A Chemical Gas Sensor from Large-Scale Thermal CVD Derived Graphene

2011 ◽  
Vol 1303 ◽  
Author(s):  
Xiaojuan Song ◽  
Brent Wagner ◽  
Zhitao Kang
Keyword(s):  
Large Scale ◽  
Chemical Vapor ◽  
Spectroscopy Analysis ◽  
Si Substrates ◽  
Sensor Structure ◽  
Hazardous Gases ◽  
Thin Nickel ◽  
A Charge ◽  
Si Wafer

ABSTRACTLarge-scale graphene sheets were grown on thin nickel film coated Si substrates using a reliable and repeatable thermal Chemical Vapor Deposition (CVD) technique. The graphene films were then transferred onto a SiO2 coated Si wafer to fabricate a 5 mm x 5 mm resistive sensor structure. Raman spectroscopy analysis confirmed the existence of graphene. Preliminary sensing results were demonstrated by the detection of hazardous gases such as NO2 and MMH (mono-methyl hydrazine). Characterization of the device channel resistivity (switching response) was conducted as a function of the analyte type and concentration. The sensor response indicates a charge transfer mechanism between the analytes and graphene.

scholarly journals Influence of plasma treatment on SiO2/Si and Si3N4/Si substrates for large-scale transfer of graphene

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Lukose ◽  
M. Lisker ◽  
F. Akhtar ◽  
M. Fraschke ◽  
T. Grabolla ◽  
...  
Keyword(s):  
Large Scale ◽  
Oxygen Plasma ◽  
Chemical Vapor ◽  
Limiting Factors ◽  
Adhesion Properties ◽  
Si Substrates ◽  
Wetting Contact Angle ◽  
Angle Measurements ◽  
Chemical Vapor Deposited ◽  
Contact Angle Measurements

AbstractOne of the limiting factors of graphene integration into electronic, photonic, or sensing devices is the unavailability of large-scale graphene directly grown on the isolators. Therefore, it is necessary to transfer graphene from the donor growth wafers onto the isolating target wafers. In the present research, graphene was transferred from the chemical vapor deposited 200 mm Germanium/Silicon (Ge/Si) wafers onto isolating (SiO2/Si and Si3N4/Si) wafers by electrochemical delamination procedure, employing poly(methylmethacrylate) as an intermediate support layer. In order to influence the adhesion properties of graphene, the wettability properties of the target substrates were investigated in this study. To increase the adhesion of the graphene on the isolating surfaces, they were pre-treated with oxygen plasma prior the transfer process of graphene. The wetting contact angle measurements revealed the increase of the hydrophilicity after surface interaction with oxygen plasma, leading to improved adhesion of the graphene on 200 mm target wafers and possible proof-of-concept development of graphene-based devices in standard Si technologies.

scholarly journals Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates

2013 ◽  
Vol 4 ◽  
pp. 726-731 ◽  
Author(s):  
Gema López ◽  
Pablo R Ortega ◽  
Cristóbal Voz ◽  
Isidro Martín ◽  
Mónica Colina ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Surface Passivation ◽  
Crystalline Silicon ◽  
Surface Recombination ◽  
Chemical Vapor ◽  
Optical Characterization ◽  
Surface Recombination Velocity ◽  
Carrier Injection ◽  
Si Substrates

The aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx) stacks on both p-type and n-type crystalline silicon (c-Si) substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD) at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD) to form anti-reflection coating (ARC) stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300–1200 nm) without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (S eff,max) was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450–1000 nm.

Characterization of High Quality, Large-Scale Growth of Monolayer WS2 Domains via Chemical Vapor Deposition Technique

2021 ◽  
Author(s):  
Somayeh Asgary ◽  
Amir Hoshang Ramezani ◽  
Zhaleh Ebrahimi Nejad
Keyword(s):  
Large Scale ◽  
Average Length ◽  
Chemical Vapor ◽  
Growth Time ◽  
High Quality ◽  
Force Microscopy ◽  
Atomic Force ◽  
Regular Triangle ◽  
Vapor Deposition Technique

Abstract WS2 flakes have been grown successfully on SiO2 substrate via chemical vapor (CVD) deposition method by reduction and sulfurization of WO3 using Ar/ H2 gas and sulfur evaporated from solid sulfur powder. The prepared samples were characterized by optical microscopy (OM), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectra and photoluminescence (PL). Large domain WS2 monolayers are obtained by extending the growth time. The perfect triangular single-crystalline WS2 flakes with an average length of more than 35 µm were achieved. The sharp PL peak (∼1.98 eV) and two distinct Raman peaks (E2g and A1g) with a ∼ 71.5 cm-1 peak split indicating that relatively high quality WS2 crystals with a regular triangle shape can be synthesized. Higher growth time shows larger triangular-shaped of WS2.

Migration-Enhanced Molecular Beam Epitaxial Growth and Characterization of GaAs on Si Substrates

1988 ◽  
Vol 144 ◽  
Author(s):  
J.H. Kim ◽  
S. Sakai ◽  
J.K. Liu ◽  
G. Raohakrishnan ◽  
S.S. Chang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
Cross Sectional ◽  
Light Emitting ◽  
Si Substrates ◽  
Molecular Beam Epitaxial

ABSTRACTWe first report on migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layers on Si substrates (GaAs/Si). Excellent surface morphology GaAs layers were successfully grown on (100) Sisubstrates misoriented 4 toward [110] direction. The MEMBE growth method isdescribed and material properties are compared with those of normal two-step MBE-grown or in-situ annealed layers. Micrographs of cross-sectional view transmission electron microscopy (TEM) and scanning surface electron microscopy (SEM) of MEMBE-grown GaAs/Si showed dislocation densities of 107 cm-2 over ten times lower than those of two-step MBE-grown or in-situ annealedlayers. AlGaAs/GaAs double heterostructure lasers and light-emitting diodeshave been successfully grown on MEMBE GaAs/Si by both metal organic chemical vapor deposition and liquid phase epitaxy. MOCVD-grown lasers showed peak output power as high as 184 mW/facet, pulsed threshold currents as low as150 mA at 300 K, and differential quantum efficiencies of up to 30 %. The LPE-grown light-emitting diodes showed output powers of 1.5 mW and external quantum efficiencies of 3.3 mW/A per facet.

Epitaxial Realignment of In-Situ Doped Polycrystalline Silicon for Advanced BiCMOS Technologies

1999 ◽  
Vol 587 ◽  
Author(s):  
K. Chang ◽  
S.G. Thomas ◽  
T-C. Lee ◽  
R.B. Gregory ◽  
D. O'meara ◽  
...  
Keyword(s):  
Polycrystalline Silicon ◽  
Chemical Vapor ◽  
Layer Growth ◽  
Native Oxide ◽  
Post Deposition Annealing ◽  
Si Substrates ◽  
Si Films ◽  
Post Deposition

AbstractIndustrial feasibility of an in-situ-doped (ISD) polycrystalline Si process using chemical vapor deposition for advanced BiCMOS technologies is presented. ISD As-doped amorphous and polycrystalline Si layers have been deposited on Si substrates at 610°C and 660°C, respectively, with the deposition rate varying from 120 to 128Å /minute. Samples are compared on the basis of having been subjected to a substrate preclean prior to deposition using an HF solution and an in-situ H2 bake. TEM micrographs reveal the presence of a thin (10-15 Å) native oxide at the deposited layer/substrate interface for samples not precleaned. This is confirmed for both the amorphous and polycrystalline Si depositions. However, for the 610°C-deposited samples given the substrate preclean, a polycrystalline structure with partial epitaxial layer growth is observed. Twins and stacking faults are found at the poly Si/single crystal Si interface, causing interfacial roughness. Post-deposition annealing of the Si films typically generates grain growth, but RBS-channeling characterization of the annealed Si provides evidence of some recrystallization, the extent of which is affected by the original growth condition. Analysis shows that the amorphous deposition at 610°C results in a mixture of epitaxial and polycrystalline Si. Epitaxial realignment of the polycrystalline Si film by post deposition annealing can result in significantly improved device performance.

Characterization of GaAs films grown on Si substrates by molecular beam epitaxy

1988 ◽  
Vol 46 ◽  
pp. 896-897
Author(s):  
J.B. Posthill ◽  
J. Tarn ◽  
T.P. Humphreys ◽  
K. Das ◽  
J.J. Wortman ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Lattice Mismatch ◽  
Chemical Vapor ◽  
Antiphase Domain ◽  
Ex Situ ◽  
Material System ◽  
Bulk Gaas ◽  
Si Substrates

Because of several potential applications and advantages afforded by the heteroepitaxial GaAs-on-Silicon material system, several groups world-wide are attempting to grow device-quality GaAs on Si substrates.eg.1 Both metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) growth techniques have been widely utilized to achieve heteroepitaxial growth. However, certain fundamental materials and growth problems have thus far prevented any group from achieving heteroepitaxial GaAs of a quality similar to that obtainable from bulk GaAs crystals. A high density of threading dislocations, microtwins/stacking faults, antiphase domain boundaries (APBs) and microfissures can form under non-ideal conditions. These defects result, in part, from stresses generated due to the ∼4% lattice mismatch and the different coefficients of thermal expansion between GaAs and Si.2 Ex-situ characterization of this materials system is essential to assess the material quality and to provide direction for future growth experiments. This contribution describes the TEM characterization methodology that we employ to analyze our GaAs grown on Si substrates by MBE.

Growth and Characterization of Silicon-Germanium Films on Oxide by VLPCVD/PE-VLPCVD

1993 ◽  
Vol 317 ◽  
Author(s):  
Julie A. Tsai ◽  
Rafael Reif
Keyword(s):  
Growth Rates ◽  
Silicon Germanium ◽  
Chemical Vapor ◽  
Thin Layers ◽  
Si Substrates ◽  
Growth Modes ◽  
Thermal Growth ◽  
Pressure Chemical ◽  
Gas Ratio

ABSTRACTResults of Si1-xGex deposition on oxide-coated Si substrates using a PE-VLPCVD (Plasma-Enhanced Very-Low-Pressure Chemical Vapor Deposition) reactor are presented. Thin layers of poly-Si1-xGex deposited with SiH4 and GeH4 at ≤ 600°C had low C and O levels. Two growth modes were examined at 500°C: plasma-initiated thermal growth (VLPCVD) and full plasma-enhanced deposition (PE-VLPCVD). In both cases, Ge incorporation increases sublinearly with gas ratio, growth rates increase with Ge content, and the transition temperature between polycrystalline and amorphous deposition is lower for Si1-xGex than Si. On the other hand, compared to thermal growth, plasma-enhanced deposition promotes not only higher growth rates but also improved structural properties such as smoother surface Morphology, More columnar and oriented grains, and the unique feature of direct deposition onto oxide.

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