Perfluorooctyl Trichlorosilane Research Articles

Mechanism of long-range hydrophobic force based on cavitation of metastable liquid film

Hydrophobic force, a key driving force in colloid physicochemical system and biological macromolecular system, exhibits a distinct multi-scale effect. The prevailing scholarly consensus attributes long-range hydrophobic force to bubble bridging, facilitated by unstable liquid film cavitation, while short-range force is thought to arise from the reorganization of water molecules at the solid-liquid interface. However, a comprehensive theoretical study remains elusive. To further elucidate the mechanism of the long-range hydrophobic force based on unstable liquid film cavitation, we carry out systematic research on the long-range hydrophobic force between perfluorooctyl trichlorosilane hydrophobic particles and the surface, by utilizing atomic force microscopy (AFM) and molecular dynamics simulations. According to AFM force tests, the long-range hydrophobic force escalates incrementally with subsequent close contacts before reaching a plateau. On the tenth contact, the penetration curve exhibits a sudden jump to an adhesion distance of 502.01 nm. A distinct step in the retraction curve suggests the rupture of the cavitation bubble capillary bridge. Importantly, the classical capillary force mathematical model provides an effective fit for the penetration curve. Our calculations estimate the volume of the capillary bridge at 0.30 μm³, offering direct theoretical evidence of the unstable liquid film cavitation bubble capillary bridge. Further insights are gained from large-scale tensile molecular dynamics simulations by using GROningen MAchine for Chemical Simulations (GROMACS). The inherent correlation mechanism of the formation, evolution, and mechanical behavior of the cavitation bubble capillary bridge in the separation process of hydrophobic particles are further explored from a molecular perspective. The results demonstrate that the local pressure drop occurring at the moment of “jump-out” separation of the hydrophobic particles attracts nitrogen molecules to diffuse into the liquid film, thereby forming a cavitation bubble capillary bridge. Simultaneously, a jumping behavior is observed in the calculated spring potential curve at the moment of capillary bridge rupture. Finally, the influence of solution gas content on long-range hydrophobic force is investigated. There is a positive correlation between gas molecule content and both the growth rate of cavitation bubble capillary bridge volume and the length of capillary bridge stretch-rupture, further demonstrating the gas concentration dependence of long-range hydrophobic forces. In a word, revealing the long-range hydrophobic force mechanism based on the cavitation of unstable liquid film can enhance our understanding of the interaction between colloid physical chemistry and biological macromolecules. Meanwhile, hydrophobic force is the fundamental driving force of particle-bubble adhesion in mineral flotation system, and the revelation of its action mechanism has important guiding significance for regulating the actual mineral flotation process.

Modified stainless steel wires with superwettability for highly efficient in-tube solid-phase microextraction

Construction of different surface wettability is meaningful for the interaction between the sorbent surface and target components. In the current study, four kinds of stainless-steel wires (SSWs) with different hydrophobic/hydrophilic property were prepared and used as the absorbents to enrich the target compounds with different polarity. Comparative extraction of six non-polar polycyclic aromatic hydrocarbons (PAHs) and six polar estrogens was carried out by in-tube solid phase microextraction (IT-SPME). The results showed that two SSWs with the superhydrophobic surfaces exhibited high extraction capacity to the non-polar PAHs with the superior enrichment factor (EF) in the range of 29–672 and 57–744, respectively. In contrast, the superhydrophilic SSWs demonstrated higher enrichment efficiency for the polar estrogens than other hydrophobic SSWs. On the basis of optimized conditions, a validated analysis method was established using six PAHs as model analytes for IT-SPME-HPLC. Acceptable linear ranges (0.5–10 μg L−1) and low detection limits (0.0056–0.32 μg L−1) were achieved using the superhydrophobic wire modified by perfluorooctyl trichlorosilane (FOTS). The relative recoveries spiked at 2, 5 and 10 μg L−1 in the lake water samples were in the range of 81.5%–113.7%. The relative standard deviation (RSD) of intraday (≤0.8%, n = 3) and interday (≤5.3%, n = 3) tests demonstrated the good extraction repeatability for the same extraction tube. Satisfactory repeatability for the preparation of extraction tubes (n = 3) was also obtained with the RSD values in the range of 3.6%–8.0%.

Open sensu shaped graphene oxide and modern carbon nanomaterials in translucent hydrophobic and omniphobic surfaces – Insight into wetting mechanisms

Thermal feathering of modern carbon nanomaterials (CNM), among them single walled carbon nanohorns (SWCNH) and carbon nanoonions (CNO), in polyethylene (PE) is applied to produce new durable, transparent hydrophobic, superhydrophobic and omniphobic surfaces. To increase SWCNH reactivity, they were converted into open sensu shaped graphene oxide (OSSGO). Next omniphobicity was introduced by fluorination. New superhydrophobic and hydrophobic translucent surfaces were deeply characterized by using spectroscopic methods, tribological analysis and contact angle (CA) measurements. Thermal feathering and fluorination by perfluorooctyl trichlorosilane (PFOTS) led to creation of grafted polysiloxanes and the attachment of fluorine-containing chains. The analysis of the Zisman plots, the adhesion tension vs. surface tension plots, CA and roll-off and hysteresis measurements results, together with Molecular Dynamics simulations, allowed to explain wetting mechanisms and the derivation on the adhesion tension vs. surface tension of liquids plots, suggesting surface freezing under the droplet as a new potential cause. Some new correlations describing the process of wetting are also discussed and explained. Fluorination creates translucent surfaces, and thus obtained materials can be used for red color filtering in self-cleaning coatings invisible for flying insects, which are a source of biological pollution of electronics that emit light in the open air at night.

Preparation of super-hydrophobic surface with micro-nano layered structure on 316 stainless steel by one-step wet chemical method

In order to simplify the traditional preparation procedure of super-hydrophobic stainless steel (SLS), a novel one-step method was developed to produce super-hydrophobic surface on 316 SLS under the simultaneous chemical etching and surface modification with cofunction of hydrogen peroxide (H2O2), hydrofluoric acid (HF) and perfluorooctyl trichlorosilane (PFOS). The effects of the mixing ratio of reagents (H2O2, HF and PFOS) and reaction time were explored by orthogonal experiments. The results indicated that H2O2 showed the most significant effect on the hydrophobicity of SLS. When the molar ratio of H2O2/HF ranged between 0.2/1–0.4/1, the prepared samples showed excellent super-hydrophobicity, with the maximum water contact angle of 161.78° and the minimum slip angle of 1.94°. The influencing mechanism of H2O2 on the etching and modification was further explored by X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM). The results showed that the ratio of H2O2/HF markedly affected the grafting of PFOS onto the surface of SLS. According to the tests of corrosion resistance and durability, the corrosion resistance of super-hydrophobic surface was 6 times higher than that of raw SLS, and the super-hydrophobicity of SLS hardly changed after 3 months of exposure in the ambient air. The water contact angle was still close to 150° after peeling adhesive tape for 12 times. The results of this study indicated a promising perspective for industrial application of the one-step method.

Microvalve array fabrication using selective PDMS (polydimethylsiloxane) bonding through Perfluorooctyl-trichlorosilane passivation for long-term space exploration

To improve the versatility and robustness of microfluidic analytical devices for space exploration, a programmable microfluidic array (PMA) has been implemented to support a variety of missions. When designing a PMA, normally closed valves are advantageous to avoid cross contamination and leaking. However, a stable fabrication method is required to prevent these valves from sticking and bonding over time. This work presents how polydimethylsiloxane (PDMS) can be bonded selectively using chemical passivation to overcome PDMS sticking issue during long-term space exploration. First, on a PDMS stamp, the vaporized perfluorooctyl-trichlorosilane (PFTCS) are deposited under − 80 kPa and 150 °C conditions. The PFTCS was then transferred onto PDMS or glass substrates by controlling temperature and time and 15 min at 150 °C provides the optimal PFTCS transfer for selective bonding. With these characterized parameters, we successfully demonstrated the fabrication of PMA to support long-term space missions. To estimate the stability of the stamped PFTCS, a PMA has been tested regularly for three years and no stiction or performance alteration was observed. A flight test has been done with a Cessaroni L1395 rocket for high g-force and vibration test and there is no difference on PMA performance after exposure of launch and landing conditions. This work shows promise as a simple and robust technique that will expand the stability and capability of PMA for space exploration.

Silica and Silane based polymer composite coating on glass slide by dip-Coating Method

Superhydrophobic coatings are widely used for various engineering applications, namely, self-cleaning and self-healing for engineering structures. Therefore, in recent decades, a number of industries have shown significant interest in the development of superhydrophobic coatings for various purposes. In view of the above demands, this study presents explicitly a cost-effective and facile method to fabricate superhydrophobic transparent coating on the glass. The superhydrophobic coating was prepared by dip-coating technique with sol-gel of polymethyl methacrylate-co-ethyl acrylate polymer (PMMA), SiO2nanoparticles (SiNps) and 1H, 1H, 2H, 2H perfluorooctyltrichlorosilane (PFOTS). Wettability, surface morphology, and the transparency of coating were investigated. Also, the stability of the coating was assessed at harsh conditions like annealing at high temperatures (4–400 °C), irradiation by UV light, and pH resistance at different alkali and acidic conditions (2–13), and mechanical durability by performing water-jet, abrasion and adhesion tests were studied. The coated glass exhibits a static water contact angle (CA) of 174 ± 2° and with a sliding angle (SA) of 4 ± 1° Furthermore, the coating exhibits excellent self-cleaning property, and more than 91% of the transparency of the coating was assessed. All the results indicated that such type of coatings could also use for self-cleaning and transparent coatings at the industrial level.

Oil-water separation through an ultrahydrophobic filter paper developed by sol-gel dip-coating technique

Eco-friendly oil–water separation substrates are mostly recommended in the present context of the world. In the present work, biodegradable and more economical ultrahydrophobic composite material was synthesized by sol–gel method using silica nanoparticles (SiO2) and poly (methyl methacrylate-co-ethyl acrylate) polymer (PMMA) with 1H,1H,2H,2H Perfluorooctyltrichlorosilane (PFOTS) coupler, and coated on 40-grade cellulose filter paper with a dip-coating method. As-prepared surfaces achieved static contact angle more than 175° and sliding angle 3.8°. The microstructure and chemical composition of ultrahydrophobic filter paper were characterized by scanning electric microscopy (SEM), X-ray spectroscopy (EDX), and Flourier transformation infrared spectroscopy (FTIR), respectively. The coated filter paper accomplished 98% oil–water separation efficiency by filtering different oils. Besides, the SiO2 nanoparticles were enhanced the thermal and UV aging resistance. The coated surfaces also showed excellent chemical inertness, and mechanical durability tested. This research work can be employed yet for domestic and industrial applications at a large scale for oil–water separation and self-cleaning.

UV-resistant and transparent hydrophobic surfaces with different wetting states by a facile dip-coating method

Hydrophobic surfaces with good resistance to UV radiation and high optical transparency are of great importance for various technological applications. In this work, we report a simple one-step approach to prepare such surfaces by the deposition of two different kinds of silanes, trimethylchlorosilane (TMCS), and perfluorooctyltrichlorosilane (PFOTCS). The surface coatings were obtained by dipping clean glass slides into the silane solutions of similar concentrations (˜ 0.1 M) in hexane. To obtain the surface with the best hydrophobic character, the immersion time of the substrate in both silanes was varied. Contact angle measurements with a goniometer showed the average static water angle values to be ˜ 110° and 120° for the TMCS- and PFOTCS-coated surfaces respectively. Sliding angle tests revealed an altogether different wetting state for the latter, Cassie impregnated state. The resulting surfaces were optically transparent having a visible light transmissivity similar to virgin glass. Atomic force microscopy (AFM) measurements showed both surfaces to be smooth with average roughness values ≤ 10 nm. X-ray photoelectron spectroscopy of the PFOTS modified surfaces confirmed fluorine enrichment at the top of the surface. Self-cleaning tests performed with dust particles showed the TMCS-coated surface to possess good cleaning characteristics. The synthesized surfaces retained their hydrophobic character after prolonged exposure (˜ 24 h) to concentrated UV light. The proposed preparation method is quite simple and can be applied to large-area substrates.

Transparent hard self-cleaning nano-hybrid coating on polymeric substrate

In this research, GPTMS-silica nano-hybrid coatings were immobilized on polycarbonate (PC) substrates by a sol-gel method. Perfluorooctyl-trichlorosilane (PFTS) was utilized to modify the prepared nano-hybrid coating surface. The modified nano-hybrid coatings were characterized by Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray Spectrometry (EDS), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), UV–vis-NIR spectrophotometer, and water contact angle analyzer methods. In addition, the self-cleaning properties of the nano-hybrid coatings were investigated. The results indicated that the formation of the nano-hybrid film improved the hardness and transmittance of the PC substrate. FE-SEM image indicated the formation of the crack free coating on the PC substrate. In addition, the modified nano-hybrid coating displays hydrophobicity (CA, 110°) and is very efficient at removing dust through water droplets.

Fabrication of Superhydrophobic Al5083 Aluminum Alloy for Marine Applications

Considering the importance of Al5083 as a most used and most promising aluminium alloy in vessels hull and marine systems, the focus of this research is on access to superhydrophobic coatings on this alloy by economical and efficient two step method composed of anodizing and chemical modification with silane. Al5XXX series of Al alloys including Al5083 have been widely used in marine industries such as fast ferries and ship building. In the present research, for fabricating superhydrophobic coatings on the aluminum alloy (Al5083) surface, anodizing in sulfuric acid and chemical modification of triethoxy octyl silane (KH-832) and 1H, 1H, 2H, 2H–perfluorooctyl trichloro silane (PFOTS), was employed. Surface characterization was carried out by scanning electron microscopy (SEM), atomic force microscopy (AFM), and ATR-FTIR tests. Also, the wettability of superhydrophobic coatings was evaluated using static wettability test. Static wetting and contact angle hysteresis tests on the aluminum alloy surfaces provided a high contact angle (about 170 and 160 degrees) and low contact angle hysteresis (about 3 and 9 degrees) respectively by modification with KH- 832 and PFOTS as a non-wettable surface. The ATR-FTIR analysis after surface chemical modification with KH-832 and PFOTS showed functionalized groups.

Formulation and characterization of black ceramic ink for a digital ink-jet printing

Formulation of black ceramic ink and its ink-jet printability on a glass substrate were investigated. The thermal and chemical stabilities of CoFe2-xCrxO4 and Ni0.925Mn0.075Fe1.875-xCrxMn0.125O4 black inorganic pigments were analyzed with various amounts of Cr substitutions. The ceramic ink was prepared using the pigment composition that demonstrated color stability during the high temperature glazing process with a minimal Cr substitutional amount. After the dispersion stability and rheological property were optimized, the ceramic ink was suitably jetted from a print head as a single sphere-shaped droplet without satellite droplets. To improve the printability of the ceramic ink, the glass substrate was treated with a perfluorooctyl trichlorosilane (PFTS) solution. As a result, the PFTS surface treatment increased the contact angle of the ceramic ink droplets on the glass substrate and effectively minimized the ink spreading phenomena.

Fabrication of hierarchical poly (vinylidene fluoride) micro/nano-composite membrane with anti-fouling property for membrane distillation

Hierarchical poly (vinylidene fluoride) (PVDF) micro/nano-composite membranes were fabricated by the immersion-deposition method. As a practical surface modification way, the immersion-deposition was explored to obtain superhydrophobic membranes via coating SiO2 nanoparticles onto PVDF membrane surface, following by fluoroalkylsilane coupling agents 1H, 1H, 2H, 2H - perfluorooctyltrichlorosilane (PFOTS) grafted on the silica. As a binder, PVDF was applied to immobilize silica nanoparticles in the process of modification. A variety of techniques were performed to examine the effects of surface modification on surface morphology, chemical composition and wettability of derived membranes, such as scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and contact angle goniometry. The surface modification endowed the membrane surface superhydrophobicity, deriving from the hierarchical structures with PVDF microspheres and nano-fluorinated silica particles deposited on the membrane surface. The results showed that the maximum value of membrane surface contact angle was up to 161.5°. The anti-fouling properties of the pristine and modified membranes were investigated by direct contact membrane distillation (DCMD) experiments with mixed solution including sodium chloride, calcium chloride and humic acid. The DCMD tests displayed that permeate flux of the modified membrane just had little decrease with the salt rejection rate above 99.99% during the long-term experiment, whereas permeate conductivity of the pristine membrane sharply increased and the permeate flux decreased gradually. The modified membrane presented excellent anti-fouling performances.

Investigation of the anti-adhesion layers for nanoimprint molding

To realize the anti-adhesion issue between silicon mold and nanostructures of hard polydimethylsiloxane (H-PDMS), anti-adhesion layers were coated on molds to improve the H-PDMS grating structure with half-pitch below 200 nm. Various deposition methods such as liquid immersion method, vapor deposition method, and plasma-enhanced chemical vapor deposition were used to coat various anti-adhesion layers, respectively. Three anti-adhesion layers including diamond-like carbon (DLC) film, fluorine-doped diamond-like carbon (F-DLC) film, and perfluorooctyl-trichlorosilane (PFOTCS) were investigated. PFOTCS was functioned as a mold-releasing agent using the liquid immersion and vapor deposition methods, respectively. The effect of those anti-adhesion layers on the molding process was characterized. The results show that the PFOTCS anti-adhesion layer coated by vapor deposition method exhibits the best separability among all of the anti-adhesion layers. The maximum contact angle using PFOTCS is about 115° under 0.5 h of heating time. Compared to DLC, the F-DLC anti-adhesion layer shows good separability when the line width exceeds 100 nm, and does not require recoating again after each use. In addition, atomic force microscopy (AFM) was adopted to measure the adhesion force between the H-PDMS and the anti-adhesion layers.

Transparent, superhydrophobic, and wear-resistant surfaces using deep reactive ion etching on PDMS substrates

Surfaces that simultaneously exhibit superhydrophobicity, low contact angle hysteresis, and high transmission of visible light are of interest for many applications, such as optical devices, solar panels, and self-cleaning windows. Superhydrophobicity could also find use in medical devices where antifouling characteristics are desirable. These applications also typically require mechanical wear resistance. The fabrication of such surfaces is challenging due to the competing goals of superhydrophobicity and transmittance in terms of the required degree of surface roughness. In this study, deep reactive ion etching (DRIE) was used to create rough surfaces on PDMS substrates using a O2/CF4 plasma. Surfaces then underwent an additional treatment with either octafluorocyclobutane (C4F8) plasma or vapor deposition of perfluorooctyltrichlorosilane (PFOTCS) following surface activation with O2 plasma. The effects of surface roughness and the additional surface modifications were examined with respect to the contact angle, contact angle hysteresis, and optical transmittance. To examine wear resistance, a sliding wear experiment was performed using an atomic force microscope (AFM).

Ceramic Ink-jet Printing on Glass Substrate Using Oleophobic Surface Treatment

Ink-jet printing has become a widespread technology with the society’s increase in aesthetic awareness. Especially, ink-jet printing using glazed ceramic ink can offer huge advantages including high quality decoration, continuous processing, glaze patterning, and direct reproduction of high resolution images. Recently, ceramic ink-jet printing has been rapidly introduced to decorate the porcelain product and the ceramic tiles. In this study, we provide an effective method to apply ceramic ink-jet decorations on the glass substrates using a oleophobic coating with perfluorooctyl trichlorosilane. The ink-jet printed patterns were much clearer on the oleophobically coated glass surface than the bare glass surface. The contact angle of the ceramic ink was maximized to the value of 64.0° on the glass surface, when it was treated with 1 vol% PFTS solution for 1 min. The effects of the printing conditions and firing process on the ink-jet printed patterns on the oleophobically coated glass were also investigated.

Amphiphobic PVDF composite membranes for anti-fouling direct contact membrane distillation

This study aimed to develop an effective method to fabricate the amphiphobic polyvinylidene fluoride (PVDF) composite membranes for membrane distillation (MD) with excellent tolerance to various organic foulants. A facial surface modification method was explored to obtain amphiphobic membranes with mechanical and thermal robustness by dynamically forming perfluorooctyl trichlorosilane (PFTS) and coating SiO2 nanoparticles onto the membrane surface. A variety of techniques such as environmental scanning electron microscopy (ESEM), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), liquid entry pressure (LEP) measurement and contact angle goniometry were applied to examine the effects of surface modification on surface chemistry, morphology and wettability of the derived membranes. The surface modification conferred the modified membrane superhydrophobicity and oleophobicity, stemmed from micro-fluorinated SiO2 particles covering the membrane surface. The anti-fouling property of the pristine and modified membranes were examined in a direct contact membrane distillation (DCMD) process using sodium chloride solution containing three model foulants (hydrophobic, hydrophilic or amphiprotic). The dynamically formed SiO2-PFTS/PVDF-2 membranes exhibited good thermal and mechanical resistance for DCMD operation. DCMD test showed that the surface modification did not sacrifice the permeate flux and the salt rejection. By adding the organic foulants, the pristine membrane displayed severe permeate flux decay and salt penetration. In contrast, the modified membrane presented a stable permeate flux and high salt rejection with the presence of three foulants respectively. The anti-fouling and anti-wetting properties of the modified membrane could be attributed to the enhanced amphiphobicity of membrane surface.

Study on Anti-Adhesion Layers Using AFM for Nanoimprint Process

This study investigates how to improve the anti-adhesion issues between Silicon mold and nanostructures of hard polydimethylsiloxane (H-PDMS). A Silicon mold with different depths and widths was made using a focused ion beam (FIB). During the soft-lithography molding process, anti-adhesion layers were needed between the Silicon mold and H-PDMS samples to prevent the de-molding failure caused by the adhesion issues between the interfaces. This study adopts three methods to deposit anti-adhesion layers, such as liquid immersion, vapor deposition, and fluorine-doped diamond-like carbon (F-DLC) film. Perfluorooctyl-trichlorosilane (PFOTCS) was used as a mold-releasing agent for the liquid immersion and vapor deposition methods. The contact angles between each film were measured to determine the effect of anti-adhesion on the molding process. In addition, atomic force microscopy (AFM) was used to measure the adhesion force between the H-PDMS and anti-adhesion layers. The results show that the coatings of anti-adhesion layers are an effective approach to improve the formability of molding.

A combined etching process toward robust superhydrophobic SiC surfaces

Large-scale porous SiC was fabricated by a combination of Pt-assisted etching and reactive ion etching. It was found that the surface roughness of combined etchings increased dramatically in comparison with metal-assisted etching or reactive ion etching only. To reduce the surface energy, the porous SiC surface was functionalized with perfluorooctyl trichlorosilane, resulting in a superhydrophobic SiC surface with a contact angle of 169.2° and a hysteresis of 2.4°. The superhydrophobicity of the SiC surface showed a good long-term stability in an 85 °C/85% humidity chamber. Such superhydrophobicity was also stable in acidic or basic solutions, and the pH values showed little or no effect on the SiC surface status. In addition, enhancement of porosity-induced photoluminescence intensity was found in the superhydrophobic SiC samples. The robust superhydrophobic SiC surfaces may have a great potential for microfluid device, thermal ground plane, and biosensor applications.

Friction behaviour of chemical vapor deposited self-assembled monolayers on silicon wafer

Friction characteristics of self-assembled monolayers (SAMs) coated on Si-wafer (1 0 0) by chemical vapor deposition technique were studied experimentally at nano and micro-scales. Four self-assembled monolayers, such as dimethyldichlorosilane (DMDC), diphenyldichlorosilane (DPDC), perfluorooctyltrichlorosilane (PFOTS) and perfluorodecanoicacid (PFDA) coated on Si-wafer (1 0 0) were used as test materials. Nano-scale friction was measured using atomic force microscopy (AFM) in the range of 0–40 nN normal loads, in LFM (lateral force microscopy) mode, using a contact mode type Si 3N 4 tip. Results showed that the friction of SAMs at this scale was influenced by their physical/chemical properties, while that of Si-wafer by its inherent adhesion. Further, micro-scale friction tests were also performed with a ball-on-flat type micro-tribotester under reciprocating motion. Friction was measured in the range of 1500–4800 μN applied normal loads using glass balls of varying radii, viz., 0.25, 0.5 and 1 mm. It was observed that the performance of SAMs was more superior to Si-wafer even at micro-scale, except for PFDA. Evidences obtained using scanning electron microscope showed that Si-wafer and PFDA exhibited wear at this scale. Wear in the case of Si-wafer was due to solid–solid adhesion and that in the case of PFDA due to the influence of humidity (moisture). The micro-scale friction in both these materials was severely influenced by their wear.

Nanopatterning of Si/SiGe Two-dimensional Hole Gases by PFOTS-aided AFM Lithography of Carrier Supply Layer

AbstractThe nanopatterning of Si/SiGe layers by PFOTS (perfluorooctyl trichlorosilane) -aided AFM (atomic force microscopy) lithography is demonstrated. We use self-assembled PFOTS monolayers as a resist for AFM exposure and then transfer patterns in to underlying SiGe layers by a two-step selective wet etching. Linewidths well under 100nm can be achieved with improved uniformity and repeatability compared to AFM lithography without PFOTS. This lithography technique was used to pattern the carrier supply layer in Si/SiGe 2-D hole gases to localize holes for epitaxially passivated quantum dot applications.