Chemical Vapor Deposition of Bi-Te-Ni-Fe on Magnesium Oxide Substrate and Its Seebeck Effect

Gan, Yong X.; Hamdan, Anan S.; Gan, Jeremy B.; Li, Mingheng

doi:10.3390/coatings7100164

Cited by 6 publications

(3 citation statements)

References 61 publications

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“…In the extreme case of collimated flux, as in molecular beam epitaxy, compact films are formed. With techniques such as metal organic chemical vapor deposition, mixing and reactions of precursors occur as they execute a diffusive motion; however, the large mean free paths and the presence of a depletion layer near the deposit imply a partially collimated flux (although dendrites may be produced in some conditions , ).…”

Section: Discussionmentioning

confidence: 99%

Effect of Adsorbate Diffusion on the Dendritic Morphology of Electrodeposited Films

2018

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We study the formation of deposits with dendritic morphology using numerical simulations of a model of electrodeposition and diffusion of the adsorbed material. The model considers a diffusive flux of cations in solution, the instantaneous adsorption and reaction in contact with the film surface, and random walks of mobile atoms on that surface, with a maximum of G hops per atom and a detachment probability ϵ per neighbor at the current position. For low temperature or large current, which corresponds to small G, the deposits are similar to the diffusion-limited aggregates growing from the flat electrode; for high temperature or very small current, which is represented by large G or ϵ, the deposits have thick rounded columns with sporadic ramification. In these conditions, the growth direction is controlled by the orientation of the electrode and of the cation flux. For the balanced conditions of adsorbate diffusion and current (typically 102 ≲ G ≲ 104 and ϵ ≲ 0.1, but also for larger G and very small ϵ), the films have a hierarchical dendritic morphology with the shape of maple leaves. The dendrite tips propagate in directions forming 45° with the electrode and are formed by three concurrent terraces, as a consequence of the simulations in a simple cubic lattice. The average dendrite size increases as a power law of G and is consequently expected to decrease with the applied current. The lowest energy configurations (terraces) are shown to be stable within the timescale of crystallization of an atomic layer, but the weakly bonded atoms have sufficiently large mobility to create those configurations. Thus, the dendritic morphology depends on the interplay between the energetics of the crystal and the electric current, which may help the interpretation of dendrite growth with other crystalline structures. The dendrite shape obtained here resembles those observed in some electrodeposited films of gold, zinc, and palladium, and the effect of the electric current on the dendrite size agrees with the observations in the electrodeposition of silver and gold. Assuming that the adsorbate diffusion is thermally activated, we propose that the average dendrite size is a ratio between an Arrhenius factor and a power law of the current; this suggests a method to estimate the microscopic energy barrier of diffusion, which may differ from the macroscopic activation energy.

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Section: Discussionmentioning

confidence: 99%

Effect of Adsorbate Diffusion on the Dendritic Morphology of Electrodeposited Films

2018

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“…The same MOCVD conditions as described above were used. The chemicals used and the process control for the Bi-Te-Ni-Fe deposition can be found in earlier work [30].…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Gold Catalyst-Assisted Metal Organic Chemical Vapor Deposition of Bi-Te-Ni-Cu-Au Complex Thermoelectric Materials on Anodic Aluminum Oxide Nanoporous Template

Gan

et al. 2018

Coatings

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Complex materials have unique thermal and electron transport properties. In this work, a novel catalyst-assisted metal organic chemical vapor deposition approach was employed to make BiTe -Ni-Cu-Au complex materials on an anodic aluminum oxide nanoporous substrate. Nickel acetate, copper nitrate, bismuth acetate, and tellurium (IV) chloride dissolved in N,N-dimethylformamide (DMF) were used as the metal sources for Ni, Bi, Cu, and Te, respectively. Hydrogen was used as the carrier gas. The anodic aluminum oxide substrate sputter-coated on a thin gold coating and was kept at 500 • C in a quartz tube in the reaction chamber. The chemical vapor deposition time was two hours. Scanning electron microscopy was used to reveal the morphology of the deposited materials. Due to metal catalyst assisted growth, the BiTe -Ni-Cu-Au materials were self-assembled into islands distributed fairly uniformly on the substrate. The mechanism for the morphological development of the materials was investigated. It was found that the Au nanoparticles facilitated the formation of the complex BiTe -Al-Ni-Cu materials. The prepared nanostructure has the highest absolute Seekbeck coefficient value of 260 µV/K, which is more than twice the value obtained from the bulk material.

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“…The coating materials can be metallic, ceramic, or polymeric, depending on the application. For Mg or Mg alloys, different surface methods have been studied and used, e.g., pack vacuum diffusion, [8,9] salt bath, [10,11] cold/ thermal spray, [12][13][14] laser processing, [15,16] chemical vapor deposition, [17,18] and physical vapor deposition, [19,20] electrodeposition, [21,22] and chemical conversion coating, [23,24] etc. These techniques can improve the corrosion resistance of Mg to different extents.…”

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confidence: 99%

A Simple Surface Treatment for Mg to Gain Enhanced Resistance to Corrosion and Corrosive Wear by Hammering Al Powder‐Covered Mg Substrate

Tang

et al. 2022

Adv Materials Inter

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rendering it widely utilized for cellular phones and notebook computers in recent years. The earth crust contains 2.1% mass of Mg, [5] making this abundant metal available for a wide range of applications. However, magnesium has shortcomings, including high chemical reactivity or low resistance to corrosion and others such as wear and creep. [6] Significant efforts have been made to modify Mg-based alloys by alloying appropriate elements [7] or modify the surface of Mg or Mg alloys [6] for improved performance. Surface modification of Mg or Mg alloys is an economical and effective approach for enhanced resistance to corrosion and wear.There are many processes for coating a more durable layer on the outmost surface of a base material for desired properties. The coating materials can be metallic, ceramic, or polymeric, depending on the application. For Mg or Mg alloys, different surface methods have been studied and used, e.g., pack vacuum diffusion, [8,9] salt bath, [10,11] cold/ thermal spray, [12][13][14] laser processing, [15,16] chemical vapor deposition, [17,18] and physical vapor deposition, [19,20] electrodeposition, [21,22] and chemical conversion coating, [23,24] etc. These techniques can improve the corrosion resistance of Mg to different extents. However, some of the techniques need costly equipment or involve complicated processes. For example, vacuum chamber and pumping system as well as gas lines are required for physical vapor deposition. For less expensive techniques such as electrodeposition, one needs to deal with electrolyte preparation, wet process, electrolyte recycling, etc. For chemical conversion coating process, which is also a wet process, different factors need to be handled, e.g., chemical solution preparation, waste solution recycling, and control of various process parameters such as temperature, pressure, and solution ion concentrations. [24] This work shows a simple approach to increase the resistance of Mg to corrosion and corrosive wear by generating a nanocrystalline aluminum layer on Mg surface, which is achieved by repeated punching or hammering an Al powdercovered Mg substrate. Al is also a light metal with excellent passivation capability. A thin Al layer on the Mg substrate can significantly increase its resistance to corrosion and corrosive Mg is abundant in the earth crust and very attractive as a base metal of lightweight alloys for the transportation industry due to its high strengthto-weight ratio. However, Mg is prone to corrosion, which largely limits its widespread applications. Here, a very simple surface treatment method is demonstrated for enhanced resistance to corrosion and corrosive wear by hammering Al powder-covered surface of Mg with subsequent recovery treatment. Such treated surface is examined with X-ray diffraction technique for information on phases, nanocrystallization, thickness, and coverage of the Al layer. Structure of the Al layer and lattice imperfections are analyzed with transmission electron microscopy. Electrochemical behavior, corrosion, and...

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Chemical Vapor Deposition of Bi-Te-Ni-Fe on Magnesium Oxide Substrate and Its Seebeck Effect

Cited by 6 publications

References 61 publications

Effect of Adsorbate Diffusion on the Dendritic Morphology of Electrodeposited Films

Effect of Adsorbate Diffusion on the Dendritic Morphology of Electrodeposited Films

Gold Catalyst-Assisted Metal Organic Chemical Vapor Deposition of Bi-Te-Ni-Cu-Au Complex Thermoelectric Materials on Anodic Aluminum Oxide Nanoporous Template

A Simple Surface Treatment for Mg to Gain Enhanced Resistance to Corrosion and Corrosive Wear by Hammering Al Powder‐Covered Mg Substrate

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