scholarly journals Porous Gig-Lox TiO2 Doped with N2 at Room Temperature for P-Type Response to Ethanol

Chemosensors ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 12 ◽  
Author(s):  
Emanuele Smecca ◽  
Salvatore Sanzaro ◽  
Clelia Galati ◽  
Lucio Renna ◽  
Leonardo Gervasi ◽  
...  
Keyword(s):  
Tio2 Film ◽  
Room Temperature ◽  
Electrical Response ◽  
High Surface ◽  
Volume Ratio ◽  
Reactive Sputtering ◽  
Deposition Process ◽  
Deposition Method ◽  
Type Character ◽  
P Type

Nanostructured materials represent a breakthrough in many fields of application. Above all for sensing, the use of nanostructures with a high surface/volume ratio is strategic to raise the sensitivity towards dangerous environmental gas species. A new Dc-Reactive sputtering Deposition method has been applied to grow highly porous p-type nitrogen-doped titanium oxide layers by modifying the previously developed reactive sputtering method called gig-lox. The doping of the films was achieved at room temperature by progressive incorporation of nitrogen species during the deposition process. Two different amounts of N2 were introduced into the deposition chamber at flow rates of 2 and 5 standard cubic centimeter per minutes (sccm) for doping. It has been found that the N2 uptake reduces the deposition rate of the TiO2 film whilst the porosity and the roughness of the grown layer are not penalized. Despite the low amount of N2, using 2 sccm of gas resulted in proper doping of the TiO2 film as revealed by XPS Analyses. In this case, nitrogen atoms are mainly arranged in substitutional positions with respect to the oxygen atoms inside the lattice, and this defines the p-type character of the growing layer. Above this strategic structural modification, the multibranched spongy porosity, peculiar of the gig-lox growth, is still maintained. As proof of concept of the achievements, a sensing device was prepared by combining this modified gig-lox deposition method with state-of-the-art hot-plate technology to monitor the electrical response to ethanol gas species. The sensor exhibited a sensitivity of a factor of ≈2 to 44 ppm of ethanol at ≈200 °C as measured by a rise in the layer resistivity according to the p-type character of the material. At the higher temperature of ≈350 °C, the sensor turned to n-type as without doping. This behavior was related to a loss of nitrogen content inside the film during the annealing. It was indeed proved that p-type doping of a gig-lox sponge during growth is feasible, even at room temperature, without losing the layer porosity and the capability to host and detect environmental species. Moreover, the material integration on a device is simply done as the last production step. Easy TiO2 doping procedures, combined with porosity, are of general purpose and interest for several applications even on flexible substrates.

scholarly journals Three-dimensional platinum nanoparticle-based bridges for ammonia gas sensing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nishchay A. Isaac ◽  
Johannes Reiprich ◽  
Leslie Schlag ◽  
Pedro H. O. Moreira ◽  
Mostafa Baloochi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Gas Sensing ◽  
Response Times ◽  
High Surface ◽  
Three Dimensional ◽  
Performance Testing ◽  
Volume Ratio ◽  
Platinum Nanoparticle ◽  
Ammonia Gas ◽  
Lift Off

AbstractThis study demonstrates the fabrication of self-aligning three-dimensional (3D) platinum bridges for ammonia gas sensing using gas-phase electrodeposition. This deposition scheme can guide charged nanoparticles to predetermined locations on a surface with sub-micrometer resolution. A shutter-free deposition is possible, preventing the use of additional steps for lift-off and improving material yield. This method uses a spark discharge-based platinum nanoparticle source in combination with sequentially biased surface electrodes and charged photoresist patterns on a glass substrate. In this way, the parallel growth of multiple sensing nodes, in this case 3D self-aligning nanoparticle-based bridges, is accomplished. An array containing 360 locally grown bridges made out of 5 nm platinum nanoparticles is fabricated. The high surface-to-volume ratio of the 3D bridge morphology enables fast response and room temperature operated sensing capabilities. The bridges are preconditioned for ~ 24 h in nitrogen gas before being used for performance testing, ensuring drift-free sensor performance. In this study, platinum bridges are demonstrated to detect ammonia (NH3) with concentrations between 1400 and 100 ppm. The sensing mechanism, response times, cross-sensitivity, selectivity, and sensor stability are discussed. The device showed a sensor response of ~ 4% at 100 ppm NH3 with a 70% response time of 8 min at room temperature.

scholarly journals Limiting the Oxidation of WS2 Nanostructures by Oleylamine Surface Passivation for Room Temperature NH3 Sensing

2020 ◽  
Author(s):  
Siziwe Gqoba ◽  
Rafael Rodrigues ◽  
Sharon Lerato Mphahlele ◽  
Zakhele Ndala ◽  
Mildred Airo ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Room Temperature ◽  
Surface Passivation ◽  
Electrical Response ◽  
Prolonged Incubation ◽  
P Type ◽  
2D Nanosheets ◽  
Type Response ◽  
And Diffusion ◽  
Hierarchical Morphology

Oleylamine capped WS2 nanostructures were successfully formed at 320 °C via a relatively simple colloidal route. SEM and TEM analyses showed that the 3D nanoflowers that were initially formed disintegrated into 2D nanosheets after prolonged incubation. XPS and XRD analyses confirmed oxidation of WS2 into WO3. Sensors based on these oleylamine capped WS2 nanoflowers and nanosheets still showed a change in electrical response towards various concentrations of NH3 vapour at room temperature in a 25% relative humidity background despite the oxidation. The nanoflowers exhibited n-type response while the nanosheets displayed a p-type response towards NH3 exposure. The nanoflower based sensors showed better response to NH3 vapour exposure than the nanosheets. The sensors showed a good selectivity towards NH3 relative to acetone, ethanol, chloroform and toluene. Meanwhile, a strong interference of humidity to the NH3 response was displayed at high relative humidity levels. The results demonstrated that oleylamine limited the extent of oxidation of WS2 nanostructures. The superior sensing performance of the nanoflowers can be attributed to their hierarchical morphology which enhances the surface area and diffusion of the analyte.

Effect of current density on the porous silicon preparation as gas sensors**

2021 ◽  
Vol 30 (1) ◽  
pp. 257-264
Author(s):  
Muna H. Kareem ◽  
Adi M. Abdul Hussein ◽  
Haitham Talib Hussein
Keyword(s):  
Porous Silicon ◽  
Gas Sensors ◽  
Current Density ◽  
Room Temperature ◽  
Low Cost ◽  
High Surface ◽  
Volume Ratio ◽  
Etching Time ◽  
Force Microscopy ◽  
Materials Used

Abstract In this study, porous silicon (PSi) was used to manufacture gas sensors for acetone and ethanol. Samples of PSi were successfully prepared by photoelectrochemical etching and applied as an acetone and ethanol gas sensor at room temperature at various current densities J= 12, 24 and 30 mA/cm2 with an etching time of 10 min and hydrofluoric acid concentration of 40%. Well-ordered n-type PSi (100) was carefully studied for its chemical composition, surface structure and bond configuration of the surface via X-ray diffraction, atomic force microscopy, Fourier transform infrared spectroscopy and photoluminescence tests. Results showed that the best sensitivity of PSi was to acetone gas than to ethanol under the same conditions at an etching current density of 30 mA/cm2, reaching about 2.413 at a concentration of 500 parts per million. The PSi layers served as low-cost and high-quality acetone gas sensors. Thus, PSi can be used to replace expensive materials used in gas sensors that function at low temperatures, including room temperature. The material has an exceptionally high surface-to-volume ratio (increasing surface area) and demonstrates ease of fabrication and compatibility with manufacturing processes of silicon microelectronics.

Morphology and I-V Characteristics of Electrochemically Deposited Zinc Oxide on Silicon

2021 ◽  
Vol 20 (3) ◽  
pp. 32-36
Author(s):  
Ahmad Bukhairi Md Rashid ◽  
Mastura Shafinaz Zainal Abidin ◽  
Shaharin Fadzli Abd Rahman ◽  
Amirjan Nawabjan
Keyword(s):  
Zinc Oxide ◽  
Electrochemical Deposition ◽  
Dark Current ◽  
Room Temperature ◽  
Volume Ratio ◽  
Deposition Process ◽  
X Ray ◽  
Current Voltage ◽  
Electrochemically Deposited ◽  
A Current

This paper reported on the electrochemical deposition of zinc oxide (ZnO) on p-silicon (p-Si) (100) substrate in the mixture of 0.1 M of zinc chloride (ZnCl2) and potassium chloride (KCl) electrolyte at a volume ratio of 1:1, 3:1 and 5:1 namely Sample A, B and C. The deposition process was done in room temperature with a current density of 10 mA/cm2 for 30 minutes. Prior to the experiment, all samples were treated by RCA cleaning steps. All samples were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The results show that all samples have the same morphology of a flake-like structure with different Zn:O ratio that were 2.81, 2.35 and 2.49 for samples A, B and C. The current-voltage (I-V) characteristic graph was obtained by dark current measurement using Keithley SMU 2400 and the threshold voltage (Vth) values were determined at 2.21 V, 0.85 V and 1.22 V for sample A, B and C respectively which correspond with the Zn:O ratio where the highest value of Zn:O ratio can be found in sample A and the lowest in sample B. Based on these results, it shows that electrochemical deposition technique is capable of being used to deposit the flake-like structure ZnO on semiconductor material to form the p-n junction which behaves like a diode. The value of Vth seems to be depended on the ratio between Zn and O. Higher ratio of Zn and O will cause the higher value of intrinsic carrier concentration and built in potential which will increase the Vth value.

Vapor Deposition of Composite Organic-Inorganic Films

2005 ◽  
Author(s):  
B. Kobrin ◽  
J. Chin ◽  
W. R. Ashurst
Keyword(s):  
Vapor Deposition ◽  
Room Temperature ◽  
Surface Coverage ◽  
Composite Coatings ◽  
Composite Films ◽  
Deposition Process ◽  
Deposition Method ◽  
Self Assembled Monolayer ◽  
Process Sequence ◽  
Inorganic Films

Results on the thermal and immersion stability of ultra-thin composite films created by a deposition method call MVD™ (Molecular Vapor Deposition [1]) are reported. It is observed that these composite films were denser and more stable in thermal and immersion applications when compared to traditional self-assembled monolayer (SAM) films. These improved films were created by a special “sequential” or “layered” deposition process sequence. The MVD™ composite coatings can be deposited at room temperature on a variety of materials such as polymers, fibers, metals, alloys and other materials which normally do not allow films to form with complete surface coverage.

scholarly journals A Room Temperature Gas Sensor Based on Sulfonated SWCNTs for the Detection of NO and NO2

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1116 ◽  
Author(s):  
Eusebiu Ionete ◽  
Stefan Spiridon ◽  
Bogdan Monea ◽  
Elena Stratulat
Keyword(s):  
Room Temperature ◽  
Gas Sensing ◽  
Electrical Response ◽  
Long Term Stability ◽  
Sensing Applications ◽  
Specific Configuration ◽  
P Type ◽  
Walled Carbon Nanotubes ◽  
Type Response

The electrical response of sulfonated single-walled carbon nanotubes (SWCNTs) to NO and NO2, for gas sensing applications, at room temperature, is reported in this work. A specific configuration based on SWCNT deposition between double pair configuration gold electrodes, supported on a substrate, was considered for the sensing device; employed characterization technique where FTIR and SEM. The experimental results showed a p-type response of the sulfonated SWCNTs, with decrease in resistance, under exposure to NO gas (40–200 ppb) and NO2 (40–200 ppb). Also, the sensor responses to successive exposures at NO2 800 ppb together with investigation of long term stability, at 485 ppb for NO, are reported. The reaction mechanism in case of NO and NO2 detection with sulfonated SWCNTs is presented.

Influence of Hf and H2O2 on Morphology of Silicon Formed by Ag Assisted Chemical Etching

2014 ◽  
Vol 953-954 ◽  
pp. 1045-1048
Author(s):  
Guo Feng Ma ◽  
Heng Ye ◽  
Hong Lin Zhang ◽  
Chun Lin He ◽  
Li Na Sun
Keyword(s):  
Silicon Substrate ◽  
Room Temperature ◽  
Electroless Deposition ◽  
Metal Salt ◽  
Substrate Surface ◽  
Volume Ratio ◽  
Type Silicon ◽  
P Type ◽  
Silicon Substrate Surface ◽  
Si Wafer

The Ag-assisted electroless etching of p-type silicon substrate in HF/H2O2solution at room temperature was investigated. In this work, the effects of HF, H2O2and their volume ratio on morphology and growth of p-type silicon substrate surface by using metal assisted etching were investigated in order to produce a highly efficient antireflecting structure. The Ag metal particles were deposited onto Si wafer by electroless deposition from a metal salt solution including HF. The experimental results show that the growth rate and morphology of the pores formed on the Ag metalized Si surfaces are strongly dependent on the volume ratio of HF and H2O2.

The Influence of Experimental Variables on the Development and Maintenance of Wear-Protective Oxides during Sliding of High-Temperature Iron-Base Alloys

1985 ◽  
Vol 199 (1) ◽  
pp. 35-41 ◽  
Author(s):  
J Glascott ◽  
G C Wood ◽  
F H Stott
Keyword(s):  
Room Temperature ◽  
Thermal Stresses ◽  
High Surface ◽  
Volume Ratio ◽  
Oxide Surface ◽  
Protective Oxide ◽  
Metal Debris ◽  
Wear Process ◽  
Metal Metal ◽  
Oxide Debris

An investigation has been carried out into the development and maintenance of wear-protective oxide on iron-12 per cent chromium-base alloys during sliding in air at 20–600°C, with particular reference to the effects of temperature, of intermittent changes in temperature, and of sliding speed. It has been established that the wear-protective surface develops on and from compacted oxide and oxide-coated metal debris and involves deformation of the oxide. The wear process in the early stages of sliding generates metallic wear debris particles. These are fractured and re-fractured until they have a high surface to volume ratio. These surfaces are oxidized at the ambient temperature, to produce considerable amounts of oxide debris. Additional amounts are generated by transient oxidation of the specimen surfaces and removal of this oxide during each transversal of the sliding action. The rate of production of such oxide debris is determined by the ease of fracture of the metal debris and the rate of oxidation. Under these sliding conditions, this results in a minimum in the time required to generate a wear-protective oxide surface at 400°C. Development of such a surface takes a longer period at higher and lower temperatures, and indeed it does not develop at all at room temperature. Once established, the wear-protective oxide remains adherent and stable during isothermal sliding at 300°C and higher temperatures. Thermal stresses imparted by cooling to room temperature and reheating to 300° C do not cause loss of effectiveness of the oxide on subsequent further sliding at 300°C. However, subsequent sliding at room temperature results in rapid breakdown of the oxide and metal-metal contact, presumably due to a decrease in plasticity of the fine oxide debris with decreasing temperature or to a decrease in the adhesion between the oxide and the metal substrate or in oxide cohesion.

Room Temperature Recrystallization of Electroplated Copper Thin Films: Methods and Mechanisms

2000 ◽  
Vol 612 ◽  
Author(s):  
D. Walther ◽  
M. E. Gross ◽  
K. Evans-Lutterodt ◽  
W. L. Brown ◽  
M. Oh ◽  
...  
Keyword(s):  
Film Thickness ◽  
Sheet Resistance ◽  
Room Temperature ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
High Surface ◽  
Volume Ratio ◽  
Data Sets ◽  
Pole Figures ◽  
Electroplated Copper

AbstractWe report a comparison of the room temperature recrystallization of electroplated (EP) copper in blanket films as a function of thickness measured by focused ion beam (FIB) microscope images and sheet resistance measurements. Both sets of data show an increase in rate with film thickness from 0.75νm up to 5νm, while little recrystallization is observed in films thinner than 0.75νm. Interestingly, the recrystallization rates from FIB analysis are consistently faster than those from the sheet resistance measurements. These data suggest that the recrystallization is initiated close to the top surface of the EP Cu film, but that in thinner films a high surface-to-volume ratio allows surface inhibition or pinning to retard the transformation. A Johnson-Mehl-AvramiKolmogorov (JMAK) analysis of the two data sets yields unusually high values for the Avrami exponent μ of up to 7 for the FIB data, while lower values of around 4 are obtained for the sheet resistance data. X-ray diffraction pole figures of the films have also been collected and correlations between the crystallographic texture, film thickness and recrystallization are discussed.

Cauliflower polyaniline/multiwalled carbon nanotube electrode and its applications to hydrogen peroxide and glucose detection*

2012 ◽  
Vol 84 (10) ◽  
pp. 2055-2063 ◽  
Author(s):  
Sujittra Poorahong ◽  
Chongdee Thammakhet ◽  
Panote Thavarungkul ◽  
Proespichaya Kanatharana
Keyword(s):  
Chemical Sensor ◽  
Limit Of Detection ◽  
High Surface ◽  
Volume Ratio ◽  
Deposition Process ◽  
Glucose Biosensor ◽  
Pani Film ◽  
Scanning Electron Micrographs ◽  
Multiwalled Carbon ◽  
Relative Standard

Vertically aligned polyaniline (PANI) structures were prepared by controlling the deposition current density during a stepwise template-free electrochemical deposition process of aniline on a glassy carbon electrode (GCE). Scanning electron micrographs (SEMs) showed the formation of cauliflower PANI structures, each with a diameter of approximately 2–3 and 10 μm in length. The cauliflower-like PANI electrode was modified with multiwalled carbon nanotubes (cauliflower PANI/MWCNTs) and used as the working electrode for electrochemical detections where H2O2 and glucose were used as the models for the chemical sensor and biosensor, respectively. The sensor provided linearity in the range of 1.0 to 150 μM of H2O2 with the limit of detection (LOD) of 50 nM. This is 100-fold better than the LOD of the bare GCE. Moreover, this sensor exhibited remarkable operational stability, i.e., 50 μM H2O2 could be analyzed up to 140 times with a 2.7 % relative standard deviation (RSD). A glucose biosensor was prepared using the modified cauliflower PANI/MWCNT electrode. This had a 3.4 times higher sensitivity than an electrode modified with PANI film/MWCNTs. The regular size and high surface-to-volume ratio of the cauliflower PANI electrode will provide good opportunities for further biosensor applications.

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