Collisions in Sputtering
During sputtering the target atoms typically collide with Ar gas as they travel to the substrate. Consider the sputter deposition of Au at 1 keV and suppose there are two collisions of Au atoms with Ar atoms prior to the Au reaching the substrate. What is the energy of the depositing Au atoms? You can assume elastic collisions and that the Ar atom is stationary in the collisions. You might also need to use an average value for which you should know from properties of the cosine. Table 5-2 also contains useful information.
Collisions in Sputtering
During sputtering the target atoms typically collide with Ar gas as they travel to the substrate. Consider the sputter deposition of Au at 1 keV and suppose there are two collisions of Au atoms with Ar atoms prior to the Au reaching the substrate. What is the energy of the depositing Au atoms? You can assume elastic collisions and that the Ar atom is stationary in the collisions. You might also need to use an average value for which you should know from properties of the cosine. Table 5-2 also contains useful information. AuAr+(1 keV) substrate
The probability that gas-phase atoms will travel a distance x without a collision is where ? is the mean-free path between collisions. For an Ar Pressure of 1 mtorr ? for Au in Ar is 5 cm. If the target-substrate distance is 12cm at what operating pressure of Ar gas will 99% of the sputtered Au atoms experience at least one gas- phase collision before being deposited on the substrate? (We have an equation for the mean free path in air. There is a similar expression for Argon with only a different constant. You have enough information to determine that constant.)
Here the equations
For air at room temperature the mean free path can be expressed as:
collision between a moving particle of mass M1 and an initially stationary particle of mass M2 is
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