Heterostructures - Science topic

you may try build structure that option, also you can sketch it. Please check there are some available built-in structures too. Then, you may choose CASTEP for running the simulation.

Thank you, Dr. Len

How to introduce Electric field effects using VASP, that is, what are the required flags?

Thanks😀 to Alexander, Antonis and Rafael for the valuable suggestions 🤝. Now, I plotted the graph.

We had the same problem on PMMA/MAA/few-layer MoS2, especially the structure which has 1-2 um gaps in between the electrodes. As mentioned above we used cold IPA, and it worked.

You may integrate the whole curve of the charge density difference to obtain the total charge transfer amount using the Origin Software. Please refer to the J. Mater. Chem. A, 2018, 6, 8923–8929 and Sustainable Energy Fuels, 2021, 5, 2249–2256, etc.

Nikolay Pavlov Thank you

The following RG link is also very useful:

Hi, I did something related in this article

In short, you must add a saw-like potential to simulate an electric field and dipole correction is also required. For this, in &CONTROL one must add the flags:

Next step, I recommend you to set the system at the middle of the periodic unit cell in the z direction. i.e., if c=10A, then your atoms lay down at z ~ 5A.

Finally in &SYSTEM, something like that should be ok:

let me know if you need something

Dear Sanchari Bhattacharya

No increasing number of iterations is not a good idea, you can just play with the projections you have chosen and the disentanglement windows. That may help!

LVHAR = .TRUE. is also fine

depending on calculate the rate

If the combinations are limited within the inorganic semiconductors, it is not very practical to achieve a bandgap shift over 500 meV, due to various limitations, such as lattice mismatch, as mentioned above. However, some organic-inorganic hybrids can achieve much stronger "quantum confinement" effects with a bandgap shift over 1 eV, and more interestingly near perfect crystal structures. See this paper:

I agree with Valentin Bogatu.

Ahmed Benyahia, you welcome

you welcome Vaishali Nimbewal.

Dear M Atikur Rahman in the context of your interesting technical question please have a look at the following potentially useful literature reference which might help you in your analysis:

Fortunately this paper is freely accessible as public full text on RG. Thus you can download it as pdf file. Please also note that a large number of closely related questions have been posted earlier on RG. It might be worth checking the answers given to some of these questions:

I hope this helps. Good luck with your research and best wishes!

Dear Abhishek, unfortunately I'm not a specialist in this field enough to give you a qualified expert answer. However, it might be helpful reading the answers given to the following closely related question which has been asked earlier on RG:

(19 answers)

Also please have a look at the following potentially useful article which has been published Open Access:

Good luck with your work and best wishes!

Dear Mario,

In many materials, both direct and indirect interband transitions can exist. The energy gap for indirect transitions is less than for direct transitions, which is quite consistent with the data that you obtained (Eg indirect is about 2.8 eV, Eg direct is about 3.1 eV). In your case, it is quite possible to speak about the existence of two types of interband transitions. Theoretical modeling will help to draw a conclusion about the correctness of the obtained values.

Warning: electronic minimisation did not converge during            finite basis set correction.   ******************************************************** Checkpoint file cannot be written. Error calculate_finite_basis : Convergence failed when doing finite basis set correction. Current trace stack: calculate_finite_basis_corr check_elec_ground_state castep Error in calculate_finite_basis:      previous calculation had total energy = -33482.98282286      eV      and this calculation has total energy = -33477.62803476      eV       => something has gone seriously wrong with minimiser Checkpoint file cannot be written. Error in calculate_finite_basis: total energies are not variational - aborting Current trace stack: calculate_finite_basis_corr check_elec_ground_state castep

Hello Abdus Samad , I am getting the same line in my case .

Can you please suggest how to get rid of these negative bands appearing.

I tried to increase the ngrid from 4 4 4 to 8 8 8 but still that doesnt work

the is often a confusion between ferrimagnetic effect and ferromagnetic ;when you use YIG like material In the microwave range) its ferrimagnetic !

Steven Van Petegem I want to investigate the evolution of HDI stress in a severely plastically deformed heterogeneous aluminium alloy. Do You think that compression (LUR) test will also be appropriate ?

Dear Gabriel G. Maia ,

For etching of Si,SiO2 or other materials used in VLSI technology you can use the standard etching solutions given in the link:https://www.microchemicals.com/technical_information/silicon_etching.pdf

In this site you find that only 1 percent diluted HF is suitable for this purpose.

Working with high concentration of HF is more precautious.

Best wishes

Hello Nisar Muhammad

Have you been able to obtain the convex hull for the heterostructure?

Dear Marco Antonio Uscanga Olea thank you for this very interesting technical question. I assume that the well-known

could be a valuable source for all this information. It is available online and as printed version in the 101st Edition:

If you find an older edition in the library of your institution this should also be perfectly OK.

Good luck and best wishes!

A physical mixture XRD will certainly show multiple peaks of different orientations for both the compound. Whereas, a clean heterostructure will have lesser number of oriented peaks. Additionally, you may see slight shift in 2 theta position in case of heterostructure due various physical and chemical interactions at the interface such as strain, lattice mismatch, hybridization etc.

In this reference paper (https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.13.044075)

you can find a clear difference between a polycrystalline physical mixture XRD (in ESI) and film XRD (Ti3AlC2/c-Al2O3 heterostructure).

Dear Vinay,

Damping reduction in some FM/NM structures has been reported in many studies to be possible by applying current density on the NM layer while the ferromagnet is under resonance. One condition to observe the reducion is that the NM has a strong spin-orbit coupling or that the two layers produce a Rashba interface. In this case, the damping reduction is promoted by a two-step process. One, the charge current in the non-magnetic metal creates a spin accumulation on the interface via spin Hall effect. And two, the ferromagnet absorbs the spins accumulated on the interface.

An investigation originating in the Indian Institute of Technology and announced in the article claims damping reduction without current induction. The addition of the non-magnetic metallic layer reduces the damping as compared to the bare FM film. This is very uncommon. I think that this is the only published study to date that claims such effect.

Thank you Nagesh!

Michael Uebel thank you sir

We published a home-made, extremely cheap machine with heater and vacuum

there are discussions of several opto-electro-mechanical aspects here. This might be helpful.

In the right side p-n junction structure the field region in the transition region will direct the electrons to the n-side where they will be accumulate on the surface of the n-side. At the same time the photognerated holes will be directed to the p-side where they will accumulate on the surface of the p-type material. So, the p-side will be source of holes which is oxidizing. The electrons accumulating on the n-side will be reducing.

The structure in the the right side is composed of two intrinsic materials with the left side has an electron affinity greater than the right side. The two materials have almost an equal energy gap. Both materials are optically active where on absorbing photons they will both generate electron hole pairs.

The electrons will be accumulated on the left side while the holes will be accumulated in the right side.

So, the right side will be oxidizing while the left side will be reducing.

Both will have photovoltaic effect.

The second structure is simpler to produce than the first p-n junction structure.

Best wishes

Thank you sir for your kind reply....i tried with the technique given in user guide but still getting the same problem....

Dear Himanshu Joshi

Thank you for sharing the paper; I already finished my work and solve the above problem.

Huo, Nengjie, Zhongming Wei, Xiuqing Meng, Joongoo Kang, Fengmin Wu, Shu-Shen Li, Su-Huai Wei, and Jingbo Li. "Interlayer coupling and optoelectronic properties of ultrathin two-dimensional heterostructures based on graphene, MoS 2 and WS 2." Journal of Materials Chemistry C 3, no. 21 (2015): 5467-5473.

Yes, of course. SEM image can also strictly identify the surface deterioration which meaning that catalyst surface and substrate may be inhibited by it.

You're welcome Muhammad Shuaib Khan.

Atom projected (site projected) DOS calculations almost always produce output for sites indexed based on the order you defined your coordinates in the input file.

So, if you know which atom is which in your input, it should be no problem working out which ofns to sum.

If your heterostructure is large, it may be convenient to use the ASE interface for QE to work out which atom indexes belong to which layer.

I hope this helps.

Hi,

Lattice Mismatch between core and shell can be calculated by using XRD patterns planes of core and shell structures by formula

% Lattice Mismatch = 100 × [ 𝑑(core) − 𝑑(shell)]/ 𝑑(core)

Note: Use the same diffraction plans of core and shell

Hi, a heterojunction is an interface that occurs between two layers or regions of dissimilar semiconductors. There are two known methods for its preparation: Top-down: Micromechanical Exfoliation. Simple as it seems, this technique is able to yield high-quality 2D crystal flakes, applied to many common-used 2D materials, such as graphene, MoS2, WSe2 . Bottom-up: Chemical vapor deposition (CVD). This method is mainly used to prepare larger films with more stable quality. One of the most popular application is to adopt it for growing MoS2 uses S and MoO3 as precursors. And used in cases such as Lasers, bipolar transistors, solar cells and field-effect transistors.(https://en.wikipedia.org/wiki/Heterojunction) And I suggest this book too: https://b-ok.cc/book/599935/386d87

Dear Dr. Md Tawabur Rahman , Dr. Farrokhfar Valizadeh Harzand and Maharshi Dey .....thank you so much for your kind suggestions. I have started looking into the resources.

Maharshi Dey , since MXenes are mostly liquid processed, it is incredibly difficult to have pristive bilayer/hetero-structure of MXenes. That's the reason we focused more on traiditional 2D materials which have established transfer protocols. MXenes are incredible materials and we really want to look into their mechanical properties. If you have any suggestion regarding the problem I state above, please let me know.

Dear Pawan,

welcome,

Would you please add details to your question to make it clear. Which barrier you mean? Is it the barrier of the two dimensional gas at the surface of GaN layer, or the barrier caused by the AlGaN?

Here i will assume that it is the barrier of the two sedimentation gas.

As the potential barrier of this two dimensional gas increases, the scattering at its wall decreases and thereby the mobility increases. This is because the electrons will flow mostly in the middle of the potential well.

Best wishes

Dear Saurav,

It will be easier if you construct each of the GaAs and GaN monolayers individually. Then, concatenate them together with considering a distance between two monolayers by adding a constant value to the coordinates of the second monolayer.

On the website Materials Project, you can find the CIF file for both intended monolayers. Also, it provides open web-based access to many crystal structures of materials.

Photoluminescence Spectroscopy analysis is used to evaluate the recombination rate of photoinduced electron and hole pairs. I think this technique is usefusefulule.

Dear Aadhityan Arivazhagan

Thanks for your reply.

You can find lots of photoelectrochemical cells in " http://adamschittenden.com/Gallery.html?category=24 " and " https://pineresearch.com/shop/products/photoelectrochemistry/single-chamber/quartz-photoelectrochemical-cells-2/ ".

Hello

You may refer to the following attachement, some materials data were refer-in.

Thanks

The dielectric confinement is exploited in the dielectric waveguides such as the glass fiber. The confinement is based on the total reflection at the boundary of the two materials. It requires a boundary with two different dielectric constant and a an incident angle greater than that required for the total reflection. So the confinement may occur in a fiber with a dimensions in the order of the ligfht wavelength.

Best wishes

Yip Hosum

Firstly, if your lattice mismatch is 0.6%, it is excellent.

Secondly, the lattice constants are mentioned in Table I for the different stacking. The lattice constants of these heterostructures as follows 3.31, 3.33, and 3.32 Angstrom for AA, AB, and BB stacking orders, respectively. in addition, it can be obtained these lattice constants from CONTCAR after the relaxation.

Thirdly, we can obtain the optical anisotropy from the values of refractive index (n), where any material become isotropic due to stabilizing the values of n (the change in n approach to zero) otherwise the material is anisotropic where Δn> 0.

But there is a better method to find the optical anisotropy in materials by finding the difference between the horizontal and vertical refractive indices, the latter method exists in the attached papers in details.

We need more information for above question

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145746/

Dear Sharad,

welcome,

What is the function of the spacer layer in the intended structure and how is the layer stack required? The choice of the material depends on its fucntion in the structure. Do you want to make multijunction tandem solar cell from three five compounds?

Best wishes

Following

HQ Graphene offers complete system: http://www.hqgraphene.com/TransferSystem.php

Hello Hicham Abou Oualid ,

Wishing you all the best with your search.

I would also suggest searching onthe following websites:

Dear Dr. Wilson,

I have no experimental experience with this problem. I found by Google search a hit for the antiferromagnet MnF2:

Epitaxial growth on silicon and characterization of MnF2 and ZnF2 layers with metastable orthorhombic structure

Journal of Applied Physics 98, 013519 (2005); https://doi.org/10.1063/1.1944909

Dear Askari,

The following article will answer your question:

Langreth, D.C., Dion, M., Rydberg, H., Schröder, E., Hyldgaard, P. and Lundqvist, B.I., 2005. Van der Waals density functional theory with applications. International journal of quantum chemistry, 101(5), pp.599-610.

P. Contreras you are welcome Prof. Contreras.

Traditionally, a heterojunction is referred to an interface of two different materials in chemical content. However, it has been extended to other situations such as an interface of the same material but different structures (e.g., ZB GaAs and WZ GaAs), of the same material but different crystal orientations (e.g., a structure known as orientational superlattice), etc.

This articles may help you

DOI: 10.1007/s11664-010-1242-0

DOI : 10.14429/dsj.67.11178,

I hope these papers will help

TEM can help if you get the high resolution images. Best of luck!

The CRYSTAL code (http://www.crystal.unito.it) can work with 2D periodic boundary conditions.

The Kramers-Kronig relations are not always valid for the effective index of a mode in waveguides. For example, the fundamental mode of a lossless dielectric waveguide (e.g., a single mode fiber) will have a dispersive effective index, but no loss. Thus the effective index cannot satisfy the Kramers-Kronig relation. It turns out that it satisfies a generalized form of the KK relations in which the mode dispersion is connected to the imaginary parts of the evanescent modes (see ).

In a quantum well laser, states are quantized in the conduction and valence bands. Therefore, the transition energy will be greater than the bandgap of the material.

You have to compare the metal sulfide and metal disulfide bond. As you know sulfur has variable oxidation states depending upon the nature of oxidation state the pattern may change. You please refer some papers on high light sulfur on silver and gold surfaces. area of the peak splitting also give you some information.

The experiment must be carried out under inert gas. What you see is the reduction of O2.

Dear Abdullah, You may post the same answer to all questions in RG forum. This would help to increase your RG score. I recommend your answer (which I consider as a spam) to help you to increase your RG score.

Hi Sukriti,

Heterostructures are the materials made up of different metals or components. They are not separate species. You will get only one morphology where they are completely blended with each other. They are interlinked. Ex. MnMoO₄, CuWO₄

Composites are the materials where 2 or more components present independently with given ratio. They will have individual identity and can be observed through SEM and TEM. Ex. Cu₂S-MoO₃.

In terms of band gap, for heterostructures usually get only one band gap energy (sometimes 2) but composites get minimum of 2 band gap energies.

Core-shell structures are those where one component is enveloped by other. These may be considered as a type of composites. Of coarse band gap energy will not be same as that of either of the components. It depends on the composition ratio.

Hope it helps

.

both VB and CB offsets are important to understand the properties of heterostructures

you might have the impression that the focus is mainly on the VB because of the experimental technique to probe the band alignment in heterostructures

first the VB alignment is determined using XPS for instance

usually band gaps are already known (from spectoscopic techniques for instance)

and finally the CB offset follows

.

For some applications 1D is advantageous and some other cases 2D is better. It depends on case-by-case. But if you want to compare 1D & 2D effects side-by-side in any particular case, you can certainly do that. In that case you should choose similar material composition for 1D & 2D materials and compare them in similar application. Here is one of my previous review paper where I was exactly trying to do that. This was the comparison between Carbon 1D material (CNT) and Carbon 2D material (Graphene) in electronic and optoelectronic applications. If you are interested you can check that out..

Dear Ali, thanks for answering . do you have any files explaining that in hetero-structure based on 2D materials