Thin Films and Nanotechnology

Thin Films and Nanotechnology

  • Karina Mireles added an answer:
    Can someone give advice on surface functionalization of TiO2 nanoparticles using silane solution ?

    Does anyone can describe the brief experimental procedure for surface functionalization of TiO2 nanoparticles using silane (3-aminopropyltriethoxysilane) solution ?

    Karina Mireles · Montreal Polytechnic

    Hi Hyuksy!!!
    I have experience in the surface characterization of magnetic nanoparticles fuctionalized with silanes as APTES, TPED, TEPSA etc. And I can tell the you that: to attach silane chains they have to be catalyzed by a tertiary amine. Why? Because the deposition will be more uniform in the surface. I did several XPS analysis and commonly when the reaccion was not catalized by a tertiaty amine the coating is thin and the time of reaction have to be increased because the deposition is slowly.
    The proposition of John looks fine and I hope be useful for you this information. Good luck with the functionalization!!

  • Vineet Kumar added an answer:
    How can one get the lyotropic LC phase of Graphene Oxide? What are the critical steps one should take care of during synthesis of GO?

    I have tried the reported steps of GO synthesis from different papers where people has shown the nematic phase of GO in aqueous medium, but I am not able to get it.

    I want to know what are the critical steps in the synthesis of GO which can show LC phase. Also what is the typical dimension for the exfoliated GO sheets which can show LC phase easily? How much time does it usually take to show LC phase after suspension in water and at what concentration?

    I have gone through so many papers, so please provide some explanation alongside references.

    Vineet Kumar · The National Institute of Science Education and Research

    Thank You Sir, for all your suggestions and references. I will defenitely contact you whenever i feel the trouble.

  • Dustin Janes added an answer:
    I want to spin-coat thin PDMS films dissolved in Toluen on gold and silicon crystals, but the films are very non-uniform, any suggestions?
    I use Sylgard 184 pdms and mixed it with the curing agent then immediatelly dissolved it in Toluen (concentrations lower then 1%) and spin-coat it on gold and silicon substrates.

    I have obtained the highest quality films of PDMS by spin coating from n-octane solution. Sylgard has filler particles which make very thin films less than optimal quality. If the films spin coated from octane are still not good enough, try one of the ambient cure solutions sold by Gelest in methyl-THF solution and dilute them with n-octane.

  • Kishan Fadadu added an answer:
    How do I save a portion of FTO for cathode connection?

    I want to protect a part of FTO for the cathode connection. I usually use spin coater to deposit thin films. To save some region of FTO for the connection , I used Teflon tape but it did not work for me. At high rpm solution which I put on FTO passed through the Teflon tape to the region which I wanted to save. Kindly suggest me any other alternative for this which I can use without damaging the FTO?

    Kishan Fadadu · Sardar Patel University

    Just use scotch tape to cover your area and remove it after coating. Covered area can be cleaned using acetone. !!!!

  • Giuseppe Curro added an answer:
    What is the advantage of PLD in comparison to other methods of deposition?

    Thanks in advance for your replies.

    Giuseppe Curro · STMicroelectronics

    I agree with amritlal in all, but not for scalability to volume production, at least when compared to other industrial techniques effectively used for small and large area coating. More importantly, the usual deposition geometry is a very tricky factor, and mainly affects reproducibility and nintrinsic parameters of the same coating like thickness uniformity. I think that such a method may play a competitive role in the case of thin or very thin films on very small area parts (an example may be impantable or injectable bio-sensor substrates with area in the range os thousends os quare micrometers).

  • Xiaoyan Qiu added an answer:
    How does ambient affect the orientation of epitaxial Pt film?

    We have deposited epitaxial  Pt films on same  substrates under same conditions except for ambient. It is found that the epitaxy direction of Pt film is sensitive ambient-dependence. That means, it is (100)-orientation epitaxy when deposited in oxygen ambient, will change to (111)-orientation epitaxy only changing to nitrogen ambient while keep the same other deposition parameters ( temperature, pressure,working power etc.) We want to know how does ambient affect the orientation of epitaxial Pt film. 

    Xiaoyan Qiu · Southwest University in Chongqing

    Thanks for György Radnóczi  and  Chonglin Chen's answers.  

    I have thought about   the difference on surface energy and  the impurity in Pt targets ( Sulfur), but ignore the possible different transmission for oxygen on 100 compared with111 face.  

  • Revathi Rajan added an answer:
    Is there a chemical method to coat silver and gold nanoparticles on glass slides which do not get washed away?
    I have tried using APES already but there is some problem in achieving the result. Is there any other method?
    how do I know that APES got coated properly on the slide?
    Revathi Rajan · University of Science Malaysia Kubang Kerian

    found this jurnal. Perhaps we can both benefit from the finding. 

  • Daniele Maria Trucchi added an answer:
    Can anyone suggest the most accurate method to calculate "electronic band gap" of thin films?

    I am calculating the optical band gap from UV-Vis absorption data of my thin films. But I want to calculate "electronic band gap" of my thin films

    Daniele Maria Trucchi · National Research Council

    Use photoluminescence and/or photoconductivity spectra at variable monochromatic wavelengths.

    In the first method, you use a overbandgap radiation (e.g. laser) on your semiconductor and measure the spectral distribution of the photoluminescence signal caused by the radiative recombination.

    In the second you need to fabricate electric contacts (planar or sandwich configuration, it depends on your geometry). You make a monochromatic radiation impinge on the semiconducture and measure the photogenerated current (pre-amplified + lock-in amplifier are suggested for high-sensitivity measurements). You make the radiation wavelength vary and build a photocurrent spectrum. Divide the photocurrent by the lamp power spectrum and obtain responsivity. Multiply it by photon energy and you obtain quantum efficiency. From quantum efficiency it is simple to derive the electronic bandgap. Limitation of this method is if the film is very thin, since the generated signal depends on the active interaction volume.

    Where to find additional informations: the techniques are widely discussed in university books and several scientific papers.

  • Paige Hall added an answer:
    Can anybody help me in finding a commercial polymer that may be covered by gold nanoparticles?
    We produce aqueous colloidal gold nano-particles of distinct size and shapes. We're interested in immobilizing them over a polymeric substrate.
    Paige Hall · Pacific University Oregon

    You can easily immobilize gold NPs on any polymer you want using electrostatic assembly. If your gold is negatively charged (citrate capped or similar), simply choose a cationic polymer.

  • Francesco Lufrano added an answer:
    In asymmetric supercapacitors, metal oxides are used as which type of electrode? And what about reduced graphene oxide?

    (Cathode and Positive) or (Cathode and Negative) or (Anode and Positive) or (Anode and Negative)?

    Francesco Lufrano · National Research Council

    For Metal oxides as MnOx, they have to be used as the positive electrode and not as negative because are unstable in that side. Therefore, the negative should be done with a carbon material, which can work as both the negative and positive electrode.

  • Pira Mahes added an answer:
    How to functionalize CNT using concentrated sulfuric acid and nitric acid?
    Currently I'm using concentrated H2SO4:HNO3=3:1 to treat the CNT. Refluxing it for 5h, at the end of my work I found that my CNT had reduced greatly in weight. From my reading I found out that the CNT might had been degraded due to the concentrated acids. What is the best way to deal with this if I were to use sulphuric and nitric acid?

    The second problem I faced was to separate the mixture of acids and cnt as the filters being chipped by the acid, the alternative way I used to separate by centrifuging the mixture. Any suggestions for that?

    Thank you
    Pira Mahes · Queen Mary, University of London

    Hi, guys is it important to use a polycarbonate membrane. Is it okay to use a regular membrane?

    Thank you

  • Kunpeng Jia asked a question:
    What is the physical mechanism behind graphene/metal contact resistance exhibiting clear gate dependence?

    And having the maximum value at Dirac point.

  • Pira Mahes added an answer:
    What is the best way to clean ITO coated glass substrate?
    For doing electron beam lithography, I am planning to use ITO coated glass substrate. I sonicate it with acetone and then rinse it with IPA and DI water. But the SEM shows that the surface is still dirty and not uniform. So my photoresist coating is also not uniform. It would be great if anyone could suggest how to clean it to make a uniform and clean ITO coated glass substrate.
    Pira Mahes · Queen Mary, University of London

    Hi guys,

    I've been trying to drop cast carbon nanotube (dissolved in water) on ITO. I'm struggling to find the best cleaning conditions to clean the cast. Also does anyone have an idea of how long I should cast the surface for?

    Thank you

  • N.E. Powell added an answer:
    Is there any formula to calculate the resistance and resistivity of a thin film by two probe method?

    I had prepared CZTS, I made electrical characterization of the film by two probe method have drawn I Vs V (I-V) plot. Now I wish to calculate the resistance and resistivity of the film. Is there any formula to calculate Resistance and resistivity of the film from the I-V graph (From two probe method), if it is so I kindly request you to suggest the formula. some people says to it is possible measure sheet resistance from the I-V graph (From two probe method), so please kindly say its formula. Thanks.

    N.E. Powell · Dow Corning Corporation

    Just some minor points: resistance terms not related to sheet resistance but present in your measurement will come from your probes and the contact resistance between the probes and your sample.  Contact resistance can be accounted for with a transmission line method (however this can be tricky without advanced equipment for low sheet resistance materials due to fit variability, i.e. low slope).

  • Richard C Krutenat added an answer:
    Can Aluminium Isoproxide be used in the process described below?

    Generally Alkoxides are better precursors

    Richard C Krutenat · Massachusetts Institute of Technology

    Alkoxides will never make pure aluminum films because the oxygen atoms will be tightly bound to the aluminum on reduction. For aluminum oxide deposits, it may be more useful.

  • Dr A. Kumar added an answer:
    How the thickness and height of thin film resistor being used in a microwave circuit be calculated?

    The black lines in the image below are the thin film resistor used as to attenuate microwave signal. I know the resistances R1 and R2 for this T-attenuator but how should I calculate this thickness. Resistivity is 20 ohms/Sq. and material used in SiCr

    Dr A. Kumar · Harcourt Butler Technological Institute

    As resistance per unit area and resistance both are known, you can calculate area of cross section. Area of cross section is thickness multiplied by the width of the film as you are using planar geometry. If width can be measured, thickness can be calculated.

  • Vasanthan Devaraj added an answer:
    What will be the conditions for achieving better rms roughness for Ge 10 nm deposition in room temperature via RF magnetron sputtering?

    In my current sputtering machine target- sample distance is fixed and not movable. I use 50 sccm Ar gas flow and tried between 20 - 50 mtorr working pressure. The base pressure was 3 x 10-7 torr. But I couldn't find smaller rms conditions below 1 nm. It is always above 2 nm? I would like to have Ge film (10 nm) with rms roughness below 1 nm.

    Vasanthan Devaraj · Chungnam National University

    I  m currently working at 50W RF power. Probably will check with Ar working pressure below 20 mtorr or above 50 mtorr. Thanks for your suggestions 

  • Fernando Vallejos-Burgos added an answer:
    How can I increase the -COOH group on Graphene oxide ?

    I need to increase COOH group for better attachement on graphene oxide...

    Fernando Vallejos-Burgos · Shinshu University

    You can use some knowledge from the vastly explored field of activated carbons, I would go first for oxidation in liquid phase. See, for example, the classical paper by Figueiredo below.

  • Jarmo Maula added an answer:
    How do you determine the optical constants of transparent thin films from transmittance data, showing no fringes?

    Is it also possible to determine the film thickness using the same transmittance data?

    Jarmo Maula · Beneq Oy

    Dear Amalia,

    You can get the answer by using optical fitting programs. Good program will give you thickness, dispersion (both n &k).

    In addition to transmittance spectrum, you need transmittance spectrum from the clean uncoated substrate.

    Look for institutes making optical work, this is task is so simple routine, that I suppose you should get help easily.

    If you want to try alone, some of the programs listed below will do the job.  I have answered the list below to another topics, but it fits in here too.

    Free software:

    So there is even some need to make choices :) depending on the wavelength range etc..

    For the sake of the topic below commercial ones (not in any particular order):

  • Gergo Vassilev added an answer:
    Is it right to use macro-hardness tests for evaluating hardness of composites with micro and nano size reinforcements?

    The composite is an Al-based MMC.

    If particles are much smaller than the penetration volume, the result should be almost  the same. If you have significant deviation from the average value, than the difference micro-macro should also be significant. If the particles are ordered, test different orientations of the sample to estimate the influence.

  • Adam Hughes added an answer:
    Is there any software to calculate the thickness and the refraction index of a thin film from transmission data?

    I have the transmission measurement of ZnO thin film, I'm looking for a software or equation to get the thickness and the refraction index.

    Adam Hughes · George Washington University

    Hey guys, I'm sorry.  I mixed up this question with another and I'm trying to help you compute transmission given that you know d and n of the material.  You want to estimate d and n, given T.  SORRY!

    In this case, you want to use the Envelope Method (as far as I know), but I can't help with the computation unfortunately.

  • Md. Aliullah Sujan added an answer:
    What is the relation between evanescent field and v parameter for gas sensors?

    I have come to learn that at incident angle slightly higher than critical angle, the higher the wavelength, the deeper the penetration depth i.e more fractional power in evanescent field which tends to higher sensitivity. But when v is less than 2.405, it becomes single mode. so, is it necessary for evanescent field gas sensor to be multi mode always? or having single mode (v<2.405) won't be a problem? please help. 

    Md. Aliullah Sujan · Rajshahi University of Engineering & Technology

    Thank you for your help.

  • How the side lobes or harmonics or ripples formation can be Exhaustively been removed in the thin film filters by maintaining overall uniformity?

    generation of ripples or harmonics in the interface of the coating.

    Vemuri Sri ranga sai praveen kumar · Central Scientific Instruments Organization

    yes sir, the sidelobes or ripples can be reduced by using graded index rugate coatings. but for fabrication of these types of filters its a challenging task. in this filter fabrication what and all necessary precautions should we need to take.

    please explain it clearly sir.

  • Mohammad Reza Alizadeh added an answer:
    Can anyone help me to find out how I would be able to shift the Fluorescence emission band?

    I do have a material that is fluorescent in short wavelength. When I have added this into the epoxy, since epoxy has a UV absorbing in a larger wavelength, it will absorb the fluorescent response. So, I am thinking to shift it somehow to a higher wavelength in order to get the fluorescent response. But don’t know how. Any information would be greatly appreciated.

    Mohammad Reza Alizadeh · Tabriz University of Medical Sciences

     Hi dear

    If your material is in nano scale, for shifting its emission you can growth your nanoparticle and check it for shifting of emission. We experienced that quantum dots fluorescence emission can be shifted if their size be increased.

  • Abbas Rahdar added an answer:
    Why the hardness may start to decrease when the grain size is below 10 nm in Nano crystalline film ?

    Why the hardness may start  to decrease when the grain size is below 10 nm in Nano crystalline film ?

    Abbas Rahdar · Zabol University

    Dear Prof.Tarik ,


    All the best,


  • Roman Shishkin added an answer:
    Is it possible to produce AlN by hydrothermal synthesis process? Apart from carbothermal reduction and nitridition method is there any other method?
    It is for AlN thin film production.
    Roman Shishkin · Ural Federal University


    You can read our article in 2 parts attached below with review of aluminum nitride synthesis methods, their advantages and disadvantages.

  • Sudhakar Reddy Bongu added an answer:
    Why is graphene related material showing exponential decay type absorption from shorter to longer wavelength?


    Can any one comment on this?

    Actually graphene based materials (graphene, graphene oxide, reduced graphene oxide) shows an exponential decay type absorption from shorter to longer wavelength. Is it related to the Boltzmann distribution of particles or any other mechanism. As we know that graphene is a nearly zero band gap material. It can absorb even a small energy (longer wavelength) of photons . While going to the towards shorter wavelength (high energy) absorption increase rapidly looks like exponential increment.

    Sudhakar Reddy Bongu · Indian Institute of Technology Madras

    Sure....sir, I will come to soon with some feed back...


  • Zaka Ullah added an answer:
    Any advice on graphene growth on Nickel and transferring onto glass substrate?


    I'm working on graphene growth on nickel thin film by CVD method. We use thin nickel film (600 nm) on SiO2/Si as a substrate. After growth,  we are trying to transfer it onto glass substrate for OLED application. I used 1 M FeCl3 solution for etching nickel but after etching, polymer/graphene doesn't leave from SiO2/Si surface porperly. I also tried to 7:1 BOE solution to etching SiO2 but, thin nickel film cracked and I didn't achive transfer it. Does any  different transferring method from these methods?

    Zaka Ullah · Chinese Academy of Sciences

    One more thing. If you're going to use the old method (i.e. via FeCl3), then you should use more concentrated FeCl3, instead of increasing its magnitude (for some reasonable scale of up to 5 cm x 5 cm). Although, 1 M concentrated solution is enough for small samples like 1 cm x 1 cm or 2 cm x 2 cm but you can use more concentrated if films are not being separated. If solution is such enough that the Nickel with Graphene/PMMA is completely dipped in the solution, then no need to further increase the quantity of solution.

  • Ranjana Varma added an answer:
    What will be instrumental broadening in a Rigaku Ultima-IV system (Cu Kα radiation)?

    I want to know that what will be the instrumental broadening in A Rigabku Ulitama-IV system (Cu Kα radiation). Literature suggest that we should take LaB6 standard for calculating the same. As we don't have standards, what is the other alternative? Has anyone has found the instrumental broadening in ultima IV system using 40kV & 40mA configuration.

    Ranjana Varma · University of Mumbai

    Thanks Shivani & Cabllero,

    Sivani, can u pls  define the parameters U, V W...

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