Silicon wafer as substrate in Zinc oxide thin films

In summary, silicon is commonly used as a substrate for growing zinc oxide thin films due to its availability, affordability, and compatibility with various processing methods. It also has a wealth of knowledge and resources for processing. Additionally, using a substrate that is compatible with silicon increases the potential for commercial applications. As for the mechanism of ZnO nucleation on silicon substrates, it is typically grown on R-cut sapphire or with a buffer layer on silicon. Most articles that mention direct growth on silicon do not require epitaxy, allowing for a wider range of substrate options. In terms of physical and chemical properties, there is limited information on ZnO diffusing into silicon, as it typically only happens with certain metals. Silicon is also unlikely to
  • #1
ralden
85
0
Good day, many articles used sillicon wafer as substrate over others (like:platinum, glass, sapphire and etc) to grow Zinc oxide thin films, but I'm don't know the real reason they choose silicon wafer as substrate compare to others. so I'm asking what are the advantages of using Silicon wafers as substrates? thanks in advance.
 
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  • #2
My guess is that it is because silicon is by far the most common substrate for all types of processing. Basically, unless there is a good reason not to use it (e.g. because you are trying to grow an epitaxial film and there is a large lattice mismatch between Si and your material) it would be the first choice for most people. Good Si is cheap and readily available (with different resistivity etc) and usually OK to use in most research cleanrooms (many cleanrooms have strict rules against using some materials because of the risk of contamination) . There is a huge amount of knowledge when it comes to how to process it.
Another reason is that is -for obvious reasons- commercially important. A process/device that is compatible with silicon is much more likely to be of commercial interest since it means it can be integrated (and fabricated) with semiconductor components.
 
  • #3
Thank
f95toli said:
My guess is that it is because silicon is by far the most common substrate for all types of processing. Basically, unless there is a good reason not to use it (e.g. because you are trying to grow an epitaxial film and there is a large lattice mismatch between Si and your material) it would be the first choice for most people. Good Si is cheap and readily available (with different resistivity etc) and usually OK to use in most research cleanrooms (many cleanrooms have strict rules against using some materials because of the risk of contamination) . There is a huge amount of knowledge when it comes to how to process it.
Another reason is that is -for obvious reasons- commercially important. A process/device that is compatible with silicon is much more likely to be of commercial interest since it means it can be integrated (and fabricated) with semiconductor components.

thanks you!, but, I'm expecting an answer about its physical and chemical properties, but aside from that, what are the mechanism or how ZnO nucleates in Silicon substrate? or what other properties silicon possessed to be become compatible in growing Zinc oxide thin films?
 
  • #4
f95toli said:
My guess is that it is because silicon is by far the most common substrate for all types of processing. Basically, unless there is a good reason not to use it (e.g. because you are trying to grow an epitaxial film and there is a large lattice mismatch between Si and your material) it would be the first choice for most people. Good Si is cheap and readily available (with different resistivity etc) and usually OK to use in most research cleanrooms (many cleanrooms have strict rules against using some materials because of the risk of contamination) . There is a huge amount of knowledge when it comes to how to process it.
Another reason is that is -for obvious reasons- commercially important. A process/device that is compatible with silicon is much more likely to be of commercial interest since it means it can be integrated (and fabricated) with semiconductor components.

I think the answer may be found by answering the question, does Zinc Oxide diffused into Silicon under certain fabrication method (like spray pyrolysis)?,does silicon breaks down during nucleation of Zinc oxide?
 
  • #5
I am not at all an expert on ZnO (I am familiar with a bunch of other oxides), but a quick google Scholar search suggest that most people who try to grow epitaxial ZnO do so on R-cut sapphire and/or use a buffer to allow them to grow it on Si. Hence, any articles you've found where they grow ZnO directly on Si probably describes work where they don't need the ZnO to be epitaxial, in which case you can use (nearly) whatever substrate you want; in which case the reasons I outlined above come into play.
Also, note that there isn't in practice that many substrates to choose from. There is of course a bewildering number of material that could potentially be used a a substrate, but only a handful or so are available as high-quality reasonably large wafers (say larger than 5x5mm2). This is another reason why most people -regardless of what they are studying- end up using Si or sapphire.

To answer your second question: I would be very surprised of ZnO diffused into Si. AFAIK this only happens with certain metals (most notably gold). I would also be surprised if SI would break down, this would only happen at temperatures way higher than what would be used in any fabrication method I've ever encountered.
 
  • #6
f95toli said:
I am not at all an expert on ZnO (I am familiar with a bunch of other oxides), but a quick google Scholar search suggest that most people who try to grow epitaxial ZnO do so on R-cut sapphire and/or use a buffer to allow them to grow it on Si. Hence, any articles you've found where they grow ZnO directly on Si probably describes work where they don't need the ZnO to be epitaxial, in which case you can use (nearly) whatever substrate you want; in which case the reasons I outlined above come into play.
Also, note that there isn't in practice that many substrates to choose from. There is of course a bewildering number of material that could potentially be used a a substrate, but only a handful or so are available as high-quality reasonably large wafers (say larger than 5x5mm2). This is another reason why most people -regardless of what they are studying- end up using Si or sapphire.

To answer your second question: I would be very surprised of ZnO diffused into Si. AFAIK this only happens with certain metals (most notably gold). I would also be surprised if SI would break down, this would only happen at temperatures way higher than what would be used in any fabrication method I've ever encountered.

How about the adsorption properties of silicon, and how bout the surface free energy needed to nucleates an oxide layer?
 
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  • #7
ralden said:
How about the adsorption properties of silicon, and how bout the surface free energy needed to nucleates an oxide layer?

I have no idea.
However, I suspect those properties are more or less irrelevant since the lattice mismatch between Si and ZnO is so large that you can't have epitaxial growth anyway. This would be a much bigger problem for high quality film growth than the those properties, especially since adsorbtion rate etc. be changed by altering the growth conditions (substrate temperature etc) which in turn affects the growth mode of the film.
 
  • #8
f95toli said:
I have no idea.
However, I suspect those properties are more or less irrelevant since the lattice mismatch between Si and ZnO is so large that you can't have epitaxial growth anyway. This would be a much bigger problem for high quality film growth than the those properties, especially since adsorbtion rate etc. be changed by altering the growth conditions (substrate temperature etc) which in turn affects the growth mode of the film.

But what is the difference of using glass substrate over silicon substrate? i think the mismatch of crystal parameters would help not to diffuse zinc oxide on Si under a fabrication method but remain on the surface of the silicon.
 
  • #9
lattice mismatch forces the deposit into a particular structure. the most energetically favorable structure will typically be that which matches the substrate, for example, if the 111 direction of film is a better match to the 100 of the substrate (assuming growth is taking place on the surface of 100) it will want to grow 111 instead of 100. unless you are trying to chemically change the substrate, you don't want much diffussion. diffussion rules are typically atomic, whereas lattice matching speaks to lattice systems and paramteters to get a particular structure (unless you just want to grow bulk, in which case the substrate is somewhat irrelevant depending on the sensitivity of yield).

zinc oxide from what i can tell wants to be wurtzite (a = 3.25 Å, c = 5.2 Å) , while silicon is diamond (5.431 A) and saphire is hexagonal R-3c (trigonal, (a=4.785, c=12.991). so i could see zinc oxide wanting to line up its long axis with that of silicon (depending on wykhoff positions) (5.2 is around 5.4), or sapphire (4.785 is around 5.2), but since wurtize is a bit closer in structure to trigonal than diamond, i would suggest using sapphire over silicon if you want 001 growth of zinc oxide on a 100 sapphire.

this article is old but gives a good idea of the obstacles of heterostructures. https://www.fkf.mpg.de/49636/kk140.pdf

apologies if this is all old news, and you were more interested in some other aspect of their differences in relation to the topic at hand
 

1. What is a silicon wafer and why is it used as a substrate in Zinc oxide thin films?

A silicon wafer is a thin, circular disc made out of silicon material. It is used as a substrate in Zinc oxide thin films because it has similar crystal structure and thermal expansion properties to Zinc oxide, making it an ideal base for the film to grow on. Additionally, silicon wafers are readily available and have a smooth surface, making it easier for the film to form a uniform layer.

2. What are the advantages of using Zinc oxide thin films on a silicon wafer substrate?

There are several advantages to using Zinc oxide thin films on a silicon wafer substrate. Firstly, the silicon wafer provides a stable base for the film to grow on, ensuring good crystal quality and structural stability. Secondly, the silicon wafer can act as a template for the growth of the Zinc oxide film, allowing for precise control over the film's properties. Additionally, the combination of Zinc oxide and silicon can result in unique properties, such as improved electrical conductivity and optical properties.

3. How is a Zinc oxide thin film deposited on a silicon wafer substrate?

There are various methods for depositing Zinc oxide thin films on a silicon wafer substrate, including physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). PVD involves heating Zinc oxide in a vacuum chamber, causing it to vaporize and deposit onto the silicon wafer. CVD uses a chemical reaction to deposit the film, and ALD involves depositing the film in a layer-by-layer fashion using a gas phase reaction.

4. What are the applications of Zinc oxide thin films on a silicon wafer substrate?

Zinc oxide thin films on a silicon wafer substrate have a wide range of applications in electronic and optoelectronic devices. They can be used as transparent conductive layers in displays and solar cells, as well as in sensors, transistors, and light-emitting diodes (LEDs). Additionally, the unique properties of Zinc oxide thin films make them suitable for use in biomedical and environmental sensing applications.

5. What are the challenges of using a silicon wafer as a substrate for Zinc oxide thin films?

One of the main challenges of using a silicon wafer as a substrate for Zinc oxide thin films is the mismatch in lattice constants between the two materials. This can lead to strain and defects in the film, affecting its properties. Another challenge is the potential formation of an interface layer between the silicon wafer and Zinc oxide film, which can impact the film's properties and performance. Careful optimization and control of the deposition process are crucial to overcoming these challenges.

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