Plasma Technology - Science topic

We developed process with Oxygen plasma combined with forming gas and fluorine gas in a remote plasma reactor with good results.

Technology is called "HDRF" for High Density Radical Flux.

It's pure chemical etch based on O*, F* and H*.

John Ireland Sure! I don't update it very often, but we can connect there if you want.

The production of core-shell nanomaterials presents several technological challenges, some of which include:

My experience with core-shell nanomaterials has primarily been in the area of nanocatalysis, where core-shell nanoparticles are used as catalysts in a variety of chemical reactions. In my experience, controlling the size, shape, and composition of the core and shell is critical for achieving high catalytic activity and selectivity. Additionally, ensuring the stability and durability of the nanoparticles is important for maintaining their performance over multiple catalytic cycles.

In terms of economic viability, finding ways to scale up the production of core-shell nanoparticles while maintaining their quality and performance is a major challenge. This often requires the development of new synthesis methods that are cost-effective and scalable, without compromising on the precision and control needed to produce high-quality core-shell nanomaterials.

Overall, the production of core-shell nanomaterials presents several technological challenges, ranging from controlling the morphology and achieving synthesis precision, to ensuring stability and durability and addressing economic viability. Overcoming these challenges will be critical for the widespread adoption and application of core-shell nanomaterials in various fields, including catalysis, energy storage, and biomedicine.

Crisis and emergency alert http://youtu.be/Ng1-KJueYiU Time for the people to stand together to bypass, help us build the bypass. We have the foundation's know

Hola Javier,

Very intereasting observation. From our research on Xe excimer discharge lamps using a quartz or borosilicate glass vessel, we observe sometimes green luminescence, which we have attributed to the loss of Oxygen which goes hand in hand with the breakage of Si-O-Si bonds and thus subsequent Si2+ formation. These low valent Silica species cause defects in the glass structure and the vessel might be destroyed upon long term operation. Possible degraded glass can show luminescence due to either an [Ne]s2-[Ne]sp transition of Si2+ or other colour centers (low valent boron species).

You may find more information on the quartz /glass damage in the following paper, while I assume that pyrex (borosilicate glass) behave similar:

Green luminescence in silica glass: A possible indicator of subsurface fracture

Appl. Phys. Lett. 100, 114103 (2012); https://doi.org/10.1063/1.3693393

The plasma discharge devices have specific I-V curve. It is in form of an S-Curve.

There are two types of models: the physical model and the behavioral model.

The simplest form of the behavioral model is the piece wise linear models. The I-V can be composed of the three linear pieces. The off branch, the on branch and the negative resistance part connecting the two pieces.

It has also a small signal linear model with R-C-L in parallel.

To operate the device into certain point it is advisable to use a consatnt current source. You can build this consatnt current source according to the measured characteristics of the tube.

It can be handled as any other electronic device.

Best wishes

Thanks for the information.

The corona plasma is not an arc, but is a plasma surrounding a conductor at a high voltage relative to its surroundings. It does not carry a current, but the electrons gain energy from the electric field surrounding the charged conductor.

The charged conductor appears to be a resistor, as seen by its power supply.

Kashif Arshad Thank you for providing me the suitable research articles that are related to my problem.

In this technology waste materials from the society are used for power generation. This is a clean energy. This process is beneficial as it helps in making environment pollution free. For detail you can go through the following reference, which will be helpful.

Yes , exactly.. but too lazy to fit this into octave or scipy.

starting pressure, deposition rate and sticking coeff. , what is the rate needed when starting at 100Pa base pressure. (chamber size, new parameter.. temperature (outgasing) next one..)

No Student without a task around?

Next step is then building the material source capable of delivering the needed rate. Of course it should run in self-sputtering mode..

also there there should be this kind of table.. which material/pressure/bias-current-density self sputtering occurs.. (Anders & Co.)

At the end one could find out if 3D plasma-sputter printing is viable or not? or one would need a kind of plasma-jet-cvd stuff. (which of course makes the equations more complex) (Bogaerts & Co)

Some are on this way.. (Lundin and friends..)

Would love to see Kousaka's MVP plasma running in self-sputtering mode.

Lukas

I think it depends on how the energy delivery to the teflon surface. How is the structure of the discharge device? I think the literature in Prof. Mohamed A. Abd Al-Halim can provide many useful information. Moreover, you can also search the other articles on the ablation controlled arc.

Best regards

A Helicon plasma can produce high hydrogen atomic flux .

you can see a review paper on this type of plasma source in the following link:

fusion source regimes within the IECF devices. are divided into five categories namely: converged core (beam-beam), embedded (beam- target), volume source (charge-exchange-neutral), beam- background reactions that occur near and inside the cathode, and wall-surface reactions (charge-exchange-target). You can found details for the beam- beam reaction rate calculations in our following publication:

Prof. R. R. Deshmukh, Physics department, Institute of Chemical Technology, Matunga, Mumbai. He is working on the cold plasma processing of food. You may see his publication in google-scholar

Ok. Thank you for your recommendation. I'll look it up. Good luck to your research anyway !

In order to check if the fiber is a bad one you can use a tungsten lamp to acquire spectra with and without the fiber and compare the results. A standard calibration lamp is the better option to do the work, but any tungsten lamp operated with a DC current power supply is worth for this purpose. A low pressure hydrogen discharge, as Dr. Andrei suggested, may also be used. With these tests you will be able to know if the problem is the fiber or the spectrometer.

The possibility of it be related with saturation can be verified just reducing the intensity of the light you are collecting.

About the Stark broadening calculation, it is possible to use it as is by fitting the peak before the calculation. But only if the peak is centered at the predicted  wavelength for the H-alpha line AND if you are sure that the peak would be symmetrical in relation to its center. Otherwise an error will be introduced in your result.

Thanks for the help. 

So the kinetic energy comes from the sheath potential and ambipolar diffusion of ions and electrons

The heating process depends on RF wave penetration depth into the plasma, which, if no magnetic field is applied, can be evaluated in planar incident wave approximation with Appleton equation, knowing the electron-neutrals&ions collision frequency and plasma frequency, which is related with electron density. The reflected power can be calculated numerically and sometimes evaluated analytically, also it can be measured. Then the efficiency can be derived from the absorbed power. Also the heated volume is related with penetration depth value. Here I don't mention the heat exchange in plasma via few mechanisms, which are significant for high energy density applications.

Look up Debye Sheath. There should be quite a bit of literature available. Basically it is caused by the accumulation of positive ions at the surface as a result of their relatively slower speed in the plasma than electrons. This charges the surface negatively and creates an ionic double layer boundary.

Dear Tomas!

Many thanks for your reply.

We are working on the durability of the corona electrodes and MD dynamics in the assymetrical surface DBD.  The discharge is always filamentary for our conditions. The technical  application- various systems utilizing the mentioned scheme- from ozone generators to aerodynamic applications.

The changes we observe for Al electodes is the deep oxidizing of the electrode edge, with the formation of tiny (0.1um) perforation of the oxide layer. By now, I have found the similar structures in the description of the electrodes erosion in negative corona, where the process is associated with dielectric film breakdown in the beginning of Trichel pulse; and also in the description of microarc processing of the Al.

The question is whether it is a studied effect in surface processing by air/oxigen DBD plasmas?It seems it should be as both method and object are widely used.

Thanks in advance for your answer.

Best regards

Ivan

As an additional thought to that of Tomáš and Gianpiero

1) Is your DMS sprayed as a liquid, or is it a gas? Before a plasma can be generated, the DMS must first change to a gas and then to the plasma state. It therefore requires far more energy to generate a plasma as you have to supply the enthalpy of vaporisation followed by ionisation. The liquid would be a pretty effective sink of electrons. Especially when you consider that the density of a liquid is 1000x greater than a gas, meaning a vast amount of energy would be required to vaporise it all! 

2) Can you move you DBD electrodes closer together? That might help you to ignite a plasma.

Well, you can only do this if you aim at a sort of bulk value for the energy density. The question is for what you need the information. I would assume e.g. that your system is arc-driven. If so, then the power density in the arc zone would be j^2/sigma where j is the current density (A/m^2) and sigma is the electrical conductivity..... But there is much more to say... likely if the purpose you are aiming at was clearer.

good question

Dear Yanli Peng,

high temperature plasmas can only be achieved when isolated from any materials. Otherwise the contact to a structure material will cause a too strong cooling of the plasma usually via impurities coming from the wall.

For the confinement 2 possibilities exist: like in the sun gravity or magnetic fields. At earth we cannot succeed with gravity but do the nect best using the inertia of a dense material while heating up (inertial confinement). The second option is a megnetic confinement of the charged particles. Due to the nature of the game the charged particles can move rather freely along the magnetic field lines while the perpendicular motion is in zero approximation inhibited by the Lorentz force. Therefore closed magnetic field lines are used to confine the plasma. Closing the field lines required a bending of the field lines.

A transport perpendicular to the field lines can happen via collisions only or by drifts in electric fields or curved magnetic fields. In any case the perpendicular transport is slow compared to the parallel one. Nevertheless, the alignment of magnetic field and vacuum vessel is not perfect and somewhere exists an outermost magnetic field line which hits the vessel wall. Particles stream with high velocity parallel to the fiel line and bombard the wall at rather high energy. The still existing perpendicular transport causes a continious filling of this field line keeping the process going.

Since this cannot be avoided it is preferable to introduce a defined contact point of plasma and wall. The limiter is a protruding wall element which can withstand high particle fluxes at rather high energies. This is supported by shallow inclination angles between wall and magnetic field to increase the area of impact therefore, reducing the incoming power density. Furthermore limiters are cooled to get rid of the energy as soon as possible. Still the incoming power density can be easily above the material limits. A limited life time due to erosion is also a concern. But even without these effects the limiter configuration has a substantial disadvantage especially when made from high Z materials: the sputtered material enters the plasma and can caus tremendous radiation losses, cooling the plasma even up to a plasma collapse.

This can be overcome by the divertor concept. Here the outermost region of the magnetic field consists of open field lines. These field lines guide the particles outside a certain plasma radius away from the confined region of closed magnetic field lines. The open field lines are connected to limiting wall structures (divertor). The  geometry is chosen in such a way that the connection length of the open field lines between the area where they are filled by the plasma to the wall structure becomes very long (~100m). This is a key feature of the divertor concept  - separating wall contact area and confined plasma - and allows the plasma to cool down.  The wall structure itself is in large fusion devices separated from the main vacuum chamber via a narrow throat. This throat allows for high neutral densities inside the divertor chamber cooling the incoming plasma further. A cold high density plasma exists in front of the divertor wall (divertor plates). The wall material can better cope with high densities than with high temperatures. This rather cold high density plasma in front of the divertor plates acts as a buffer for the material and also prevents sputtered impurities to reach the confined plasma.  This is a key feature for future fusion devices. Otherwise the impurities will cause a radiation collapse of the confined plasma. The inclination angle between magnetic field lines and divertor plates is also kept small to allow for a wide power spreading.

Hope this explanation helps.

Best regards,

Werner Müller

The color of a plasma is determined by the photons, which are emitted when the electrons recombine with the ions (or when excited electrons relax into a lower energy state). The photon energy and, hence, it's wavelength (which determines the color) is dependent on the energy difference between the two energy levels.

Hi Julin

I think that you can use geometrical method where ; Risetime: (10 − 90%) = Tr and Pulse duration: (50 − 50%) = Td.

The double exponential pulses happen to be very simple to treat. The effect of variation of pulse amplitude, rise time and pulse duration can easily be studied. The real pulses have a large variation in appearance, which makes it feasible to describe bands within which spectra can fall with various probability. The double exponential time function can be characterized as: f(t) = A ∗ (exp(−at) − exp(−bt))

For more informations see Wik's article : Manuel W Wik, Double Exponential Models for Comparison of Lightning, Nuclear and Electrostatic Discharge Spectra, Defence Materiel Administration,S-115, Sweden, 1985.

Good Luck,

Omar

I expect successful etching and increasing of wettability and roughness of wood surface during first stage (oxygen plasma treatment). Then you want to use fluorocarbon containing gas to eliminate wettability and increase water contact angle. Here the problem starts. It is possible but I expect problem because of atmospheric pressure reactor. Residual moisture will split to hydroxyl group and hydrogen, certain amount of hydrogen will bond to florine and fly off and it could decrease the efficiency rapidly. That's the reason, why this treatment is mostly made in vaccum systems with strong pumps as you read. Lower base pressure better. The wood could hold residual water also.

Dear Sir,

Pls find herewith attached reference article.

Ceriodaphnia dubia as a Potential Bio-Indicator for Assessing Acute Aluminum Oxide Nanoparticle Toxicity in Fresh Water Environment (Sunandan Pakrashi et al., 2013), PLOSONE. Published: September 5, 2013 http://dx.doi.org/10.1371/journal.pone.0074003

First of all, you got 15 nm of deposition, so obviously the growth works in principle (in general the deposition rate in any plasma assisted process is highly dependent on a lot of parameters and, frankly, I have to say the reproducibility is not always given as well as it should be due to the highly non-linear nature of the plasma). I guess you used exactly the same conditions that you had in your training with the specialist. If you don't achieve any growth at all (which is not the case in your experiment), you can either be well of the "sweet spot" in your plasma parameter regime or you have a substrate that has a totally different lattice constant then the film, which you want to have (or some chemical inertness, which hinders the film particles to bind on the substrate).

However, as I said, there are hundreds of publications from the solar cell community who deposited Si3N4 on Si wavers, so there is a large set of data that confirms that it can be done (a general piece of advice - be always skeptical, if someone tells you that something cannot be done without giving any good reason - sometimes, someone was not able to do something but that doesn't mean that it is impossible in general ;))

Whenever using O2 plasma to PDMS, the surface becomes hydrohilic. However this is temporarily, so you need to perform bonding directly after treatment. When the bonding is not succesful, you might consider a simple cleaning in ethanol in a sonicating bath, After drying in N2 you can expose the PDMS again to plasma for another bonding. 

You might also consider to use one a thin not-fully cured PDMS intermediate layer. This will result in a much stronger bond.

Hi Do Hyun Kim,

Very familiar problem. Noble metals do not adhere well to oxidic surfaces (SiO2, Al2O3) since they do not form an oxide bond (Ti-O-Pt) with TiO2. You normally would need an adhesion layer but since you cannot use this the only way to get (temporary) adhesion is to sputter the Pt with low pressure (large mean free path) and high power (voltage) to give the Pt neutral atoms coming from the target as much kinetic energy as possible so you will get some atom mixing at the TiO2 surface. A sputter etch of the substrate normally improves adhesion enormously but since you do not have that make sure you have very good vacuum and very low H2O and O2 levels. Surface water normally lessens the bond strength. So, heating the sample before you put it into the vacuum will help you to make the sample more waterfree. Leave the sample long enough at base pressure to degass. Make sure you have low H2O (<10-7 Torr) and low O2 (<10-9) partial pressures.

It could well be the adhesion will only be temporary, you see this a lot with Au and Pt layers without adhesion layers. Using lift-off and spraying with high velocity agressive solvents on the film will not help you in that sense. If for some reason it does not work, Try finding a system which does have sputter cleaning.

Look please my Article in Condensed Matter Physics 5(3) January 2002

Oxygen plasma is applied to PDMS to achieve OH groups at the surface and enhance the bonding between PDMS and glass. You can achieve a bonding between two glass substrates if they are thoroughly cleaned and pressed together. However this bond is caused by Vanderwaals forces and is not so strong. This bond is also called a prebond in fusion bonding. If you want to have a permanent bond, you need to additionally anneal the substrates close to the glass transition temperature for a few hours. If you are limited in using high temperatures, then you could also think of adhesive bonding. 

Hi Davood,

you can detect plasma spectra by Avantes compact spectrometers  with the spectral resolution not better than 0.8 nm (with the slit width 10 mkm and a grating with 600 grooves/mm you will be able to detect the spectra within the range 520 nm). If you will get HR4000 spectrometer from Ocean Optics (the slit width 5 /10 mkm and grating with 600 grooves/mm) you will be able to detect the spectra within the range 450 nm and the spectral resolution 0.25/0.46 nm respectively.

The better way is to buy an Andor Shamrock SR500 spectrograph  equipped with CCD detector and a switchable support for 3 different gratings. Then you can see spectra within whole broad optical range of interest with the low spectral resolution or in some specific regions with the higher spectral resolution (up to some tenth of Angstrom). Such a solution will be 5-6 times more expensive. 

Dear Nathan,

For Langmuir probe measurements in RF discharge plasma please check a book Raizer Yu P, Shneider M N, Yatsenko N A "Radio-frequency Capactive Discharges" (Boca Raton: CRC Press, 1995), Chapter 4. The question of RF discharge physics discussed in the other chapters of the book may also be helpful.

It depends on your need and the strength of the signal.

May be attched design would be useful. Also, you may check the feasibility using your FIFO system. Else look for some degita delay generator.

Good luck.

I think it is not that easy to answer this question without addtitional information - what kind of discharge do you have? - DBD, mini arc, rf, microwave

What kind of specimen do you use? - is the specimen biased, is it conductive...?

What is the distance between your source and the sample?

It is also not necessarily the hydrogen - I myself used hydrogen admixtures at atmospheric pressure (several %) and I had no sparking whatsoever.

I had the same issue with my analysis and I can name several factors which impacted my data.  

- Fluctuations in general background light: usually a dark spectrum correction can solve this problem during acquisition, or reduce your acquisition time if possible);

- Fluctuations in your excitation source power: I'm currently using a blue laser with low power and the crystal takes some time to "warm up", so I always turn the laser on at least 15 minutes before taking measurements. Even though, you are always going to have some variation in power (and consequently, the number of photons emitted/scattered are also going to vary and you Raman spectra will have different intensities). If you are working with unpolarised light, this is not a big issue.

- Normalization, baseline correction and mathematical filters: check if your signal/noise ration is constant among your measurements and try to correct the baseline from your data. You can try to normalize them based on the area below the curve; you can also apply some smoothing filter as Savitzky–Golay (first or second order, it depends on your data).

I hope these information can be useful.

Hi Deepak, Thank you for your response. I will look into this reference

For OH, this might be useful: Eur. Phys. J. D 54, 77–86 (2009), DOI: 10.1140/epjd/e2009-00174-9

Other than that, if you have to calculate something more in-depth, here are some cross sections for OH A-X band generated from H2O cracking by e- impact: J. Phys. Chem. Ref. Data, Vol. 34, No. 1, 2005

Dear Paul, thanks for the reply yes I had MHD in mind. But the idea of inserting electrodes sounds far fetched to me. The temperature of the plasma is so high anything would vapourise surely? I think there should be another way of using MHD. If the current in the plasma could be made to oscillate the resultant magnetic field would alternately grow and then shrink. If this change in magnetic field were to link with electical coils an induced EMF would result. Faraday learnt that the inductive effect only occurs as the field changes. But if we could have an unsteady field we dont need the electrodes at all! I am sure the physicists have sweated blood to stop oscillations, but maybe its just what is needed to extract power.

cheers Martin

Hi Rob

Citrate is the recommended anticoagulant for plasma to be used in coagulation tests. 

By definition, plasma has to be anticoagulated – if it isn’t, the blood clots and you end up with serum, which is deficient in clotting factors.

Regards, Rosemary

Take a look at attached article & reference thering. I think it will explain some of your questions and lead you to further references.

As far as I know, the only way to reduce background is to keep your experiment in clean air. We take great care to use only the cleanest air - either blow top grade bottled air over your experiment or install special air conditioning for the whole lab with positive pressure to avoid contamination from outside. Neither of these solutions is cheap. I hope someone else has a more affordable suggestion...

Thanks for your answer, Ron. According to your phrase tips, I found excactly what I was looking for. I tried to google it myself, but obvious not with a good phrase.

Plasma provides an unprecedented opportunity for combustion and emission control owing to its unique capability in producing active species and heat and modifying transport processes. New reaction pathways, such as atomic O production from the collisions between high energy electrons/ions and oxygen molecules, can be introduced into combustion systems to modify the fuel oxidation pathways considerably.

Plasma is a collection of neutral and charged particles which are electrically neutral on average and exhibit collective effects.

There are two types of plasmas, one is the equilibrium plasma in which the electron temperature, rotational and vibrational temperatures of particles are in equilibrium and the neutral gas temperature and electron number density are very high.

The plasma torch and spark plugs belong to this category.

The other is the non-equilibrium plasma in which the electronic, vibrational, and rotational temperatures are very different and the neutral gas temperature and electron number density are relatively low.

Plasmas such as microwave discharge, dielectric barrier discharge, gliding arc, streamer discharge, and glow discharge belong to this category.

Compared to equilibrium plasma, non-equilibrium plasma has higher electron temperature (1–100 eV) and is more kinetically active due to the rapid production of active radicals and excited species via electron impact dissociation, excitation, and subsequent energy relaxation.

Hope you can now select the plasma for your pupose.

Simple way is to use calorimetric diagnostic by calorimetric probe.

As you know you are using two electrodes and they are open. So when you apply some current (or voltage), there should be some return path. So to make the circuit complete plasma develops a displacement current through this dielectric. May be Maxwell's 4 th law will give you beter idea.

Dear Mr. Sahu, My point was not towards the type of power supply used in plasma jet rather I had queried about the discharge pattern like does it work nicely in only one particular configuration like center electrode positive or vice versa. If yes, then there is no use of AC supply of whatever frequency across the electrodes.

When you take an incompressible fluid in a pipe with samll diameter d_s and another pipe with large diameter d_l. The viscosity should be the same in both systems (same fluid). Then you will observe that in both cases turbulence sets in at about Re=2300. This requires a higher velocity at smaller radius. But you must be aware that we talk about the diameter averaged mean velocity.

Two different systems (e.g. different size) will deliver the same answer when they show the same Re number. The art is to define the adequate characteristic length of the system when the geometry is getting more complex.

The concept of the Re number is also useful to trasnlate the result not only from one pipe system to another but also to do measurements in oe fluid and to translate the result to another one. Same behaviour at same Re number.

Best wishes.

Hi

I think there could be two reasons: the first is that the Cu mask is heating up and with expasion stress it's peeling off. If this the case you might need to check have better adhesion of the mask on silicon. The seconnd reason could be that Cu mask is charging up and micro-arcing could happen. But in this case you should traces of arcing. If this is the case you can connect electrically your mask to substrate holder to evacuate the caharges during plasma etching. Of course be carrefull to short-circuit. 

Hello 

in non-thermal plasmas R-T relaxation time is shorter than V-T, therefore usually a non-thermal plasma has two different temperatures, translational and vibrational. A high rotatonal temperature has the short lifetime against the common time intervals in plasma, meanwhile  rotatonal energy levels are close together and excitation to very high energies for this channel is difficult .usually rotational temperature is equal to translational temperature  with good approximation. For more information you can see "plasma chemistry " by freedman.

Best regards 

For the conrol of early fractionation of plasma you may need some serom to use and rovoke reactions.

Dear Amiya,

Sparks in the chamber, did u mean arching? If so please check the RF generator capability. Try changing it once if you have a spare. 

Also I would recommend pls check the RF connectors also - if they turned black at the male and female connection points.  

Also pls check the chamber contamination after 2 hrs of continuous plasma - do an eds on sputtered film. May be some thing is getting sputtered from the weld joints. 

Pressure could be constant and we cannot rely on the pressure when comes to ionic impurities. 

Also if you are using any coolant for the chamber, pls check if the coolant/water is clean if not pls replace with DI water so there is no chance of ionic impurities. Continuous plasma may generate ionic impurities if the coolant is not good. Which may create arcing in the chamber and in turn the RF generator may switch the generator off. 

Hope it helps.

best regards,

vamsi

piranha will also attach nickel

Next is how much current can be carried?

I was fantazising on 3D-printing. Now there is laser melting (or arc melting) of powders. What if a beam of material is available?

any way a clean atmosphere will be needed to prevent chemistry, so we may go back to vacuum, and then it is nothing else than some kind of PVD.

Well some very high-speed local PVD still has its charm.

So mass carrying capacity of a plasma is the key. A neutralized focused ion-beam with A/mm^2.  No electron torch but metal-torch.. I believe electrostatics won't help.

just for fun..

The peak at 1577 is small and sharp peak.

I wouldn't do that if i were you. I would just develop a bit longer (60s at RT in a 1:3 MIBK;IPA, eventually with a few % MEK) and I would use in situ Ar plasma for a few tens of seconds before the evaporation. This should be enough to remove any remaining MMA without enlarging too significantly your EBL features. You can also use PMMA 50k to get less residues instead of the 495k. Anyway, I almost never do any of this and the lift off works very nicely, as long as you put an adhesion layer (a few nm of Ti, Cr, Ta) and your total thickness is below half of the bottom PMMA... If you really wish to use the RIE, pay attention to the bias; in our system we get to 100V at 10W (not sure about the pressure; could be a few tens of uBar) for max 30s. In principle you can measure the etch rate of the PMMA by using a profilometer before and after the etch by assuming, in first approximation, that you have almost no PMMA on the exposed/developed areas. I get around 10nm/min for the Ar, so I expect around 100nm/min for the O2, but this will depend of course on the parameters you will be using (power, pressure, bias). 

Graphene materials could be synthesized by Plasma,in vacuum to atmospheric pressure of Gas phase,at interface between gas/liquid ,and submerged liquids. our group have developped submerged liquid plasma[SLP] method.

Hi, 

Because u said u r beginner, two stream instability is probably the best problem to start with to study dispersion relation. It needs minimum PIC tools to solve this problem and to understand basic logics underlying PIC code. Two stream instability can be solved for an electrostatic plasma problem in minimum one dimension. Hence one don't need solving Maxwell's equations to start with PIC and just solving Poisson's equation will work. There are several free/open-source 1-D electrostatic PIC codes available on web in C++/fortran/Matlab(I started with this version) and in possibly all high level languages.  Just google search. If you having trouble, write be back and I will send you those beginners code.

You should try and contact scientists at

1) Central electronic Engineering institute, Pilani.

2) Also Hind Hivac systems in Bangalore manufacture PECVD systems, you can check from them if they have supplied anywhere and thereby contact the users.

3) You can rite to the Director of "Solid state physics labs, Timarpur, Delhi, and find out if any kind o training is possible on their PECVD systems.

4) IISc Bangalore has a center for microfabrication facility for MEMS devices, and and you check with them or look at the website, and contact the actual people working there.

5) Anna university has a CVD system, check with them in case they have  PECVD system.

I hope some of these leads will be useful to begin with.

K. Sreenivas 

the decay of ion saturation current may be due to the collisions of ions with probes causes to heated  the tip of probes which cause to increasing its resistance and then the ion current decreases.

Please check my publication which is given below:

Effect of Argon addition on plasma parameters and dust charging in hydrogen plasma, B. Kakati · S.S. Kausik · M. Bandopadhyay · B.K. Saikia · Y.C. Saxena

Journal of Applied Physics, 10/2014 116(16) 116304. 

In that publications, I have explained about the degree of dissociation of hydrogen molecules in plasma. Please check my profile which is attached in my publication list. 

Hi,

what Timothee says is true, but I also would recommend to look up the dissociation cross sections (by electron impact) of your substances as at low energies there might be an energetic threshold that increases the energy needed for dissociation. Hence the binding energy alone will only give you a minimum limit, which is very unlikely to hold.

Thank you very much Talita.

Dear Satyajit Chowdhury,

from my point of view there are 3 subjects which have to be taken into account:

a) pick up noise

b) measuring the RF plasma dynamics

c) averaging over the RF plasma dynamics

for a) One has to assure with a proper diagnostic set-up to pick-up any noise of the RF. Your probe/wire/(DAQ) system is in principle a nice RC circuit vulnerable by any EM radiation.Therefore, a set-up using shielded wires and proper grounding is vital. 

If a) is fine you will measure the RF modulated plasma. Usually you can measure slowly. With the according low pass filter the fast modulation by the RF will not occur in your signals.

But there comes (c) in. While with a sufficient high biasing for saturation current measurements the mean saturation current will correspond to your mean density the situation is more complicated for your charcteristic. As mentioned above thr RF field is able to vary your sheath. Since the characteristic is nothing else but the measurement of the sheath resistence this has to affect your characteristic. Now there is the exciting question if the mean characteristic represents the undisturbed characteristic to drive the electron temperature. Most probable not. Nevertheless often it is assumed that non-linear effects are small and the mean characteristic is a good approximation. At least you can estimate the maximum error by applying extreme fits for the analysis. In general it is a good approximation that the real temperature is in between these extrems.

 Best regards,

Werner Müller

We dry clean our reactors regularly - though they are aluminum, not stainless.  In order to keep process repeatability, it is common do run a short "pre dep" process of the film of interest with no wafer to condition the system immediately after the dry clean process - prior to running additional product wafers..

I think that use some numerical model to get some optimal parameters before performing an experiment if possible.

Comsol might help you to save time and resources.

Thermocouple will be Ok, which is uesd to detect the environmental temperature in vacuum.

Dear Ahmed,

The I-V characteristic of the gas discharge tubes is in form of an S-curve. To set an operating point which is stable you must use constant current sources rather than voltage sources. So, You have to stabilize the current in tube at the required value.

The best operation is achieved by a constant current sources. Constant current sources can be built by transistor with the collector or drain current passing through the gas discharge tube and the current is controlled by the voltage on the gate or the base current according to the transistor type.

It will work ISA.

Best wishes

Dr. Rao:  I understand that most of the same phenomena are observed in both DC and pulsed sputter magentrons.  I believe the subject abstract from Yang et al was mostly about DC plasmas.  They mention prior studies on HiPIMS merely to point out that the direction of rotation is sometimes opposite from DC magnetrons (as well as possibly other differences).  But my understanding is DC magnetron plasmas are quite complex.

Mangilal, your statement "if we put a cylindrical object in this plasma then it sits on a potential to balance the electron and ion current." implies that your cylindrical probe is floating  (floating = no net current, i.e. electron and ion current cancel or "balance").  The sheath around the probe forms to accomplish exactly this: making the electron and ion currents cancel.  

This is not the case for the sheath at the cathode of your glow discharge.  There, the sheath establishes itself  to get the right current to the cathode, i.e. for the current determined primarily by the circuit of the discharge.   

Now, the sheaths will always adjust to fulfill their functions.  When these two sheaths connect you get a complicate situation as you combine a planar geometry (cathode) with a cylindrical geometry (probe).  The situation is 3D and may be treated in 2D as one could still apply axial symmetry with the probe axis as the axis of symmetry.   As the probe's sheath touches the cathode sheath, the sheath will connect but assume a complicate shape and internal potential structure is which determined by their function of controlling currents.

Finally, I'm not so sure the statement "potential profile will follow the exponential rule from the surface to the sheath edge" is applicable at the pressure of a glow discharge.  There are collisions in the sheath at glow discharge pressures.  You cannot assume that the rules of a collisionless sheath apply.  

I suggest reading this paper, where a full description of the situation is presented: http://link.springer.com/article/10.1007%2FBF02874624

Depending on your hardmark, you could use dHF wet etch to get you higher selectivity.

The main difference of cathode and anode spots is their creation mechanism. While  anode spots mostly ignite via electrons that are excited in the sheath that surrounds the spot and make additional impact ionisations, cathode spots are more complicated. The opinion of the formation of the latter ones include sputtering on the cathode surface, evaporation processes or even micro explosions on the cathode (along with other possible reasons).

This depends on the definition of the "volume". It also depends on the condition for charged particle generation and transport, mainly pressire and power. At low pressure, the plasma always extends to the wall.