Why do we need a substrate while growing?

  • Thread starter Weimin
  • Start date
  • Tags
    Substrate
In summary, mismatching between materials is a common problem in growing materials. While it is possible to use the same material as the substrate for homoepitaxy, in some cases a specific crystallographic orientation is needed, requiring the film to be grown in situ. Lattice mismatch can be managed by using buffer layers, and in some cases, it can even be desirable for the production of certain films. Commercially available substrates may not always be suitable for epitaxial growth, requiring alternative methods such as MBE, VPE, or CVD to be used.
  • #1
Weimin
38
0
Mismatching is the problem in growing materials. I wonder why they did not use the same crystal to grow the sample. For example, GaN is grown on Al203, why not take GaN as the seed?
 
Physics news on Phys.org
  • #2
That depends on what exactly you want to grow.
It is possible to use the material you want to grow as substrate (homoepitaxy), but sometimes mismatching is not a problem, but highly welcome.
For example the growth of low dimensional heterostructures (quantum dots, quantum wells, ...) requires some mismatching to work.
 
  • #3
Weimin said:
Mismatching is the problem in growing materials. I wonder why they did not use the same crystal to grow the sample. For example, GaN is grown on Al203, why not take GaN as the seed?

But in many cases, what you want is a pristine surface with a particular crystallographic orientation. If that's the case, you can't just use a pre-made surface that have been exposed to air. So you have to make the film in situ and then study it.

The lattice mismatch for GaN, for example, is mostly solved by depositing a buffer layer first such as AlN. Furthermore, in films such as GaAs, the lattice mismatch is actually desirable because it produces a strain in the film that breaks the degeneracy of the crystal, allowing for the production of spin-polarized photoelectrons.

Zz.
 
  • #4
I got it, thank you.
 
  • #5
Also, usually the reason for growing using a deposition method such as MBE, VPE, or CVD as opposed to the Czochralsky method is because the Czochralsky method does not work. Such is the case with AlN, since at temperatures where Al is molten nitrogen is of course a gas so Czochralsky isn't possible. Therefore, AlN wafers are simply not commercially available for epitaxial growth and you need to use a substrate such as sapphire (Al2O3) to grow AlN. However, as mentioned before, the lattice mismatch is not significant usually, and the strain can be minimized by first growing a annealed buffer layer. Then the epitaxial film is grown on the buffer layer.
 

1. Why is a substrate necessary for plant growth?

A substrate is necessary for plant growth because it provides essential nutrients and physical support for the plant. It also helps to retain moisture and oxygen, which are crucial for the plant's survival and growth.

2. What are the different types of substrates used for plant growth?

There are various types of substrates used for plant growth, including soil, sand, peat moss, vermiculite, perlite, and rockwool. Each substrate has different properties and is suitable for different types of plants and growing conditions.

3. Can a plant grow without a substrate?

In some cases, a plant can grow without a substrate, such as in water or using hydroponic systems. However, a substrate provides a stable and nutrient-rich environment for the plant to thrive, making it essential for most types of plant growth.

4. How does the substrate affect plant growth?

The substrate can significantly impact plant growth by providing nutrients, water, and physical support. It also plays a role in the aeration and drainage of the plant's roots, which are essential for healthy plant growth.

5. Do different types of plants require different substrates?

Yes, different types of plants have different growing requirements and may require specific types of substrates. Some plants may thrive in well-draining soil, while others may need a more water-retaining substrate. It is essential to research and choose the right substrate for the specific plant you are growing.

Similar threads

Replies
16
Views
2K
  • Electrical Engineering
Replies
7
Views
1K
  • Atomic and Condensed Matter
Replies
5
Views
1K
  • Atomic and Condensed Matter
Replies
2
Views
5K
  • Biology and Medical
Replies
13
Views
3K
  • Set Theory, Logic, Probability, Statistics
Replies
9
Views
269
Replies
69
Views
4K
Replies
6
Views
905
  • Atomic and Condensed Matter
Replies
5
Views
3K
  • Biology and Chemistry Homework Help
Replies
2
Views
1K
Back
Top