Laser pulse deposition technology-ShangHai RunQia Electronics Technology Co.,Ltd.

Laser pulse deposition technology

Pulsed fiber laser deposition is a method of depositing a thin film on a substrate by focusing the laser on a small area of the target material, utilizing the high energy density of the laser to evaporate or even ionize a portion of the target material, allowing it to detach from the target material and move towards the substrate.

Principle of pulsed fiber laser deposition (PLD)

The laser beam is focused on the surface of the target material. At a sufficiently high energy density and short pulse time, the target material absorbs the laser energy and rapidly raises the temperature at the spot to above the evaporation temperature of the target material, resulting in high temperature and ablation. The target material vaporizes and evaporates, with atoms, molecules, electrons, ions, and molecular clusters, as well as micrometer sized droplets, solid particles, etc. escaping from the surface of the target. These evaporated substances, in turn, continue to interact with the laser, further increasing their temperature and forming a localized high-temperature and high-density plasma. The plasma absorbs light energy through the reverse tough absorption mechanism and is heated above 104K, forming a bright plasma flame with a dense core.

After the formation of the plasma flame, it continues to interact with the laser beam, further ionizing. The temperature and pressure of the plasma rapidly increase, and a large temperature and pressure gradient is formed in the normal direction of the target surface, causing it to expand isothermally (during laser action) and adiabatically (after laser termination) outward in that direction. At this time, the non-uniform distribution of the charge cloud forms a strong acceleration electric field. Under these extreme conditions, the high-speed expansion process occurs within tens of nanoseconds, rapidly forming a slender plasma plume that extends outward along the normal direction.

Plasma nucleates and grows on the substrate to form a thin film. High energy particles in laser plasma bombard the surface of the substrate, causing varying degrees of coarse beam damage, one of which is atomic sputtering. A thermalization zone is formed between the incident particle flow and the sputtered atoms. Once the agglomeration rate of the particles is greater than the splashing rate of the sputtered atoms, the thermalization zone will dissipate and the particles will grow into a thin film on the substrate.

Characteristics of pulsed fiber laser deposition (PLD)

Pulsed fiber laser deposition technology is currently a promising film-forming technique, which is simple and has many advantages:

(1) Fully equivalent coating can be applied to composite materials with complex chemical compositions, ensuring stable chemical stoichiometry after coating. The biggest advantage of PLD is its easy consistency with the target material composition, which is a distinguishing feature from other technologies.

(2) Quick response and rapid growth. Normally, a thin film of about 1 μ m can be obtained in one hour.

(3) Strong directionality, high film resolution, and the ability to achieve micro deposition.

(4) Multiple gases can be introduced in situ during the growth process, and the introduction of active or inert gases and mixed gases is of great significance for improving the quality of thin films.

(5) Easy to fabricate multilayer films and heterojunctions, especially those with multiple oxides, by simply switching targets.

(6) The target material is easy to prepare without heating, with high plasma energy greater than 10 eV and ion energy around 100 eV. Such high energy can reduce the substrate temperature required for the film, making it easy to grow uniformly oriented structures and epitaxial single crystal films in situ at lower temperatures.

(7) High vacuum environment can produce high-purity films with less pollution to the film; Yuhui only transports evaporation in local areas, so it causes much less pollution to the Chenzhi cavity.

(8) There are many types of films that can be made, and almost all materials can be made using PLD, unless the material is transparent to the laser.

(9) Under high pressure conditions, high-density thin films can be produced, with a density and adhesion far exceeding other coating technologies.

Application of pulsed laser deposition (PLD)

Among numerous thin film preparation methods, pulse laser deposition technology is the most widely used, which can be used to prepare various material thin films such as metals, semiconductors, oxides, nitrides, carbides, borides, silicides, sulfides, and fluorides. It is even used to prepare some difficult to synthesize material films, such as diamond, cubic nitride films, etc.

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