ELECTROCHEMICAL CHARACTERIZATION OF BORON DOPED ...
ELECTROCHEMICAL CHARACTERIZATION OF BORON DOPED NANOCRYSTALLINE DIAMOND FILMS GROWN ON POROUS SILICON 1
L. M. Silva1*; M. Santos1; M. R. Baldan1; A. F. Beloto1; N. G. Ferreira1 Laboratório Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, Jardim da Granja, 12227-010, São José dos Campos, SP, Brazil.
Boron doped nanocrystalline diamond (BDND) films were grown and characterized on PS substrates. PS samples were prepared from n-type monocrystalline silicon wafers (100) with 1-20 Ω.cm of resistivity, by electrochemical etching, using HF-acetonitrile solution as electrolyte. BDND films were grown by Hot Filament CVD technique using CH4, H2 and Ar. The doping process consisted of an additional hydrogen line, passing through a bubbler containing B2O3 dissolved in methanol, with boron/carbon ratio of 20000 ppm in solution. Raman spectroscopy and X-Ray diffraction were used to evaluate the quality of the films. Scanning electron microscopy was used for morphological characterization, and confirmed that the films covered the pores without filling them. Electrochemical response and capacitance behavior of the electrodes were explored, by cyclic voltammetry. Samples presented high capacitance, confirming that BDND/PS electrodes are promising for application as electrochemical capacitors.
Keywords: Boron doped nanocrystalline diamond film, porous silicon, electrochemical characterization, capacitance. Introduction Porous silicon consists of a superficial film with randomly spaced pores, formed during chemical or electrochemical etching of silicon, in hydrofluoric acid solution [Cho et al., 2012]. PS has been used as substrate to diamond films growth, in order to increase the number of diamond nucleation sites, improving the crystalline structure of the films [Ferreira et al., 2005]. Diamond p-type doping has been achieved by boron substitutional process during the film growth. Doping with boron allows the determination of the electrical resistivity as a function of its concentration [Barros et al., 2005]. In this work, boron doped nanocrystalline diamond (BDND) films were grown on porous silicon substrate, in order to evaluate the electrochemical behavior of these electrodes. Experimental part PS samples were obtained from n-type monocrystalline silicon wafers (100) with 1-20 Ω.cm of resistivity, by electrochemical etching, using HF-acetonitrile solution as electrolyte. The electrodes were polarized under 56.5 mA/cm² for 120 min. BDND films were grown by Hot Filament Chemical Vapor Deposition, using CH4, H2 and Ar, during 3 and 4 h. The doping process consisted of an additional hydrogen line, passing through a bubbler containing B2O3 dissolved in methanol, with boron/carbon ratio of 20000 ppm in solution. Structural characterization was made by Raman scattering spectroscopy and X-Ray diffraction. Scanning electron microscopy (SEM) was used for morphological characterization. Electrochemical response and capacitance behavior of the electrodes were explored, by cyclic voltammetry. Results and discussion SEM image showed that the film covered the pores without filling them, presenting uniform morphology (Figure 1). Raman spectrum (Figure 2) exhibited the expected nanocrystalline diamond features: the characteristics bands of transpolyacetylene at 1150 and 1490 cm-1, as well as the D band at 1345 cm-1 and the G band at 1580 cm-1. The X-ray diffraction spectrum
(Figure 3) showed the peaks at 43.9º and 75.3º, corresponding to the (111) and (220) diamond diffraction peaks. Work potential window of the electrodes are presented in Figure 4, showing a high capacitive effect, which can be associated to the large surface area of these electrodes. Figure 5 shows the capacitance results for BDND/PS electrodes compared to that for BDND/Si sample.
Fig. 1 – SEM image of BDND/PS electrode.
Fig. 2 – Raman spectrum of BDND/PS electrode.
Fig. 4 – Work potential window of the electrodes.
Fig. 3 – X-ray spectrum of BDND/PS electrode.
Fig. 5 – Capacitance values of the electrodes.
Conclusions SEM image confirmed that BDND film covered the whole PS surface including the pores bottom and their internal walls, maintaining the substrate porous structure and providing greater surface area. Raman spectroscopy and X-ray diffraction analyzes confirmed the diamond presence. Electrochemical characterization showed the high capacitance of BDND/PS electrodes. References [1] Cho, B.; Jin, S.; Lee, B.-Y.; Hwang, M.; Kim, H.-C.; Sohn, H.; 2012. Investigation of photoluminescence efficiency of n-type porous silicon by controlling of etching times and applied current densities. Microelectronic Engineering. 89, 92-96. [2] Ferreira, N. G.; Azevedo, A. F.; Beloto, A. F.; Amaral, M.; Almeida, F. A.; Oliveira, F. J.; Silva, R. F.; 2005. Nanodiamond films growth on porous silicon substrates for electrochemical applications. Diamond and Related Materials. 14, 441-445. [3] Barros, R. C. M.; Ribeiro, M. C.; An-Sumodjo, P. T.; Julião, M. S. S.; Serrano, S. H. P.; Ferreira, N. G.; 2005. Filmes de diamante CVD dopado com boro, parte I - Histórico, produção e caracterização. Química Nova. 28, 317-325. Acknowledgement: CAPES and CNPq.
L. M. Silva1*; M. Santos1; M. R. Baldan1; A. F. Beloto1; N. G. Ferreira1 Laboratório Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, Jardim da Granja, 12227-010, São José dos Campos, SP, Brazil.
Boron doped nanocrystalline diamond (BDND) films were grown and characterized on PS substrates. PS samples were prepared from n-type monocrystalline silicon wafers (100) with 1-20 Ω.cm of resistivity, by electrochemical etching, using HF-acetonitrile solution as electrolyte. BDND films were grown by Hot Filament CVD technique using CH4, H2 and Ar. The doping process consisted of an additional hydrogen line, passing through a bubbler containing B2O3 dissolved in methanol, with boron/carbon ratio of 20000 ppm in solution. Raman spectroscopy and X-Ray diffraction were used to evaluate the quality of the films. Scanning electron microscopy was used for morphological characterization, and confirmed that the films covered the pores without filling them. Electrochemical response and capacitance behavior of the electrodes were explored, by cyclic voltammetry. Samples presented high capacitance, confirming that BDND/PS electrodes are promising for application as electrochemical capacitors.
Keywords: Boron doped nanocrystalline diamond film, porous silicon, electrochemical characterization, capacitance. Introduction Porous silicon consists of a superficial film with randomly spaced pores, formed during chemical or electrochemical etching of silicon, in hydrofluoric acid solution [Cho et al., 2012]. PS has been used as substrate to diamond films growth, in order to increase the number of diamond nucleation sites, improving the crystalline structure of the films [Ferreira et al., 2005]. Diamond p-type doping has been achieved by boron substitutional process during the film growth. Doping with boron allows the determination of the electrical resistivity as a function of its concentration [Barros et al., 2005]. In this work, boron doped nanocrystalline diamond (BDND) films were grown on porous silicon substrate, in order to evaluate the electrochemical behavior of these electrodes. Experimental part PS samples were obtained from n-type monocrystalline silicon wafers (100) with 1-20 Ω.cm of resistivity, by electrochemical etching, using HF-acetonitrile solution as electrolyte. The electrodes were polarized under 56.5 mA/cm² for 120 min. BDND films were grown by Hot Filament Chemical Vapor Deposition, using CH4, H2 and Ar, during 3 and 4 h. The doping process consisted of an additional hydrogen line, passing through a bubbler containing B2O3 dissolved in methanol, with boron/carbon ratio of 20000 ppm in solution. Structural characterization was made by Raman scattering spectroscopy and X-Ray diffraction. Scanning electron microscopy (SEM) was used for morphological characterization. Electrochemical response and capacitance behavior of the electrodes were explored, by cyclic voltammetry. Results and discussion SEM image showed that the film covered the pores without filling them, presenting uniform morphology (Figure 1). Raman spectrum (Figure 2) exhibited the expected nanocrystalline diamond features: the characteristics bands of transpolyacetylene at 1150 and 1490 cm-1, as well as the D band at 1345 cm-1 and the G band at 1580 cm-1. The X-ray diffraction spectrum
(Figure 3) showed the peaks at 43.9º and 75.3º, corresponding to the (111) and (220) diamond diffraction peaks. Work potential window of the electrodes are presented in Figure 4, showing a high capacitive effect, which can be associated to the large surface area of these electrodes. Figure 5 shows the capacitance results for BDND/PS electrodes compared to that for BDND/Si sample.
Fig. 1 – SEM image of BDND/PS electrode.
Fig. 2 – Raman spectrum of BDND/PS electrode.
Fig. 4 – Work potential window of the electrodes.
Fig. 3 – X-ray spectrum of BDND/PS electrode.
Fig. 5 – Capacitance values of the electrodes.
Conclusions SEM image confirmed that BDND film covered the whole PS surface including the pores bottom and their internal walls, maintaining the substrate porous structure and providing greater surface area. Raman spectroscopy and X-ray diffraction analyzes confirmed the diamond presence. Electrochemical characterization showed the high capacitance of BDND/PS electrodes. References [1] Cho, B.; Jin, S.; Lee, B.-Y.; Hwang, M.; Kim, H.-C.; Sohn, H.; 2012. Investigation of photoluminescence efficiency of n-type porous silicon by controlling of etching times and applied current densities. Microelectronic Engineering. 89, 92-96. [2] Ferreira, N. G.; Azevedo, A. F.; Beloto, A. F.; Amaral, M.; Almeida, F. A.; Oliveira, F. J.; Silva, R. F.; 2005. Nanodiamond films growth on porous silicon substrates for electrochemical applications. Diamond and Related Materials. 14, 441-445. [3] Barros, R. C. M.; Ribeiro, M. C.; An-Sumodjo, P. T.; Julião, M. S. S.; Serrano, S. H. P.; Ferreira, N. G.; 2005. Filmes de diamante CVD dopado com boro, parte I - Histórico, produção e caracterização. Química Nova. 28, 317-325. Acknowledgement: CAPES and CNPq.
