Why argon gas is used in sputtering

Target Utilization and Sputtering Rates. When designing to optimize target utilization, the most important region of the magnetic field is generally located 0. The following examples are provided to explain the influence of the magnetic field on target utilization and rate. Resulting Erosion Profile for 0. The graphs show the magnetic field lines for unbalanced above and balanced below magnet arrays for 6 inch diameter targets, the path of the ions, the target surface and the nominal location of the region of greatest plasma intensity.

The path of the ions indicates what erosion profile will result on the target. The region and depth of erosion depends on the strength of the magnetic field and how parallel it is to the target surface at 0. Also, the depth depends upon the angle at which ions hit the target. A graph of cos 3 q is remarkably close to the actual erosion q is the angle that the incident ion makes with the normal at the target surface.

Use of targets which are significantly thicker or thinner results in worse target utilization, narrower operating pressure range, distribution profiles which vary significantly from predicted results and degraded performance. The meaning of sputter is the state that produces the sound of the popping fly ing, such as a crackling, a juju. Derived from it, it has the meaning of splash action. The sputtering, in a space filled with inert gas such as Ar argon , argon is atomized by discharging a high voltage to the material target , it is knocked out the target atom by colliding with the target, It is a technology that adheres to the substrate and forms a thin film.

Argon is an inert gas. Oxygen is active. Aluminum and oxygen react, but aluminum and argon do not. This is called an inert gas. The morphology and structure of the coatings were studied by X-ray diffraction XRD. Potentiodynamic polarization was used to study the corrosion behavior of the coatings.

The results obtained from potentiodynamic polarization curves showed that TiO 2 coatings possessed higher corrosion resistance than uncoated substrate. Over the last few years, a great attention has been focused on the titania. TiO 2 coatings are extensively used in a wide range of applications such as gas sensor, high refractive index, nontoxicity, good mechanical properties, and the photocatalysts due to remarkable optical, electrical, and chemical properties [ 1 — 4 ].

Coatings such as TiO 2 , SiO 2 , and Al 2 O 3 with very low electronic conductance or insulating properties are known to effectively protect metals and alloys from corrosive environment. Titanium dioxide TiO 2 exhibits wide band gap and possesses good passivating surface with low anodic dissolution rate making it one of the promising materials for corrosion protection [ 5 — 7 ].

Different deposition techniques, such as chemical vapor deposition [ 8 ], dip coating [ 9 ], magnetron sputtering [ 10 ], are used to deposit TiO 2 coatings. TiO 2 coatings were deposited by r. The details of the deposition chamber can be found in our previous work [ 11 , 12 ]. The gases used are high-purity argon After evacuating the sputtering chamber down to a pressure of 1.

Thereafter the samples were ultrasonically cleaned in an acetone bath for 10 min, followed by rinsing with alcohol and then air dried prior to the deposition process. In our previous work [ 12 , 13 ], we showed that the physical and chemical properties of TiO 2 films are strongly influenced by the value of applied negative bias on the substrate in the magnetron sputtering. In the present work, we limit our investigation to the effect of oxygen partial pressure on the TiO 2 films deposited by magnetron sputtering, while keeping the rest of the parameters constant see Table 1.

In order to avoid the effect of nonuniformity of the coating, a series of 10 indents were performed and the results were averaged.

The measurement was conducted using a conventional three-electrode electrochemical cell in 3. Commonly, TiO 2 is found in two stable crystalline phases, anatase and rutile, when it is deposited by reactive magnetron sputtering.

The phase composition of the TiO 2 films is shown in Figure 1. The patterns show that the obtained films are crystalline and exhibited diffraction peaks at The planes of anatase , , , and are localized at Safeen et al. This is attributed to low-surface mobility of deposition particles, and hence, the deposition particles do not possess enough energy to crystallize [ 18 ].

Majeed et al. When the substrate is biased, more energy is transferred from ions driven by the substrate bias to the growing film, which can make the film more compact [ 19 ]. The grain size of the TiO 2 thin films decreases from These results corresponded to the result of Safeen et al.

Also, similar result was reported by Zhao et al. However, Zhao et al. According to Chandra Sekhar et al. Figure 3 gives the variation of the hardness Hi and elastic modulus values of TiO 2 coatings. The results were given in Figure 5. The application of a negative bias to the substrate leads to an increase of the hardness and the elastic modulus.

This result could be related to the same evolution of the grain size. Two other parameters are commonly used to evaluate the resistance to contact damage; they are expressed by two ratios: and [ 28 , 29 ]. The higher ratios of or mean higher elastic and high resistance of coatings to plastic deformation and hence a higher wear resistance with low rigidity. The is an indicator of film durability and is related to the elastic strain to failure capability and resilience in a surface contact, which is clearly important for the avoidance of wear [ 30 ].

The ratio is commonly used to evaluate the resistance to plastic deformation during wear or abrasion [ 28 , 30 ]. Figure 4 shows the ratios and for the various TiO 2 deposited under different flux rate of oxygen.

It is clear that the largest resistance to plastic deformation i. Before each polarization test, the samples were immersed in aerated NaCl 3. Figure 5 clearly shows that the presence of TiO 2 coatings on the metal surface in NaCl solution shifts both the anodic and cathodic branches of the Tafel plots to lower values of current density.

This suggests that the modified TiO 2 coatings clearly retard the anodic dissolution process of stainless steel and increase its anticorrosion properties. The electrochemical kinetic parameters in the polarization curves, such as the corrosion potential , corrosion current density , polarization resistance Rp , corrosion rate , porosity , and the anodic and cathodic Tafel slopes and are listed in Table 1.

It reveals from Table 3 that the corrosion current density was reduced in the presence of TiO 2. Additionally, as shown in Table 3 , values in the presence of the TiO 2 coatings were less negative than that in the absence of the TiO 2 coatings.

On the other hand, the slight shifts of values towards positive direction are found with the increase of oxygen partial pressure O 2. The pitting corrosion which occurs mainly depends on the concentration of Cl ions on the electrode surface. When the coatings are immersed in the solution rich in Cl ions, Cl ions absorb and concentrate on the surfaces of the specimens. The metal is dissolved into the solute because of the replacement of oxygen ions in the oxides of the coating by Cl ions.

This condition induces the pitting. With the process of pitting reactions, a microgalvanic cell is gradually formed between the bared substrate in the pitting spot and the coating around the pitting spot, in which the former and the latter can be regarded as the anode and the cathode, respectively. This process will further accelerate the concentration of Cl ions in the pitting spot [ 31 ]. Dense coating provides very low permeability for electrolytes to establish an ionic conduct.

The decrease in current density can be ascribed to the compact surface structure [ 32 ] and improved adhesion after decrease in oxygen partial pressure; at a lower oxygen flow rate, the nature of the substrate and oxygen flow can be an important factor influencing the quality of the coating [ 33 ], thereby reducing solution penetration and consequent localized corrosion.

According to the corrosion surface, it was concluded that, after immersion for a period, the failure of the coatings could be ascribed to the micropores in the surface of coatings [ 34 ]. In our work, the current density of TiO 2 in 3. This result could be related to the grain size Table 2 ; the film exhibiting the lowest grain size gives a high protective efficiency and a good hardness.

The X-ray diffraction results show that the coatings are crystalline. These coatings improve the corrosion resistance of stainless steel in NaCl solution with 3. A TiO 2 coating with lower oxygen partial pressure showed the best protective properties. Madaoui et al. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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