Electron beam evaporation is bombading a n object with a beam of electrons which cause high energy for doing the evaporation but thermal evaporation is to use heat for causing evaporation.

Thanks Dr. Hatem Maraqah.

Based on these two different metal evaporation principles, which technique is more suitable for forming conductive drain/source? Is thermal evaporation suitable for coating metal onto a heat-sensitive plastic substrate?

Dear Boon

Thermal evaporation is more suitable for coating metal onto a heat semsetive substrate

Both titanium and gold can be thermally evaporated. I have never tried titanium myself but have previously thermally evaporated gold onto PDMS without any problems.

Dear Jun Woom

You can not control electron beam evaporation as thermal evaporation

Dear Maraqah. Thanks for your correction. I deleted my answer.

Dear Jun Woom

You are very welcome

Electron beam Gun (EBG) evaporation will give you high energy evaporent compared to therrmal evaporation; but as Hatem Marqah pointed out it will be difficult to control thicness of the order of 5 nm. A good thermal evaporator with thicness monitor and shutter will be suitable for your purpose.

Well titanium is strong / hard metal compare to gold hence bombardment using electron is a advisable although i have never ed tried titanium using thermal evaporation but with e-beam i get the best result also at 5nm-10nm. But controlling the deposition is another factor which you need to concern too..

Vacuum thermal evaporation using resistive heating is good option for gold thin films but titanium is a reactive element also requiring little higher temperature electron beam heating for evaporation seems a better option if that can be controlled for such a thin layer as 5 nm. It also depends upon the thermal stability of the polymeric substrate being used.

More straightforward method for titanium is electron beam evaporation, nevertheless you sholl callibrate evaporation conditions. Consider using of a shutter to start and cut off layer deposition on a substrate. I recommend heating the substrate up to 10% of the melting temp.

Thermal evaporation of gold is very good controllable.

With my respect to all answers which have a lot of logic.

I would not consider substrate heating as a criterion since substrate can be controlled carefully.

The issue is the source material itself. Normally low melting point materials such as organic polymers, gold (1,064 °C) and aluminum (660.3 °C), we need electrical resistance evaporation (so called thermal).

But for metal oxides which need elevated temperatures (e.g. above 1600 C) resistance evaporation is insufficient, and e-beam is needed.

Titanium oxide needs e-beam.

Titanium melts at 1,668 °C, therefore you have better use e-beam evaporator, unless your resistance evaporator is especially efficient.

In any way I wish you best luck

Hi to all,

I think that the vacuum conditions will be critical - if a pure Ti-metal film of only 5 nm thickness is to be deposited, then any contaminations evaporating from the Ti source will be critical. Thus a shutter with adequate control is necessary to shield the plastic substrate from the evaporated contaminants (a freshly installed Ti source will always be oxidized due to the contact with the air). furthermore the deposition rate should be adjusted while the shutter is still closed!

As mentioned above, the evaporation of gold is not critical at all - so the is the limiting element here. Good luck, Dirk

Evaporation materials are intended for use in thin film production process employing physical vapor deposition (PVD), and especially thermal evaporation deposition.

An e-beam is suitable for use in ion-assisted deposition and plasma-assisted deposition.

Thank you so much for the constructive comments. I appreciate that.

In order to prepare uniform metal coating we can use Thermal evaporation method. Most of the monolayer self assembled of thiols studies we need a gold or silver substrate. So thermal evaporation method is required to prepare thinfilm of gold and sillver in high purity.

Electron beam Gun evaporation will give a high energy evaporent compared to therrmal evaporation; but it will be difficult to control thickness of the order of 5 nm. A good thermal evaporator with thickness monitor and shutter will be suitable

E-beam offers better control of the substrate temperature. Using e-beam you are heating a small point of the material being evaporated. E-beam is more desired if you are evaporating a compound. It preserves the chemical composition of the film deposited. I would not worry about the low level x-rays as much because they are absorbed by the vacuum enclosure.

Thermal evaporator uses high resistivity evaporation boats that you heat in order to melt the material being evaporated.

I suggest you evaporate both metals using e-beam. Please make sure that you have a shutter between the Au and Ti sources and the substrate. It will help you control you’re the thickness deposited and prevent substrate heating and possible degradation. In absence of thickness monitor the shutter can help you control of the layer deposited.

I used both methods for my MIS solar cells deposition. Oxide layers as thin a 1 nm and gold layers as thick as 5 nm were easily reproduced.

Depending on the properties and stability of your plastic substrate, you may consider Sputtering, PECVD or some form of electroless deposition. They could help you better preserve the substrate and offer you better substrate temperature control.

E-beam evaporation has better control on deposition rate compared to thermal

I have been used thermal evaporation to make silver film on plastic film substrate for solar purpose and worked perfectly. I believe that in your case you must to do some adjustment.

Dear. Dr. Christian Punckt,

So far, I haven't tried without Ti. To the best of my knowledge, Ti is required to improve the adhesion between gold and the polymeric layer (containing reduced graphene oxide). Is there a protocol for metal deposition (type of metal, thickness, etc.), which is needed for photocurrent measurement?

Thanks in advance.

Pl refer my JACS paper and Langmuir paper for further details.The same thermal evaporation method can be utilised for the OLED and Solar Cell application.

Thanks Dr. Pandian Kannaiyan.

Any further detail please write to me without any hesitation

Thank you so much.

I mean e beam technique is un controlable techniqu e due to the high temperature on the metal surface. If vacuum is not so important you can use termal evaporation .

EBD is also a thermal evaporation technique (PVD). Rather compare EBD with resistive evaporation (RE). Ti needs quite a high T to evaporate so you may find only e-beam is applicable. EBD has the disadvantage that sensitive electronic materials are damaged during deposition - not so for RE. Why adhesion may be better is not easy to explain. The evaporant particles are not accelerated, ie only 1% are ionized but there is no applied bias to substrate. Bottom line: if damage is a problem - use RE; otherwise use EBD. When the defects become a problem (should not) then there is a way around that, published 2013.

Hi, happy new year 2014!

e-beam evaporation is performed using a electron beam that scan the surface of the sample and then evaporate or sublimate the material just from its surface, without melting it in the crucible. In general, the crucible is cooled down using a water cooled circuit. this way the impurities located in the crucible do not diffuse in the charge and thus do not contaminate the very pure piece of material used for evaporation.

Evaporation is performed by heating a piece of material in a crucible, both the crucible and the charge inside are heated to the desired temperature, thus the crucible may contaminate the charge due to impurity diffusion from the crucible to the charge. However, some crucible such as PBN-made crucibles, are now of good purity, but if you do not want to contaminate your charge you should use each crucible to evaporate only one type of material. contamination-free crucibles are expensive and they all have a range of temperature of use. for very high temperature evaporation sometime the only choice of crucible is graphite and thus there is a significant probability to find carbon in the material you evaporate.

Best whishes,

Alain

Hi Alain, Happy New Year to you too and thanks for those helpful info.

for nobel metals it is preferable to use PLD.

if we need to say between e-beam and Thermal evaporation e-beam is preferable

Since gold is quite expensive, could I replace gold with other type of metal (Al or Ag)?

Will that affect the phocurrent measurement?

As you are evaporating on "plastic", I am guessing purity of the obtained film is not really a concern. If so, my biggest worry would be heat. If your substrate is rather close to the source (you do have a shutter, right?!) and your thermal evaporation rate of gold is 3-5A/sec, then after two minutes (60nm) with open shutter the surface of that plastic will get quite hot, possibly surface/melting and/or sagging. E-beam evaporation is somewhat better at that, as the hot source is smaller and the distance to target is usually greater.

If you are measuring the photocurrent of your "plastic", then I would use as little as possible Ti (0.5-1nm), and first try without it at all. You want efficient charge injection/collection at the metal/plastic interface, and titanium is not the best material for that. Depending on the "plastic" material, a thin layer of platinum or palladium, capped with gold/silver (you can exchange these, provided there are no sources of sulfur in the vicinity of your samples) may work. Alternatively, a low-work function metal is what you would need for charge injection (alkali, calcium, something like that ). Of course you will need a good capping layer on top of that.

Good luck!

Hi there, the two methods represent thermal evaporatiin , but the diffrence between of them in

1- we can constract the electron beam to heat the material only without any effects on the substrates

2- we can use it for metal and materials wich has high evaporation temperature asTi, Tio2, SiOx

E beam evaporation is better for metal deposition.

The main difference between e-beam evaporation and thermal evaporation is their operational temperature. Thermal evaporation is used for materials having low melting points such as Aluminum or Gold. However, for Titanium (Ti), the melting temperature is quite high (1668 degree C). Hence, the current required for thermal evaporation might be too high and therefore not advisable.

Hello! Good to read many different views on thermal and e-beam evaporation techniques. Let me, very briefly, describe different deposition techniques here.

The physical vapor deposition processes are classified into sputtering and thermal processes. Sputtering is a non-thermal process, and has been widely used for the deposition of multilayers, granular alloys, and high-moment nanoparticles, mostly because it permits almost any combination of elements to be deposited. It has been useful for depositing high melting point metals.

Thermal deposition processes are further classified into resistive heating, molecular beam epitaxy (MBE), e-beam evaporation, and pulsed laser deposition methods. The resistive heating process is the heating of source materials and evaporating them using resistive filament at pressure below 1×10-6 Torr. The operation process has already be explained by other researchers above, and therefore, I am not including here. MBE is a slow deposition process and it demands ultra-high vacuum, at or below 10-11 Torr, at all times

E-beam evaporation method used in the growth of the buffer layers and multilayers, principally similar to the MBE method and is simpler to operate. The non-equilibrium pulsed laser deposition method is an improved thermal process, and is considered good to deposit alloys and oxide films with a controlled chemical composition. Other non-equilibrium processes such as melt-spun have been used in the preparation of a long ductile ribbon whereas mechanical alloying has been used in the preparation of granular alloys, however, their use is mostly limited to bulk films. I hope this helps.

In thermal evaporation the materials to be evaporated is put on conductive (graphite or tungsten) crucibles which are intensely heated by Joule effect, until its evaporation.

In the e-beam evaporation the necessary vapours for the production of the coating are obtained by focussing an energetic electron beam on the crucible containing the material, and heating it until reaching its evaporation.

The electrons dissipate their kinetic energy in the material, the power of the e-beam has to be regulated in such a way to reach the temperature at which the vapour tension is enough in order to obtain the desired speed of evaporation. In the e-gun evaporation the speed of evaporation of the material is unstable and can vary even quickly; in order to maintain an adequately constant speed of deposition, it is necessary to control in real time the growth rate of the film and to use it as a feedback for the power of the e-beam. This is obtained thanks to an instrument, called quartz microbalance, consisting of a piezoelectric quartz crystal placed in vibration at its background frequency and exposed to the flow of condensing material. The material deposited progressively adds to the weight of the quartz, lowering its background frequency. Measuring in real time the oscillation frequency of the quartz, the power of the electronic beam can be regulated and correspondingly the instantaneous speed of growth of the film will be regulated.

The evaporated material diffuses into the deposition chamber following linear trajectories and reaches therefore only the areas in line of sight with the crucible. Given the above limitation on the positioning of the crucible, the obtainment of a suitable coating uniformity imposes, in this technique, the adoption of complex manipulation of substrates. In e-gun evaporation, the important amount of melted material causes a rather high heating of the pieces to coat, hence it is not suited to use under a deposition temperature of 350° C. The condensation of vapours happens eventually in the presence of reactive gases (O2, N2) introduced in a controlled way in the deposition chamber, leading to the so called process of reactive evaporation.

In the more sophisticated applications, the growing film is subjected to ion bombardment, either by ion beams (IBAD process) or by creating a plasma in the chamber (Ion Plating process).

QUESTION -

Besides purity, is there any advantage of sputtering technology over thermal evaporation for making metallised films? Which one is better if less adhesion is required on same substrate ?

Is there any difference in the final appearance of the film made using these two technologies - texture or gloss wise ?

Thanks for raising such a nice question. I am also learning many missing informations from this researchgate. We use thermal evaporation method to deposit an uniform of coating of 100 nm coating of pure gold on silicon wafer buffered with Cr.  We do lot of pretreatment before and after coating to achieve Au(111) plane and we use for making selfassembled monolayer studies. By this method we can able to make substrate for STM and AFM studies. I have a lot of experience in this method. On the other hand I saw the e-beam evaporation setup but i donot have any experience. 

Thanks

In a nutshell: e-beam evaporation is just one of many thermal evaporation methods (which also include evaporation from effusion cells or even simply from resistiveley heated boats etc.) . However, it is probably the one with the lowest likelyhood of contamination with atoms of a foreign species / impurities

In terms of what's best to use to coat a plastics substrate with Au or Ti, I have to say, I cannot answer for sure. Adhesion will be a problem in either case, I am afraid. Like in most sample growth processes, which I often like to refer to as alchemy, trial and error is probably the fastets way to success. By experience, things that work for others, unfortunately in reality most of the times never work as well if one simply tries to copy them.

Re: Mr. Mitesh Parmer: Understand that Ti and Ta are high refractory metals and need high temperature to melt them. However, in my case, have no problems depositing them using e-beam evaporator.

Since gold will not react with the plastic, it will have notoriously poor adhesion. Ti, which reacts with everything will adhere well. It is common practice to add a Ti adhesion layer below a gold layer as gold will adhere reasonably well to Ti. With e-beam you can evaporate just about anything, for resistance heating you are limited to those with melting temperatures considerably lower than the filament used.

The main differences beteen them ,the evausedporation methode can be depostion materiales with low metling point as thermally ,but electon beam which is e-beam can be deposited materials that have high melting point such as Ti,Wo.....

A very valuable discussion .

We routinely deposit titanium films with the aid of resistive evaporation.

Be advised to use the tungsten boat, and keep in mind that melted Ti reacts with W material and finally damages the boat. Therefore they typically work for 1-2 times and then need to be replaced.

It's a good practice to start evaporation when the pressure drops below some 5x10^(-6) mbar.

And then it's a very good sign if you see the vacuum gets better during the Ti evaporation, because the deposited film on the chamber walls works as a getter pump.

As to electron beam deposition and thermal deposition, which method will cause a stronger adhesive force between the deposited metal (such as Cu) and the substrate (such as Al2O3)?

My understanding is that because the thermal deposition will cause the heating of the substrate, maybe it will cause a stronger force than e-beam deposition?

My guess uis that they would be equivalent. In both cases the metal is heatiedto vaporization. The substrate heats up from the incoming atoms.

Thermal management of the substrate is truly important for the adhesion properties. Sometimes it is heated significantly by the back-side heater to improve the sticking of the deposited material.

Nevertheless, I wouldn't expect that the thermal (=resistive) deposition will provide better adhesion compared to the e-beam. At the very start of this process the substrate is still not heated by the radiation from the boat/crucible, - unless it's done intentionally by e.g. exposing the substrate to the source running at lower currents (when deposition rate is still zero).

Instead, the subsequent heating might become a problem at some point, for example in case the substrate has a photoresist mask.

Moreover, at some conditions the excessive heat from the resistive source might make the adhesion worse, e.g. when the heavy outgassing from the contaminated chamber walls is imposed on the deposition process.

Just a remark: both e-beam and resistive depositions are thermal.