Morphology of Titanium Nanocluster Films Prepared by Gas Aggregation Cluster Source

Drábik, M.; Choukourov, Andrei; Artemenko, Anna; Kousal, Jaroslav; Polonskyi, Oleksandr; Solař, Pavel; Kylián, Ondřej; Matoušek, Jindřich; Pešička, Josef; Matolı́nová, Iva; Slavı́nská, D.; Biederman, Hynek

doi:10.1002/ppap.201000126

Cited by 42 publications

(47 citation statements)

References 25 publications

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“…The same thing can be argued here as well at the lower pressures. Due to the design of cluster sources, the pressure is often set by the gas flow, and thus when the flow is increased, so is the pressure in the aggregation zone [42]. Thus the results in the literature cannot be directly compared to the results found here.…”

Section: Size Control By Pressure and Gas Flowcontrasting

confidence: 50%

“…A metal core and an oxide shell is found when synthesizing copper [41] and iron with the pulsed hollow cathode sputtering process. In a cluster source a titanium core and an oxide shell has been observed [42]. However, in a plasma gas condensation cluster deposition system, nanoparticles without any core shell structure were synthesized.…”

Section: Influence On Oxygen Content and Crystal Structurementioning

confidence: 99%

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Titanium oxide nanoparticle production using high power pulsed plasmas

Gunnarsson¹

2016

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This thesis covers fundamental aspects of process control when growing titanium oxide nanoparticles in a reactive sputtering process. It covers the influence of oxygen containing gas on the oxidation state of the cathode from which the growth material is ejected, as well as its influence on the particles oxidation state and their nucleation. It was found that a low degree of reactive gases was necessary for nanoparticles of titanium to nucleate. When the oxygen gas was slightly increased, the nanoparticle yield and particle oxygen content increased. A further increase caused a decrease in particle yield which was attributed to a slight oxidation of the cathode. By varying the oxygen flow to the process, it was possible to control the oxygen content of the nanoparticles without fully oxidizing the cathode. Because oxygen containing gases such as residual water vapour has a profound influence on nanoparticle yield and composition, the deposition source was re-engineered to allow for cleaner and thus more stable synthesis conditions. The size of the nanoparticles has been controlled by two means. The first is to change electrical potentials around the growth zone, which allows for nanoparticle size control in the order of 25-75 nm. This size control does not influence the oxygen content of the nanoparticles. The second means of size control investigated was by increasing the pressure. By doing this, the particle size can be increased from 50 -250 nm, however the oxygen content also increases with pressure. Different particle morphologies were found by changing the pressure. At low pressures, mostly spherical particles with weak facets were produced. As the pressure increased, the particles got a cubic shape. At higher pressures the cubic particles started to get a fractured surface. At the highest pressure investigated, the fractured surface became poly-crystalline, giving a cauliflower shaped morphology.

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Section: Size Control By Pressure and Gas Flowcontrasting

confidence: 50%

Section: Influence On Oxygen Content and Crystal Structurementioning

confidence: 99%

Titanium oxide nanoparticle production using high power pulsed plasmas

Gunnarsson¹

2016

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“…The same thing can be argued here as well at the lower pressures. Due to the design of cluster sources, the pressure is often set by the gas flow, and thus when the flow is increased, so is the pressure in the aggregation zone [40]. Thus the results in the literature cannot be directly compared to the results found here.…”

Section: Pa) This Indicates That Oxygen Is An Important Component Thcontrasting

confidence: 50%

“…Surprisingly, no pure titanium core and oxide shell were ever found on the titanium nanoparticles produced in the high vacuum system. This is different from the nanoparticles synthesized that can be found in the literature [40] [63]. The results from paper 3 show that the reason for the lack of a core shell structure in the nanoparticles is because the impurity level of the vacuum system is too high in combination with a too high gas temperature that prevents pure titanium nanoparticles to nucleate.…”

Section: Influence On Oxygen Content and Crystal Structurementioning

confidence: 64%

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Controlling the growth of nanoparticles produced in a highpower pulsed plasma

Gunnarsson¹

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Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidation state) and size of the particles can be varied. The experimental results are supported by theoretical modeling.If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation of the cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significant oxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within which the nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters' internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature. The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new iv possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electr...

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Enhanced Synthesis of Aggregates by Reduced Temperature, Pulsed Magnetron Sputtering, and Pulsed Buffer Gas Delivery

Straňák

Hippler

2017

Gas‐Phase Synthesis of Nanoparticles

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Morphology of Titanium Nanocluster Films Prepared by Gas Aggregation Cluster Source

Cited by 42 publications

References 25 publications

Titanium oxide nanoparticle production using high power pulsed plasmas

Titanium oxide nanoparticle production using high power pulsed plasmas

Controlling the growth of nanoparticles produced in a highpower pulsed plasma

Enhanced Synthesis of Aggregates by Reduced Temperature, Pulsed Magnetron Sputtering, and Pulsed Buffer Gas Delivery

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