of films with dielectric constants of 4,69 and 6,46 for the dielectric of Al2O3 and HfO2, in this order. The dielectric constant for TiO2 could not be calculated. In addition, leakage currents of 5 pA and 50 pA in -5 V for Al2O3 and HfO2, respectively, were measured. Among the high-k dielectrics manufactured, Al2O3 presented the best electrical properties, such as lower density of entrapped loads ( ), higher dielectric rupture voltage (22,47 V) and electric field rupture (10,40 MV/ cm). Al2O3 then becomes a viable substitute for the problem of the high tunneling current in SiO2 thin films in MOS transistors, by changing these films by thicker Al2O3 layers of the same capacitance, however, resulting in a decrease In the tunneling stream

Estudo das propriedades eletrônicas e estruturais de filmes de In(0.5-x)AlxSb0.5 depositados por magnetron sputtering e irradiados por feixes de íons

Filmes de In(0.5-x)AlxSb0.5 foram depositados sobre substratos de SiO2/Si, a 420°C, por co-sputtering dos alvos de InSb, Al e Sb e as suas propriedades estruturais foram investigadas com o auxílio das técnicas de Grazing incidence X-ray diffraction (GIXRD) e Rutherford backscattering spectrometry (RBS). Filmes com quatro concentrações relativas de Al (0 %,9%,15% e 18%) foram irradiados com íons de Au+6 de 14 MeV de energia e fluências no intervalo 1x1013 - 2x1014 cm-2. Para todos os filmes de In(0.5-x)AlxSb0.5, o espectro de GIXRD mostrou a formação de um composto policristalino com estrutura zincblende, de forma que, quanto maior a concentração de Al nesta liga, menor o respectivo parâmetro de rede. Quando irradiados, observou-se que é mais fácil amorfizar o composto ternário (In(0.5-x)AlxSb0.5) que os seus membros binários InSb e AlSb, sendo que neste último não foi observado nenhuma evidência de amorfização no seu padrão de difração. Além disso, por meio da microscopia eletrônica de varredura (MEV), verificou-se que essa liga ternária torna-se porosa, a partir de uma certa fluência, para todas as concentrações de Al (exceção de AlSb), de modo que a porosidade dos filmes de In(0.5-x)AlxSb0.5 diminui, para uma mesma fluência (1x1014 cm-2), segundo a concentração relativa de Al aumenta. Em relação às propriedades eletrônicas dos filmes, mostrou-se, através da técnica de X-ray photoelectron spectroscopy (XPS), tanto nos filmes não irradiados como nos irradiados, que não havia ligação Al-Sb e que tinha maior quantidade relativa de oxigênio nas amostras irradiadas frente as não irradiadas.In(0.5-x)AlxSb0.5 films were deposited on SiO2/Si substrates, at 420°C, by co-sputtering of the InSb, Al and Sb targets and their structural properties were investigated by Grazing incidence X-ray diffraction (GIXRD) and Rutherford backscattering spectrometry (RBS). Films with four relative Al concentrations (0%, 9%, 15% and 18%) were irradiated with Au+ 6 ions of 14 MeV of energy and fluences in the interval 1x1013 - 2x1014 cm-2. For all In(0.5-x)AlxSb0.5 films, the GIDXRD diffractograms showed the formation of a polycrystalline compound with zincblende phase, so that the higher the Al concentration in this alloy, the lower the respective lattice parameter. When irradiated, it was found that it is easier to amorphise the ternary compound (In(0.5-x)AlxSb0.5) than its binary InSb and AlSb, and in the latter, no evidence of amorphization was observed in its diffraction pattern. Furthermore, by scanning electron microscopy (SEM), it was found that this ternary alloy becomes porous, after irradiation with sufficient fluence, for all concentrations of Al (except AlSb), so that the porosity of the In(0.5-x)AlxSb0.5 films decreases, for the same fluence (1x1014 cm-2), as the relative Al concentration increases. In relation to the electronic properties of the films, X-ray photoelectron spectroscopy (XPS) showed that there was no Al-Sb binding at the surface and that there was a greater relative amount of oxygen in the irradiated than non-irradiated samples

Investigação dos parâmetros ideais para fabricação de filmes de In(x) Al(1-x) Sb por sputtering

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Local and extended atomic structure of strained polycrystalline In(1-x)Al(x)Sb alloys

In(1-x)Al(x)Sb films were deposited on amorphous SiO2 by magnetron sputtering with four different In/Al concentration ratios and the local and extended atomic structure were investigated through extended x-ray absorption fine structure (EXAFS) spectroscopy and grazing incidence x-ray diffraction (GIXRD) analyses, respectively. GIXRD showed the deposited films are strained polycrystalline, however, preserving the cubic symmetry of zinc blende structure due to homogeneous compression. EXAFS analysis of In and Sb atoms in strained In(1-x)Al(x)Sb films provided information about the interatomic distance distributions of the first three nearest-neighbor (NN) shells. For the first NN, the average cation-anion distances presented only the alloying effect, resembling the unstrained ternary alloy with a relaxation parameter of ε = 0.77±0.01 and ε = 0.79 ± 0.01 for the dilute limit InSb:Al and AlSb:In, respectively, and with the extra structural modifications due to the strain factor appearing in higher coordination shells only. In the second NN shell distance it was observed that the strain effect is more pronounced in In–Al than In–In interatomic distance, which is, within uncertainty, independent of strain, evidencing an anisotropy in the process of accommodating the strain in the mixed sublattice, which is favored by bond bending over bond stretching, similarly to unstrained III-V ternary alloys. On the other hand, anion-anion distances exhibited a bimodal distribution, showing a tendency to retain the values of unstrained pure compounds. The third NN shell mean distances vary linearly with concentration. Moreover, the core effect in(1-x)Al(x)Sb alloys was described via EXAFS demonstrating that elastic continuous medium theory is not adequate to describe this system. Using x-ray absorption near edge structure, it was observed that In K-edge position is constant with In/Al ratio in(1-x)Al(x)Sb alloys, whereas Sb K-edge position changed, evidencing its relation with the local atomic arrangement

Ion irradiation-induced foams in antimonide binary alloys : a combination of small energy bandgap with giant surface-to-bulk ratio

This is a short review about the ion irradiation-induced foams in antimonide films. III–V semiconductors like InSb and GaSb can be transformed into solid foams with nanometric dimensions upon irradiation with swift heavy ions, increasing significantly the effective surface area of the material. The giant surface-to-bulk ratio of solid nanofoams, combined with the small energy bandgap of antimonide binary compounds offer new possibilities for the development of electronic devices with improved energy efficiency. The characterization of antimonide nanofoams structure, composition and electronic properties is thus essential to fully exploit their promising technological advantages. Here we show that InSb and GaSb films deposited by magnetron sputtering on SiO2/Si substrates can be rendered porous upon irradiation with 17 MeV Au +7 ions, while no evidence of porosity was observed in AlSb films irradiated under similar conditions. InSb films initially amorphous, become polycrystalline with zincblende phase upon irradiation with fluence 2x1014 cm−2, at the same time as the accumulation of voids result in the complete transformation of the films from compact-continuous to foam-like structure. Single-crystalline InSb films can also be transformed into solid foams upon irradiation, however, the ion fluence required to attain similar levels of porosity (compared to amorphous InSb deposited by magnetron sputtering) is significantly higher. GaSb films, in a similar way, can also be transformed into solid foams upon irradiation, although, for GaSb films deposited by magnetron sputtering, the structure of the foams is amorphous with significant increase of oxide fraction upon irradiation. The ion irradiation effects on the electronic properties of single crystalline InSb films are also presented. We compare the ion irradiation effects in different antimonide binary compounds with results about their crystalline structure and morphology using X-ray diffraction analysis and scanning electron microscopy