Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition
Описан метод термоионной вакуумной дуги (ТВД) как новый наиболее подходящий метод для осаждения тонких пленок высокой чистоты с компактной структурой и очень гладких, удобный для получения пленок с наноструктурой. ТВД может производить источник плазмы чистых металлов внутри вакуумной камеры (включая...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Cite this: | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition / H. Ehrich, G. Musa, I. Mustata // Вопросы атомной науки и техники. — 2002. — № 1. — С. 169-171. — Бібліогр.: 6 назв. — англ. |
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| author | Ehrich, H. Musa, G. Mustata, I. |
| author_facet | Ehrich, H. Musa, G. Mustata, I. |
| citation_txt | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition / H. Ehrich, G. Musa, I. Mustata // Вопросы атомной науки и техники. — 2002. — № 1. — С. 169-171. — Бібліогр.: 6 назв. — англ. |
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| description | Описан метод термоионной вакуумной дуги (ТВД) как новый наиболее подходящий метод для осаждения тонких пленок высокой чистоты с компактной структурой и очень гладких, удобный для получения пленок с наноструктурой. ТВД может производить источник плазмы чистых металлов внутри вакуумной камеры (включая высоковольтные условия), обеспечивая эффективную ионную бомбардировку наносимой пленки атомами напыляемого материала. Энергия ионов полностью контролируется и даже может изменяться в течение осаждения. Описана также возможность нанесения тонких пленок углерода, эти пленки полностью свободны от водорода.
Описаний метод термойонної вакуумної дуги (ТВД) як новий найбільш придатний метод для осадження тонких плівок високої чистоти з компактною структурою та дуже гладких, який зручний для отримання плівок із наноструктурою. ТВД може генерувати джерело плазми чистих металів всередині вакуумної камери (включаючи високовольтні умови), забезпечуючи ефективне іонне бомбардування плівки, що
наноситься, атомами матеріалу, який наноситься. Енергія іонів повністю контролюється і навіть може змінюватися протягом осадження. Описана також можливість нанесення тонких плівок вуглецю, ці плівки цілком вільні від водню.
Thermionic Vacuum Arc (TVA) is described as a new very suitable for deposition of high purity thin films with compact structure and extremely smooth, just convenient for nanostructure film realization. TVA can generate pure metal vapor plasma source inside of a vacuumed vessel (including H. V. conditions), ensuring energetic ions bombardment of the just depositing material own atoms of the condensing film. The energy of ions can be fully controlled and changed even during deposition. Possibility of condense the carbon thin films is also described, these films being completely hydrogen free.
|
| first_indexed | 2025-11-30T15:56:05Z |
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УДК 621
THERMOIONIC VACUUM ARC (TVA) - ONE OF THE BEST SUITABLE
METHOD FOR HIGH PURITY COMPACT SMOOTH THIN FILMS
DEPOSITION
H. Ehrich, G. Musa*, I. Mustata*
Essen University, Essen, Germany;
* National Institute of Physics for Laser, Plasma and Radiation, Bucharest, Romania;
G. Musa e-mail address: musa@alpha1.infim.ro
Описаний метод термойонної вакуумної дуги (ТВД) як новий найбільш придатний метод для осадження
тонких плівок високої чистоти з компактною структурою та дуже гладких, який зручний для отримання
плівок із наноструктурою. ТВД може генерувати джерело плазми чистих металів всередині вакуумної
камери (включаючи високовольтні умови), забезпечуючи ефективне іонне бомбардування плівки, що
наноситься, атомами матеріалу, який наноситься. Енергія іонів повністю контролюється і навіть може
змінюватися протягом осадження. Описана також можливість нанесення тонких плівок вуглецю, ці плівки
цілком вільні від водню.
Описан метод термоионной вакуумной дуги (ТВД) как новый наиболее подходящий метод для осажде-
ния тонких пленок высокой чистоты с компактной структурой и очень гладких, удобный для получения
пленок с наноструктурой. ТВД может производить источник плазмы чистых металлов внутри вакуумной ка-
меры (включая высоковольтные условия), обеспечивая эффективную ионную бомбардировку наносимой
пленки атомами напыляемого материала. Энергия ионов полностью контролируется и даже может изменять-
ся в течение осаждения. Описана также возможность нанесения тонких пленок углерода, эти пленки полно-
стью свободны от водорода.
Thermionic Vacuum Arc (TVA) is described as a new very suitable for deposition of high purity thin films with
compact structure and extremely smooth, just convenient for nanostructure film realization. TVA can generate pure
metal vapor plasma source inside of a vacuumed vessel (including H. V. conditions), ensuring energetic ions bom-
bardment of the just depositing material own atoms of the condensing film. The energy of ions can be fully con-
trolled and changed even during deposition. Possibility of condense the carbon thin films is also described, these
films being completely hydrogen free.
Extended studies on thermionic vacuum arc has been
performed during past ten years in the form of a suc-
cessful bilateral cooperation between Romanian and
German team [l-5].
The main advantages of this new method are:
- deposition of pure metal film in high or ultra- high
vacuum conditions;
- no gas consumption;
- thin film is condensing from the plasma of the
evaporating metal or compound;
- the growing thin film is bombarded just during de-
position with the ions of the depositing material avoid-
ing any gas inclusion in the film and insuring a compact
film (no columnar structure);
- the energy of bombarding ions can be controlled at
will and even changed during deposition;
- the surface of the deposited film is smooth, the
TVA technology being a good candidate for nanostruc-
ture (thin film deposition technology);
- no micro - particles in the deposited thin film;
- low heat transfer from plasma source to the sam-
ple because at high vacuum conditions the heat transfer
is due only to the e.m. radiation;
- quite high deposition rate.
Experimental arrangement
In figure 1 is given schematically the experimental
arrangements used to produce thermionic vacuum arc:
Fig.1. The experimental arrangements used to produce
thermionic vacuum arc
The material to be evaporated (solid particles of mm.
size) is filling the anode. (A) is a spoon like tungsten
crucible. The cathode (C) is a tungsten filament (wire
diameter 0,5…0,8 mm) which is mounted inside a
molybdenum whenelt cylinder having a front hole with
a diameter of 5…6 mm. This assembly is mounted in-
side of a vacuum vessel. The cathode is grounded and a
high voltage is applied via a resistor to anode (crucible).
169
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2002. №1.
Серия: Вакуум, чистые материалы, сверхпроводники (12), с.169-171.
There are two main geometrical working parameters
namely the relative cathode - anode position given by
interelectrodic distance d and the 0 angle between
whenelt cylinder axis and the imaginary vertical line
passing through tungsten crucible center.
The sample is usually positioned on vertical line at a
distance D from the anode.
TVA ignition
In order to ignite the thermionic vacuum in arc, in
the vacuum vessel, pressure must be lower then lO torr.
The filament of the cathode is heated at high temper-
ature in order to have a significant termo-electronic
emission. An adjustable (d. c.) high voltage V is applied
over cathode - anode space. Due to the incident power
on anode, (the product VI, where I is the discharge cur-
rent), the material from the crucible starts to melt and
then to boil. A steady state density of atoms (of the
evaporating material) is established in the interelectrod-
ic gap. At further increase of the applied high voltage
(V), a heated cathode arc in the vapors generated from
anode is established. We will call this necessary voltage
as breakdown voltage of TVA. In fact, this ignition is
different from the well - known breakdown of lumines-
cent discharge. Indeed in the case of TVA, the applied
voltage is ensuring also the gas (in this case metal va-
pors) necessary to support discharge current. Moreover,
just after ignition the steady state density of the evapo-
rated atoms from the anode must be maintained, in
spite of the fact that part of the voltage is lost on ballast
resistor and on the plasma potential drop. Otherwise,
just after ignition, the discharges extinguish the process
of ignition being periodically repeated. We may say that
the breakdown voltage to ignite TVA must fulfill the
following conditions:
- to ensure enough density of evaporated atoms in
the interelectrodic space;
- to generate using thermoelectrons enough ions per
second to have a charge multiplication of metal vapor
plasma or compound plasma and generation;
- after ignition must maintain at least the same rate
of atom evaporation from the anode.
Because the evaporation rate must be proportional
with the power dissipated at the anode, the rate before
ignition is proportional with V-L After ignition, a plas-
ma is established in the interelectrodic space the passing
current being larc. The power at anode level will be lar-
c·Uanode potential drop. So the last condition can be writ-
ten:
Ithermoelectronic·V = Iarc·Uanode potential drop..
The plasma of the termionic vacuum arc
The studies of the TVA plasma have been performed
mainly using metal as evaporating material from the an-
ode. In this case, the plasma generation is easier because
of low energy levels of the metal atoms. In addition,
plasma density is quite high.
It results that the plasma potential drop is low, the
applied high voltage being practically divided between
cathode fall and anode fall. In Fig. 2 is given the as-
sumed potential distribution in the TVA.
As we can see from figure two plasma is at a poten-
tial Vc against the ground because cathode is grounded.
In fact, the plasma produced steadily in the interelec-
trodic space is continuously expanding away from its
source. We measured plasma potential against the cath-
ode starting nearby plasma using the electric probe
source in the direction of the expanding plasma. The re-
sults show that plasma potential is steadily decreasing.
It results that in this potential decrease we have an elec-
tric field accelerating the ions towards the sample.
Therefore, at 250 mm distance from the source, metal
ions are incident on substrate surface with high energy.
Both plasma parameters (charge density, electron tem-
perature) as well as ion energy and ion flux has been
previously reported by our team. The measurements us-
ing ion energy analyses have proved that at convenient
conditions, the energy of ions in TVA can achieve val-
ues of 250…300 eV.
Fig.2. The assumed potential distribution in the TVA
The control of the energy of ions in TVA using
the working parameters
Before describing the simple method to adjust at will
the energy of ions even during deposition we must
stress from the very beginning the importance of ener-
getic ion bombardment of sample during deposition. In-
deed, a large number of papers have stressed the strong
relation between deposited thin films quality and the
process of bombarding the layer during deposition with
energetic ions. Due to the impact of energetic ions, the
deposited atoms are rearranged and the film processed
in this way is more compact, without voids having pro-
prieties close to the bulk metal. Also, the thin film sur-
face is very smooth. In many experiments, the growing
metal film is bombarded with noble gas ions (for exam-
ple in magnetron sputtering) but in this case, noble gas
atoms are trapped inside of thin films. In the case of
thermionic vacuum arcs, the film is bombarded with the
ions of the just deposed material. Both compactness and
smoothness of the films are obtained if the energy of
ions is over a critical value. It results that we need a
technology that permits to adjust the value of the energy
of ions any time during deposition process.
Let us return to figure 2. We can see that we must
control in fact the value of the energy of ions through
the cathode potential fall. Indeed the potential of the
plasma against the ground (i. e. vacuum vessel wall and
also cathode) is just equal with cathode potential fall.
170
Performed measurement has showed that very low
energy value for ions are obtained if the thermoeleip-
tronic current source is close to the plasma. This is the
situation when (p = 0 and d = 2…3 mm (see figure 1).
If the electron source is away from the plasma, for ex-
ample <p = 80°, d = 4…5 mm, the cathode fall is high
because in order to have the same arc current, highest
voltage must be applied to get a convenient cathode fall,
able to collect electrons. Similar effect is obtained if for
(p = 30° the distance d) is increased to 6…8 mm.
Moreover, extended studies on various working con-
ditions have provided finally that between voltage drop,
Uplasma, over entire discharge and measured energy of
ions, Eions, there is a simple relation:
Eions = k·Uplasma.,
where k is a constant usually between 0,2…0,35. In this
way, the energy of ions can be easily adjusted at a
known value only changing the applied voltage. At this
stage, it is worthwhile to say that the increased ion ener-
gy proved out to decrease the deposited lower roughness
as shown in figure 3. The AFM measured roughness is
given against the ions directed energy, Eions, represented
through Vplasma when MgO layers were deposited by
TVA technology.
In fact, in order to increase the energy of ions, it is
necessary to make difficult to get enough electrons from
the cathode, arriving to the anode. Of course we
checked successfully other methods like the decrease of
the heating current of the cathode (very efficient but
shortening the cathode lifetime) decreasing the whenelt
cylinder front hole or changing the position of the cath-
ode (filament) inside of the whenelt cylinder.
Uplasma(V)
Fig.3. The ion energy versus average roughness
Hydrogen free carbon thin film deposition
An increased interest is paid today to hydrogen free
carbon film deposition the aim being diamond like layer
production with low friction, increased hardness, etc.
Because of the elevated temperature for carbon sub-
limation (>4000K), in most of the laboratories, the car-
bon films have been obtained using plasma chemical
technologies. In all such experiments, the obtained car-
bon film contains incorporated hydrogen atoms.
Three methods have been used up today to produce
hydrogen free carbon layer, namely filtered carbon arc
in vacuum, mass - separated carbon ion beam or pulsed
laser deposition through carbon ablation.
Thermionic vacuum arc has been considered by us
as a possible candidate for such deposition because it is
not difficult to heat the carbon rod by the accelerated
electrons to temperatures higher than 4600K. Also, the
optimum value of energy of carbon ions 70…80 eV
necessary to obtain sp3 bound carbon films [6] can be
easily obtained and due to high vacuum condition, hy-
drogen presence is avoided when TVA is used.
In figure 4 is shown a simplified view of the used
experimental arrangement:
Fig.4. The experimental arrangement
Conclusions
The developed system for thin film deposition using
thermionic vacuum arc (TVA) is a very promising one
both to obtain high quality of the film and extreme puri-
ty.
In order to avoid any suspicion of crucible material
contamination of metal vapor plasma when very high
purity film must be obtain, we generated using TVA va-
por plasma just as a spot on bulk material surface simul-
taneously cooling the bulk material (spot TVA evapora-
tion).
Because of large number of parameters directly con-
trolling the film quality, TVA will be soon considered
as one of the best systems to produce thin films for
nanostructures.
References
1. G. Musa, Horst Ehrich and Jorg Schumann. Pure
Metal Vapor Plasma Source with Controlled Energy
of Ions //IEEE transactions on plasma science. April
1997, v. 25, N 2.
2. G. Musa, Horst Ehrich and M. Mausbach. Studies of
Thermionic Cathode Anodic Vacuum Arcs //J. Vac.
Sci. Technol. Sep/Oct 1994, v.A 12(5).
3. G. Musa, Horst Ehrich, A. Popescu, I. Mustata, A.
Salabas, M. Cretu, G. F. Leu. MgO Thin Film Depo-
sition Using TVA //Thin Solid Films. 1999, v.343 -
344, p.63 – 66.
4. G. Musa, I. Mustata, A. Popescu, Horst Ehrich and
Jorg Schumann. Adhesive Metal Films Obtained by
Thermionic Vacuum Arc (TVA) Deposition //Thin
Solid Films. 1998, v.333, p.95 –102.
5. G. Musa, Horst Ehrich, invited paper. Thermionic
Vacuum Arc //Int. Symposium on Phenomena in
Ionized Gases, SPIG. 1998, Kotor, Yugoslavia.
6. J.C. Lascovici, S. Scaglione //Appl. Surf. Science.
1994, v.78, p. 17-23.
171
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| id | nasplib_isofts_kiev_ua-123456789-79510 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-30T15:56:05Z |
| publishDate | 2002 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Ehrich, H. Musa, G. Mustata, I. 2015-04-02T17:02:43Z 2015-04-02T17:02:43Z 2002 Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition / H. Ehrich, G. Musa, I. Mustata // Вопросы атомной науки и техники. — 2002. — № 1. — С. 169-171. — Бібліогр.: 6 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/79510 621 Описан метод термоионной вакуумной дуги (ТВД) как новый наиболее подходящий метод для осаждения тонких пленок высокой чистоты с компактной структурой и очень гладких, удобный для получения пленок с наноструктурой. ТВД может производить источник плазмы чистых металлов внутри вакуумной камеры (включая высоковольтные условия), обеспечивая эффективную ионную бомбардировку наносимой пленки атомами напыляемого материала. Энергия ионов полностью контролируется и даже может изменяться в течение осаждения. Описана также возможность нанесения тонких пленок углерода, эти пленки полностью свободны от водорода. Описаний метод термойонної вакуумної дуги (ТВД) як новий найбільш придатний метод для осадження тонких плівок високої чистоти з компактною структурою та дуже гладких, який зручний для отримання плівок із наноструктурою. ТВД може генерувати джерело плазми чистих металів всередині вакуумної камери (включаючи високовольтні умови), забезпечуючи ефективне іонне бомбардування плівки, що наноситься, атомами матеріалу, який наноситься. Енергія іонів повністю контролюється і навіть може змінюватися протягом осадження. Описана також можливість нанесення тонких плівок вуглецю, ці плівки цілком вільні від водню. Thermionic Vacuum Arc (TVA) is described as a new very suitable for deposition of high purity thin films with compact structure and extremely smooth, just convenient for nanostructure film realization. TVA can generate pure metal vapor plasma source inside of a vacuumed vessel (including H. V. conditions), ensuring energetic ions bombardment of the just depositing material own atoms of the condensing film. The energy of ions can be fully controlled and changed even during deposition. Possibility of condense the carbon thin films is also described, these films being completely hydrogen free. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Пленочные материалы и покрытия Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition Article published earlier |
| spellingShingle | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition Ehrich, H. Musa, G. Mustata, I. Пленочные материалы и покрытия |
| title | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition |
| title_full | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition |
| title_fullStr | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition |
| title_full_unstemmed | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition |
| title_short | Thermoionic Vacuum Arc (TVA) - one of the best suitable method for high purity compact smooth thin films deposition |
| title_sort | thermoionic vacuum arc (tva) - one of the best suitable method for high purity compact smooth thin films deposition |
| topic | Пленочные материалы и покрытия |
| topic_facet | Пленочные материалы и покрытия |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79510 |
| work_keys_str_mv | AT ehrichh thermoionicvacuumarctvaoneofthebestsuitablemethodforhighpuritycompactsmooththinfilmsdeposition AT musag thermoionicvacuumarctvaoneofthebestsuitablemethodforhighpuritycompactsmooththinfilmsdeposition AT mustatai thermoionicvacuumarctvaoneofthebestsuitablemethodforhighpuritycompactsmooththinfilmsdeposition |