What are the roles of gas and solid in nanowire growth using the VLS method?

In summary: I don't understand why the solid is used as a reference.The chemical potential of the solid is the same as the equilibrium condition (which is the same as zero).
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If you don't know anything about this please just read the first 20 lines on the below link and help me understand (I don't know anything either).
The vapour liquid solid method:
http://en.wikipedia.org/wiki/Vapor–liquid–solid_method
uses a solid, liquid and gas phase to grow nanowires. While I understand the overall ideas I am unsure about some things. As far as I can see the idea is:
Place a thin layer of an alloy on a substrate. Heat up until the alloy liquifies. At this point it will absorb some of the gaseous phase to form supersaturated droplets from which the nanowires are grown.
But what exactly are the roles of gas/solid in this proces? Which of these phases supplies the atoms that form the nanowires. On the link both the solid and the gas contain Si, but it seems that it is the gaseous phase which the liquid catalyst absorbs and uses to grow the nanowire. So if this is understood correctly what is the role of the solid substrate?
 
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  • #2
The gas supplies the material from which the growth occurs; the growth can be seen in the solid whiskers.

The liquid is an intermediary: it absorbs the material from the gas, and as it becomes super-saturated it deposits it onto the solid surface.

By choosing different liquids (referred to as catalysts because they are no used up) one can obtain different growth characteristics. Thus an additional degree of control is provided when attempting to engineer specific materials.
 
  • #3
Okay but what is then the effect of the solid other than being a surface where to deposit the catalyst?
 
  • #4
The material being drawn from the gas is deposited on the solid surface.

The liquid catalyst accelerates the process.
 
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Okay thank you. You have been very helpful. I am now starting to read about the basic thermodynamical theory behind (III/V)-nanowire growth which I think refers to growth of nanowires of atoms from group (III) and (V), e.g. GaAs.
But the general ideas are giving me some trouble. I have attached a few lines, which I hope you might be able to help me understand.
Can you explain to me what is the basic idea of this section? I have some trouble understanding it, maybe because I am not really sure how to interpret chemical potential. The most fruitful definition of the chemical potential for me is the energy required to add another particle to the system.
So what is it that is used as an equilibrium reference (and what does this mean exactly?) - is it the solid. I should expect so since the solid is practically infinite and thus its chemical potential doesn't change as the growth proceeds (apart from if the temperature changes).
But how do they arrive at the condition of the last equality?
 

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1. What is the VLS method for nanowire growth?

The VLS (vapor-liquid-solid) method is a technique used to grow nanowires. It involves the use of a catalyst, typically a liquid or solid metal, to initiate the growth of the nanowire from a gas or vapor phase.

2. How does the VLS method work?

In the VLS method, a substrate is coated with a thin layer of the catalyst material. The substrate is then exposed to a gas or vapor containing the material that the nanowires will be made of. The catalyst then acts as a nucleation site for the nanowire growth, drawing in the material and allowing the nanowire to grow in the desired direction.

3. What are the advantages of using the VLS method for nanowire growth?

The VLS method allows for precise control over the size, shape, and orientation of the nanowires. It also allows for the growth of multiple nanowires at once, making it a more efficient method for producing large quantities of nanowires. Additionally, the use of a catalyst can help to reduce defects and improve the overall quality of the nanowires.

4. What materials can be used with the VLS method for nanowire growth?

The VLS method can be used with a variety of materials, including semiconductors, metals, and oxides. Some common materials used for nanowire growth using the VLS method include silicon, gallium arsenide, and zinc oxide.

5. What are some applications of nanowires grown using the VLS method?

Nanowires grown using the VLS method have a wide range of potential applications, including in electronics, energy storage, and sensing. They can also be used in biomedical applications, such as drug delivery and tissue engineering. Additionally, the precise control over nanowire size and shape afforded by the VLS method makes them useful for nanoscale devices and components.

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