Si Carriers Research Articles

Study of Spatial Distortion in InP Nanophotonic Membranes on Different Carrier Substrates

Electron Beam Lithography (EBL) metrology and least-square estimation of wafer-scale distortions is used to determine InP membrane deformation as a result of bonding to different substrate materials. First, the accuracy of EBL as a metrology tool for this particular application was assessed. Next, modelling of distortions was tested on unbonded InP wafers as a reference for extracting post-bonding distortions. Then we investigated the effect of substrate material choice on InP membrane deformation after bonding. We found residual expansion factors of 4.53±1, 312.4±1, and 317±1 ppm of the InP membrane bonded to InP, Si, and 3C-SiC carriers, respectively. For the SiO2 carrier, the 3inch InP membrane split into smaller membranes to reduce the stress, highlighting the importance of substrate choice.

Biolistic Delivery of Photosensitizer‐Loaded Porous Si Carriers for Localized Photodynamic Therapy (Adv. Mater. Technol. 23/2023)

Biolistic Delivery of Photosensitizer‐Loaded Porous Si Carriers for Localized Photodynamic Therapy (Adv. Mater. Technol. 23/2023)

Biolistic Delivery of Photosensitizer‐Loaded Porous Si Carriers for Localized Photodynamic Therapy

AbstractAmong numerous approaches for treating cancer, clinically approved photodynamic therapy (PDT) is considered a promising non‐invasive therapeutic strategy for solid tumors. While PDT has distinct advantages over conventional cancer treatments, systemic exposure to the photosensitizer and its stability are some of the limitations of clinical PDT. Herein, a therapeutic strategy for highly localized focal PDT is introduced based on direct biolistic delivery of photosensitizer‐loaded carriers to cancerous tumors. Degradable porous silicon microparticles (PSiMPs) are used as efficient carriers for the photosensitizer, meso‐tetrahydroxy‐phenylchlorin (mTHPC), and its conjugates with gold nanoparticles (AuNP‐mTHPC conjugates). The loaded PSiMP carriers are successfully bombarded using a pneumatic gene gun to breast cancer cells in vitro and into tumor xenografts in vivo, and subsequent uptake of the released photosensitizer payload is demonstrated. PDT irradiation is commenced after 24 h based on the release profile, resulting in complete cell death in vitro and substantial inhibition of tumor growth in vivo. Notably, using empty PSiMP carriers also leads to some tumor growth inhibition, ascribing to its intrinsic photosensitizing activity. Treatment with AuNP‐mTHPC‐loaded PSiMPs exhibits a superior therapeutic effect in comparison to bombarded mTHPC‐loaded carriers and administration of free mTHPC. This biolistic delivery scheme may be advantageous for precision photodynamic therapy.

Inorganic and Natural Silicon Sources as Soil Amendment on Growth of Local Aromatic Rice Variety

Lodging causes a yield loss of approximately 1 ton per hectare as 20% of the total rice production. Silicon(Si) fertilisers significantly improve paddy grain yield, and lodging resistance by improving leaf firmnessbesides promoting better plant canopy and boosting photosynthesis. The objective of this study was todetermine the effects of Si derived from calcium silicate (CaSiO3), rice husk ash, and rice straw on paddyplant growth. A pot study was conducted at MARDI Seberang Perai during the main season (2019/2020)and the off-season (2020) using the MRQ 76 rice variety to evaluate 10 Si carriers. The growth parametersof the paddy plants such as number of tillers, plant height, and chlorophyll content at different growth stageswere evaluated. During season 1, treatment with 100% CaSiO3 (T4) significantly improved the plant height.Nevertheless, the organic Si (T1, T2, and T3) and combination between organic Si with CaSiO3 (T5, T6,T7, and T8) resulted in the tallest plants during season 2. Treatment T7 increased the tillering number permeter square during season 1 whereas in season 2 treatment T8 performed better compared to the standardfertiliser (T9) and control (T10). However, the treatments evaluated in this study did not significantly affectthe chlorophyll content of the paddy plants. Applying a combination of rice straw (50%) and rice husk ash(50%) a day before transplanting, followed by CaSiO3 (100%) as a silicate material during panicle initiation,along with additional NPK fertiliser (17:3:25:2MgO) during heading stage (T7), and without additionalNPK fertiliser (17:3:25:2MgO) at the heading stage (T8) were most effective in enhancing crop growth andmaintaining the paddy cultivation. Therefore, the findings in this study suggested the potential of usinginorganic and organic Si to improve the growth and development of aromatic rice variety.

Graphene oxide microrolls as high- content Si carriers boosting Li-ion storage

As attractive anode materials of lithium-ion batteries, both microsized and nanosized silicon particles have been investigated widely, but each has lots of insurmountable problems to restrict their practical applications. In this work, combining the advantages of microsized and nanosized Si particles, we reported a new thought for constructing micrometer-sized Si/C particles by embedding Si nanoparticles into graphene oxide (GO)-based mirorolls. Differing to the traditional spherical shape, the resulted Si/C microrolls exhibit a unique elastic coil structure with opening ends, facilitating the stress buffer and fast charge diffusion. Besides, in order to maintain the stability of Si nanoparticles in microrolls, we chose the elastic and deformable liquid metal (LM) as the “cloth”, and sodium alginate (SA) as the “thread”, successfully tailor a novel “tight suit” for each Si nanoparticle by a facile self-assembly process. Thanks to the double protection of the conductive-elastic LM-SA coating and the microroll architecture, the resulted Si@LM-SA@GO microroll anode not only has a high Si content of 69 %, a high tap density of 0.62 g cm−3 and a high initial coulombic efficiency of 85.1 %, but also exhibits a superior volumetric capacity of 2506 mAh cm−3, and a superior cycling performance of 660 mAh cm−3 after 500 cycles at 2 A g−1. The full cell constructed using a LiNiCoMnO2 cathode can achieve a high reversible capacity of 150 mAh g−1 at 1C after 250 cycles, delivering a high-energy density of 510 Wh kg−1.

Time-resolved imaging of flyer dynamics for femtosecond laser-induced backward transfer of solid polymer thin films

We have studied the transfer regimes and dynamics of polymer flyers from laser-induced backward transfer (LIBT) via time-resolved shadowgraphy. Imaging of the flyer ejection phase of LIBT of 3.8μm and 6.4μm thick SU-8 polymer films on germanium and silicon carrier substrates was performed over a time delay range of 1.4–16.4μs after arrival of the laser pulse. The experiments were carried out with 150fs, 800nm pulses spatially shaped using a digital micromirror device, and laser fluences of up to 3.5J/cm2 while images were recorded via a CCD camera and a spark discharge lamp. Velocities of flyers found in the range of 6–20m/s, and the intact and fragmented ejection regimes, were a function of donor thickness, carrier and laser fluence. The crater profile of the donor after transfer and the resulting flyer profile indicated different flyer ejection modes for Si carriers and high fluences. The results contribute to better understanding of the LIBT process, and help to determine experimental parameters for successful LIBT of intact deposits.

Bombarding cancer: biolistic delivery of therapeutics using porous Si carriers.

A new paradigm for an effective delivery of therapeutics into cancer cells is presented. Degradable porous silicon carriers, which are tailored to carry and release a model anti-cancer drug, are biolistically bombarded into in-vitro cancerous targets. We demonstrate the ability to launch these highly porous microparticles by a pneumatic capillary gene gun, which is conventionally used to deliver cargos by heavy metal carriers. By optimizing the gun parameters e.g., the accelerating gas pressure, we have successfully delivered the porous carriers, to reach deep targets and to cross a skin barrier in a highly spatial resolution. Our study reveals significant cytotoxicity towards the target human breast carcinoma cells following the delivery of drug-loaded carriers, while administrating empty particles results in no effect on cell viability. The unique combination of biolistics with the temporal control of payload release from porous carriers presents a powerful and non-conventional platform for designing new therapeutic strategies.

Mathematical modeling of drug release from nanostructured porous Si: Combining carrier erosion and hindered drug diffusion for predicting release kinetics

A novel, empirical, macroscopic model is developed to describe the release of a model anticancer drug, Mitoxantrone, from native and chemically modified porous Si (PSi) thin films. Drug release from these carriers results from a combination of two mechanisms, i.e. out-diffusion of the drug molecules and erosion of the Si scaffold. Thus, the proposed mathematical model adapts the Crank model to lump the effects of temporal changes in molecular interactions and carrier scaffold erosion into a comprehensive model of hindered drug diffusion from nanoscale porous systems. Careful characterization of pore size, porosity, surface area, drug loading, as well as Si scaffold degradation profiles, measured over the same time-scale as drug release, are incorporated into the model parameter estimation. A comparison of the experimental and model results shows accurate representation of the data, emphasizing the reliability of the model. The proposed model shows that drug diffusivity values significantly vary with time for the two studied carriers, which are ascribed to the distinctive role of the prevailing physical mechanisms in each system. Finally, secondary validation of the proposed model is demonstrated by showing adequate fit to published data of the release of dexamethasone from similar mesoporous Si carriers.

Non-uptake of silicon and variable nematode species relationships between different levels of this element in sugarcane

Silicon (Si) is known to alleviate biotic and abiotic stresses in many crops. Much of the research on the biotic influence of Si has dealt with insects and fungi, with no proper studies on the effect of Si on plant-parasitic nematodes. To investigate this effect, a replicated field trial was planted with sugarcane in KwaZulu-Natal, comparing Si carriers, bagasse, filtercake and fly ash, added either by themselves or in combination with condensed molasses stillage (CMS), thume, CMS alone and aldicarb (a synthetic nematicide) to untreated plots. Applying the Si carriers to the soil was not always sufficient to increase levels of Si in the sugarcane leaves. Uptake of Si by sugarcane required a particular chemical balance in the soil, which was not found uniformly in this field. As a consequence,the addition of Si carriers, per se, had no effect on the nematode community. However, a comparison between Si-rich and Si-poor plots, selected independently of the treatments, showed that total numbers of plant-parasitic nematodes and numbers of Pratylenchus zeae and Helicotylenchus dihystera in the soil were significantly lower in plots where foliar Si levels were higher. The same trend was true for the number of P. zeae in the roots, but the difference was not significant. Multivariate analysis showed that while numbers of some of the nematodes in the soil were depressed in the higher Si plots, numbers of the more damaging nematodes were unaffected. As a result there was still a potential risk in the long term for damage to the crop caused by these nematodes.

Light extraction enhancement of sapphire‐free InGaN LEDs using single‐ and double‐side surface roughening techniques

AbstractWe compare the performance of three types of GaN‐based light‐emitting diodes (LEDs) epitaxially grown on patterned sapphire substrates (PSSs). For the devices with a single roughened p‐GaN surface, the light output power of the original LEDs with the PSS and Ag reflector (Sample A) is lower than that of thin‐film LEDs transferred onto Si carriers via glue bonding (Sample B). While the thin GaN LEDs with double‐side roughening (both p‐GaN and micropillar undoped‐GaN surfaces) and glue/Ag omnidirectional reflector (Sample C) shows much higher light output power than that of Sample B. As compared with the Sample A, the Sample C shows a performance enhancement of 50.3% in light output power and 46.3% in power efficiency at 350 mA. These results reflect that the contribution of the micropillar undoped‐GaN texturing for the light extraction is dominant. The employment of Si carrier decreases the junction temperature of the Sample C, a 46.6 °C lower than that of the conventional LEDs on PSS. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Characterization of atmospheric aerosols using Synchroton radiation total reflection X-ray fluorescence and Fe K-edge total reflection X-ray fluorescence-X-ray absorption near-edge structure

In this study a new procedure using Synchrotron total reflection X-ray fluorescence (SR-TXRF) to characterize elemental amounts in atmospheric aerosols down to particle sizes of 0.015 um is presented. The procedure was thoroughly evaluated regarding bounce off effects and blank values. Additionally the potential of total reflection X-ray fluorescence–X-ray absorption near edge structure (SR-TXRF-XANES) for speciation of FeII/III down to amounts of 34 pg in aerosols which were collected for 1 h is shown. The aerosols were collected in the city of Hamburg with a low pressure Berner impactor on Si carriers covered with silicone over time periods of 60 and 20 min each. The particles were collected in four and ten size fractions of 10.0–8.0 μm, 8.0–2.0 μm, 2.0–0.13 μm 0.13–0.015 μm (aerodynamic particle size) and 15–30 nm, 30–60 nm, 60–130 nm, 130–250 nm, 250–500 nm, 0.5–1 μm, 1–2 μm, 2–4 μm, 4–8 μm, 8–16 μm. Prior to the sampling “bounce off” effects on Silicone and Vaseline coated Si carriers were studied with total reflection X-ray fluorescence. According to the results silicone coated carriers were chosen for the analysis. Additionally, blank levels originating from the sampling device and the calibration procedure were studied. Blank levels of Fe corresponded to 1–10% of Fe in the aerosol samples. Blank levels stemming from the internal standard were found to be negligible. The results from the Synchroton radiation total reflection X-ray fluorescence analysis of the aerosols showed that 20 min of sampling time gave still enough sample material for elemental determination of most elements. For the determination of the oxidation state of Fe in the aerosols different Fe salts were prepared as a reference from suspensions in isopropanol. The results from the Fe K-edge Synchroton radiation total reflection X-ray fluorescence-X-ray absorption near-edge structure analysis of the aerosol samples showed that mainly Fe(III) was present in all particle size fractions.

Reliability of a Silicon Stacked Module for 3-D SiP Microsystem

Solder joint reliability of 3-D silicon carrier module were investigated with temperature cycle and drop impact test. Mechanical simulation was carried out to investigate the solder joint stress using finite element method (FEM), whose 3-D model was generated and solder fatigue model was used. According to the simulation results, the stress involved between flip chip and Si substrate was negligible but stress is more concentrated between Si carriers to printed circuit board (PCB) solder joint area. Test vehicles were fabricated using silicon fabrication processes such as DRIE, Cu via plating, SiO deposition, metal deposition, lithography, and dry or wet etching. After flip chip die and silicon substrate fabrication, they were assembled by flip chip bonding equipment and 3-D silicon stacked modules with three silicon substrate and flip chip dies were fabricated. Daisy chains were formed between flip chip dies and silicon substrate and resistance measurement was carried out with temperature cycle test (C, 2 cycles/h). The tested flip chip test vehicles passed T/C 5000 cycles and showed robust solder joint reliability without any underfill material. Drop test was also carried out by JEDEC standard method. More details on test vehicle fabrication and reliability test results would be presented in the paper.

Efficient Isotope Ratio Analysis of Uranium Particles in Swipe Samples by Total-Reflection X-ray Fluorescence Spectrometry and Secondary Ion Mass Spectrometry

A new particle recovery method and a sensitive screening method were developed for subsequent isotope ratio analysis of uranium particles in safeguards swipe samples. The particles in the swipe sample were recovered onto a carrier by means of vacuum suction-impact collection method. When grease coating was applied to the carrier, the recovery efficiency was improved to 48±9%, which is superior to that of conventionally-used ultrasoneration method. Prior to isotope ratio analysis with secondary ion mass spectrometry (SIMS), total reflection X-ray fluorescence spectrometry (TXRF) was applied to screen the sample for the presence of uranium particles. By the use of Si carriers in TXRF analysis, the detection limit of 22 pg was achieved for uranium. By combining these methods with SIMS, the isotope ratios of 235U/238U for individual uranium particles were efficiently determined.

Fabrication of single nanofluidic channels in poly(methylmethacrylate) films via focused-ion beam milling for use as molecular gates

Focused-ion beam (FIB) milling provides rapid fabrication of individual cylindrical submicrometer channels with reproducible dimensions (±5% diameters) through 8-μm thick poly(methylmethacrylate) (PMMA) films. PMMA films are spincast on sacrificial Si carriers and sputter-coated with Au before the 30-kV gallium FIB milling process. By adding a trace amount of poly(ethyleneoxide) and poly(dimethylsiloxane) to the PMMA solution before casting, the films can be released for subsequent mounting in microfluidic devices to create hybrid microfluidic-nanofluidic multilevel architectures. In situ FIB sectioning demonstrates the smooth cylindrical surface within the pore. Placing a milled film in contact with an aqueous fluorescein solution fills the channel by capillary action, as verified by confocal fluorescence microscopy. Confocal fluorescence of dyed films reveals that the pores span the thickness of the PMMA film. Small arrays of channels with a defined number and density and arbitrary in-plane spatial arrangement are fabricated with this process, allowing a unique testbed for high aspect ratio nanofluidic devices.

The use of Si carriers for aerosol particle collection and subsequent elemental analysis by total-reflection X-ray fluorescence spectrometry

The adoption of polished Si carriers was studied for the sensitive elemental analysis of aerosol particles using total-reflection X-ray fluorescence (TXRF) spectrometry. The surface roughness of the Si carrier measured by atomic force microscopy was found to be smaller than those of glassy carbon and quartz glass carriers, which are commonly used for TXRF analysis. The detection limits of elements for the Si carrier were superior to those for the glassy carbon and the quartz glass carriers, presumably due to its smaller surface roughness. For example, the detection limit of Sr for the Si carrier was 9 pg, which was 100 times and 3 times lower than those for the glassy carbon and the quartz glass carriers, respectively. The Si carriers could be successfully applied to the direct aerosol particle collection by impaction and the subsequent elemental analysis by TXRF. From the results of the elemental analysis of aerosol particles, the variations in the concentrations of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn Sr and Pb with time could be clarified.

Models of deep centres in gallium phosphide

The effects of varying the ammonia flux on the concentrations of background Si and free carriers and on deep traps for majority and minority carriers in n-GaP layers grown by vapour epitaxy have been studied by secondary ion mass spectrometry and deep level transient spectroscopy. The contribution from the background silicon to the free carrier concentration in samples variously doped with nitrogen is discussed. It is shown that the deep centre at eV may be attributed to silicon. The model of this centre in the form accounts for experimental results obtained in the present work and those already reported. The concentration of the dominant nonradiative recombination centre at eV is studied, depending on growth conditions, and its model is proposed in the form of a complex consisting of intrinsic defects.

Ternary V–Ti–Si catalysts and their behaviour in the CO + NO reaction

De-NOx catalysts with strong mechanical properties and high surface area have been prepared by coating silica microspheres with titania according to the homogeneous deposition–precipitation method. The proportion of titania incorporated was varied between 0.5 and 3.0 theoretical monolayers. These catalysts possess a titania-like behaviour and strong acid properties. Although the Ti–Si carriers are titania-rich, the TiO2 phase is relatively well dispersed and the change in the coordination sphere of TiO2 induced by the silica substrate may account for its strong acid properties. Upon incorporation of vanadium, both dispersed vanadium species and V2O5 crystallites are developed, the former being similar to vanadia species on TiO2. These systems exhibit both strong acidity and redox properties which are primarily associated with characteristics peculiar to the support and the V2O5 components, respectively, which play a key role in the de-NOx reaction. Preliminary results on the CO + NO reaction indicate that these catalysts have a much better performance than VTiO2.