Si Pillars Research Articles

Silicon nanopillar anodes for lithium-ion batteries using nanoimprint lithography with flexible molds

The lithium ion battery, a preferred energy storage technology, is limited by its volumetric and gravimetric energy densities, as well as its capacity retention with prolonged cycling. In this work, the authors exploited the extremely high lithium storage capacity of Si as an anode material and tackled the issue of lithium-induced volume expansion by patterning the Si into a nanopillar array using nanoimprint lithography and reactive-ion etching. Arrays of 200 nm-pitch Si pillars of 50–70 nm diameter and 200–500 nm height were fabricated on stainless steel substrates, assembled into coin cells, and tested against lithium counter electrodes. Initial charge capacities in excess of 3000 mAh/g, and a low rate-dependence, were obtained with these Si pillar anodes. This represents an improvement over previously reported nanoimprint-patterned Si anodes. Though this initial capacity is roughly equivalent to previously reported values for bulk Si anodes, our nanopillar anodes exhibit far superior capacity retention with subsequent charge–discharge cycles.

Improved field emission properties from carbon nanotubes grown onto micron-sized arrayed silicon pillars with pyramidal bases

Carbon nanotubes (CNTs) were synthesized onto micron-sized arrayed silicon (Si) pillars with pyramidal bases in order to mitigate the electric-field-screening due to densely grown CNTs. Compared with the CNT emitters grown on a flat Si substrate, CNT emitters grown on arrayed Si pillars showed improved field emission properties with a low turn-on field of 2.16V/μm at 10μA/cm2 and current density of 550μA/cm2 at 3.46V/μm. Field enhancement factor was calculated according to the Fowler–Nordheim theory. The resultant field enhancement factor of CNT emitters on arrayed Si pillars was higher than that of CNT emitters on a flat substrate, which revealed that the formation of arrayed Si pillars could be an effective method to suppress electric-field-screening among adjacent CNT emitters.

Electrochemical Deposition of Manganese Oxides on Carbon Nanosheets

We report on electrodeposition of thin Mn-oxide films on Carbon Nanosheets (CNS) and explore the potential of this high-surface area Mn-oxide/nanocarbon for applications in fast charge/discharge thin-film lithium ion micro-batteries. We examined physical-chemical properties of Mn-oxide/CNS composite films electrodeposited on both flat substrates and high-aspect-ratio Si pillars coated with TiN and CNS. In addition to electrochemical methods, such as cyclic voltammetry (CV), Mn-oxide/CNS structures were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy (RS).

(Invited) Three-Dimensional Epitaxial Si1-XGex, Ge and SiC Crystals on Deeply Patterned Si Substrates

We show that geometric shielding of the reactive flux in chemical vapor deposition by tall neighboring structures obtained by deep substrate patterning, along with short surface diffusion lengths, can provide nearly space filling arrays of high-quality epitaxial crystals despite large mismatches of lattice parameters and thermal expansion coefficients. The density of extended defects is strongly reduced by the method, and wafer bowing and crack formation largely inhibited. The concept is shown to be valid for SiGe/Si heterostructures ranging from pure Si to pure Ge both on Si(001) and Si(111) substrates. Here, dislocations are efficiently eliminated from three-dimensional faceted crystals with high-aspect ratios on top of micron-sized Si pillars. The application to 3C-SiC/Si(001) ridges, characterized by a lattice mismatch of nearly 20%, provides significantly lower stacking fault densities compared with layers grown on planar substrates.

Bacterial Diagnostic Chip By the Detection of Fluorescence from Legionella pneumophila in a Microbeads Suspension

Sensing of bacteria is attracting a great deal of interest to avoid an outbreak of bacterial infection [1, 2]. The sensors used for this purpose should integrate at least two functions in a small volume: trapping bacteria and detecting them such as by a photo detector on a chip, as schematically illustrated in Fig. 1. We successfully devised a microfluidic chip with Si-pillar structure for trapping Legionella pneumophila (L. pneumophila) that is widely known as one of a pathogenic bacterium and confirmed its effectiveness by observing fluorescence produced by the trapped L. pneumophila [1]. In the chip, Si pillars work as a kind of sieve in which the introduced L. pneumophila cells are captured. During the course of this study, we further found that L. pneumophila might emit fluorescence just when they are squeezed in a narrow space such as one surrounded by the Si pillars, although its detailed mechanism is still unclear. The Si-pillar structure was indeed effective for trapping L. pneumophila, however, the amount of L. pneumophila cells trapped in the Si pillars was not necessarily sufficient to observe fluorescence because the introduced L. pneumophila cells were stuffed at the inlet side of Si pillars as shown schematically in Fig. 2(a). To solve this problem, we put L. pneumophila cells in a narrow space surrounded by glass microbeads instead of Si pillars as shown in Fig. 2(b). Figure 3 illustrates how L. pneumophila cells are squeezed among the beads in a microfluidic chip: We previously make a mixed suspension of L. pneumophila cells and the beads, and then inject them into a microfluidic chip having protrusions which work as stoppers both for the cells and the beads. This method enables us to expect the observation of fluorescence from almost all the L. pneumophila cells injected into the chip. The microfluidic bacterial trap chip was fabricated by using poly(dimethylsiloxane), (PDMS), in which the depth was 30 um, the channel between stoppers was 10 um (Fig. 4). We made a mixed suspension consisting of 1x106 cells of L. pneumophila, 5×107 microbeads with the diameter of 7 um, and 1 mL of pure water. After injecting the 1 mL of mixed suspension into the chip and making the cells densely packed among the beads, the fluorescence was observed by a fluorescence microscope. Spectroscopic analyses of the fluorescence showed that the shape of the spectrum for the mixture of the cells and beads are different from that of the beads and PDMS as shown in Fig. 5, indicating that the L. pneumophila cells packed densely among microbeads emit fluorescence. In summary, making narrow space by microbeads instead of Si pillars is effective way for detecting the fluorescence from L. pneumophila. Applying this simple microbeads approach paves the way for making L. pneumophila sensor by the combination with a photo detector.

A Structural Characterization of GaAs MBE Grown on Si Pillars

C. Frigeria,∗, S. Bietti, A. Scaccabarozzi, R. Bergamaschini, C.V. Falubc,‖, V. Grillo, M. Bollani, E. Bonera, P. Niedermann, H. von Kanel, S. Sanguinetti and L. Miglio CNR-IMEM Institute, Parco Area delle Scienze 37/A, I-43100 Parma, Italy L-Ness and Dipartimento di Scienza dei Materiali, Via Cozzi 53, I-20125, Milano, Italy Laboratory for Solid State Physics, ETH Zurich, Schafmattstr. 16, CH-8093 Zurich, Switzerland CNR-IFN, L-NESS, via Anzani 42, I-22100, Como, Italy Centre Suisse d'Electronique et Microtechnique, Jaquet-Droz 1, CH-2002 Neuchatel, Switzerland

Electrochemical Deposition of Manganese Oxides on Carbon Nano-Sheets

We have electrodeposited Mn-oxide films on Carbon nano-sheets (CNS), thin (< 10 nm) vertical standing graphitic sheets, having in mind potential energy storage applications of this high-surface-area composite structure. We examined the deposition kinetics of Mn-oxides and physical-chemical properties of Mn-oxide/CNS composite films on substrates ranging from flat to high-aspect-ratio (HAR) Si pillars. We have also explored the possibility to integrate this process into production line typical for microelectronics industry.CNS was grown using RF-PECVD technique [1] onto both blanket 200 mm Si wafers coated with 70 nm thick PVD TiN, and wafer pieces with high-aspect-ratio Si pillars coated with 10 nm ALD TiN. CNS was grown on TiN from CH4/H2mixture [1] to a height of approximately 1 µm.Anodic electrodeposition of Mn-oxide, often also termed electrolytic manganese-dioxide (EMD), was performed on both blanket CNS/TiN/Si and patterned CNS/ALD TiN/Si samples using 0.3 M MnSO4·xH2O + 0.55 M H2SO4aqueous electrolyte. Plating experiments were performed using a three-electrode clip-on Teflon cell connected to a computer controlled Autolab potentiostat PGSTAT100 (Metrohm), with Ag/AgCl as a reference electrode (RE) and Pt mesh as a counter electrode (CE). Characterization of EMD/CNS films was performed using Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and X-ray photoelectron spectroscopy (XPS). Figure 1 shows SEM images of as-grown CNS (a) and EMD coverage as a function of deposition current (b and c). EMD is plated galvanostatically, and potential-time responses were analyzed to help optimize deposition parameters for desired film thickness and structural properties. The analysis was based on the theories of galvanostatic nucleation and growth [2], and proposed reaction mechanisms during galvanostatic deposition of EMD [3]. Further surface area enhancement was attempted through EMD/CNS deposition on HAR Si pillars coated with 10 nm ALD TiN. Figure 2 shows HAR ALD TiN/Si pillars before and after CNS and EMD deposition, respectively. CNS coating was applied to various ALD TiN/Si structures having different aspect ratios and spacing between pillars, and then followed by EMD deposition.A typical Raman spectrum of our EMD/CNS structure, shown in Figure 3, contained broad features in the range 450 to 730 cm-1 where characteristic EMD peaks are expected [4 and references therein], and showed characteristic CNS peaks in 1000 to 3500 cm-1range [5]. Thanks to its sensitivity to local structure/symmetry Raman spectroscopy proved to be a useful tool for characterization of disordered and defective EMD. We were able to detect EMD structural changes upon annealing at various temperatures and lithiation in anhydrous propylene carbonate solvent with 1 M LiClO4, and also monitor the effects of plating and post-plating processing on CNS.

Electrodeposition and Characterization of Manganese Dioxide Thin Films on Silicon Pillar Arrays for 3D Thin-Film Lithium-Ion Batteries

Due to the increasing power requirements of the electronic devices and emerging technologies (e.g., wireless transmission), Li-ion batteries should be improved to provide higher energy and power densities on a small area (e.g. <1 cm2). To date, one promising way to maximize the energy and power densities of battery is to be built using 3D structured electrodes. Such electrodes are designed to make shorter ions diffusion paths and improving electrons harvesting pathways [1,2].In this context, the present work focuses onthe electrochemical deposition of manganese dioxide thin films on high aspect ratio silicon pillar arrays coated with carbon as a technologically-relevant current collector and the investigation of their properties as positive electrode material for Li-ions batteries. As 3D electrode array, hexagonally arranged Si pillars of 2um in diameter and 2um spacing were etched 60um deep in the silicon by reactive ion etching (RIE) using a SiO2 hard mask. The pillars were coated with about 20nm TiN by atomic layer deposition (ALD), acting as diffusion barrier for lithium into silicon. Cases of conformal coatings of electrolytic manganese dioxide (EMD) directly on the conductive TiN barrier were compared with seeded TiN / silicon pillars. In this respect, thin carbon coatings were evaluated as technological relevant alternative for platinum. For this, about 30nm of carbon was grown on ALD TiN / silicon pillars by chemical vapor deposition (CVD) from CH4/H2 mixture. The platinum seed films were made by ALD process. The electrolytic manganese dioxide (EMD) films were anodically deposited from an aqueous solution of 0.3 M MnSO4·xH2O + 0.55 M H2SO4. Since the oxidation of TiN takes place in the same potential region as does EMD deposition a protective layer such as platinum can be used to prevent TiN from oxidation during the aqueous deposition of MnO2 [3]. Here we evaluated carbon as technologically relevant alternative. Figure 1 shows cyclic voltamogrammes for uncoated and carbon coated planar TiN substrates. The EMD film thickness on TiN is strongly limited due to oxidation of the TiN. The carbon successfully protects the TiN from oxidation such that much thicker films can be made similarly to what was found with Pt seed layers before [4].The physical characteristics of the EMD films has been primarily investigated on planar substrates. The crystal structure of the EMD films before and after lithiation were characterized by X-ray diffraction (XRD). The porosity of the EMD films was determined by comparison of Rutherford backscattering (RBS) and Scanning electron microscopy (SEM). The porosity of the films typically ranges between 40-60%, depending on film thickness and substrate.After removing the water content in the films by thermal annealing, the electrochemical activity of EMD films was studied in propylene carbonate solvent with 1M LiClO4.Reversible insertion and extraction of Li+ was observed. Electrochemical lithiation and delithiation experiments showed an improved cycle performance for carbon coated TiN substrates compared to Pt coated TiN substrates. The difference is attributed to decreased porosity (attachment) for the EMD to the C surface compared to platinum surface. The average lithium storage capacity for planar EMD films is about 50mAh/cm2 per mm (at 10mV/s comparable with charging rate of 20C). Based on a surface area gain of 28for the 3D pillar structures, a capacity of 0.2mAh/cm2is expected for conformal coated 200 nm film at these high rates.REFERENCES[1] M. Roberts, P. Johns, J. Owen, D. Brandell, K. Edström, G. Enany, C. Guery, D. Golodnitsky, M. Lacey, C. Lecoeur, H. Mazor, E. Peled, E. Perre, M. M. Shaijumon, P. Simon, P. L. Taberna, J. Mater. Chem. 21, 9876 (2011)[2] A. H. Whitehead and M. Schreiber, Journal of The Electrochemical Society, 152, A2105 (2005) [3] D. J. Cott, M. Verheijen, O. Richard, I. Radu, S. De Gendt, S. van Elshocht, and P. M. Vereecken, Carbon, 58 59 (2013).[4] "Effect of Film Morphology on the Li-ion Intercalation Kinetics in Anodic Porous Manganese Dioxide Thin-Films" A. Etman, A. Radisic, E. Mahmoud, C. Huyghebaert, P.M. Vereecken, submitted to Journal of Physical Chemistry.

Strain relaxation of GaAs/Ge crystals on patterned Si substrates

We report on the mask-less integration of GaAs crystals several microns in size on patterned Si substrates by metal organic vapor phase epitaxy. The lattice parameter mismatch is bridged by first growing 2-μm-tall intermediate Ge mesas on 8-μm-tall Si pillars by low-energy plasma enhanced chemical vapor deposition. We investigate the morphological evolution of the GaAs crystals towards full pyramids exhibiting energetically stable {111} facets with decreasing Si pillar size. The release of the strain induced by the mismatch of thermal expansion coefficients in the GaAs crystals has been studied by X-ray diffraction and photoluminescence measurements. The strain release mechanism is discussed within the framework of linear elasticity theory by Finite Element Method simulations, based on realistic geometries extracted from scanning electron microscopy images.

Controlled formation of GeSi nanostructures on periodic Si (001) sub-micro pillars

Self-assembled GeSi nanostructures on periodic Si (001) sub-micro pillars (SMPs) are systematically studied. Different GeSi nanostructures, including circularly arranged quantum dots, quantum rings and quantum dot molecules can be readily obtained at the edge of the pillars by controlling the growth temperatures and the diameter of the pillar. These phenomena are explained by taking into account the surface chemical potential around the top terrace of SMPs, which is considerably affected by the formation of {113} facets. Our results demonstrate a feasible route to obtain novel periodic Si pillars embedded with the desired GeSi nanostructures, which have promising applications in optoelectronic devices.

Vertical Arrays of SiO2 Micro/Nanotubes Templated from Si Pillars by Chemical Oxidation for High Loading Capacity Buoyant Aquatic Devices

A simple and facile method to fabricate SiO2 micro- or nanotubes has been demonstrated based on room temperature wet chemical oxidation of a porous layer of Si pillar templates that have been prepared by metal-assisted chemical etching (MaCE). Under typical conditions, Si pillars produced by the MaCE have been found to be covered with a thin nanoporous Si layer. The porous Si skin layer has been chemically oxidized by simple dipping in AgNO3 solution at room temperature, which has led to seamless SiO2 shell layer thanks to the accompanying volume expansion during the wet oxidation. Following wet removal of core Si by KOH yields the SiO2 micro- or nanotubes, either in test tube shape or in open shape at both ends, depending on processing method. The vertical arrays of the SiO2 tube on the Si substrate, after hydrophobic siloxane oligomer printing, has been found to have very large loading capacity on water, due to extremely high porosity (>90%) and good enough mechanical stability. The novel method to fabricate SiO2 tubes can shed new light in design of novel aquatic devices, other than simple mimicking the leg of a water strider. Also, the method may be very helpful in various applications of SiO2 nanotubes.

3D heteroepitaxy of mismatched semiconductors on silicon

We present a method for monolithically integrating mismatched semiconductor materials with Si, coined three-dimensional (3D) heteroepitaxy. The method comprises the replacement of conventional, continuous epilayers by dense arrays of strain- and defect-free, micron-sized crystals. The crystals are formed by a combination of deep-patterning of the Si substrates and self-limited lateral expansion during the epitaxial growth. Consequently, the longstanding issues of crack formation and wafer bowing can be avoided. Moreover, threading dislocations can be eliminated by appropriately choosing pattern sizes, layer thicknesses and surface morphology, the latter being dependent on the growth temperature. We show this approach to be valid for various material combinations, pattern geometries and substrate orientations. We demonstrate that Ge crystals evolve into perfect structures away from the heavily dislocated interface with Si, by using a synchrotron X-ray beam focused to a spot a few hundred nanometers in size and by recording 3D reciprocal space maps along their height. Room temperature photoluminescence (PL) experiments reveal that the interband integrated PL intensity of the Ge crystals is enhanced by almost three orders of magnitude with respect to that of Ge epilayers directly grown on flat Si substrates. Electrical measurements performed on single heterojunction diodes formed between 3D Ge crystals and the Si substrate exhibit rectifying behavior with dark currents of the order of 1mA/cm2. For GaAs the thermal strain relaxation as a function of pattern size is similar to that found for group IV materials. Significant differences exist, however, in the evolution of crystal morphology with pattern size, which more and more tends to a pyramidal shape defined by stable {111} facets with decreasing width of the Si pillars.

(Invited) Bio-MEMS Chip for Bacteria Detection -A Challenge of Si Technology to Biomedical Field-

This work describes a Bio-MEMS chip with Si-pillar structure for trapping a bacterium Legionella pneumophila (L. pneumophila) and subsequently for making a bacteria sensor. Applying MEMS technology made a microfluidic chip having Si pillars. They operated as a sieve for trapping L. pneumophila cells injected into the microfluidic chip. Observation of fluorescence produced by the trapped L. pneumophila confirmed their capture in the Si-pillar structure. Spectroscopic analyses of the fluorescence found to have a broad peak at around 450 nm. The peak intensity was proportional to the square root of concentration for L. pneumophila cells injected into the microfluidic chip. This quantitative relationship indicates that a bacterial sensor that has Si pillar structure as a bacterial trap can be realized by using Si technology.

Facile generation of surface structures having opposite tone in metal-assisted chemical etching of Si: pillars vs. holes

Easy control on etched surface structures, either pillars or holes, in metal-assisted chemical etching (MaCE) of Si is presented. Starting with Ag mesh film with holes, which is generated by Ag evaporation in combination with a colloidal monolayer mask, the usual MaCE process has led to the vertical arrays of Si pillars. On the other hand, O2 reactive ion etching (RIE) on such Ag mesh film has led to sputtering and re-deposition of Ag on empty sites. During the following MaCE, the damaged Ag mesh spontaneously delaminates off the substrate and thus the etching with remaining Ag dot patterns results in holes array. Mechanistic studies of these etching behaviours have been performed and thus optimized, including the spontaneous mesh delamination. The obtained Si surfaces, either pillars or holes, were found to have comparable anti-reflection properties to other texturing approaches, which would be useful for photon management in applications such as photovoltaics, photoelectrochemical processes, etc.

Self-assembled titanium calcium oxide nanopatterns as versatile reactive nanomasks for dry etching lithographic transfer with high selectivity

We report the simple preparation of ultra-thin self-assembled nanoperforated titanium calcium oxide films and their use as reactive nanomasks for selective dry etching of silicon. This novel reactive nanomask is composed of TiO(2) in which up to 50% of Ti was replaced by Ca (Ca(x)Ti(1-x)O(2-x)). The system was prepared by evaporation induced self-assembly of dip-coated solution of CaCl(2), TiCl(4) and poly(butadiene-block-ethylene oxide) followed by 5 min of thermal treatment at 500 °C in air. The mask exhibits enhanced selectivity by forming a CaF(2) protective layer in the presence of a chemically reactive fluorinated plasma. In particular it is demonstrated that ordered nano-arrays of dense Si pillars, or deep cylindrical wells, with high aspect ratio i.e. lateral dimensions as small as 20 nm and height up to 200 nm, can be formed. Both wells and pillars were formed by tuning the morphology and the homogeneity of the deposited mask. The mask preparation is extremely fast and simple, low-cost and easily scalable. Its combination with reactive ion etching constitutes one of the first examples of what can be achieved when sol-gel chemistry is coupled with top-down technologies. The resulting Si nanopatterns and nanostructures are of high interest for applications in many fields of nanotechnology including electronics and optics. This work extends and diversifies the toolbox of nanofabrication methods.

GaN growth on Si pillar arrays by metalorganic chemical vapor deposition

GaN growth on high aspect ratio Si micro-pillar arrays prepared by deep reactive ion etching (DRIE) was investigated using Si(111), Si(110), Si(112), and Si(100) substrates. The sidewall roughness of the Si pillars resulting from DRIE was reduced by thermal annealing at 1100°C in H2 for 5min. Conformal AlN buffer layers were grown at 1100°C on the pillars. In contrast, GaN films grown at 1100°C were always faceted since GaN preferentially nucleated and grew on the Si{11¯0} and Si{11¯1} sidewall planes of the Si pillars. The preferential growth lead to unique symmetries for the independent GaN fins depending on pillar orientation. Lateral growth of the GaN fins at 1100°C was enhanced with increasing V/III ratio up to 22710. However, the GaN fins did not coalesce seamlessly. A lower growth temperature of 800°C gave rise to a conformal polycrystalline GaN shell. Post-annealing of the GaN shells at 1100°C in H2 for 15min after growth at 800°C induced highly textured GaN films although the GaN films became partly faceted.

Separations using a porous‐shell pillar array column on a capillary LC instrument

We investigated the achievable separation performance of a 9-cm-long and 1-mm-wide pillar array channel (volume = 0.6 μL) containing 5 μm diameter Si pillars (spacing 2.5 μm) cladded with a mesoporous silica layer with a thickness of 300 nm, when this channel is directly interfaced to a capillary LC instrument. The chip has a small footprint of only 4 cm × 4 mm and the channel consists of three lanes that are each 3 cm long and that are interconnected using low dispersion turns consisting of a narrow U-turn (10 μm), proceded and preceded by a diverging flow distributor. Measuring the band broadening within a single lane and comparing it to the total channel band broadening, the additional band broadening of the turns can be estimated to be of the order of 0.5 μm around the minimum of the van Deemter curve, and around some 1 μm (nonretained species) and 2 μm (retained species) in the C-term dominated regime. The overall performance (chip + instrument) was evaluated by conducting gradient elution separations of digests of cytochrome c and bovine serum albumin. Peak capacities up to 150 could be demonstrated, nearly completely independent of the flow rate.

Hierarchical and Multifunctional Three‐Dimensional Network of Carbon Nanotubes for Microfluidic Applications

Three-Dimensional network of carbon nanotubes: The 3D network of CNTs have hierarchical structures comprised of interconnected SWNTs between Si pillars in microfluidic channels. The Al(2)O(3) coated 3D networks were used for size different nanoparticles filtration and streptavidin capturing in very diluted solution. The 3D network of SWNTs systems will provide a robust multifuncitonal platform for a variety of biomedical and environmental applications.

Preparation and characterization of Ge epitaxially grown on nano-structured periodic Si pillars and bars on Si(001) substrate

The selective epitaxial growth of germanium on nano-structured periodic silicon pillars and bars with 360nm periodicity on Si(001) substrate is studied to evaluate the applicability of nano-heteroepitaxy on the Ge–Si system for different fields of application. It is found that SiO2 used as masking material plays the key role to influence the strain situation in the Si nano-islands. To analyze this in detail, X-ray diffraction techniques in combination with theoretical simulations based on the kinematical X-ray scattering from laterally strained nano-structures and finite element method (FEM) calculations of the strain field are applied. The oxide related strain in the Si scales about linearly with the thickness of the SiO2 mask, but FEM simulations supposing a homogeneous stress distribution in the oxide are not sufficient to describe the local strain distribution in the nano-structures. It is demonstrated that the Ge lattice relaxes completely during growth on the Si nano-islands by generation of misfit dislocations at the interface, but a high structural quality of Ge can be achieved by suited growth conditions.

Large scale microstructuring on silicon surface in air and liquid by femtosecond laser pulses

Large-scale microstructures were imprinted on the surface of silicon with dimensions of 1mm×1mm by femtosecond laser line-by-line scanning irradiation. The scanning was made under air and under chlor/hydrogen based liquid layers. Scanning electron microscope investigations evidenced homogeneous surface microstructures, such as: ripples with sub-wavelengths dimensions, Si pillars and directional oriented bacilliform structures. The dependence of the surface morphology on laser energy, scanning speed and irradiation media was analyzed. In air, the microstructure changes from directional-arranged bacilliform structures to well-known ripple structures with a width of about 525nm. When using the liquid media, we observe ripple structures with a width of about 370nm and an overlapping of those that evolve in certain regions into Si pillars. The surfaces show interesting gradient topography behaviour which could be used as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell adhesion and growth. By using chlor and hydrogen based liquids we were able to explore the microstructuring of the silicon by line-by-line irradiation process using the femtosecond laser.