scholarly journals Al/Si Nanopillars as Very Sensitive SERS Substrates

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1534 ◽  
Author(s):  
Giovanni Magno ◽  
Benoit Bélier ◽  
Grégory Barbillon
Keyword(s):  
Native Oxide ◽  
Native Oxide Layer ◽  
Aluminum Layer ◽  
Large Area ◽  
Sers Substrates ◽  
Random Arrangement ◽  
Raman Enhancement ◽  
Sers Detection ◽  
Fdtd Simulations ◽  
Sers Sensing

In this paper, we present a fast fabrication of Al/Si nanopillars for an ultrasensitive SERS detection of chemical molecules. The fabrication process is only composed of two steps: use of a native oxide layer as a physical etch mask followed by evaporation of an aluminum layer. A random arrangement of well-defined Al/Si nanopillars is obtained on a large-area wafer of Si. A good uniformity of SERS signal is achieved on the whole wafer. Finally, we investigated experimentally the sensitivity of these Al/Si nanopillars for SERS sensing, and analytical enhancement factors in the range of 1.5 × 10 7 − 2.5 × 10 7 were found for the detection of thiophenol molecules. Additionally, 3D FDTD simulations were used to better understand optical properties of Al/Si nanopillars as well as the Raman enhancement.

Plasma Etching Conditioning of Textured Crystalline Silicon Surfaces for a-Si/c-Si Heterojunctions

1999 ◽  
Vol 557 ◽  
Author(s):  
R. De Rosa ◽  
M.L. Addonizio ◽  
E. Chiacchio ◽  
F. Roca ◽  
M. Tucci
Keyword(s):  
Plasma Etching ◽  
High Efficiency ◽  
Crystalline Silicon ◽  
Amorphous Layer ◽  
Native Oxide ◽  
Process Conditions ◽  
Native Oxide Layer ◽  
Plasma Process ◽  
Large Area ◽  
Layer Deposition

AbstractThe development of a hybrid heterojunction fabricated by growing ultrathin amorphous silicon by Plasma Enhanced Chemical Vapor Deposition using temperatures below 250°C offers the potential of obtaining high efficiency solar cells deposited on glassy substrates. The surface preparation represents one of the most critical steps. The first aim of etching is to remove the native oxide layer from the surface of the crystalline wafer, before amorphous layer deposition. The possibility of obtaining this goal with a dry procedure that reduces the exposure of the sample to the environment is not trivial.We performed several dry etching processes but the best results were obtained using an etching process involving CF4/O2 gases. We have found evidence that plasma etching acts by removing the native oxide and the damaged surface of textured silicon and by leaving an active layer on silicon surface suitable for the emitter deposition. SEM analysis has confirmed that it is possible to find plasma process conditions where no appreciable damage and changes in surface morphology are induced. Detailed investigation was performed to find compatibility and optimization of amorphous layer deposition both on flat and textured cast silicon by changing the plasma process parameters. By using this process we achieved on cast silicon for solar applications photovoltaic conversion efficiencies of 12.9% on 51 cm2 and 9.2% on 45 cm2 active areas for amorphous crystalline heterostructure devices realized on monocrystalline and polycrystalline silicon respectively. We also investigated the compatibility of the process with industrial production of large area devices.

scholarly journals Low-Cost, Disposable, Flexible and Highly Reproducible Screen Printed SERS Substrates for the Detection of Various Chemicals

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Wei Wu ◽  
Li Liu ◽  
Zhigao Dai ◽  
Juhua Liu ◽  
Shuanglei Yang ◽  
...  
Keyword(s):  
Screen Printing ◽  
Large Scale ◽  
Low Cost ◽  
Large Area ◽  
Sers Substrates ◽  
Sensing Applications ◽  
Relative Standard ◽  
Sers Detection ◽  
On Line ◽  
Liquid Milk

Abstract Ideal SERS substrates for sensing applications should exhibit strong signal enhancement, generate a reproducible and uniform response and should be able to fabricate in large-scale and low-cost. Herein, we demonstrate low-cost, highly sensitive, disposable and reproducible SERS substrates by means of screen printing Ag nanoparticles (NPs) on a plastic PET (Polyethylene terephthalate) substrates. While there are many complex methods for the fabrication of SERS substrates, screen printing is suitable for large-area fabrication and overcomes the uneven radial distribution. Using as-printed Ag substrates as the SERS platform, detection of various commonly known chemicals have been done. The SERS detection limit of Rhodamine 6G (R6G) is higher than the concentration of 1 × 10−10 M. The relative standard deviation (RSD) value for 784 points on the detection of R6G and Malachite green (MG) is less than 20% revealing a homogeneous SERS distribution and high reproducibility. Moreover, melamine (MA) is detected in fresh liquid-milk without additional pretreatment, which may accelerate the application of rapid on-line detection of MA in liquid milk. Our screen printing method highlights the use of large-scale printing strategies for the fabrication of well-defined functional nanostructures with applications well beyond the field of SERS sensing.

Wettability in pressure infiltration of SiC and oxidized SiC particle compacts by molten Al and Al-12wt%Si alloy

2007 ◽  
Vol 22 (8) ◽  
pp. 2273-2278 ◽  
Author(s):  
J.M. Molina ◽  
J. Tian ◽  
C. Garcia-Cordovilla ◽  
E. Louis ◽  
J. Narciso
Keyword(s):  
Contact Angle ◽  
Oxide Layer ◽  
Low Temperatures ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Threshold Pressure ◽  
Pressure Infiltration ◽  
Surface Conditions ◽  
Infiltration Behavior ◽  
Sic Particle

The infiltration behavior of compacts of SiC particles in two surface conditions, as-received and thermally oxidized, was investigated by using pure Al and Al-12wt%Si as infiltrating metals. Analysis of the threshold pressure for infiltration revealed that the process is governed by the same contact angle for all different systems, no matter the metal or particle condition. This leads to the conclusion that oxidation does not modify the wetting characteristics of the particles, most probably because they are already covered by a thin native oxide layer that remains unaltered in processing routes involving short contact times and low temperatures, such as actual conditions of pressure infiltration at 700 °C.

The Effect of Surface States on Secondary Electron (SE) Dopant Contrast from Silicon p-n Junctions

2007 ◽  
Vol 1026 ◽  
Author(s):  
Augustus K. W. Chee ◽  
Conny Rodenburg ◽  
Colin John Humphreys
Keyword(s):  
Oxide Layer ◽  
Computer Modelling ◽  
Surface States ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Element Analysis ◽  
Surface Band ◽  
Band Bending ◽  
Wide Range ◽  
Se Doping

AbstractDetailed computer modelling using finite-element analysis was performed for Si p-n junctions to investigate the effects of surface states and doping concentrations on surface band-bending, surface junction potentials and external patch fields. The density of surface states was determined for our Si specimens with a native oxide layer. Our calculations show that for a typical density of surface states for a Si specimen with a native oxide layer, the effects of external patch fields are negligible and the SE doping contrast is due to the built-in voltage across the p-n junction modified by surface band-bending. There is a good agreement between the experimental doping contrast and the calculated junction potential just below the surface, taking into account surface states, for a wide range of doping concentrations.

Nano-Thick Amorphous Oxide Layer Produced by Plasma on Type 316L Stainless Steel for Improved Corrosion Resistance Under Plastic Deformation

CORROSION ◽  
10.5006/2674 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 1011-1022 ◽  
Author(s):  
Megan Mahrokh Dorri ◽  
Stéphane Turgeon ◽  
Maxime Cloutier ◽  
Pascale Chevallier ◽  
Diego Mantovani
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Oxide Layer ◽  
Electrochemical Impedance ◽  
Open Circuit ◽  
Localized Corrosion ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Amorphous Oxide ◽  
Amorphous Oxide Layer

Localized corrosion constitutes a major concern in medical devices made of stainless steel. The conventional approach to circumvent such a problem is to convert the surface polycrystalline microstructure of the native oxide layer to an amorphous oxide layer, a few micrometers thick. This process cannot, however, be used for devices such as stents that undergo plastic deformation during their implantation, especially those used in vascular surgery for the treatment of cardiac, neurological, and peripheral vessels. This work explores the feasibility of producing a nano-thick plastic-deformation resistant amorphous oxide layer by plasma-based surface modifications. By varying the plasma process parameters, oxide layers with different features were produced and their properties were investigated before and after clinically-relevant plastic deformation. These properties and the related corrosion mechanisms were mainly evaluated using the electrochemical methods of open-circuit potential, cyclic potentiodynamic polarization, and electrochemical impedance spectroscopy. Results showed that, under optimal conditions, the resistance to corrosion and to the permeation of ions in a phosphate buffered saline, even after deformation, was significantly enhanced.

scholarly journals Facile Detection and Quantification of Acetamiprid Using a Portable Raman Spectrometer Combined with Self-Assembled Gold Nanoparticle Array

Chemosensors ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 327
Author(s):  
Panxue Wang ◽  
Yan Sun ◽  
Li Wang ◽  
Xiang Li ◽  
Miaomiao Liu ◽  
...  
Keyword(s):  
Gold Nanoparticle ◽  
Correlation Coefficients ◽  
Nanoparticle Array ◽  
Sers Signal ◽  
Sers Substrates ◽  
Specificity And Sensitivity ◽  
Exciting Opportunity ◽  
Sers Detection ◽  
Self Assembled ◽  
Detection And Quantification

Rapid and facile determination of pesticides is critically important in food and environmental monitoring. This study developed a self-assembled gold nanoparticle array based SERS method for highly specific and sensitive detection of acetamiprid, a neonicotinoid pesticide that used to be difficult in SERS analysis due to its low affinity with SERS substrates. SERS detection and quantification of acetamiprid was conducted with self-assembled gold nanoparticle arrays at the interface of chloroform and water as the enhancing substrate. Since targets dissolved in chloroform (organic phase) also have access to the hot-spots of Au NP array, the developed method exhibited good sensitivity and specificity for acetamiprid determination. Under the optimal conditions, SERS intensities at Raman shifts of 631 cm−1 and 1109 cm−1 displayed a good linear relationship with the logarithm concentration of acetamiprid in the range of 5.0 × 10−7 to 1.0 × 10−4 mol/L (0.11335 ppm to 22.67 ppm), with correlation coefficients of 0.97972 and 0.97552, respectively. The calculated LOD and LOQ of this method were 1.19 × 10−7 mol/L (0.265 ppb) and 2.63 × 10−7 mol/L (0.586 ppb), respectively, using SERS signal at 631 cm−1, and 2.95 × 10−7 mol/L (0.657 ppb) and 3.86 × 10−7 mol/L (0.860 ppb) using SERS signal at 1109 cm−1, respectively. Furthermore, the developed SERS method was successfully applied in determining acetamiprid on the surface of apple and spinach. This method offers an exciting opportunity for rapid detection of acetamiprid and other organic pesticides considering its advantages of simple preparation process, good specificity and sensitivity, and short detection time (within 1 h).

scholarly journals Образование акцепторных центров в CdHgTe под воздействием воды и термообработок

2021 ◽  
Vol 55 (4) ◽  
pp. 331
Author(s):  
Г.Ю. Сидоров ◽  
Ю.Г. Сидоров ◽  
В.А. Швец ◽  
В.С. Варавин
Keyword(s):  
Refractive Index ◽  
Water Treatment ◽  
Epitaxial Films ◽  
Heat Treatments ◽  
Deionized Water ◽  
Native Oxide ◽  
Water Medium ◽  
Native Oxide Layer ◽  
Formation Heat ◽  
Lower Refractive Index

Influence storage and boiling in deionized water and heat treatments of epitaxial films CdxHg1-xTe on the Hall and ellipsometric parametres is investigated. Water treatment reduces refractive index of native CdxHg1-xTe oxide from 2.1 to 1.2-1.4. It means that matter with a lower refractive index, such as water, is introduced in the oxide. Boiling in water leads to formation of acceptors in CdxHg1-xTe with concentrations up to 1019 cm-3. Change of medium’s pH from alkaline to the acidic decreases the speed of acceptors formation. Heat treatments after storage in water also leads to formation of acceptors. The conclusion is made, that water medium or water absorbed by native oxide layer leads to formation of acceptors in CdxHg1-xTe. Concentration of acceptors grows with temperature of treatments and quantity of accessible water.

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