Morphologies and optical properties of black silicon by room temperature reactive ion etching

Atteia, F.; Rouzo, Judikaël Le; Denaix, Lou; Duché, David; Berginc, Gérard; Simón, J.J.; Escoubas, Ludovic

doi:10.1016/j.materresbull.2020.110973

Cited by 28 publications

(12 citation statements)

References 17 publications

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“…(1) Pillar base spacing . We know from previous work , that a decreased center-to-center distance, p , between nanostructures is associated with lower reflectance. Using an effective medium/multilayer approach, Elsayed et al have shown that the reflectance of their simulated BSi cones increased as their base-spacing increased due to a more abrupt change in the effective refractive index, n eff .…”

Section: Resultsmentioning

confidence: 97%

Optimized Deep Reactive-Ion Etching of Nanostructured Black Silicon for High-Contrast Optical Alignment Marks

Yusuf

Herring

Neustock

et al. 2021

ACS Appl. Nano Mater.

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High-contrast alignment marks are promising optical elements for the high-precision alignment of X-ray gratings in phase-contrast X-ray imaging systems. These marks contain micrometer-scale bands of optically absorptive and reflective areas that determine their relative degree of optical contrast. Nanostructured black silicon (n-BSi) enabling the broadband, quasi-omnidirectional absorption of light, is a promising material to define these absorptive areas. In this work, we have developed an optimized deep reactive-ion etching (DRIE) process to fabricate n-BSi for these alignment marks. The DRIE process was optimized by systematically changing the polymer deposition time, T, while keeping all other process conditions constant. As T varied from 0.6 to 2.5 s, three distinct etching regimes were observed: (1) smooth etching, (2) n-BSi, and (3) etching stop. During the n-BSi regime (T = 1.6 to 2.1 s), varying T altered the n-BSi morphology, resulting in a broad spectrum of nanostructures: nanopillars to nanopores. Our investigation of the process–structure–property relationships among the process etching, morphology evolution, and reflectance of n-BSi revealed that morphologies with an increased height, aspect ratio, and degree of tapering and a lower base spacing were most effective at suppressing reflection for λ = 500–800 nm. Our results demonstrated the lowest reflectance of the absorptive areas, = 0.01 (∼1%) and = 0.03 (relative with respect to Si) at λ = 600 nm for T = 1.9 s (100 cycles), thus giving the highest contrast ratio, ϕ = 0.9. To increase the device throughput, we varied the cycle number from 5 to 100 times at T = 1.9 s to study its effect on growth, morphology, and reflectance of n-BSi. Our results demonstrate that , , and ϕ plateaued at 50 cycles, cutting in half our total fabrication time, t. In addition, our alignment marks demonstrated rotational and translational precision alignment capabilities. Lastly, we present two design principles for T and the cycle number to fabricate the optimal n-BSi morphology for the targeted application using any DRIE tool.

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Section: Resultsmentioning

confidence: 97%

Optimized Deep Reactive-Ion Etching of Nanostructured Black Silicon for High-Contrast Optical Alignment Marks

Yusuf

Herring

Neustock

et al. 2021

ACS Appl. Nano Mater.

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“…The FDTD method was used to calculate the spectral absorptivity of the model [ 17 , 18 , 19 , 20 ]. The FDTD method discretized the time-domain Maxwell’s equations by central difference approximation of the spatial and temporal partial derivatives.…”

Section: Methodsmentioning

confidence: 99%

Structure of Randomly Distributed Nanochain Aggregates on Silicon Substrates: Modeling and Optical Absorption Characteristics

et al. 2022

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Nanoparticle aggregate structures allow for efficient photon capture, and thus exhibit excellent optical absorption properties. In this study, a model of randomly distributed nanochain aggregates on silicon substrates is developed and analyzed. The Gaussian, uniform, and Cauchy spatial distribution functions are used to characterize the aggregate forms of the nanochains and their morphologies are realistically reconstructed. The relationships between the structural parameters (thickness and filling factor), equivalent physical parameters (density, heat capacity, and thermal conductivity), and visible absorptivity of the structures are established and analyzed. All the above-mentioned parameters exhibit extreme values, which maximize the visible-range absorption; these values are determined by the material properties and nanochain aggregate structure. Finally, Al nanochain aggregate samples are fabricated on Si substrates by reducing the kinetic energy of the metal vapor during deposition. The spectral reflection characteristics of the samples are studied experimentally. The Spearman correlation coefficients for the calculated spectral absorption curves and those measured experimentally are higher than 0.82, thus confirming that the model is accurate. The relative errors between the calculated visible-range absorptivities and the measured data are less than 0.3%, further confirming the accuracy of the model.

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“…In this regard, BSi has been widely scrutinized for its noticeable textured surface with a light-trapping feature that can increase Si solar cell efficiency by reducing its reflectivity and boosting the absorption of incident photons [8]. To fulfill the criteria for developing BSi solar cell surface fabrication, several methods have been established, for instance, reactive ion etching [9], metal-assisted chemical etching [10], plasma etching [11], laser texturing [12], and wet chemical (anisotropic) etching [13], plasma immersion ion implantation, and atmospheric pressure dry texturing. Among them, one well-known method is metal nanoparticle-assisted chemical etching or metal-assisted chemical etching (MACE).…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Black Silicon via Metal-Assisted Chemical Etching—A Review

et al. 2021

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The metal-assisted chemical etching (MACE) technique is commonly employed for texturing the wafer surfaces when fabricating black silicon (BSi) solar cells and is considered to be a potential technique to improve the efficiency of traditional Si-based solar cells. This article aims to review the MACE technique along with its mechanism for Ag-, Cu- and Ni-assisted etching. Primarily, several essential aspects of the fabrication of BSi are discussed, including chemical reaction, etching direction, mass transfer, and the overall etching process of the MACE method. Thereafter, three metal catalysts (Ag, Cu, and Ni) are critically analyzed to identify their roles in producing cost-effective and sustainable BSi solar cells with higher quality and efficiency. The conducted study revealed that Ag-etched BSi wafers are more suitable for the growth of higher quality and efficiency Si solar cells compared to Cu- and Ni-etched BSi wafers. However, both Cu and Ni seem to be more cost-effective and more appropriate for the mass production of BSi solar cells than Ag-etched wafers. Meanwhile, the Ni-assisted chemical etching process takes a longer time than Cu but the Ni-etched BSi solar cells possess enhanced light absorption capacity and lower activity in terms of the dissolution and oxidation process than Cu-etched BSi solar cells.

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Morphologies and optical properties of black silicon by room temperature reactive ion etching

Cited by 28 publications

References 17 publications

Optimized Deep Reactive-Ion Etching of Nanostructured Black Silicon for High-Contrast Optical Alignment Marks

Optimized Deep Reactive-Ion Etching of Nanostructured Black Silicon for High-Contrast Optical Alignment Marks

Structure of Randomly Distributed Nanochain Aggregates on Silicon Substrates: Modeling and Optical Absorption Characteristics

Fabrication of Black Silicon via Metal-Assisted Chemical Etching—A Review

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