- Cameron A Moore asked a question:NewAny advice on the vapor pressure behavior of Rose Bengal: outgassing or volatilization behavior?
I am using Rose Bengal as a photosensitizer coated on a substrate. To cure this layer we are considering use of a vacuum oven to remove the solvents but are concerned about outgassing of the RB. Does anyone have knowledge of the vapor pressure properties of RB (i.e., pressure developed versus temperature)?Following
- Bhupinder Singh added an answer:2Any advice about remove (rid from) surface roughness on PDMS after Trichloro(1H,1H,2H,2H-perfluorooctyl)silane silianisation?
I am doing the PDMS surface silanization using Trichloro(1H,1H,2H,2H-perfluorooctyl)silane with vacuum deposition method. In my experiment, I am putting my sample (with few drops of Silane) in vacuum for overnight (12-14 hr).
But after the silanization, I am getting some surface roughness on my PDMS sample.
Could you please help me in this regard. How to get rid from this.?
Are you performing Chemical Vapor Deposition (CVD) of your fluorosilane on to PDMS surface? what is the temperature of your vacuum chamber? Do you really need 12-14 hours to do your deposition? How did you measure the roughness of your sample? what is the roughness?
If you are performing CVD by keeping your vacuum chamber at high temperatures, my guess is that you are killing it with time and the roughness that you are observing is due to physical adsorption/condensation of silane on to your substrate.
Please feel free to share more details and any follow up questions you might have!
- Reed Schmell added an answer:4Why is etch Ni rate so slow?
I have 20nm Nickel evaporated on SiO2 layer.
TFB was used for wet etch. According to its data sheet, a 25 A etch rate should be achieved, which means an etch time of 40 second.
However, after 10 mins my shiny Nickel layer is still there.
I also tried concentrated Nitric acid. After around ten minutes, it still doesn't work.
What is wrong?
Possible oxide layer on your NI. Ni needs to be passivated so oxide layer does not form.Following
- Leonid Mochalov added an answer:2Is anyone familiar with an absorption trap for Trichloro(1H,1H,2H,2H-perfluorooctyl)silane for DPMS-PDMS debonding?
I am using Trichloro(1H,1H,2H,2H-perfluorooctyl)silane for making a anti-stiction layer during PDMS-PDMS molding.
I am using Silane Vapor deposition technique (under vacuum desiccator). But during vacuum process, there may be a chance of "Silane vapor particle contamination residue to Vacuum pump".
How might I avoid this residue contamination? Should I use some intermediate absorption trap with NaOH (Not sure :( ).
We usually use the trap with two taps made of stainless steel and cooled by liquid nitrogen.Following
- Tilo Drusedau added an answer:2How can I decide Mass Flow Rate of carrier gas and monomer / precursor for PECVD process to be done at 0.1 mbar operating pressure ?
I want to deposit SiOx coating from HMDSO/ Oxygen mixture by PECVD method. My operating pressure is 0.1 mbar and base vacuum is 10 -5 mbar. Vacuum system dimensions are 60 cm dia x 30 cm height cylindrical system. System is evacuated by 1000 liters / sec diffusion pump and 250 liters / minute rotary pump combination. Want to learn the basis of calculation of mass flow rate in this process condition.
Pressure equals massflow devided by pumping speed: p=F/S. So, if your rotary pump has roughly S = 4 l/s you need a flow of 40 Pa l/s which are a little more than 20 sccm. You have also to consider that S is gas-dependent and also influenced by the tubes connecting your vessel to the pumps!Following
- K. Sreenivas added an answer:4I need help in scaling up the magnetron sputter system regarding its constructional features?aspects to be concerned..changes to be made??
we are planning to scale up the magnetron sputter system in our facility to coat bigger objects (at least 1 m x 1m).what are the changes to be made..in terms of maintaining vacuum...magnetron arrangements..power to be used..and all other process parameters..
Cylindrical magnetron sputtering system is the best option.
Of course you may need a large chamber to hold your 1m x 1m substrates inside the chamber itself.
he substrates can be fixed. and the Cylindrical magnetron cathod can be moved up and done. With glass plates on either side, you can achieve deposition on two different substrates in one go.
good to have a strong pumping system.
It all depnds on which coating you plan to develop, and on what kind of substrates ( is it glass).
What is the quality of the films you desire. Because based upon this you pumping system can be easily specified.
Pl. do let me know what kind of the coating you plan to develop.
Prof. K. SreenivasFollowing
- Guy Olivier added an answer:2How can I reproducibly achieve high work- function (~6.4 eV) MoOx thin films by vacuum sublimation?
I am facing issues getting working fullerene (C60 or C70) solar cells with MoOx as a hole transporting layer. I am using the standard dimple tantalum boat to resistively heat the material. The layer is deposited at a rate of 0.5A/s. However, though the film does coat uniformly, the cells are not performing well (Voc:0.5 V, FF:22%, Jsc~0mA). I suspect the MoOx film does not have the stoichiometry needed to yield a high work function layer required for the schottky cell I am trying to make.
Thanks very much for the very useful answer. I am very optimistic that following this advice will help solve the issues I have with the MoOx films. Thanks for the paper as well.
- Edward Patrick added an answer:3Can we put black material on something kept inside vacuum chamber so to remove the reflection of light when doing spectroscopy?I need to keep an aluminium stand inside the vacuum chamber running with a TMP for doing Laser Induced Breakdown Spectroscopy. When I was taking a spectrum a lot of reflection was coming from the Al stand. Is there any black material that is available commercially to coat the stand so that the reflection will be stopped?
There is also Aquadag...
...and black copper oxide. Aluminum can also be hard coated in various ways, with black being one of the coatings. As a caveat, all of these approaches increase the surface area (i.e., surface outgassing) of the material.Following
- Richard C Krutenat added an answer:2What should be the vacuum level maintained for vacuum casting of Titanium?
Please specify the range in mm of Hg or mm of water column
Pressure should be less than 1 Millitorr. The quality of the vacuum is important. An online mass spec is useful to measure water partial pressure, indicating possible water leaks. And prior outgassing is important too. In a system containing outgassing material, porous ceramics for example should be considered as sources of outgassing. Remember, molten titanium itself is an excellent getter pump.Following
- Christian Hannemann added an answer:3Can anyone tell me the details about vacuum casting for Titanium?
Melting of metal using induction furnace,
The ALD furnaces described above are one of the very view ways to melt Titanium in a pure state. As these devices are quite expensive we use induction heating for the melting of Titanium in high vacuum inertial atmosphere in an graphite crucible that is placed inside a ceramic crucible. That way we get some contamination by carbides but it's still kind of all right.Following
- Per Arvid Löthman added an answer:4Any suggestion for rapid cooling of coated wire after passing through molten alloy?
I am working on coating of different alloys on metallic wire in vacuum condition. I want rapid cooling of coating with the help of helium /argon gas or electrical driven cooling device . Is anyone of you know about electrical device or any suggestion which can do rapid cooling of the coated wire after passing through molten alloy? I used Helium/ argon gas for cooling purpose but i did not complete amorphous nature of coating.
Quenching is the key word! Construct a simple double walled elongated cylinder and fill it with liq. nitrogen. Let the wire be drawn through the inner opening of the cylinder. Hope it helps :)
- Kiril A Pandelisev added an answer:4How can one deposit ZnO powder in Vacuum coating unit?
I want to coat ZnO powder in vacuum coating unit. So please provide me with the necessary parameter and minimum Amps required for coating ZnO films. the ZnO powder temperature is 1975 degree
Have you tried e-beam evaporation? This will be the first approach for me.Following
- Sibasish Dutta added an answer:3Is it possible to observe Surface Plasmon Resonance due to thin silver film produced by Tollen's reagent ?
Tollens reagent test produces a thin film of silver. Can we control the thickness of this film sufficiently less(50-80 nm) to produce surface plasmons rather than depending on bulky vacuum coating unit?
- Prashant Thankey added an answer:14Which one is better for a UHV (ultra high vacuum) leak sealant - Vacseal or Epoxy glue?We have an UHV chamber with base pressure 1xE(-10) mbar. There is a manipulator inside the chamber which contains one SS tube used for liquid nitrogen flow to cool down the sample. Recently we got a leak on that tube, which increases the base pressure up to 1xE(-7)mbar. We have to seal the leak. We are debating whether we should use vacseal or silver Epoxy glue. We know vacseal can degas in UHV chamber for a long time if not cured properly (we have experience using it before). On the other hand, we do not know whether silver epoxy is suitable for this purpose or not, because it is on the liquid nitrogen line. Can anybody suggest a solution?
The sealants you mentioned can be used for temporary leak sealing purposes. As a permanent solution, I suggest what Vittorio suggested.Following
- Sibasish Dutta added an answer:11What are the chemical methods available for the deposition of silver film of nanometer thickness on glass prism to observe surface plasmon resonance?
To deposit silver or gold film of nanometer thickness, we need an expensive Vacuum coating machine. Since such expensive machines cannot be afforded everywhere, how can one deposit silver or gold film of nanometer thickness on a glass prism or glass slides? I mean to say that is there any chemical route available?
Thank you for your suggestionFollowing
- P. Y. Nabhiraj added an answer:10Does anyone have experience with materials to avoid in vacuum systems?
I would like to know what kind of materials should be avoided in sputtering processes. I deposit evacuating the chamber around 10^-6/-5 mbar and at working pressures around 1x10^-3 mbar. By the moment I am considering using new materials to deposit different alloys, and because of that I would like to know what materials could generate outgassing around those values. The vacuum chamber is not intentionally heated and therefore the temperatures used are around 60 ºC.
You are planning to use those metals that have bad vapour pressures. So there is no way to avoid these materials since you want their alloys. So you need larger pumping system to maintain good vacuum. If you are wanting to study the alloys of certain metals that you have mentioned you need to use them!!!!!..
Only way is to optimize the system. Use small targets and large pumping system.Following
- Mohammad Kooti added an answer:19Why is oxide incorporated when we do pulsed dc reactive sputtering of Aluminium nitride?We are trying to deposit Aluminium nitride using pulsed dc reactive magnetron sputtering with pure Aluminium target. However, when we perform EDS analysis of the sample, we are getting 15-20% atomic weight of oxygen in addition to aluminium and nitrogen. Can this be aluminium oxide? Why do we get high percentage of oxygen content even though we are only supplying Argon and nitrogen to the chamber? What can be done to reduce the oxygen content in the sample?
In contrast, when we try to deposit Aluminium oxide using pulsed dc reactive magnetron sputtering by supplying oxygen and argon, we do not get any nitrogen content in the sample, as seen by EDS analysis. Does Aluminium have more affinity for oxygen instead of nitrogen? Why is this so?
Try passing the N2:Ar mixture through an appropriate oxygen scavenger to get rid of the probable oxygen impurity.Following
- Silvan Pretl added an answer:2What are the best practices for thermal evaporation of organic conductive materials?Would anybody share any suggestions and recommendations regarding the thermal evaporation of temperature sensitive organic conductive compounds, e.g. pentacene, for experimental preparation of functional electronic structures (diodes, OFETs etc.)?
I think this shared knowledge could help a lot of people in the beginnings of their experimentation with this class of insoluble functional organic materials.
Please share your valuable gained experiences with:
- thermal evaporation process of organic conductivities deposition,
- particular heating elements, evaporation sources,
- issues related to film quality,
- suitable substrates and their preparation, cleaning.Mr. Abbas: Thank you for your valuable input. I will try to look for some book to get to the heart of this matter.Following
- Kobus Venter added an answer:8E-beam evaporation of zirconium oxide for optical coating?Can anyone offer any advice on e-beam evaporation of zirconium oxide? Anecdotally, I’ve been told that it’s very difficult to melt the material ‘evenly’.
The material I have is supplied in tablet form, ~1cm diameter x 5mm thickness. I was able to melt the material to a reasonable degree, but this required quite a high beam current and small beam diameter.
Additionally, I had some problems with the material spattering during the melt process.
I’ve heard that there may be doped ZrO2 available, possibly containing a small fraction of magnesium oxide to improve the melting characteristics, but haven’t seen this myself yet.ZrO2 does not melt properly and predominantly sublimes causing an uneven material surface with craters etc. ZrO on the other hand, does melt well into a pool of molten material that evaporates stable. The material is usually coated directly from the water cooled copper crucible or from a Mo liner. Index and intrinsic stress can be controlled by optimizing the process parameters such as oxygen partial pressure, rate and substrate temperature. Spitting is normally not a problem given that pure material and proper control parameters are used. Granules are usually better to use as starting material, but if only tablets are available, it can be crushed into smaller pieces. The material is melted in small amounts, layer by layer until the crucible or liner is full. Durable layers can be manufactured at low substrate temperature. The material is however in-homogeneous and of limited value in multilayer AR coatings without using an IAD process to control this aspect.Following
- Artoni Kevin Ang added an answer:12How can you quantify cracks or other defects on the surface of a metal thin film?Right now I only have microscope images of my films, and I want to quantify how many cracks and buckles develop on my film.Thanks for the help everyone.
Santiago Royo, yes, thats what I'm trying to do now, but I'm currently using Matlab. I might try switching to ImageJ.Following