Thin Films and Nanotechnology - Science topic

I have just found this interesting paper where they have discussed the comparison between Gold and Platinum as the electrode material when fabricating TiO2 memristor.

Also, you can make memristor with NTC (Negative Temperature Coefficient) thermistors, which can be really chip.

Please let me know if you have already found some other chip materials to fabricate memristors.

It looks like Ti/TiN are common to be used as adhesion layer as the adhesion is usually poor between W and dielectrics.

Ref:

Rita Joshi, did you measure the electrical resistance/conductivity of your substrate after rGO coating? Films of graphene are nearly 90% transparent.

@Uday Saha Thanks for the information sir

Nonlinear behaviour means, your materials doesn't obey the Ohm's law, but it has Diode Behaviour mateials.

Nonlinear means - how ?

generally graphically 4 quardent, urs, graaph 1 to 3 or 1 to 4 via 3

Do you have found the impedance value? I am also seeking it.

Dear all, it is without indue doubt that TTIP is the most promising precursor it the conditions such solvent, concentration, are well selected. The following documents deal with the keytools for a successfull preparation of TiO2 nanostructures with the desired properties. Please check the following documents. I attached also the document recommended by Prof. Frank T. Edelmann. My Regards

10.1016/j.jeurceramsoc.2008.02.017

Mikhail Pylnev

The nanoparticles on the surface have an unfinished crystal lattice. If the synthesis conditions (temperature, pressure) favor the formation of another allotropic modification, then it appears.

If you are interested in details write a letter to Pugachevsky. He knows this problem.

Hi Muhammad, six years since you posted this question, would you like to share your own experience on what you have? A private message will be OK if you prefer. Many thanks for considering my request.

can anyone tell me please my AlGaN-BASED samples not showing any optical properties by PL test, is it possible to test CL or EL please anyone knows about this, and can CL or EL will be able to characterize my samples or it will be the same

Before encapsulation you can coat your solar cells with silicon dioxide layer using spin on techniques. Such layer will make the bare side sealed against effect of oxygen and moisture.

We developed a novel encapsulation method named three flat plates modules.

For such method please follow the link:

and the book chapter:

Best wishes

you can use solar cell analysis provided at analysis group library to generated charge carrier in respect to illuminated source, however I suppose that's not your problem, as far as I know, there is no direct way to perform doping to materials, FDTD knows material only with their index, you can look for your doped material permittivity then import that data to FDTD, at the Device module you can simply perform a doped material for electrical matters.

Hi

I totally agree with Michael

​Kind regards,

I think you can use solvent of higher boiling point and lower molar concentration of solution. Because solvent with lower boiling point evaporates from a certain height and form the powder. Solvent with higher boiling point can bring the droplet closer and due to levitation of the droplet it easily absorbs by the substrate. So, the film will be uniform and dense.

Also on etching silver ― at this forum: https://www.researchgate.net/post/What_liquid_can_etch_silver_Ag_gently

Martin Friedl I am the author of this software and just came across your reply as I was perusing the web for other RHEED software! Sorry for resurrecting an old thread, but if anybody would like to use FRHEED, I have recently made some major improvements to it (I have also created an installer for 1-step implementation). I will update the Github page this week as well for improved documentation. It can even run using a simple USB webcam if you would like to test it before committing to buying the CCD it was developed with (FLIR GigE Vision camera - Blackfly S Model 31S4M, ~$500).

Dear Thomas:

The working pressure is 10^-7 torr

The CdS and PbS were grown by Chemical Bath Deposition, these deposits were conducted in a different site, previously than the e-beam deposits.

I agree with your second comment,

Do you think that the big difference in the roughness of the films (between those of the CdS and PbS deposition). This hypothesis could be logical if I were try to grow 10 nm of Al, but I'm trying to grow 200 nm. What end deposited on the surface of the 200 nm-contacts should be affected by the roughness of the substrates. However, the roughness of my PbS thin films is on the order of microns, I saw the surface on SEM, and it is composed of big particules of PbS, measuring between 1-100 microns, the surface is highly non-uniform.

In opposition to the CdS films, where which the roughness isn't at the order of microns.

Do you think the morphology of the surface, in this case could be the problem ?

Even, I placed one of my PbS films and a black glass substrate in the same deposit, and the Al deposited on the glass ended up with a metalic aspect, but the Al deposited on the PbS film ended up with the white aspect, in the same deposition run. So same run and same conditions, but one ended metallic, and the other one ended white

Thanks for help ,

Regards !

Dear Qaisar,

welcome again,

The doping atoms as they are impurity atom are different in size than the native silicon atoms in addition they are mostly ionized. When the electrons or holes passing near them when the drifting under the electric field applied they will be linked from their original path and therefore the doping atoms are considered as obstacles in the path of the electrons or holes and therefore they slow down the motion of these carriers. Consequently their mobility will be degraded due to the presence of the doping atoms.

I would like to get more information about the mobility by refering to trhe book in the link:

Best wishes

You can achieve the result if you use ion-plasma sputtering.

The Richardson constant is expressed by

A* = 4 pi q m* k^2/h^3,

All what do you need is to search for m* of indium oxide and the the values of the physical constant and then you can calculate the Richardson constant.

The value for A= 120 A/cm^2 K^2 for m*=m0

For the derivation of the Richardson constant please refer to the book in the link:

Best wishes

Hi all,

We've been developing a metal-organic resist which we believe has excellent etch properties. A recent paper appeared in Nano Lett., 2019, 19, 6043-6048 where we showed we could etch sub-10 nm structures into silicon and tungsten. I'd be very happy to send anyone a reprint or talk further if you are interested.

it depends on the type of support you use. we usually use slightly hydrophilic support as it doesn't hinder the movement of amine form aqueous phase to organic phase. If we use a strongly hydrophilic support, we would end up with less cross-linked polyamide film as the support will attract more amine

First of all, sorry for my late answer, two years after the question !

If you think about film thickness less than 1 µm, thus deposited on a thick support, and about nanoporosity, i.e. microporosity (pore size < 2 nm) and mesoporosity (2 nm < pore size < 50 nm), BET analysis with commercial apparatus based on volumetric measurements is not sensitive enough or you need to analyse a very large amount of surface to analyse enough porous material. A small number of techniques exists to overcome this issue. They are generally based on techniques that couple adsorption-desorption (like BET measurements) with a technique dedicated to thin film analysis. It can be quartz crystal microbalance (QCM), spectroscopic ellipsometry, X-ray reflectometry (XRR), small angle X-ray diffraction, neutron diffusion, ...

For instance, I can advise to consult the article

V. Rouessac, A. van der Lee, F. Bosc, J. Durand, A. Ayral, Microporous Mesoporous Mat. 111 (2008) 417-428.

but also more recent articles.

Regards,

Vincent

https://www.researchgate.net/post/Measuring_density_of_thin_films-can_anyone_help

Dear Sushil K Shukla,

I strongly recommend you to read this publication:

"Optical Imaging and Characterization of Graphene and Other 2D Materials Using Quantitative Phase Microscopy"

Below papers may helps

The easiest, IMHO, is to export gif file from VESTA and use CIF2CELL code to generate an input file for Abinit.

Substrate and liquid cleanliness is vital here. That's the usual reason for pinholing.

I assume you're working in Class 100 conditions.

Clean the glass with warm (50 - 60 C) Decon 90 (5%) solution in filtered 18 Mohm DI water. Then wash the surfactant solution off by 18 Mohm water for 20 minutes or so. The water should then drain off the substrate as a film and not showing spots or particulate manner

Work in a Class 100 environment and filter all solutions to 0.02 um. Ensure the liquid wets the substrate with appropriate concentration and perhaps use of a surfactant.

Dear Reed Petersen,

Sheet resistance (R_s) or surface resistance or surface resistivity is electrical property used to characterise thin films of conducting and semiconducting materials. It is a measure of the lateral resistance through a thin square of material, i.e. the resistance between opposite sides of a square.

The key advantage of sheet resistance over other resistance measurements is that it is independent of the size of the square - enabling an easy comparison between different samples. Another advantage is that it can be measured directly using a four-point probe. The sheet resistance of the electrodes will effect amount of current that reaches the LED, impacting its performance.

The resistivity and conductivity can be calculated if the sheet resistance and material thickness are known. This allows for the materials to be electrically characterised, purely by measuring their sheet resistance.

A low sheet resistance is preferable from electrical point of view, but the lower the sheet resistance, the lower the transmission of the ITO. To decide its optimum value depends on the current density & the amount of transparencey needed.

A 100 nm thick ITO layer shows a transparency above 80% in the visible part of the spectrum and provides a low sheet resistivity of 20 Ω/sq (Sigma Aldrich Co, St Louis, MO.)

Most LED manufacturers characterize a product's thermal resistance for only one drive current, ambient temperature, and junction temperature. However, these parameters may change when LEDs are packaged into a system, which in turn may change the thermal resistance coefficient.

I hope I have answered your question.

With Best Wishes,

Samir G. Pandya

place in or on an anion exchange resin and adjust the pH with a buffer solution to above the pKa for silicic acid. SiOH groups will deprotonate creating a negative charge Si surface and will be immobilized by the anion exchange resin.

Dear Cyril,

welcome,

If you have a two terminal electronic device having nonlinear I-V characteristics and you want to characterize it then there are three type of characterizations:

-The DC characterization by measuring its static I-V curve,

-The small signal ac characteristics by measuring its small signal impedance as a function of frequency. For its representation you just plot the imaginary versus the real part of the complex small signal impedance with the frequency as a parameter. An ideal p-n junction diode has an impedance diagram as a semicircle pointing out its small signal equivalent circuit as a parallel combination of small signal diode resistance parallel with its small signal junction resistance. It must be said that one has to keep the DC bias of the diode constant.

Lastly, it remains the dynamic or switching performance where one applies a unit step voltage voltage or current and measure the dynamic response as I(t) or V(t)

To see all these measurements including the impedance spectroscopy plot please see the link:

If the diodes are not ideal then one can get more than semicircle pointing out the presence of other interfaces than the major junction acting in series with it and contributing in limiting the current conduction in the diode.

Best wishes

This reference and those that accompany it could help you:

Electron-trapping and energy localization in insulating materials. Technological impact of space charge electron-beam characterization

AIP Advances 8, 095228 (2018); https://doi.org/10.1063/1.5047673

The answer should be yes. You can take this as your reference.

Optics & Laser Technology

Volume 34, Issue 3, April 2002, Pages 209-211

Calculation of the absorption coefficients of optical materials by measuring the transmissivities and refractive indices

Electrical insulators as a new phase state of quantum matter with some bulk gap and some odd number of Dirac formations have recently been entangled with a two-dimensional model by us through an external magnetic field. The magnetic field used has its own impurities so much so that the eccentricity resulting from the turning point of magnetic critical insulation leads to aspects of compilation that have never been revealed by the “approximate approximation calculus” mostly used in a run under such circumstances.

Crystal and electronic structures have given us the topology that have made it likely for us to depend more on over-stuck service rather than on projections that go into manifolds and submanifolds of various dimensions. In additions, fulton heaters in this specific setting of complex systems where technique does not exist for efficient approximation, has led us to find even lower than submanifolds: something like up-submanifolds and down-submanifolds whereby the cloesed set of combining topological insulators itself has become the target in insulating the whole bulk without any regard for the gapless and/or edge services states. This means that the topological insulators that we are working on have been both gapless at surface and without such states so that they might be able to carry a pure spin current. However, this pure spin current is the point where we have made our own initiative provided through the closure of those areas where points cannot satisfy every path from one origin-set of the insulator to another point of it simulacrum. Therefore, we are actually depending on, so to speak, closure models for creating metainsulators, giving yet more models of simulations of magnetic insulators.

The surface of state of spin resolved ARPES works so that the focus of one direction is in Riemannian contrast to the zones that consequently appear throughout the folding holes as borderlines between submanifolds. For this, without any doubt, means that the dimensions of submanifolds where we are working on our different froms have been entangled with ergodicity as the totality of anisotropy that rises from insulation through coupling strength. The simplest form is, of course, happening within a two-dimensional partially anisotropic plane. In the most complex forms, they can even go into the quantum mechanic levels such as N-Hilbert dimension.

Roya Attarzadeh

Don Senior Prof. Reza Sanaye

Dear Moohee The best laser for your application depends on the reflection and absorption index based on the different laser wavelength. You have to check your material and find out the absorption and choose the appropriate laser wavelength. Besides, you have to pay attention to your laser parameters such as adequate repetition rate, laser pulse energy threshold, scribing speed and appropriate yield energy factor. The less amount of these parameters makes no cut and the higher ones make a rough cut and high HAZ effect. Good luck Azhdast

For my monitor the Z-value is defined by acoustic impendence of the crystal divided by acoustic impedence of the evaporated material.

Do you have any method to test the thickness after evaporation? You could simply evaporate some material with a guessed acoustic impedence setting. If you make several samples with different thickness, a totallyincorrect impedence value should be noticable as a non-linear deviation from your tooling value.

This way you could tweak the impedence setting by fitting the target thickness to the measured one. But still, I would first try to simply evaporate some material without worring about the impedence value at all.

Dear Sir,

How to prepare PVA 4 mm sheet and PVA + GA sheet ??

Using vacuum assisted Compression moulding.

After lot of useful discussion on this topic, I want to say that UV-Vis-NIR spectra can give information about the presence of defects. These defcts may be generated either by addition of some impurity or by the irradiation of samples by any ionizing radiation. The changes in the spectra will be observed in the form of shift in the position of original peak or in the change in the intensity of peaks. However exact peak generated due to defects can be obtained from difference spectra of sample before and after irradiation. FTIR spectra as well as difference spectra also can provide sufficient information about defects.

J. of Luminescence 130 447 (2010)

J. Non Crystalline Solids 357 3757 (2011)

Ind. J. Pure and Appl. Phys. 55 775 (2017)

morphology and also crystallographic structure

This would be highly unusual for western quality glass. The float glass forming process uses high purity tin specifically to avoid issues like these. With that said if you are finding the contamination only on the tin side of the glass it is possible that the glass is coming from a low quality supplier who isn't using a high enough purity tin in their bath.

Kajal

You can get a larger area uniformly thick 2 mm PDMS sheet by creating a mold that dictates the shape of the PDMS, and then pressing or casting the PDMS into that mold. Let me know if you need help.

Andrew H. Cannon, Ph.D.

Another question, wich evaporation boat should work better for CdS CdSe, CdTe, molybdenum, Tantalum or Tungsten?

EDX could work if the doping is higher than 0.5 at.%, i.e. you should have alloying, not doping. SIMS is a good idea. You can see the depth distribution of boron and confirm the layer thickness. I hope you have good standards for the SIMS measurements.

By FTIR is also possible to determine the doping concentration of B in Si from the area of the absorption peak.

SNR to COD relationship for the above data set at location "800" on topograph.

Dear colleague Dr. Amr,

Peace be up on you, your question's readers and all RG members

There three methods to check and measure film thickness; you can use one of the following according to condition of the film.

Film thickness can be checked by

1- An interferometric method, more details is available at: TOLANSKY S. Multiple beam interferometry of surfaces and films. London: Oxford University Press, 1988: 147.

2- Using mass of the film, m according to the next details::

W1 is the weight of cleaned substrate

W2 is the weight of cleaned substrate plus film

W2-W1= the weight of the film

ΔW=mg

m = ΔW/g

m=ρXV ; ρ, is the density of film material and V is the volume of the film

the Volume = (Width X Length X Thickness) of the film

3- SEM or AFM (film-substrate ) cross section

I wish this is useful and help you.

A. El-Denglawey

thanks your interests.

X-ray absorption spectroscopy (EXAFS and XANES) will give distinct results specific for all the different Co-O species.

thank for all

@Vicent

Dear colleague Umi Zalilah Zaidi

Have a nice time and good day.

Herein fined an attached paper teach you easy how to calculate crytallite size and strain of thin films.

I wish this is useful and help you.

Yous

A. El-Denglawey

If still interested in similar problems, you may use the classical potential described here https://arxiv.org/pdf/1707.09059.pdf

External field-assisted laser ablation in liquid: An efficient strategy for nanocrystal synthesis and nanostructure assembly

Author links open overlay panelJ.XiaoP.LiuC.X.WangG.W.Yang

Dear Aswin,

                  Could you plz specifiy the silicon substrate required? It is helpful for my research also.

A method of photo-assisted electrochemical machining of micromechanical structures from a silicon substrate having both p and n regions in a hydrofluoric electrolyte solution is disclosed. Both p and n regions of the silicon substrate may be selectively etched, with differing regions as etch stops, at controlled rates by the appropriate choice of cell bias p-n junction bias and illumination intensity.

Dear Muhamad, 

You need to read this paper which employed low temperature TiO2 and simple deposition method by spin coating. The PCE is above 20%.

Good luck.

Here the paper about Schottky devices which deposit PbS-QD on top of ITO. [http://dx.doi.org/10.1063/1.4804614] You can check the experimental section.

Hej Joseph!

we have managed to successfully spin coat the second layer and the film was visually thicker (so less transparent); however I have admittedly not measured the thickness, neither the surface roughness. no visual inhomogeneities were present though.

best,

Karen

Please see the following paper:

Good Luck

Thank you all for helping me and sharing such good research articles. i have found solution to my problem as now am using simple silicon sealant and drying it on plastic sheets and then peel them off. the resulting sheets formed are highly transparent flexible and strechable heat resistant upto 300 C

Hi Chong In Shin, 

Can you try some type of vacuum in order to remove the particles?

Are the particles on the surface of a piece of PDMS or inside of a channel? I feel that you expand a little bit more your question, I may be able to help you more.

the key point is the thickness of masking tape. For each coating you should use same masking tape and a sharp blade (not glass or plastic rod). Also, if you decrease the area of film, thickness errors will decrease.

Dear Kamaraj Sir,

I am very new to Quantum Espresso. I am trying to get a charge density difference plot for a gas molecule adsorbed on the single layer graphene surface. Presently I am following your technique as written in your previous communication:

∆ρ=ρAB – ρA-ρB

Where, systems AB, A and B have the different number of atoms each. Then how can I make the charge files having same number of atomic coordinates?

Presently I am getting an error: incompatible gcutm or dual or ecut

Can you help me to solve this problem?

Thanks.

Bibhas Manna

IIT Kharagpur, India

Hi Sivagami,

The solution is to have a proper sintering of the TiO2 film. Just see our publication, link is given below. TiO2 sol is stable over a period exceeding an year (its not a tough job to do so). Just follow the simple steps given in the experimental section, Use cold water (10 degree) helps to form better sol with small particle sizes. Addition of TTIP should be very slow. Rest of the details for the film formation you can see in the publication. 

'https://www.researchgate.net/publication/315331616_TiO_2_colloid-based_compact_layers_for_hybrid_lead_halide_perovskite_solar_cells'

DOI: https://doi.org/10.1016/j.apmt.2017.01.009

All the best

thank you so much

@Ainan

Go through this paper. You may find your answer.

Good Luck.

Thanks a lot. It was very helpful.

Ｄｉｓｐｅｒｓｉｏｎ　ａｎｄ　Ｎｏｎｌｉｎｅａｒ

Silicon is single or poly crystalline and so the Raman features are quite sharp and homogeneous. Small shifts due to strain are therefore relatively easy to measure and monitor. I imagine, in organic films, the bands are broader and more inhomogreneous, so it may be more difficult to monitor the effects of strain.

Dear Zeinab,

1 cm² sample is not really small. I guess, your sample must be a thin film when you mentioned the area.

Use a thick and large size glass (at least 2 mm thick * 1-inch area). X-rays cannot penetrate up to that depth. In this situation, there should not be any peak due to the amorphous nature of glass. 

Also, use a 2 mm or 5 mm slit for passing X-rays and place your sample exactly at the center of the holder. 

Hope it helps.

As was pointed out before, it depends on which WF you're interested in. If you mean WF as measured from the top surface (e.g. the famous photoelectric effect experiment) then this would indeed be the WF of gold.

Since you refer to your film as a top contact, I assume that you refer to a device underneath it (e.g. this is a gate electrode, or a contact). In that case you'd be interested in the WF as "seen" by the substrate. This is often referred to as an Effective WF (EWF), especially in the context of Schottky contacts and MOS gates.

If this is indeed the case, the EWF is determined by the bottom few monolayers of the metal (i.e. a much thinner layer than your 3nm of Cr), meaning that you expect to get the EWF of Cr.

HOWEVER, this is not necessarily the case, and you need to consider several other possibilities:

Dear Jose,

Layer L is a typo error.

My brief process floe is like this,

1. Silicon wafer 100 orientation

2. SiO2 development on the device layer

3. TMAH etching from back side

4. Then development of Polysilicon on top os SiO2 using CVD

so my question is once I perform TMAH, can I take my device to CVD chamber, is that allowed. Please tell me if their any other alternate way to deposit Polysilicon after TMAH process. (provided DRIE/RIE is not an option as those machines are not available)

Hi Jaspreet,

More info on your TFT structure would be helpful. The following is just general comments.

- Did you check the thickness of SiO₂? Turn-on voltage might be too high if it is very thick.

- Was ODTS treatment done after the evaporation of Au? If it stays on Au surface, it could make the charge injection more difficult.

- ODTS treatment sometimes makes the surface too hydorphobic to spin-coat the solution on it. Did you check the polymer actually remains on the surface?

I would suggest to first try BGTC structure without ODTS treatment. BGTC has less trouble with the charge injection and P3HT would work even without ODTS (the apparent mobility would be lower, though).

Thank you for your answer and I really appreciate the info provided. What exactly I was looking is 'to find the phonon assisted recombination experimentally'. is there a way? anybody has ever done experiments related to that?

Please check with this:

Regards,

Amin

Dear Dr. Zekry,

As I have found red shifting in SZO thin films, but its not due to doping level increment. On that result, should I go with the application of red shifting or be stick with grain boundary deficiencies? Which one should work better? It will be great if you help me with valuable suggestions. 

Dear Abhijit Roy

As you know, the Raman spectroscopy of metals usually accompany by low intensities. When you use Ag nanoparticles deposited on Si non-epitaxially, it's usual that your peaks have low intensities because you measure dispersions in Raman spectroscopy. But crystals can make higher intensities in some special cases and also it may cause some shifts because of the size of your particles. I must see your Raman spectra after depositing epitaxial layer and the SERS spectra of Rodamine (R6G) to explain more and more.

with regards

Thanks a lot Prof. Oscar. Sure, I will have a look at this book. 

you may try the deposition of multilayers by dip-coating method