Questions related to 2D Materials
As 2D material are polymorphic in nature and through mechanical exfoliation these different structure of same material is studied. and based on optical images how we can identify different structure that is based on colour contrast ?
I am facing an issue using gold as substrate for the deposition of tellurium in PVD technique. Tellurium and gold interdiffuse during the deposition. I would like to know if there is any way to avvoid this and passivate the surface of gold? Thanks
Hello seniors Im new, I want to make calculations of Electronic, magnetic, optical and thermoelectric properties 2D materials by VASP. please help me. Which properties I need to find first and then order.....
I want to simulate a reaction on different terminations of TiC (Mxene). carbon-terminated TiC (Mxene) surface is a system that I need. I don't want to create a new slab.
I'm facing a problem with vc-relax optimization. Our structure is hexagonal and I apply a vacuum in the z-direction for 2D material and run this optimization. After optimization, the vacuum decreased very fast and the structure went to bulk, After this problem, I changed in the input file in $Cell cell_dofree= 'xy' but had some error
task # 0
from checkallsym : error # 2
not orthogonal operation
then what I do . if have have any suggestions regarding this problem please help me. I searched a lot but didn't get any solution for this problem.
It is well-known that 2D materials are used to improve tribological properties either as solid lubricants or as lubricant additives. Few layers of 2D materials are known to provide reduced friction than monolayers because of the easy shearing between the layers due to the presence of van der Waals forces. However, monolayers also reduce friction, so is it due to the chemistry, inertness, and atomic level smoothness of monolayers or lower adhesion between the two contacting surfaces, or something else? Please enlighten me with your thoughts.
We are collecting information to write a review to reflect recent developments in the characterisation of liquid-exfoliated 2D materials, in particular analytical protocols to assess size and to track covalent as well as noncovalent functionalisation. We would appreciate input should you have work that we should not miss out on accidentally!
Thanks in advance!
I was solving the tight binding model for graphene mono layer and found the zero band gaps at dirac points but then I saw some literatures stating that hBN which is a 2D material , also known as white graphene , has a BG of ~6ev , I am not able to understand what makes graphene different from hBN , is it the symmetry of Carbon atoms over B and N atoms or anything else ,Because tight binding model will apply the same way on hBN as in graphene
In xrd test I got two values like Intensity and two theta ....I calculated in scarrer equation & attached some file...Please anyone can help me and also recalculated the nanoparticle size in Nanometer...
We are using glass and iridium substrate for the deposition of Y2O3 by PLD. Under the same deposition conditions, the Y2O3 was successfully deposited on glass substrate but we did not found thin film on the Iridium substrate. We also confirmed it by SEM images and found only few particles of Y2O3 on iridium substrate but on glass substrate it was a complete thin film with reasonable coverage. We are looking for the expert opinion for understanding/resolving this issue or any other deposition technique suitable for the deposition of Y2O3 on iridium substrate.
Currently, I am manufacturing 2D-based semiconductors through semiconductor process. However, if metal is deposited on SiO2 or WSe2 after the photolithography process and lift-off is performed with acetone, some parts metals fall off. This problem was partially seen in Ni case, and the problem becomes serious when Ag is used. At first, it was thought that a problem occurred in the process of shining UV, so it was made by completely contacting the mask on the substrate, but it was not solved. Metal deposition was performed at a high vacuum of -6 or -7, and the substrate was cleaned again and PR or Developer was used as a new one.
Still, it hasn't been solved.
If you have experienced or solved the same problem, please help me.
Substrate : Sio2 OR Sio2/WSe2 (PMMA trasfer)
Resist : Positive PR, az5214E, soft bake 120'c for 10min after develop
Metal Deposition : Ag or Ni using E-beam Evaporation, 50~60nm,
0.1A/sec for rate
Lift off in acetone with ultra sonication
Have a nice day everyone looking at the questions. Thank you.
I am attaching the picture for someone's understanding.
That's the result I got a while ago.
Thank you :)
Dear professors and Experts,
According to recent research and articles, it seems that materials science and engineering is going to have a critical role of the future of science and even engineering. As you all know it's a vast field of research. I would like to have your opinions in this regard. What will be the next of materials science? Which branches will do well and is critical than others?
Please let me find your awesome answers.
I have used OQMD for convex hull calculations of bulk Heusler compounds. But, now I have 2D materials and want to find their hull distance. Is this possible? Is there a paper for this or a software for this?
We are working on the fabrication of Hall devices from exfoliated flakes of 2D materials. We are exfoliating these 2D materials on polymer stamps (PDMS) and then deterministically transferring them on pre-patterned Hall geometry devices(Ti/Au contacts 5/70nm respectively) on SiO2/Si substrate using 2D dry transfer setup. After the successful transfer of 2D flakes on device geometry, we inspect the devices microscopically (in high-resolution 100X). Optically the 2D flake appears to be in perfect physical contact with all contact leads. But when we are characterizing them electrically, in the first 2-3 sets of I-V measurements, we are getting the expected resistivity range and also the Ohmic nature of our contacts. But after 2-3 sets of measurements, the resistance of the sample reaches to giga-ohm range, and also, the contacts are losing their ohmic nature.
While inspecting the device optically after IV measurements, it appears in perfect working order (i.e. the flake is still in the same condition as it was before the measurements).
It would be a great help if you could suggest something regarding the issue based on thhe expertise in bottom contact devices.
I want to calculate the lattice thermal conductivity of a 2D layer. Can anyone suggest me which package (phono3py, ShengBTE) give the appropriate results with the 2D material.
I study the delamination of laminates upper and bottom skins of honeycomb composite structure simple supported from two sides and under bending stress.
I consider the developed tension on the bottom skin as the main peeling force that cause delamination.
Is my thinking correct?
Also, do you suggest textbooks?
I have calculated the Spin Magnetic moment for all individual atoms of a 2-D material via simulation. Is the total magnetic moment of this 2-D material just the sum of all individual magnetic moments?
I am trying to exfoliate MoS2 using Scotch tape method (exactly using Blue tape, Nitro) then put in contact with commercial PDMS (exactly,GelPack grade 4) and I would like to enhance the yield of monolayer and few layers. Not concerned now with the size of the flake, if it is few microns it is fine for me.
Your help is appreciated.
Hi everyone. It is known that all Si-SiO2 wafers absorb the liquids around them due to their low hydrophobic properties. For some nanofabrication purposes, it is critical to have a sample free from this layer. Some people heat samples on the hotplate in air or vacuum to remove the fluid layer. Has anyone investigated how effective it is? Any good thoughts on this problem?
Thank you in advance!
In the case of Bulk Semiconductors, for downward band bending, positive charges exist at the surface, and electrons accumulate in the semiconductor near the surface; this space charge region in the semiconductor is called the accumulation layer due to the accumulation of electrons in the semiconductor. In the upward band bending condition, negative charges exist at the surface, and positive charges accumulate near the surface; this space charge region is called the depletion layer. In both cases, carriers move from the bulk area to the surface and accumulate to screen the external electric field. Now my question is that what happens if a vertical electric field sets near a single-layer semiconductor (no Bulk, only surface)? for the two cases when (1) Single layer semiconductor on a dielectric substrate. (2) on a metallic substrate.
Thanks in advance for your answers.
Hi everyone, I am new to simulation and learning quantum espresso code. I am trying to Manipulate crystal structure in 2D materials, like MoS2, by replacing one or both Sulphur(s) with H-atom. in doing so, I partially used Vesta, but I couldn't get convergence. Can any one guide me how they actually do this stuff?
I just receive an email from email@example.com as follows. Is it reliable? Anyone gets the same email?
I am delighted to inform you that your name has been nominated for Fellow of Vebleo by the committee members for your notable contribution in the field of materials science research including graphene & 2D materials, biomaterials & devices, functional, composite, polymer, energy- and nano science, and technology. ........
I am trying to use the Gaussian PBC tool to obtain the normal modes of vibration of an organic molecule on the surface of a 2D material.
I have the structure of the system optimized and I introduce the PBC on the 2 dimensions of the material, but when trying to calculate the normal modes of vibration of the molecule in some tests I get this error: "DSDGMF failed for ItDFit" and in others "NB too large for integers on this machine".
In all cases I select only the calculation of the vibration modes of C or H atoms (only of the atoms of the molecule).
I made 2D material using CVD and measured it using Raman spectroscopy equipped by Circular polarized light system, as I know (calculate the Raman tensor) , the Ag mode if the helicity is same (sigma ++/sigma - -) the intensity will emerge, and if the helicity is different (sigma + -/ sigma - +) the intensity will be vanish. in my case I got the intensity of different helicity is half of the intensity of same helicity, why did this happen?
When I try to calculate the phonon dispersion of a 2D material with the CASTEP module of Materials Studio, the calculation stops with
'Error: magres_apply_green_function_s2: not converged'
Can anyone please explain why am I getting this error and which parameter(s) should be modified to resolve this issue?
Hello all, I am interested in the interaction between 2D materials and cellular uptake.
But several articles I read just showed difference modification of 2D materials, and I need to know the difference between 2D materials and nanoparticles.
Are there some advantages of 2D compare to nanoparticles in cellular uptake especially immune cells?
Could anyone have any idea or opinion?
Every reply is valuable, thanks for your help!
I usually calculate the lattice thermal conductivity of a bulk material using the finite-difference method by VASP + Phono3py. However, I'm trying to calculate this parameter of only one layer of h-BN now, but all results are greatly underestimated. Does anyone an idea about how to calculate it in a better way?
I found "the correlative plot for monolayer mos2 " in a publication "Spectroscopic evaluation of charge-transfer doping and strain in graphene/MoS2 heterostructures" in (Figure-2b).
However, I can't draw it in origin.
Any idea, how to draw this correlative plot?
I plan to divide my long research article(simulation + mathematical) into two parts, but I am clueless about how to do this. (I can not separate the simulation and mathematical analysis)
I have a few questions regarding the same
1) Do I need to show the common mathematics in both parts?
2) Can the introduction be the same?
3) Can some explanations remain the same in both parts?
Can someone give me the reference of any article divided into two parts?
I want to prepare a gap(less then 10 um) for my experment. I know silicon wafer might be a good choice(it`s easy to cleave). I try to cleave a wafer with diamond tip(or diamond pen) and push them together, but the effect was not ideal. The gap is about 20um, and the gap isn't straight enough. I want to know is there any way to get a um gap? I can also try other materials. I look forward to your suggestions.
I understand that graphitic 2D materials (i.e graphene or hBN) have occupied 2Pz orbitals that repel one another to create atomically flat planes with an equilibrium bond distance throughout the hexagonal lattice. Energetically working against this is that as the sheet grows, more unsatisfied dangling bonds are formed. Thus for a small number of atoms, there is a critical number of atoms that favors forming a closed structure such as fullerenes as shown by D. Tomanek & M. Schluter in "Growth Regimes of Carbon Clusters".
However, I am unsure where the transition between fullerenes, nanosheets, & nanotubes occur but I assume they are dictated by a similar balance between 2Pz overlap & stretching of bond length due to curvature, and dangling bonds.
I would like to develop an energy expression to describe the balance between curvature & unsatisfied bonds for 2D materials that would allow me to predict the size/number of atoms where a 2D material would transition to a closed structure (i.e. fullerene or open end nanotube) assuming there is no activation energy barrier to trap the structures in local energy minima. I would also like to add the ability to predict this for different thicknesses of sheets (i.e. singular or multiple sheet layers)
Currently, the only parameters I can think of are the increases in potential from the overlapping of orbitals and increase in bond length at a given curvature coupled with the geometrical hexagonal lattice as a structural constraint to describe the number unsatisfied bonds. For multiple layers, I assume I would treat it like a beam to develop the tensile strain felt by the bonds at the outer layer. I have been unable to find anything in literature describing the transitions between these structures.
Please suggest or share your experience in drawing 2D materials (graphene, MoS2, WS2, WSe2...) and their devices (FETs) using free or paid software.
I have my IV characteristics curve and along I extracted EQE and IQE curve but I'm in the need of responsivity curve which I'm confused to get. Can anyone please help me to get it in case of a photodetector?
In many materials we can observe linear band crossing even above or below the fermi level. So what is the importance of having DIrac points somewhat away from fermi level (lets say around 2eV) ?
Can any crossing of bands which is linear leads to a DIrac point ?
Unlike graphene, it is usually very difficult to exfoliate few layers (~10 nm thick) of hBN on SiO2 substrate due to lip-lip interaction at the edges. Au substrates have been proven very useful to exfoliate TMDs.
Is there any suggestion what kind of substrates can be used to exfoliate few layers of hBN (except SiO2)?
actually I am looking to calculate the mobility for 2D materials using BoltzTraP code.
If anyone know about it, I will be highly thankful.
I want to see the effect of transverse electric field on band structure of heterostructure. However I am unable to reproduce the reported results using tefield, dipfield, emaxpos, parameters. Please help me to get the desired results. If possible, please share the input files
To achieve superlubricity in two-dimensional heterostructures, do we need to stack it at a certain angle? or directly through mechanical exfoliation, we can achieve superlubricity in 2D heterostructures. Please provide some useful suggestions.
I am aware of the concept of commensurate and incommensurate, but in the heterostructure, do we need to follow that?
Which software can I use to simulate and study the effect of substrate on the photoluminescence of 2D material?
Generally observed at low strain rate for fine grained material.
For industrial scale
which are viable materials?
which parameters need to alter?
Kindly express your views.
Merry Christmas all,
I remember a really useful tool which you could access online using a browser. It had a list of different 2D materials, and displayed a phonon band structure and a stick-and-ball model of the lattice of the selected material. You could click at a point on the phonon dispersion, and it would animate the lattice model to show what the vibration looked like in real-space.
Does this tool still exist? Can anybody help me to find it again?
I have been working on 1D and 2D materials; now, I would like to measure the vibrational properties using the Raman spectroscopy of these samples in the liquid state measurement.
I am doing my thesis on the determination of thermal conductivity of 2D materials using LAMMPS by NEMD process. My system seems not to be working properly. Can anybody help me with the input file for this work?
I am looking for a research work that implemented an uncertainty or statistical framework to study the impact of the geometric parameters on the fracture response.
I appreciate any help.
Thank you in advance,
Hello, I run in to some troubles with the mechanical exfoliation of WSe2 and MoS2 on SiO2. I could get quite good flakes (~50um size) to direct exfoliate on PDMS, however 300nm SiO2/Si substrate does not work for me. The substrate is cleaned by ultrasonic in Acetone/ IPA/ DI water.
I read about some researchers also treat the substrate with Oxygen Plasma to remove organic adsorbents after the cleaning procedure I mentioned above. Is this a crucial step? If so, can I remove organic adsorbents by piranha?
many thanks in advance
Polymer gets softened at glass-transition temperature (Tg), so the bonding of two polymeric layers is possible.
What are the operating procedures for thermally bonding PDMS to PMMA?
I want to calculate the in-plane speed of sound from the phonons spectrum of a 2D materials, let say graphene, which can be calculated from the slope of w(k) of acoustic LA mode. I did a linear fit and found the slope. I used the relation f = c/lambda, where c= speed of light and lambda is the slope in meters (changed from cm). Then, this value of f is multiplied by 2pi. The resultant unit became radian/sec. I have two questions, 1) how to convert rad/s to m/s? and 2) Is this procedure correct? If not, what will be the correct way of calculation in-plane speed of sound from phonons dispersion?
Thank you very much.
Hello everyone. How can we verify from band diagram, weather the band crossing is pointing towards Dirac metals or weyl metals or it is just normal band crossing.? What observation we should make? What confirmations we need to do ? More generally, just looking at the band structure how could we could say. Please guide me. Thanks.
Is it possible to change or form new chemical bonding using frictional heating during high sliding operations?
I am trying to fabricate photo-detectors based on 2D black phosphorous material. The Au/Cr contacts are deposited by e-beam on top of BP flakes. I was wondering if anyone could mention the detailed procedure and highlight the common problems that we can encounter during such fabrication of contacts on top of 2D materials.
Thanks for your anticipation.
From literature, both flows have been assumed. However, I read that compressible flow is valid after a certain mach speed which generally is not used in a typical 2d materials CVD. Thus, is it correct to assume the fluid flow in 2d materials CVD as incompressible?
Basically, I have start calculations on WEIN2K for 2D structure but i was troubling in an issue of force convergence. I can not run SCF by using min_lapw command due to not convergence of force.
I am wondering how the thermal transport properties of 2D materials impacting the S/N ratio of Raman measurements when 2D material is used as a Raman substrate. How is graphene's higher thermal conductivity is beneficial compared to other 2D materials as a substrate in Raman measurements for achieving a higher signal-to-noise ratio in particular?
I am researching the control of bulk 2D material to apply to devices that the layered structure is needed. To understand the growth process of the bulk 2D material in detail, I am finding a professional person. If someone know the person, Please let me know.
However, these materials have demonstrated a relatively slow photoresponse, and because of the large bandgap of Mo- and W-based compounds, they are suited for applications in only part of the visible range of the electromagnetic spectrum. A material with a direct and small bandgap together with fast photoresponse is needed to extend the detection range accessible with 2D materials.
I am looking for an alternate 2d hydrocarbon material that can be used alongside CNT as a hybrid material to design a membrane or supercapacitor.
Interested in using commercially available heterocyclic/non-heterocyclic aromatic S-sources for making metallic sulfides under pyrolytic conditions.
Any relevant reading suggestions are also much appreciated. Thanks.
I have been preparing MoS2 through a hydrothermal process by combining thiourea and ammonium molybdate with 2.28 g and 1.2 grams, respectively, in a 35ml DI water and place it in 70 ml teflon autoclaves, at the end I would get 1g of MoS2 powder. Now, the issue is that I am forced to switch for thioacetamide as sulfur source, so I started with the same proportions as the thiourea (2.28g) but it appears that it is too much I get a very thick slurry in the autoclave instead of just light slurry that I can wash. So,any recommendations of proportions and weights that I can use to get similar results as the thiourea one?