Boron-doped microcrystalline silicon films were deposited in a plasma enhanced chemical vapor deposition (PECVD) system using silane (SiH4) diluted in hydrogen, and diborane (B2H6) as a dopant gas. The effects of the Boron concentration on the optical and structural properties were investigated by the constant-photocurrent method (CPM) and atomic force microscopy (AFM) measurements. The variations in the optical constants (refractive index, absorption coefficient and optical gap) as a function of wavelength were carried out from the optical transmission and CPM spectra. By increasing the doping level, a systematic increase in the absorption coefficient spectra in the low-energy region between 0.7 - 1.2 eV was observed. It was found that the increase of Boron concentration in the samples results in changes of the grain size. Correlations between optical properties and the density of states (DOS) were also studied.Fil: Dussan, A.. Universidad Nacional de Colombia; ColombiaFil: Koropecki, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Arce, Roberto Delio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Schmidt, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Arce, Roberto Delio

Dussan, A.

Koropecki, Roberto Roman

Schmidt, Javier Alejandro

Revista Mexicana de Física

English

CONICET Digital

REVISTA MEXICANA DE F´ISICA S 53 (7) 253–255 DICIEMBRE 2007Structural and optical properties of compensated microcrystalline silicon filmsA. DussanDepartamento de Fı´sica, Universidad Nacional de Colombia, Bogota´, COLOMBIA,Fax.: 57-1-3165135,e-mail: adussanc@unal.edu.coR.R. Koropecki, R. Arce, and J.A. SchmidtINTEC (CONICET-UNL),Gu¨emes 3450, 3000 Santa Fe, Argentina.Recibido el 30 de noviembre de 2006; aceptado el 8 de octubre de 2007Boron-doped microcrystalline silicon films were deposited in a plasma enhanced chemical vapor deposition (PECVD) system using silane(SiH4) diluted in hydrogen, and diborane (B2H6) as a dopant gas. The effects of the Boron concentration on the optical and structuralproperties were investigated by the constant-photocurrent method (CPM) and atomic force microscopy (AFM) measurements. The variationsin the optical constants (refractive index, absorption coefficient and optical gap) as a function of wavelength were carried out from the opticaltransmission and CPM spectra. By increasing the doping level, a systematic increase in the absorption coefficient spectra in the low-energyregion between 0.7 - 1.2 eV was observed. It was found that the increase of Boron concentration in the samples results in changes of thegrain size. Correlations between optical properties and the density of states (DOS) were also studied.Keywords: Optical properties; AFM; structural properties;thin films.Se depositaron pelı´culas delgadas de silicio microcristalino con bajas concentraciones de Boro por late´cnica de deposicio´n quı´mica en fase devapor asistida por plasma (PECVD) usando silano (SiH4) diluido en hidro´geno y diborano (B2H6) como gas dopante. Se realizaron estudiosde los efectos del Boro sobre las propiedades o´pticas y estructurales a trave´s del me´todo de fotocorriente constante (CPM) y medidas demicroscopı´a de fuerzaato´mica (AFM). A partir de las medidas de transmisio´n o´ptica y los espectros de CPM se obtuvieron las constanteso´pticas (ı´ndice de refraccio´n, coeficiente de absorcio´n y gap o´ptico) en funcio´n de la longitud de onda. Debido al aumento en el nivel dedoping se observo´ un crecimiento sistema´tico en los espectros del coeficiente de absorcio´n en la regio´n de baja energı´a entre 0.7 - 1.2 eV. Seencontro´ que el incremento en la concentracio´n de Boro en las muestras produce un cambio en el taman˜o de grano. Se presenta tambie´n unacorrelacio´n entre las propiedades o´pticas y la densidad de estados (DOS) en el material.Descriptores: Propiedades o´pticas; AFM; propiedades estructurales; pelı´culas delgadas.PACS: 78.20.Ci; 68.55.Jk; 78.40.Fy1. IntroductionIn recent years, hydrogenated microcrystalline silicon (µc-Si:H) has been increasingly used in the production of thinfilm based solar cells due to its higher stability comparedto hydrogenated amorphous silicon (a-Si:H) [1, 2]. µc-Si:His usually deposited by plasma enhanced chemical vapordeposition (PECVD) from silane-hydrogen mixtures, at afrequency of 13.57 MHz [3, 4]. The successful usage ofthin µc-Si:H films for photovoltaic applications requires re-liable techniques to characterize its properties. In this workwe present results from the characterization of thin µc-Si:Hfilms doped with boron. We measured optical propertiesfrom spectral transmittance and the constant photocurrentmethod (CPM), structural properties from atomic force mi-croscope (AFM) observations, and electrical transport prop-erties from the modulated photoconductivity (MPC) tech-nique [5]. These last measurements were used to estimate theeffect of boron incorporation on the density of states (DOS)within the forbidden gap of the material. Structural propertieswere obtained from X-ray diffraction measurements.2. ExperimentalSamples were prepared in a capacitively coupled PECVDreactor described in a previous work, [6] operated at a fre-quency of 50 MHz. The substrate was Corning 7059 glassand the substrate temperature was set at 160◦C. We used amixture of 94% hydrogen - 6% silane as source gas, with atotal flux of 20 sscm. Diborane was used as a dopant gas, witha concentration in the gas phase varying between 0 and 100ppm relative to silane. The base pressure in the reactor previ-ous to the deposition was lower than 10−6 Torr, while duringthe sample deposition, it was fixed at 4.5×10−1 Torr. Thepower density was 50 mW/cm2. The films’ thickness, calcu-lated from the interference of the transmittance spectra in thenear infrared region, ranged from 0.6 to 1 µm. The absorptioncoefficient for energies lower than 2 eV was determined fromconstant photocurrent measurements (CPM [7]). The MPCmeasurements were performed on samples provided with in-terdigitated aluminum contacts, separated 0.01 cm and witha total length of 25 cm, deposited by photolithography. Sam-ples were mounted in a cryostat provided with an optical win-dow, connected to a vacuum system. A 10 mW He-Ne laserwas used as a light source. The incident light intensity waspartially modulated (12.5%) by using an electro-optical mod-ulator driven by a function generator (HP 3325A). We appliedto the samples a voltage of 100 V, provided by a stabilizedpower source. For dc photoconductivity measurements weused a Keithley 617 electrometer, while for the MPC mea-254 A. DUSSAN, R.R. KOROPECKI, R. ARCE, AND J.A. SCHMIDTsurements, we used a lock-in amplifier (Stanford 830) to de-tect the modulus and phase shift of the ac photocurrent. Toevaluate the DOS from the MPC measurements we assumeda DOS at the conduction band edge of 1×1021 cm−3eV−1and a mobility gap of 1.8 eV. To study the morphologicalproperties, we used an atomic force microscope (Park Scien-tific Instruments). X rays diffractio was used to confirm themicrocrystalline nature of the samples.FIGURE 1. α(hν) spectra obtained by CPM for the set of µc-Si:Hsimples deposited varying the doping concentration [B2H6]/[SiH4]between 12.5 and 100 ppm.FIGURE 2. Density of occupied states extracted from the CPMmeasurements by using the de-convolution procedure proposed byJensen [9], for the samples with diborane concentrations of 12.5,50 and 100 ppm.FIGURE 3. Effect of boron compensation on the DOS of µc-Si:Hsamples. The DOS in the upper gap region was obtained from MPCmeasurements, while in the lower bandgap region, it was obtainedfrom CPM measurements. The Fermi level position for the com-pensated sample (25 ppm diborane) is marked with an arrow.3. Results and discussionIn Fig. 1 we present the α(hν) spectra obtained by CPM forthe whole set of µc-Si:H samples. In this figure, a clear in-crease of the absorption coefficient in the region of energieslower than 0.9 eV can be seen when the diborane concen-tration increases from 12.5 to 100 ppm. The absorption co-efficient in this subgap region is known to be related to thepresence of defects in the material [8]. In Table I we reportthe refractive index, optical bandgap and thickness of the dif-ferent samples, as obtained from the analysis of the spectraltransmittance data, and the grain size and roughness obtainedfrom the AFM observations.In Fig. 2 one can observe that the DOS of the samplesincreases with the increase of the doping concentration in theregion of energies lower than from the conduction band edge.This fact is consistent with the observations of Fig. 1, wherethe absorption coefficient gradually increases in the subgapregion with the increase of the diborane concentration. Forthe sample doped with 12.5 ppm of diborane, the α(hν) spec-trum could only be obtained for photon energies larger than1.05 eV. The DOS changes are closely related to the levelof doping of the material, and can be attributed to the boronincorporation during the sample deposition. The increase ofthe boron concentration leads to an increase of the numberof B-H-Si sites, and consequently, to the creation of dan-gling bonds. These type of sites are known as B-H com-plexes [10]. It has been shown [11] that the incorporationof small amounts of boron to compensate the sample close tothe unset of microcrystallinity leads to the creation of defects.Thus, the DOS in the subgap region changes.In Fig. 3 we show the effect of doping on the DOS of theµc-Si:H samples, detected through MPC (DOS in the upperRev. Mex. Fı´s. S 53 (7) (2007) 253–255STRUCTURAL AND OPTICAL PROPERTIES OF COMPENSATED MICROCRYSTALLINE SILICON FILMS 255FIGURE 4. AFM images of hydrogenated microcrystalline silicon with different diborane concentrations. a)12.5 ppm, b) 50 ppm andd) 100 ppm.TABLE I. Optical constants and morphological parameters of thethin c-Si:H samples obtained varying the [B2H6]/[SiH4] concentra-tion between 12.5 and 100 ppm. n stands for the refractive index, dfor the thickness, Eg for the optical bandgap, Z for the mean grainsize, and R for the root mean square roughness of the surface.[B2H6]/[SiH4] (ppm) n d (nm) Eg (eV) Z (A˚) R (A˚)12.5 3.17 500 1.28 562 9025 3.19 618 1.30 564 92.150 3.17 619 1.29 986 10575 3.15 649 1.30 1040 84.7100 3.17 916 1.13 1510 93.6half of the bandgap) and CPM (DOS in the lower half of thebandgap) measurements. This figure clearly shows that boronincorporation leads to an increase in the DOS of the sam-ples. The Fermi level position for the compensated sample(25 ppm of diborane) is indicated by an arrow (EF = 0.68 eV,midgap).Through AFM observations we gained information aboutthe morphological properties of the thin boron-doped µc-Si:H samples. In Fig. 4 we present AFM images of someof the samples.Figure 4 shows an increase in the grain size of the sam-ples with the increase of the diborane concentration. We no-tice that when the Boron concentration is increased from 12.5ppm to 50 ppm (Figs. 4a and 4b), the grain size changes from562 A˚to 564 A˚, whereas we observed that when the Boronconcentration is 100 ppm, the grain size was 986 A˚(Fig. 4c))(see Table I). On the other hand, it can be seen that the rough-ness of the samples is not strongly affected by the boron in-corporation at concentrations higher than 12.5 ppm (see Ta-ble I). The mean grain size values and the rms roughness havealready been reported in Table I.4. ConclusionIn this work we have presented a study of the optical andstructural properties of thin hydrogenated microcrystallinesilicon samples with different boron concentrations. Wefound that the absorption coefficient in the subgap region isstrongly influenced by the boron incorporation. From thestudy of the morphological properties, we found that themean grain size increases when the diborane concentrationin the gas phase is increased from 0 to 100 ppm; however,the roughness of the samples is not strongly affected. Weobserved that the DOS changes are directly related to the in-corporation of boron to the samples.AcknowledgementsThis work was partially supported with grants of ANPCyT(PICT 12-06950) Argentina.1. Haijun Jia, Jhantu K. Saha, Naoyuki Ohse, and Hajime Shirai,J. Non-Cryst. Solids 352 (2006) 896.2. P. Delli Veneri, L.V. Mercaldo, C. Minarini, and C. Privato,Thin Solid Films 451 (2004) 269.3. G. Ambrosone et al., Solar Energy Materials and Solar Cells87 (2005) 375.4. Michio Kondo, Hiroyuki Fujiwara, and Akihisa Matsuda, ThinSolid Films 430 (2003) 130.5. R. Bruggermann, C. Main, J. Berkin, and S. Reynolds, Philos.Mag. B 62 (1990) 29.6. R.H. Buitrago et al., Avan. Energ. Renv. 2 (1998).7. M. Vanecek et al., Solar Energy Materials 8 (1983) 411.8. M. Vanecek, A. Poruba, Z. Remes, N. Beck, and M. Nesladek,J. Non-Cryst Solids 227-230 (1998) 967.9. P. Jensen, Solid State Commun. 76 (1990) 1301.10. P. Stahel, P. Roca I Cabarrocas, P. Sladek, and M.L. Theye, Mat.Res. Soc. Symp. Proc. 507 (1998) 649.11. S. Sheng, X. Liao, and G. Kong, Appl. Phys. Lett. 78 (17)(2001) 2509.Rev. Mex. Fı´s. S 53 (7) (2007) 253–255

Structural and optical properties of compensated microcrystalline silicon films

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REVISTA MEXICANA DE FÍSICA S53 (7) 253–255 DICIEMBRE 2007Structural and optical properties of compensated microcrystalline silicon filmsA. DussanDepartamento de F́ısica, Universidad Nacional de Colombia, Bogotá, COLOMBIA,Fax.: 57-1-3165135,e-mail: adussanc@unal.edu.coR.R. Koropecki, R. Arce, and J.A. SchmidtINTEC (CONICET-UNL),Güemes 3450, 3000 Santa Fe, Argentina.Recibido el 30 de noviembre de 2006; aceptado el 8 de octubre de 2007Boron-doped microcrystalline silicon films were deposited in a plasma enhanced chemical vapor deposition (PECVD) system using silane(SiH4) diluted in hydrogen, and diborane (B2H6) as a dopant gas. The effects of the Boron concentration on the optical and structuralproperties were investigated by the constant-photocurrent method (CPM) and atomic force microscopy (AFM) measurements. The variationsin the optical constants (refractive index, absorption coefficient and optical gap) as a function of wavelength were carried out from the opticaltransmission and CPM spectra. By increasing the doping level, a systematic increase in the absorption coefficient spectra in the low-energyregion between 0.7 - 1.2 eV was observed. It was found that the increase of Boron concentration in the samples results in changes of thegrain size. Correlations between optical properties and the density of states (DOS) were also studied.Keywords:Optical properties; AFM; structural properties;thin films.Se depositaron pelı́culas delgadas de silicio microcristalino con bajas concentraciones de Boro por latécnic de deposición qúımica en fase devapor asistida por plasma (PECVD) usando silano (SiH4) diluido en hidŕogeno y diborano (B2H6) como gas dopante. Se realizaron estudiosde los efectos del Boro sobre las propiedadesópticas y estructurales a través del ḿetodo de fotocorriente constante (CPM) y medidas demicroscoṕıa de fuerzaatómica (AFM). A partir de las medidas de transmisión óptica y los espectros de CPM se obtuvieron las constantesópticas (́ındice de refracción, coeficiente de absorción y gapóptico) en funcíon de la longitud de onda. Debido al aumento en el nivel dedoping se observ́o un crecimiento sisteḿatico en los espectros del coeficiente de absorción en la regíon de baja energı́a entre 0.7 - 1.2 eV. Seencontŕo que el incremento en la concentración de Boro en las muestras produce un cambio en el tamaño de grano. Se presenta también unacorrelacíon entre las propiedadesópticas y la densidad de estados (DOS) en el material.Descriptores:Propiedadeśopticas; AFM; propiedades estructurales; pelı́culas delgadas.PACS: 78.20.Ci; 68.55.Jk; 78.40.Fy1. IntroductionIn recent years, hydrogenated microcrystalline silicon (µc-Si:H) has been increasingly used in the production of thinfilm based solar cells due to its higher stability comparedto hydrogenated amorphous silicon (a-Si:H) [1, 2].µc-Si:His usually deposited by plasma enhanced chemical vapordeposition (PECVD) from silane-hydrogen mixtures, at afrequency of 13.57 MHz [3, 4]. The successful usage ofthin µc-Si:H films for photovoltaic applications requires re-liable techniques to characterize its properties. In this workwe present results from the characterization of thinµc-Si:Hfilms doped with boron. We measured optical propertiesfrom spectral transmittance and the constant photocurrentmethod (CPM), structural properties from atomic force mi-croscope (AFM) observations, and electrical transport prop-erties from the modulated photoconductivity (MPC) tech-nique [5]. These last measurements were used to estimate theeffect of boron incorporation on the density of states (DOS)within the forbidden gap of the material. Structural propertieswere obtained from X-ray diffraction measurements.2. ExperimentalSamples were prepared in a capacitively coupled PECVDreactor described in a previous work, [6] operated at a fre-quency of 50 MHz. The substrate was Corning 7059 glassand the substrate temperature was set at 160◦C. We used amixture of 94% hydrogen - 6% silane as source gas, with atotal flux of 20 sscm. Diborane was used as a dopant gas, witha concentration in the gas phase varying between 0 and 100ppm relative to silane. The base pressure in the reactor previ-ous to the deposition was lower than 10−6 Torr, while duringthe sample deposition, it was fixed at 4.5×10−1 Torr. Thepower density was 50 mW/cm2. The films’ thickness, calcu-lated from the interference of the transmittance spectra in thenear infrared region, ranged from 0.6 to 1µm. The absorptioncoefficient for energies lower than 2 eV was determined fromconstant photocurrent measurements (CPM [7]). The MPCmeasurements were performed on samples provided with in-terdigitated aluminum contacts, separated 0.01 cm and witha total length of 25 cm, deposited by photolithography. Sam-ples were mounted in a cryostat provided with an optical win-dow, connected to a vacuum system. A 10 mW He-Ne laserwas used as a light source. The incident light intensity waspartially modulated (12.5%) by using an electro-optical mod-ulator driven by a function generator (HP 3325A). We appliedto the samples a voltage of 100 V, provided by a stabilizedpower source. For dc photoconductivity measurements weused a Keithley 617 electrometer, while for the MPC mea-254 A. DUSSAN, R.R. KOROPECKI, R. ARCE, AND J.A. SCHMIDTsurements, we used a lock-in amplifier (Stanford 830) to de-tect the modulus and phase shift of the ac photocurrent. Toevaluate the DOS from the MPC measurements we assumeda DOS at the conduction band edge of 1×1021 cm−3eV−1and a mobility gap of 1.8 eV. To study the morphologicalproperties, we used an atomic force microscope (Park Scien-tific Instruments). X rays diffractio was used to confirm themicrocrystalline nature of the samples.FIGURE 1. α(hν) spectra obtained by CPM for the set ofµc-Si:Hsimples deposited varying the doping concentration [B2H6]/[SiH4]between 12.5 and 100 ppm.FIGURE 2. Density of occupied states extracted from the CPMmeasurements by using the de-convolution procedure proposed byJensen [9], for the samples with diborane concentrations of 12.5,50 and 100 ppm.FIGURE 3. Effect of boron compensation on the DOS ofµc-Si:Hsamples. The DOS in the upper gap region was obtained from MPCmeasurements, while in the lower bandgap region, it was obtainedfrom CPM measurements. The Fermi level position for the com-pensated sample (25 ppm diborane) is marked with an arrow.3. Results and discussionIn Fig. 1 we present theα(hν) spectra obtained by CPM forthe whole set ofµc-Si:H samples. In this figure, a clear in-crease of the absorption coefficient in the region of energieslower than 0.9 eV can be seen when the diborane concen-tration increases from 12.5 to 100 ppm. The absorption co-efficient in this subgap region is known to be related to thepresence of defects in the material [8]. In Table I we reportthe refractive index, optical bandgap and thickness of the dif-ferent samples, as obtained from the analysis of the spectraltransmittance data, and the grain size and roughness obtainedfrom the AFM observations.In Fig. 2 one can observe that the DOS of the samplesincreases with the increase of the doping concentration in theregion of energies lower than from the conduction band edge.This fact is consistent with the observations of Fig. 1, wherethe absorption coefficient gradually increases in the subgapregion with the increase of the diborane concentration. Forthe sample doped with 12.5 ppm of diborane, theα(hν) spec-trum could only be obtained for photon energies larger than1.05 eV. The DOS changes are closely related to the levelof doping of the material, and can be attributed to the boronincorporation during the sample deposition. The increase ofthe boron concentration leads to an increase of the numberof B-H-Si sites, and consequently, to the creation of dan-gling bonds. These type of sites are known as B-H com-plexes [10]. It has been shown [11] that the incorporationof small amounts of boron to compensate the sample close tothe unset of microcrystallinity leads to the creation of defects.Thus, the DOS in the subgap region changes.In Fig. 3 we show the effect of doping on the DOS of theµc-Si:H samples, detected through MPC (DOS in the upperRev. Mex. F́ıs. S53 (7) (2007) 253–255STRUCTURAL AND OPTICAL PROPERTIES OF COMPENSATED MICROCRYSTALLINE SILICON FILMS 255FIGURE 4. AFM images of hydrogenated microcrystalline silicon with different diborane concentrations. a)12.5 ppm, b) 50 ppm andd) 100 ppm.TABLE I. Optical constants and morphological parameters of thethin c-Si:H samples obtained varying the [B2H6]/[SiH4] concentra-tion between 12.5 and 100 ppm. n stands for the refractive index, dfor the thickness, Eg for the optical bandgap, Z for the mean grainsize, and R for the root mean square roughness of the surface.[B2H6]/[SiH4] (ppm) n d (nm) Eg (eV) Z (Å) R (Å)12.5 3.17 500 1.28 562 9025 3.19 618 1.30 564 92.150 3.17 619 1.29 986 10575 3.15 649 1.30 1040 84.7100 3.17 916 1.13 1510 93.6half of the bandgap) and CPM (DOS in the lower half of thebandgap) measurements. This figure clearly shows that boronincorporation leads to an increase in the DOS of the sam-ples. The Fermi level position for the compensated sample(25 ppm of diborane) is indicated by an arrow (EF = 0.68 eV,midgap).Through AFM observations we gained information aboutthe morphological properties of the thin boron-dopedµc-Si:H samples. In Fig. 4 we present AFM images of someof the samples.Figure 4 shows an increase in the grain size of the sam-ples with the increase of the diborane concentration. We no-tice that when the Boron concentration is increased from 12.5ppm to 50 ppm (Figs. 4a and 4b), the grain size changes from562 Åto 564 Å, whereas we observed that when the Boronconcentration is 100 ppm, the grain size was 986Å(Fig. 4c))(see Table I). On the other hand, it can be seen that the rough-ness of the samples is not strongly affected by the boron in-corporation at concentrations higher than 12.5 ppm (see Ta-ble I). The mean grain size values and the rms roughness havealready been reported in Table I.4. ConclusionIn this work we have presented a study of the optical andstructural properties of thin hydrogenated microcrystallinesilicon samples with different boron concentrations. Wefound that the absorption coefficient in the subgap region isstrongly influenced by the boron incorporation. From thestudy of the morphological properties, we found that themean grain size increases when the diborane concentrationin the gas phase is increased from 0 to 100 ppm; however,the roughness of the samples is not strongly affected. Weobserved that the DOS changes are directly related to the in-corporation of boron to the samples.AcknowledgementsThis work was partially supported with grants of ANPCyT(PICT 12-06950) Argentina.1. Haijun Jia, Jhantu K. Saha, Naoyuki Ohse, and Hajime Shirai,J. Non-Cryst. Solids352(2006) 896.2. P. Delli Veneri, L.V. Mercaldo, C. Minarini, and C. Privato,Thin Solid Films451(2004) 269.3. G. Ambrosoneet al., Solar Energy Materials and Solar Cells87 (2005) 375.4. Michio Kondo, Hiroyuki Fujiwara, and Akihisa Matsuda,ThinSolid Films430(2003) 130.5. R. Bruggermann, C. Main, J. Berkin, and S. Reynolds,Philos.Mag. B62 (1990) 29.6. R.H. Buitragoet al., Avan. Energ. Renv.2 (1998).7. M. Vaneceket al., Solar Energy Materials8 (1983) 411.8. M. Vanecek, A. Poruba, Z. Remes, N. Beck, and M. Nesladek,J. Non-Cryst Solids227-230(1998) 967.9. P. Jensen,Solid State Commun.76 (1990) 1301.10. P. Stahel, P. Roca I Cabarrocas, P. Sladek, and M.L. Theye,Mat.Res. Soc. Symp. Proc.507(1998) 649.11. S. Sheng, X. Liao, and G. Kong,Appl. Phys. Lett.78 (17)(2001) 2509.Rev. Mex. F́ıs. S53 (7) (2007) 253–255

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Structural and optical properties of compensated microcrystalline silicon films

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