فیلمها و مطالب آموزشی

Surface and Thin Film Analysis

The interaction particles& thin layer

The interaction X Ray with thin layer

The interaction   Light with thin layer

SEM: Scanning Electron Microscopy

TEM:Transmission Electron Microscopy

SPM : Scanning probe   Microscopy

AFM : Atomic   Force    Microscopy

STM : Scanning Tunneling Microscopy

Sims: Secondary ion mass Spectroscopy

RBS: Rutherford Backscattering Spectroscopy

XRD:      X_Ray Diffraction

XPS: X_Ray Photoelectron

Spectrophotometer

Ellipsometry

Thin film Structure

Electron_Beam Gun

Resistant Evaporation

Sputtering

PLD : Pulse Lasr Deposition

MBE: Molecular Beam Epitaxy

Chemical Deposition CVD

Chemical Deposition PECVD

Chemical Deposition MOCVD

Vacuum      About

Rotary           Pump

Turbomolecular   Pump

Cryojenic           Pump

Diffusion            Pump

The barometer History

Low vacuum range gauge


Thickness Monitoring

Electron Beam Gun Evaporation

(Electron Beam Gun Evaporation)
In this way, for energy transfer, used a high-energy electron beam instead of electrical current, which will focus on the surface of substance and is located within the boat and creates heat. This technique causes to temperature range rise very high for evaporate the material and thus, the evaporation of refractory materials, becomes possible.
Electron beam used in this system is produced, in three ways:
1. thermoionic
2. The field emission
3. The combination of thermoionic and field emission
However, the most common used method in these systems is thermoionic method, in which, for electron emission use from generated heat by the flow of current through a wire filament. Often tungsten is used to manufacture of filament and thorium oxide, is used on it to increase its emission. Figure 1 shows an example of a filament.

Figure 1: An example of an electron gun filament

In electron gun, as shown in Figure 2, electrons are accelerated toward the boat after that filament was being heated due to passing free flow by the electrical and Lorentz magnetic fields. The applied force on emitted electrons given by the following equation: F=-e*(E+V*B)
That is,
V: electron velocity vector,
E: electric field intensity,
B: magnetic field intensity,
And F: the applied force on electron.

Figure 2: Schematic view from the electron beam.

In general, the sources evaporation (or sublimation) process, by electron gun system, can be divided in three stages:
1. The current passing through the filament (the cathode), heating it and therefore, the electrons emission from it toward the anode (used Transistor for this part is usually 12 volts AC).
(2) It is done, giving acceleration to electrons with use of high voltage power supply. The used power supply is often between 15-5 kW and maximum required current is usually 1 amp. Due to the high voltage of power supply in these systems, suitable insulations are used to prevent system connection to the wall, among which can be pointed out, alumina, zirconia, silicon nitride, carbide silicon and beryllium oxide.
3. Direction control and focus the electrons on the source.

Figure 3 shows an example of an electron gun inside a vacuum chamber.

Produced waves of electromagnetic fields, as shown in Figure 4, are in different shapes, such as sinusoidal, triangular or circular, and swept the surface of the material by electrons, carried by the magnetic coil.

Figure 4 shows an example of scanning electron beam.

Depending on the type of application, may be used different electron gun systems. However is used generally a system similar to Figure 2, in which the electron beam after accelerating, travels one 270 degrees direction and then, collide to copper boat. This track is 270 degrees, in order not to interference vapored particles of inside the vacuum chamber with emitted electron beam of filament. Boat’s material is usually copper.

In addition, this fact that, in most coating used more than one source, as shown in Figure 3, is used usually Multi-Boat. This type of boats are cooled to prevent from their reaction with the source. In order to use of all available sources in the boats, to evaporate, should be rotatable the Multi-Boat holder. To do this work use of a Step Motor.
The use of different sources, in electron evaporation systems is very high, and can be evaporate (or sublimation) various dielectric, conductive and semi-conductive materials, with this method. The growth rate of these source is different according to their nature and the amount of vacuum and current and voltage.
In Table 1, shown the most commonly used sources, and their evaporation conditions, such as deposition rate, and current used.

Table 1: evaporation characteristics for some of conventional in electron gun system

Deposition rate A/S	Current (mA )	Material	Deposition rate A/C	Current (mA )	Material
3	300	Ni	5/4	500	Al
50	100	Pd	13	150	Ag
1	300	Si	9	200	Co
25	40	SiO₂	13	50	Cr
8	500	Ta	2/2	500	Cu
20	300	Ti	3	300	Ge
5/7	150	TiO₂	7	250	Hf
8	500	W	18	200	In
10	200	ZrO₂	7	10	MgF₂

The best conditions for materials deposition is concerned to the type of application. For example, an aluminum layer is used both for reflection and for electrical conductivity. In this case, to optimize its properties, in the first case, we consider reflections factor, and in the second case, the conductivity factor.

In addition to choice of material, substrate election also has a great influence on the final product, and should be considered parameters such as surface smoothness, reactive nature of the substrate material and source, and sticking them together. Few parameters of device, such as source places, substrate, and vacuum changes, are also important. However, creating ideal conditions is difficult, and should be done, a series of different experiments, in order to achieve the best conditions for the deposition desired source coating.

فیلمها و مطالب آموزشی

Electron Beam Gun Evaporation

Training movie about electron gu beam evaporation