Solid state - the thermal motion kinetic energy of the microscopic basic components is less than the interaction potential energy between the components → mutually bound spatial positions are relatively fixed

Liquid state - the thermal motion energy of molecules is equivalent to the potential energy of intermolecular interaction → molecules can move on their own, but most molecules cannot overcome the surface binding energy at the boundary

Gas state - the thermal motion of molecules can overcome the interaction barrier between molecules (including surface binding energy) → the molecules become free individuals with each other, occupying the largest possible space

Plasma state - when the temperature increases to the point where the kinetic energy of thermal motion between atoms/molecules is equivalent to the ionization energy → partially ionized gas, the basic components of the system become ions and electrons (may contain a large number of atoms and molecules)

Plasma actually as a gaseous medium

Net charge is 0

There are relatively few charged ions (there may be one charged ion in 1,000,000 neutral atoms)

Requires energy to be applied to the gas

Formation process

Place two parallel electrode plates in a closed container. The generated electrons will excite neutral atoms or molecules. When the excited particles return to the ground state, they will release energy in the form of light.

Luminous area

dark area

High ionization rate, easy to glow

Inert gas, non-reactive

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The electrons collide with argon atoms while accelerating towards the substrate under the action of the electric field → ionize a large number of argon ions and electrons, and the electrons fly towards the substrate

Argon ions accelerate and bombard the target under the action of the electric field, sputtering out a large number of target atoms/molecules, and the neutral target atoms/molecules are deposited on the substrate to form a film.

The secondary electrons are affected by the Loren magnet force while accelerating towards the substrate, and are bound in the plasma area close to the target surface. The plasma density in this area is high, and the secondary electrons collide and ionize under the action of the magnetic field to produce a large amount of Argon ions bombard the target. After multiple collisions, the energy of the electrons gradually decreases, and they break away from the constraints of the magnetic lines → move away from the target, and are finally deposited on the substrate.

In magnetron sputtering, due to the setting of the magnetic field, the direction of the magnetic field and the electric field are perpendicular to the target surface, limiting the electron trajectory to near the target surface.

The resulting material particles have strong adhesion to the matrix

The thickness distribution of the sputtered film is more uniform than that of the evaporated film

Suitable for film formation of high melting point metals, alloys and compound materials

Gas molecules break down into smaller "free radicals"

Free radicals will automatically recombine into a stable state

(avalanche ionization)

After the electron collision, the atom remains intact, but changes to an excited state → the excited state falls back, The excess energy is converted into photons, and the energy is released → the plasma will emit light (relaxation)