Surface Morphology Of Silicon Research Articles

Silicon Surface Morphology after Annealing in Ambient Hydrogen Containing a Trace Amount of Hydrogen Halide Gas

The semiconductor silicon substrate surface morphology was studied after annealing in ambient hydrogen containing a trace amount (ppm level) of hydrogen chloride gas and hydrogen fluoride gas at atmospheric pressure. The silicon substrate surface became significantly rough after the annealing at substrate temperatures higher than 1100 °C. The surface had many randomly-shaped deep pits without any crystalline orientation. In contrast, the silicon surface was still specular after annealing at 1000 °C with the root mean square roughness of ca. 0.2 nm. Hydrogen chloride gas and hydrogen fluoride gas at very low concentrations are considered to be inactive toward the silicon surface at temperatures lower than 1000 °C.

Silicon Surface Morphology after Annealing in Ambient Hydrogen Containing a Trace Amount of Hydrogen Halide Gas

Silicon Surface Morphology after Annealing in Ambient Hydrogen Containing a Trace Amount of Hydrogen Halide Gas

飞秒激光微构造硅表面镀AZO膜的形貌及其光学吸收性能

飞秒激光微构造硅表面镀AZO膜的形貌及其光学吸收性能

Amorphous silicon carbide heterojunction solar cells on p-type substrates

The performance of silicon heterojunction (SHJ) solar cells is discussed in this paper in regard to their dependence on the applied amorphous silicon layers, their thicknesses and surface morphology. The emitter system investigated in this work consists of an n-doped, hydrogenized, amorphous silicon carbide a-SiC:H(n) layer with or without a pure, hydrogenized, intrinsic, amorphous silicon a-Si:H(i) intermediate layer. All solar cells were fabricated on p-type FZ-silicon and feature a high-efficiency backside consisting of a SiO 2 passivation layer and a diffused local boron back surface field, allowing us to focus only on the effects of the front side emitter system. The highest solar cell efficiency achieved within this work is 18.5%, which is one of the highest values for SHJ-solar cells using p-type substrates. A dependence of the passivation quality on the surface morphology was only observed for solar cells including an a-Si:H(i) layer. It could be shown that the fill factor suffers from a reduction due to a reduced pseudo fill factor for emitter thicknesses below 11 nm due to a lower passivation quality and/or a higher potential for shunting thorough the a-Si emitter to the crystalline wafer with the conductive indium tin oxide layer. Furthermore, the influence of a variation of the doping gas flow ( PH 3 ) during the plasma enhanced chemical vapor deposition of the doped amorphous silicon carbide a-SiC:H(n) on the solar cell current–voltage characteristic-parameter has been investigated. We could demonstrate that a-SiC:H(n) shows in principle the same dependence on PH 3 -flow as pure a-Si:H(n).

Porous silicon nanowires fabricated by electrochemical and laser-induced etching

Electrochemical and laser-induced etching processes were simultaneously used to synthesize the nanowires structure of porous silicon (PS). Surface morphology and structural properties of nanostructured silicon were characterized by using scanning electron microscopy (SEM) and atomic forces microscopy (AFM) images. Nanowires with dimensions of few nanometers were formed on the whole etched surface. The optical properties of silicon nanostructures were studied. Raman spectra were shifted and broadened relatively to 519.9 cm−1 of PS prepared by electrochemical etching, and shifted to 517.2 cm−1 for laser-induced etching process and to 508.9 cm−1 for electrochemical and laser etching simultaneously. Blue shift luminescence was observed at 649.6 nm for PS produced by electrochemical etching, and at 629.5 nm for laser-induced etching. PS produced a blue shift at 626.5 nm using both etching procedures simultaneously. X-Ray diffraction (XRD) was used to investigate the crystallites size of the PS as well as to provide an estimate of the degree of crystallinty of the etched sample.

Fabrication and characterization of silicon pillars formed by nanosecond pulsed excimer laser in vacuum

AbstractArrays of well defined silicon microcolumns were formed by cumulative nanosecond pulsed excimer laser irradiation of single‐crystal silicon in vacuum. The changes in silicon surface morphology were systematically determined and compared as the number of KrF laser shots was increased from 1 to 15 000 in vacuum. Moreover, as the number of laser shots increases, formation of well defined silicon pillars oriented towards the laser beam has been observed. Finally, the reflectance spectra show a total reflectance of 5%–6% in the wavelength region 375–800 nm and that of 0% at a wavelength of about 870 nm. Copyright © 2010 John Wiley & Sons, Ltd.

Nanostructure formation via print diffusion etching through block copolymer templates

The present work demonstrates nanoscale etching of silicon with standard aqueous fluoride etchants running through the hydrophilic domains of a vertically aligned copolymer template. The delivery of etchants was unprecedentedly achieved by an etchant-solution-saturated agarose gel stamp, a technique we call print diffusion etching. Three-dimensional nanoprotrusion features with controllable shapes and sizes (about 20 nm) were formed. To prove that the block copolymers serve to direct the silicon surface morphology by controlling the spatial location of the reaction as well as concentration of reagents, the same etching steps both on silicon and PS-b-PEO (polystyrene-block-polyethyleneoxide) templates were carried out for comparison. The mechanism of the nanoprotrusion formation was elucidated, and the morphology evolution vs. etching time studied.

Optimization of porous silicon preparation technology for SERS applications

A series of porous silicon samples prepared at different etching parameters, namely etchant composition, etching time and current density, was investigated as substrates for surface-enhanced Raman scattering (SERS). Silver nanostructures were deposited on porous silicon by immersion plating method and Rhodamine 6G was used as analyte. The relation between the etching parameters, morphology of porous silicon surface and its SERS efficiency after silver deposition is examined. We show that a high HF content in the etchant allows the formation of a film with close-packed silver nanocrystals, which possess strong surface enhancement properties.

Orientation-dependent surface morphology of crystalline silicon during anisotropic etching using a continuous cellular automaton

The formation of morphological protrusions on the surface during anisotropic wet etching is addressed computationally by modifying a step-flow-based continuous cellular automaton (CCA) in order to incorporate the stochastic adsorption and desorption of impurity particles on the surface. The CCA method is characterized by the possibility of calibrating the site-specific atomistic removal rates of the step-flow model in order to describe the macroscopic orientation dependence of the etch rate obtained in an experiment. Interestingly, the combination of the deposition model with previously calibrated site-specific atomistic removal rates leads to a realistic description of the experimental surface morphologies for a wide range of crystalline orientations. This is shown by considering the wet etching of crystalline silicon in two very different etchants, namely pure KOH and KOH with isopropanol (IPA). The modified CCA makes possible the realization of accurate and realistic simulations of anisotropic etching in realistic engineering applications.

The effect of Al and B on the luminescent property of porous silicon

In this paper, we studied the PL property and the surface morphology of porous silicon prepared from N-type single silicon wafers coated with and without Al film. By introducing the Al film on the surface of silicon wafer before etching, the morphology of porous silicon exhibits obvious discrimination compared with that of the conventional porous silicon, which can be explained by the formation mechanism of the samples, and the emission property of two-type porous silicon also showed the clear difference, which may be attributed to the discrepancy in the structural configuration of the samples. Furthermore, it was found that the blue emission decreased and the green emission was almost completely quenched after boron-particle deposition, which is attributed to the structural change or annihilation of the emission defects during annealing process.

Influence of Additives on Alkaline Etching of Silicon(111)

Apart from temperature and alkaline concentration, the surface morphology of silicon surfaces after wet chemical etching is also profoundly influenced by the presence of additives in the etchant solution. In this study, the influence of several organic (aprotic, protic, and ionic) additives on the density and shape of etch pits on etched Si-(111) surfaces is investigated using optical microscopy and the Lichtfigur technique. For all the additives used, the number density of the pits increases by 1−3 orders of magnitude. The triangularity of the pit shape, expressed by a dimensionless number, Rab, increases substantially as well. These alterations are attributed to local desolvation of reaction products by the organic additives in a thin “surfactant” layer in the vicinity of the silicon surface. Chemisorption of additive molecules does not play a role in this process.

Femtosecond laser-induced silicon surface morphology in water confinement

This article investigates the use of femtosecond laser induced surface morphology on silicon wafer surface in water confinement. Unlike irradiation of silicon surfaces in the air, there are no lase...

A cost-effective alkaline multicrystalline silicon surface polishing solution with improved smoothness

In the present paper, intragain surface morphology of multicrystalline silicon (mC-Si) wafer surface of area 3 μm×3 μm polished by the acid-based solution comprising of hydrofluoric (HF), nitric (HNO 3) and acetic (CH 3COOH) acids and new alkaline solution containing sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl) has been studied using an atomic force microscope (AFM). From the roughness and section analysis study of the intergrain surface by the AFM, it is revealed that the NaOH–NaOCl polishing process is quite superior to the existing acid polishing one. Quantitative measurements indicate better smoothness of polished silicon surface after the NaOH–NaOCl treatment as compared with acid polishing. Also process cost per wafer involved in the NaOH–NaOCl polishing process is far lower than that by the acid polishing process along with additional advantageous features of high productivity, environment friendliness and safety. All these factors finally contribute to make the NaOH–NaOCl solution a better polisher for mC-Si surface.

Topography measurement of nano silicon oxide film

The Si (111) – 7 x 7 is a semimetal which its surface morphology has been normally studied with using STM (scanning tunneling microscopy) technique, whilst the other kind of silicon, such as Si(100) – 2 x 1 is not a semimetal. For letter surface structure, the AFM (atomic force microscopy) technique can be used as well. There are two main issues which are threatening the use of STM technique as a good technique for studying the silicon surface morphology. First issue is that STM suffers from the impossibility to decouple the anodization bias from the tip – sample separation and second issue is due to heating the sample surface in contact mode. For this purpose, we used AFM technique because it can be applied independently of the feedback and controlled with governing the tip – sample spacing. Moreover, AFM in tapping mode does not touch the sample and can thus eliminate lateral shear forces and overcome tip – sample adhesion forces (e.g. capillarity). In this case, we could grow homogeneous film on the silicon substrate. Key words: Thin Film, silicon dioxide, STM, AFM, surface topography.

Femtosecond laser-induced silicon surface morphology in water confinement

This article investigates the use of femtosecond laser induced surface morphology on silicon wafer surface in water confinement. Unlike irradiation of silicon surfaces in the air, there are no laser induced periodic structures, but irregular roughness is formed when the silicon wafer is ablated under water. The unique discovery of a smoothly processed silicon surface in water confinement under certain laser parameter combinations may help improve laser direct micromachining surface quality in industrial applications.

Laser induced plasma plume imaging and surface morphology of silicon

Shot-to-shot variation in the characteristics of laser produced plasma plume and surface profile of N-type silicon (1 1 1) are investigated. In order to produce plasma, a Q-switched Nd: YAG laser (1064 nm, 10 mJ, 9–14 ns) is tightly focused on silicon target in air at room temperature. Target was exposed in such a way that number of laser shots was increased from point to point in ascending order starting from single shot at first point. Target was moved 2 mm after each exposure. In order to investigate shot-to-shot variation in the time integrated emission intensity regions within the plasma plume, a computer controlled CCD based image capture system was employed. Various intensity regimes were found depending strongly on the number of incident laser pulses. Plasma plume length was also found to vary with the number of pulses. The topographic analysis of the irradiated Si was performed by Scanning Electron Microscope (SEM) which shows the primary mechanisms like thermal or non-thermal ablation depend on the number of shots. Surface morphological changes were also studied in terms of ripple formation, ejection, debris and re-deposition of material caused by laser beam at sample surface. The micrographs show ripples spacing versus wavelength dependence rule [ Λ ≈ λ/(1 − sin θ)]. Intensity variations with number of shots are correlated with the surface morphology of the irradiated sample.

Is it possible to use external stress to tune silicon surface morphology?

Our goal was to check if an external mechanical stress can be used to control the morphology of a Si surface. We show that: (1) due to plastic relaxation, a mechanical stress does not allow destabilization of a flat silicon surface by means of the Asaro–Tiller–Grinfeld mechanism; (2) the faceting period of vicinal Si surfaces destabilized by electromigration is not influenced by mechanical stresses but becomes more defective; (3) anisotropic surface reconstructions can be modified by a mechanical stress whereas isotropic surfaces seem to be less sensitive.

Wet chemical etching of silicon {1 1 1}: Etch pit analysis by the Lichtfigur method

The Lichtfigur method is introduced to determine the average pit morphology of etched silicon surfaces. It is an effective method in surface analysis complementary to optical microscopy. The surface morphology of silicon {1 1 1} after wet chemical etching in aqueous KOH solution has been investigated by this technique. The morphology does not change significantly in pure KOH solutions as a function of time. In solutions containing additive isopropanol, however, the etch pits evolve from circular to triangular, with a final shape that depends on the isopropanol concentration. It has been experimentally proven that the IPA additive does not participate in the etching reaction and no etching occurs in the absence of water, which implies that OH − only serves as a catalyst.

Nanosecond pulsed laser ablation of silicon in liquids

Laser fluence and laser shot number are important parameters for pulse laser based micromachining of silicon in liquids. This paper presents laser-induced ablation of silicon in liquids of the dimethyl sulfoxide (DMSO) and the water at different applied laser fluence levels and laser shot numbers. The experimental results are conducted using 15 ns pulsed laser irradiation at 532 nm. The silicon surface morphology of the irradiated spots has an appearance as one can see in porous formation. The surface morphology exhibits a large number of cavities which indicates as bubble nucleation sites. The observed surface morphology shows that the explosive melt expulsion could be a dominant process for the laser ablation of silicon in liquids using nanosecond pulsed laser irradiation at 532 nm. Silicon surface’s ablated diameter growth was measured at different applied laser fluences and shot numbers in both liquid interfaces. A theoretical analysis suggested investigating silicon surface etching in liquid by intense multiple nanosecond laser pulses. It has been assumed that the nanosecond pulsed laser-induced silicon surface modification is due to the process of explosive melt expulsion under the action of the confined plasma-induced pressure or shock wave trapped between the silicon target and the overlying liquid. This analysis allows us to determine the effective lateral interaction zone of ablated solid target related to nanosecond pulsed laser illumination. The theoretical analysis is found in excellent agreement with the experimental measurements of silicon ablated diameter growth in the DMSO and the water interfaces. Multiple-shot laser ablation threshold of silicon is determined. Pulsed energy accumulation model is used to obtain the single-shot ablation threshold of silicon. The smaller ablation threshold value is found in the DMSO, and the incubation effect is also found to be absent.

Preparation of polystyrene brush film by radical chain-transfer polymerization and micromechanical properties

A radical chain-transfer polymerization technique has been applied to graft-polymerize brushes of polystyrene (PSt) on single-crystal silicon substrates. 3-Mercapto-propyltrimethoxysilane (MPTMS), as a chain-transfer agent for grafting, was immobilized on the silicon surface by a self-assembling process. The structure and morphology of the graft-functionalized silicon surfaces were characterized by the means of contact-angle measurement, ellipsometric thickness measurement, Fourier transformation infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The nanotribological and micromechanical properties of the as-prepared polymer brush films were investigated by frictional force microscopy (FFM), force–volume analysis and scratch test. The results indicate that the friction properties of the grafted polymer films can be improved significantly by the treatment of toluene, and the chemically bonded polystyrene film exhibits superior scratch resistance behavior compared with the spin-coated polystyrene film. The resultant polystyrene brush film is expected to develop as a potential lubrication coating for microelectromechanical systems (MEMS).