Photoacoustic thermal characterization of spark-processed porous silicon

Cruz‐Orea, A.; Delgadillo, I.; Vargas, H.; Gudiño‐Martínez, A.; Marı́n, E.; Vázquez-López, C.; Calderón, A.; Alvarado‐Gil, J. J.

doi:10.1063/1.362626

Cited by 24 publications

(17 citation statements)

References 19 publications

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“…We shall return to this point later. In terms of this series two-layer system, the thermal diffusivity for the heat flow perpendicular to the sample surface may be written as [16][17][18][19] …”

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Photothermal Characterization of Electrochemical Etching Processed n-Type Porous Silicon

et al. 1997

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The room temperature thermal diffusivity evolution of electrochemically formed porous silicon as a function of the etching time is investigated. The measurements were carried out using the open-cell photoacoustic technique. The experimental data were analyzed using a composite two-layer model. The results obtained strongly support the existing studies, indicating the presence of a high percentage of SiO 2 in the composition of porous silicon material. [S0031-9007(97) PACS numbers: 44.30. + v, 61.43.Gt, 81.05.Cy, 81.05.Rm Since the discovery of its room-temperature visible luminescence [1][2][3][4][5], porous silicon (PS) has become a subject of considerable interest, especially for its promising use as an optoelectronic device [6,7]. There are several methods [8][9][10][11] for fabricating PS from crystalline silicon wafers. The electrochemical etching [1,8] is, however, the most extensively used so far. The morphology of the resulting porous layer is strongly dependent upon the fabrication controlling parameters such as electrolyte composition, current density, etching time, etc., as well as on the type of substrate used.In general, an electrochemically formed n-type PS layer consists essentially of a double-layer system on top of the silicon substrate [1,12]. The outermost thin layer, known as the microporous layer, is typically 10-15 mm thick and is responsible for the observed photoluminescence. Except for very small etching times, the inner layer adjacent to the crystalline substrate, designated as the macroporous layer, consists of a parallel array of airembedded free-standing n-PS columns.Despite the large body of literature that already exists on PS [13,14], so far there has been no reported detailed investigation of the thermophysical properties of this important system. In this Letter we apply the modern photothermal techniques to the evaluation of the thermal properties of electrochemically formed n-PS.The samples used in our experiments were prepared by electrochemical etching on (100) oriented, nondegenerated, n-type ͑2.1 3 10 18 cm 23 ͒ crystalline silicon. The samples had a thickness of roughly 300 mm and an electrical resistivity of 1-5 V cm. The electrochemical etching was carried out following the procedure outlined in Ref. [12]. The crystalline samples, with an appropriate Pt network electrode attached to them, were immersed in a 150 ml Becker filled with HF. A current density of 40 mA͞cm 2 was then applied to the samples using a HP-model 6206B dc power supply operating between 5-10 V. During the etching period the samples were always kept under the irradiation of a 250 W infrared lamp positioned roughly 20 cm away from the etching bath. By controlling the etching time, ranging from 10 to 83 min, we could fabricate samples with different macroporous thicknesses.In Fig. 1 we show the side view optical micrograph of a typical n-PS sample, produced with 60 min etching time. The three distinct regions mentioned above, namely, the microporous and macroporous layers on top of the crystalline sub...

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Photothermal Characterization of Electrochemical Etching Processed n-Type Porous Silicon

et al. 1997

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“…This last value may be compared to the other effective values for PS, a = 0.047 cm 2 /s and a = 0.053 cm 2 /s found by CruzOrea et al [17] and Calderón et al [18], respectively, with open photoacoustic cell method.…”

Section: Discussionmentioning

confidence: 91%

“…Moreover due to a very low roughness and thickness of the PDLC thin film compared to silicon substrate we treat the thermal diffusivity as an effective mean value. This has been done for porous silicon with very good results [16][17][18].…”

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confidence: 99%

Optical and morphological properties of porous diamond-like-carbon films deposited by magnetron sputtering

Baroni

Conceição

Rosa

et al. 2006

Journal of Non-Crystalline Solids

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Porous diamond-like-carbon (PDLC) thin films obtained on silicon substrate by DC low energy magnetron sputtering have been investigated by photoluminescence, transmission and reflection spectroscopy, photoacoustic and spectroscopic ellipsometry. The absorption features observed for these films show similarities with those of porous silicon (PS) as well as in the performed gradient structural pattern classification of the SFM porosity, by means of the computational GPA-flyby environment on PS and PDLC samples. The dielectric function is also calculated for the bulk diamond-like carbon using the full-potential linearized augmented plane wave method within the framework of local density approximation to density functional theory. From the measurement a low real dielectric constant of about 4.5 at 0.8 eV was found whereas the calculated e 1 (0) for the bulk diamond has a value of 5.5.

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“…Although PL spectra were reported for PS [3,6], no careful analysis on the effect of scattering * Corresponding author. E-mail: toshi@cc.nda.ac.jp seems to have been considered and only a few photoacoustic (PA) measurements are reported in the PS samples [7,8].…”

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“…The efficient visible-light emission in red was reported first, but the blue emission was reported to be related to the oxidized PS samples [4,5] and gave a promise for the Si-based optical devices. Although PL spectra were reported for PS [3,6], no careful analysis on the effect of scattering seems to have been considered and only a few photoacoustic (PA) measurements are reported in the PS samples [7,8]. The nano-structure that is expected to lead to the quantum confinement effect [9], believed to be essential for the light emission from PS, will also play a decisive role in the scattering effect.…”

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Effects of boundary reflection on photoacoustic spectrum of porous silicon

Kawahara

Morimoto

Tahira

et al. 2000

Applied Physics A: Materials Science & Processing

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Photoacoustic (PA) amplitude and phase spectra are studied on porous silicon (PS) samples. For the sample with a thinner PS layer and a rough interface observed by field-emission scanning electron microscope (FE-SEM), PA amplitude decays rapidly at short wavelengths but stays at a higher level above 650 nm compared with a sample with a thicker PS layer and a smooth interface. In this latter longwavelength region, phase delay for the former sample is smaller. A model calculation for the two-layer model taking account of scattering of light in the porous media and interface reflection of light gives at least a qualitative explanation of these differences. 78.20.Hp; 65.90.+i Photoacoustic spectroscopy (PAS) detects the thermal signals generated in materials under light illumination and enables one to study the non-radiative recombination processes and evaluate both the optical and acoustic properties of the materials [1]. In contrast, photoluminescence (PL) spectroscopy characterizes the luminescent properties from the radiative processes. When these methods are applied to the scattering media, the analysis based on some models regarding the effect of scattering is required. In the case of PAS in the lightscattering media, Helander's model [2] can be employed in which the modified distribution of photons in the media is taken into account to estimate the heat generated by the scattered light. The light-scattering is expected to be important in the porous media. The complicated shape of pores can induce the complicated scattering of light in the media. PACS:The light emission of porous Si (PS) was discovered in 1990 [3]. The efficient visible-light emission in red was reported first, but the blue emission was reported to be related to the oxidized PS samples [4,5] and gave a promise for the Si-based optical devices. Although PL spectra were reported for PS [3,6], no careful analysis on the effect of scattering seems to have been considered and only a few photoacoustic (PA) measurements are reported in the PS samples [7,8]. The nano-structure that is expected to lead to the quantum confinement effect [9], believed to be essential for the light emission from PS, will also play a decisive role in the scattering effect.In this paper, both amplitude and phase PA signals are studied over a wavelength region 400-1600 nm on the two PS samples with different interface characteristics between the porous layer and the Si substrate. The difference in PA spectra is attributed to the combined effect of the scattering in the porous layer and the difference in roughness observed from the scanning electron microscope pictures of the interface between the PS layer and the Si substrate. The experimental PA data are qualitatively analyzed based on the calculated PA spectra in which the reflection effects of light at the interface and the subsequent scattering are included. Experimental proceduresThe PS films were made by the anodization of the 2-4 Ω cm p-Si wafers under galvanostatic conditions. The Si wafer was also used as one elec...

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Photoacoustic thermal characterization of spark-processed porous silicon

Cited by 24 publications

References 19 publications

Photothermal Characterization of Electrochemical Etching Processed n-Type Porous Silicon

Photothermal Characterization of Electrochemical Etching Processed n-Type Porous Silicon

Optical and morphological properties of porous diamond-like-carbon films deposited by magnetron sputtering

Effects of boundary reflection on photoacoustic spectrum of porous silicon

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