Rapid Thermal Deposition Research Articles

Thin film synthesis of hybrid ultramicroporous materials (HUMs)- a comparative approach

The thin-film synthesis of the hybrid ultramicroporous material (HUM) TIFSIX-3-Ni on glass substrates are reported for the first time. Several methods of film formation are employed including dip-coating, seeding and secondary growth, vapour-assisted conversion, rapid thermal deposition and in-situ coating. Using the in-situ approach with dimethylformamide as solvent, we were able to grow homogeneous TIFSIX-3-Ni films at relatively low temperatures (85 °C) and short times (5 h) without substrate modification. During this study, we also significantly reduced the TIFSIX powder synthesis time to 15 h.

Rapid thermal deposited GeSe nanowires as a promising anode material for lithium-ion and sodium-ion batteries

It is important to develop a simple, facile and environmentally friendly strategy for improving the properties of materials in various energy storage systems. Herein, a binder-free anode based on self-assembled nanowires structures with GeSe particles is formed through a rapid box thermal deposition and first reported as an advanced anode for lithium/sodium-ion batteries. For LIBs, it delivers an excellent energy storage performance with high specific capacity (~815.49 mAh g−1 at 200 mA g−1 after 300 cycles), superior rate capability (~578.49 mAh g−1 for 10 cycles at 4000 mA g−1) and outstanding cycling stability (~87.78% of capacity retention after 300 cycles). It even shows a high reversible capacity of 359.5 mAh g−1 at 500 mA g−1 after 2000 cycles. For SIBs, it shows good cycling stability (~433.4 mAh g−1 at 200 mA g−1 after 50 cycles with ~85.3% capacity retention) and rate performance (~299.7 mAh g−1 for 10 cycles at 1000 mA g−1). In this electrode, GeSe nanowires (GeSe-NWs) consist of nanoparticles with voids between them that shorten the diffusion length for lithium/sodium ions and electrons and buffer the volumetric variation during the lithium/sodium ion insertion/extraction process. In addition, the introduction of Ni foam frameworks enhances the electrical conductivity of the electrode and retains the structural integrity upon cycling. This approach provides a new perspective for investigating and synthesizing various novel and suitable materials for energy storage fields.

ZIF-8 Membrane Separation Performance Tuning by Vapor Phase Ligand Treatment.

Vapor phase ligand treatment (VPLT) of 2-aminobenzimidazole (2abIm) for 2-methylimidazole (2mIm) in ZIF-8 membranes prepared by two different methods (LIPS: ligand induced permselectivation and RTD: rapid thermal deposition) results in a notable shift of the molecular level cut-off to smaller molecules establishing selectivity improvements from ca. 1.8 to 5 for O2 /N2 ; 2.2 to 32 for CO2 /CH4 ; 2.4 to 24 for CO2 /N2 ; 4.8 to 140 for H2 /CH4 and 5.2 to 126 for H2 /N2 . Stable (based on a one-week test) oxygen-selective air separation performance at ambient temperature, 7 bar(a) feed, and 1 bar(a) sweep-free permeate with a mixture separation factor of 4.5 and oxygen flux of 2.6×10-3 mol m-2 s-1 is established. LIPS and RTD membranes exhibit fast and gradual evolution upon a 2abIm-VPLT, respectively, reflecting differences in their thickness and microstructure. Functional reversibility is demonstrated by showing that the original permeation properties of the VPLT-LIPS membranes can be recovered upon 2mIm-VPLT.

ZIF‐8 Membrane Separation Performance Tuning by Vapor Phase Ligand Treatment

AbstractVapor phase ligand treatment (VPLT) of 2‐aminobenzimidazole (2abIm) for 2‐methylimidazole (2mIm) in ZIF‐8 membranes prepared by two different methods (LIPS: ligand induced permselectivation and RTD: rapid thermal deposition) results in a notable shift of the molecular level cut‐off to smaller molecules establishing selectivity improvements from ca. 1.8 to 5 for O2/N2; 2.2 to 32 for CO2/CH4; 2.4 to 24 for CO2/N2; 4.8 to 140 for H2/CH4 and 5.2 to 126 for H2/N2. Stable (based on a one‐week test) oxygen‐selective air separation performance at ambient temperature, 7 bar(a) feed, and 1 bar(a) sweep‐free permeate with a mixture separation factor of 4.5 and oxygen flux of 2.6×10−3 mol m−2 s−1 is established. LIPS and RTD membranes exhibit fast and gradual evolution upon a 2abIm‐VPLT, respectively, reflecting differences in their thickness and microstructure. Functional reversibility is demonstrated by showing that the original permeation properties of the VPLT‐LIPS membranes can be recovered upon 2mIm‐VPLT.

Inorganic Nanoparticles/Metal Organic Framework Hybrid Membrane Reactors for Efficient Photocatalytic Conversion of CO2.

Photocatalytic conversion of carbon dioxide (CO2) to useful products has potential to address the adverse environmental impact of global warming. However, most photocatalysts used to date exhibit limited catalytic performance, due to poor CO2 adsorption capacity, inability to efficiently generate photoexcited electrons, and/or poor transfer of the photogenerated electrons to CO2 molecules adsorbed on the catalyst surface. The integration of inorganic semiconductor nanoparticles across metal organic framework (MOF) materials has potential to yield new hybrid materials, combining the high CO2 adsorption capacity of MOF and the ability of the semiconductor nanoparticles to generate photoexcited electrons. Herein, controlled encapsulation of TiO2 and Cu-TiO2 nanoparticles within zeolitic imidazolate framework (ZIF-8) membranes was successfully accomplished, using rapid thermal deposition (RTD), and their photocatalytic efficiency toward CO2 conversion was investigated under UV irradiation. Methanol and carbon monoxide (CO) were found to be the only products of the CO2 reduction, with yields strongly dependent upon the content and composition of the dopant semiconductor particles. CuTiO2 nanoparticle doped membranes exhibited the best photocatalytic performance, with 7 μg of the semiconductor nanoparticle enhancing CO yield of the pristine ZIF-8 membrane by 233%, and methanol yield by 70%. This work opens new routes for the fabrication of hybrid membranes containing inorganic nanoparticles and MOFs, with potential application not only in catalysis but also in electrochemical, separation, and sensing applications.

The growth of high density network of MOF nano-crystals across macroporous metal substrates – Solvothermal synthesis versus rapid thermal deposition

Fabrication of metal organic framework (MOF) films and membranes across macro-porous metal substrates is extremely challenging, due to the large pore sizes across the substrates, poor wettability, and the lack of sufficient reactive functional groups on the surface, which prevent high density nucleation of MOF crystals. Herein, macroporous stainless steel substrates (pore size 44×40μm) are functionalized with amine functional groups, and the growth of ZIF-8 crystals investigated through both solvothermal synthesis and rapid thermal deposition (RTD), to assess the role of synthesis routes in the resultant membranes microstructure, and subsequently their performance. Although a high density of well interconnected MOF crystals was observed across the modified substrates following both techniques, RTD was found to be a much more efficient route, yielding high quality membranes under 1h, as opposed to the 24h required for solvothermal synthesis. The RTD membranes also exhibited high gas permeance, with He permeance of up to 2.954±0.119×10−6molm−2s−1Pa−1, and Knudsen selectivities for He/N2, Ar/N2 and CO2/N2, suggesting the membranes were almost defect free. This work opens up route for efficient fabrication of MOF films and membranes across macro-porous metal supports, with potential application in electrically mediated separation applications.

Synchronous Formation of ZnO/ZnS Core/Shell Nanotube Arrays with Removal of Template for Meliorating Photoelectronic Performance

We report herein an innovative approach to remove the anodic aluminum oxide (AAO) template completely without any further treatments, just through a subsequent sulfidation process to convert ZnO/AAO nanotubes to ZnO/ZnS core/shell nanotubes. The sulfidation treatment to attain well-ordered ZnO/ZnS core/shell arrays was conducted using a developed rapid thermal deposition methodology at low temperatures. During the sulfidation conversion process, the renowned Kirkendall effect was demonstrated to be responsible for the magic reactions. In addition, the sample maintained the well-ordered morphology without any deterioration after AAO template removal. The yielded nanostructures possessed a nice crystalline quality and superior optical and photoelectronic performances over the counterpart, ZnO/AAO. Thus, this technique broadens the possibility of fabricating well-ordered tubular core/shell structures with various compositions for multiple applications.

Rapid thermal chemical vapor deposition of in situ boron-doped polycrystalline silicon-germanium films on silicon dioxide for complimentary-metal-oxide-semiconductor applications

In situ boron-doped polycrystalline Si1−xGex (x>0.4) films have been formed on the thermally grown oxides in a rapid thermal chemical vapor deposition processor using SiH4-GeH4-B2H6-H2 gas system. Our results showed that in situ boron-doped Si1−xGex films can be directly deposited on the oxide surface, in contrast to the rapid thermal deposition of undoped silicon-germanium (Si1−xGex) films on oxides which is a partially selective process and requires a thin silicon film pre-deposition to form a continuous film. For the in situ boron-doped Si1−xGex films, we observed that with the increase of the germane percentage in the gas source, the Ge content and the deposition rate of the film are increased, while its resistivity is decreased down to 0.66 mΩ cm for a Ge content of 73%. Capacitance-voltage characteristics of p-type metal-oxide-semiconductor capacitors with p+-Si1−xGex gates showed negligible polydepletion effect for a 75 Å gate oxide, indicating that a high doping level of boron at the poly-Si1−xGex/oxide interface was achieved.

Selective Deposition of Silicon and Silicon-Germanium Alloys by Rapid Thermal Chemical Vapor Deposition

AbstractSelective deposition of SiGe alloys by rapid thermal deposition has been studied using a commercially available Rapid Thermal Chemical Vapor Deposition (RTCVD) cluster tool. The precursors used in this work were dichlorosilane and germane diluted in either hydrogen or argon. An initial characterization was performed to find the appropriate temperature and GeH4 flow ranges to deposit epitaxial layers with low surface roughness. For layers with higher germanium concentration lower deposition temperatures are required to minimize surface roughness. The effects of the dilutant gas on the deposition were examined. An H2 dilutant affects the deposition by consuming chlorine released by the SiCl2H2 and forming HCI. When Ar is used as the dilutant, more chlorine is available for other reactions that can result in etching of the silicon surface. Finally, the effects of pre-deposition treatment were determined. When compared to a wet HF dip, a gas/vapor phase HF/methanol native oxide removal treatment appears to increase the initiation time for the epitaxial deposition reaction. This is most likely due to increased fluorine termination of the surface. When a wet HF or HF/methanol native oxide removal is followed by a UV-Cl2 process, the deposition reaction initiation time is reduced. The UV-Cl2 process was also found to etch silicon through the native oxide.

A Fractal Study of Silcon Surfaces

In this work the variation method is used to extract the fractal dimension of rough surfaces. Rough silicon surfaces from chemical etching and rapid thermal deposition were measured with atomic force microscopy and are shown to exhibit fractal properties.

Ohmic contacts to InP-based materials induced by means of rapid thermal low pressure (metallorganic) chemical vapor deposition technique

A rapid-thermal-low-pressure-metallorganic-chemical-vapor-deposition (RT-LPMOCVD) technique was executed in order to deposit non-semiconductor thin layer materials, necessary for producing metal contact to InP-based microelectronic devices. Silicon dioxide (SiO2) films were deposited onto InP substrates in rapid thermal cycles, using O2 and 2% diluted SiH4 in Ar, with very fast growth kinetics and low activation energy. The SiO2 film exhibited excellent properties, such as refractivity index, density, internal stress, and wetp-etch rates. The SiO2 films were dry etched in a given pattern to allow for the formation of a small metal contact to the InP-based material, onto which the SiO2 layer was deposited. Subsequently, titanium-nitride (TiNx) thin films were deposited onto the InP substrate through rapid thermal deposition cycles, using a tetrakis (dimethylamido) titanium (DMATi) metallorganic liquid source as the precursor for the process, with fast kinetics. The deposited TiNx films had a stoichiometric structure and contained nitrogen and titanium in a ratio close to unity, but incorporated a large amount of carbon and oxygen. The film properties, such as resistivity (40–80 μΩ·mm) and stress (compressive; −0.5 to −2.0×109 dyne·cm−2), were studied in addition to an intensive investigation of its microstructure and morphology, and their performance as an ohmic contacts while deposited ontop−In0.53Ga0.47As material (Zn doped 1.2×1018 cm−3).