Sapphire Wafer Al2O3 8inch C Plane A Plane M Plane KY Double Slide Polished SSP

In 1992, Japanese engineer Shuji Nakamura revolutionized the field by successfully utilizing sapphire substrates to prepare GaN epitaxial layers thereby achieving the production of blue LEDs. This breakthrough led to a rapid expansion in the development of blue and green LEDs. Sapphire, known for its extremely high hardness and stable physical and chemical properties at high temperatures, along with its excellent optical performance, gradually became the mainstream choice for blue and green LED production.

Sapphire wafers exhibit anisotropy, with the C-plane <0001 being the most commonly used crystal plane for sapphire. Other major crystal planes include the A-plane <11-20>, M-plane <1-100>, and R-plane <1-102>.
Single crystal thin films of molybdenum disulfide (MoS2) can be grown on misaligned sapphire substrates. Misaligned sapphire substrates refer to substrates where the end face crystal orientation is slightly tilted from the C-axis <0001>towards the A-axis <11-20>or the M-axis <1-100> by a certain angle, typically within the range of 0.5 degrees to 6 degrees.
Sapphire wafers can also be used as optical windows, carriers, and panels. Due to sapphire's high hardness and stable physical and chemical properties, it is also used in the production of various functional products such as crucibles, bearings, gaskets, and other components.

Character

1.Sapphire wafer's excellent optical properties make it an ideal material for optical components. Sapphire has high transmittance, especially in the ultraviolet to near-infrared range (150nm to 5500nm), with a refractive index of around 1.76. These characteristics have led to the widespread use of sapphire in high-precision optical instruments.

2.In terms of electronic properties, sapphire wafer is a wide bandgap material (approximately 9.9 eV), making it perform exceptionally well in high-voltage and high-frequency electronic devices. Due to its high insulation and low dielectric loss, sapphire is commonly used as a substrate material for semiconductor devices, particularly in applications such as high-electron-mobility transistors (HEMTs) and gallium nitride (GaN)-based devices.

3.Sapphire wafer has a Mohs hardness of 9, second only to diamond, giving it outstanding advantages in terms of wear resistance and scratch resistance. It has high mechanical strength, able to withstand high pressure and impact.

4.Sapphire wafer also possesses an extremely high thermal conductivity of around 25 W/m·K, enabling it to maintain stable physical and chemical properties in high-temperature environments. With a high melting point of 2054°C and a low coefficient of thermal expansion (8.4 x 10^-6/K), sapphire wafer can retain dimensional stability in high-temperature applications.

Applications:

Sapphire wafers are a type of material known for their high transparency, hardness, and chemical stability, which results in various excellent properties. They are widely used in the manufacturing of electronic products, optical devices, and precision instruments. Below are some of the key application areas:

1. Optical Devices:
Used as lenses, windows, polarizers, etc., in optical equipment.
In high-end laser cutting, welding, and marking machines, sapphire lenses can protect and stabilize laser outputs, enhancing equipment precision and stability.
2.Precision Instruments:
Used as positioning elements, bearings, bushings, etc., in precision instruments.
In watchmaking, sapphire wafers are employed in the movement's oscillating core, watch cover, case, etc., improving scratch resistance, UV protection, and aesthetics.
3.Electronic Products:
Utilized in mobile phone camera protection glass, panel protection, fingerprint sensors, etc.
Enhances product hardness, transparency, and wear resistance, finding extensive application in the high-end electronics market.

Introduction to long crystal method of sapphire

Since the first synthetic gemstone was obtained using the flame fusion method in 1902, various techniques for artificial sapphire crystal growth have continued to evolve, giving rise to over a dozen crystal growth methods such as the flame fusion method, the Czochralski method, and the hydrothermal method. Each of these methods has its own advantages and disadvantages, with different applications in various fields. The main industrial processes currently in use include the hydrothermal method, the Czochralski method, the edge-defined film-fed growth (EFG) method, and the vertical horizontal gradient freeze (VHGF) method. The following section will introduce typical crystal growth methods for sapphire.

1. Flame Fusion Method (Verneuil Process)

The Verneuil process, also known as the flame fusion method, is named after the famous French chemist Auguste Victor Louis Verneuil, who invented the first commercially viable method for synthesizing gemstones. In 1902, he discovered the "flame fusion" method, which is still used today as a cost-effective method for producing synthetic gemstones. In regions like Guangdong in China and Switzerland, the Verneuil process supplies the majority of flame fusion gem materials. Besides being commonly used for the synthesis of rubies and blue sapphires, the flame fusion method is also utilized for creating spinel, synthetic corundum, synthetic star rubies, synthetic blue sapphires, and synthetic strontium titanate, among many other gemstones available in the market.

2. Kyropoulos Method

The Kyropoulos Method, also known as the Ky method, was first proposed by Kyropoulos in 1926 for crystal growth. For a significant period thereafter, this method was primarily used for the preparation and research of large-sized halide crystals, hydroxides, and carbonates. In the 1960s and 1970s, with improvements by Musatov from the former Soviet Union, this method was applied to the preparation of single-crystal sapphires, making it one of the effective methods for producing large sapphire crystals where the Czochralski method falls short. Crystals grown using the Kyropoulos Method exhibit high quality, low cost, and are suitable for large-scale industrial production.

Currently, around 70% of sapphire substrates used for LEDs worldwide are grown using the Kyropoulos Method or various modified versions of it. The significance of sapphire substrates in LED manufacturing is well-documented in numerous research papers. In China, the majority of sapphire crystal growth enterprises use the Kyropoulos Method.

Crystals grown using this method typically have a pear-shaped appearance and can reach diameters up to 10-30mm smaller than the diameter of the crucible in which they are grown. The Kyropoulos Method is an effective and mature technique for growing large-diameter sapphire single crystals and has successfully produced large-sized sapphire crystals. In recent news, on December 22nd, Crystal Sheng Crystal Laboratory and its subsidiary Crystal Ring Electronics jointly developed the latest innovative achievement—a 700kg ultra-large sapphire crystal.

3. Crystal Growth Method - Czochralski Method

The Czochralski method, also known as the Czochralski process or simply CZ method, is a technique where a crystal is pulled from a molten solution in a crucible. Discovered by the Polish chemist Jan Czochralski in 1916, it was further developed by the Bell Laboratories in the United States in 1950 for growing single-crystal germanium. Over time, it has been adopted by other scientists for growing semiconductor single crystals like silicon, metal single crystals, and synthetic gemstones. This method is capable of growing important gemstone crystals such as colorless sapphires, rubies, yttrium aluminum garnet, gadolinium gallium garnet, spinel, and spinel.

The Czochralski method is one of the most important methods for growing single crystals from a melt. The most commonly used Czochralski method for large-scale applications is the induction-heated crucible Czochralski method. The choice of crucible material varies depending on the crystal being grown and can include materials like iridium, molybdenum, platinum, graphite, and high melting point oxides. In practical applications, iridium crucibles have the least contamination for sapphires but are very expensive, resulting in higher costs. On the other hand, tungsten and molybdenum crucibles are cheaper but may introduce more contamination.

The Czochralski-CZ method crystal growth process involves heating the raw material to its melting point to form a melt, then using a single crystal seed to make contact with the surface of the melt. The temperature difference at the solid-liquid interface between the seed and the melt causes undercooling. As a result, the melt begins to solidify on the surface of the seed, growing a single crystal with the same structure as the seed. The seed is slowly pulled upward at a controlled rate while rotating, allowing the melt to solidify gradually at the liquid-solid interface of the seed, forming a single crystal ingot with axial symmetry.

4. EFG Method - Edge-Defined Film-Fed Growth

The Edge-Defined Film-Fed Growth (EFG) method, first independently invented by Harold LaBelle from the UK and Stepanov from the Soviet Union in the 1960s, is a near-net shaping technology that involves growing crystal blanks directly from a molten material. This method is a variation of the Czochralski method and offers several advantages over traditional crystal growth techniques.

EFG overcomes the need for extensive mechanical processing of artificial crystals in industrial production, leading to material savings and reduced production costs. It allows for the direct growth of crystals in the desired shapes, eliminating the need for extensive shaping processes.

One of the key advantages of the EFG method is its material efficiency

5. HEM Method - Heat Exchanger Method

In 1969, F. Schmid and D. Viechnicki invented a novel crystal growth method known as the Schmid-Viechnicki method, later renamed the Heat Exchanger Method (HEM) in 1972. The HEM method stands out as one of the most mature techniques for growing large-sized, high-quality sapphires, with crystal growth directions along the a-axis, m-axis, or r-axis, commonly using the a-axis direction.

Principle: The HEM method utilizes a heat exchanger to remove heat, creating a vertical temperature gradient within the crystal growth zone, where the lower region is cooler than the upper region. This gradient is controlled by adjusting the gas flow (typically helium) within the heat exchanger and varying the heating power to facilitate the gradual solidification of the melt from bottom to top, forming a crystal.

A notable feature of the HEM process, unlike other crystal growth methods, is that the solid-liquid interface is submerged beneath the surface of the melt. This submersion helps suppress thermal and mechanical disturbances, resulting in a uniform temperature gradient at the interface, promoting even crystal growth. This uniform growth environment enhances the chemical homogeneity of the crystal, leading to higher-quality crystals. Additionally, as in-situ annealing is part of the HEM solidification cycle, the defect density is often lower compared to other methods.

the ability to grow materials in various special shapes. However, reducing defect levels remains a challenge. As a result, EFG is more commonly used for growing non-standard materials. With advancements in technology in recent years, EFG has also found applications in materials used for Metal-Organic Chemical Vapor Deposition (MOCVD) epitaxial substrates to a certain extent.

FAQ

Q: What are the advantages of using sapphire wafers in electronic applications?
A: Sapphire wafers offer benefits such as high thermal conductivity, electrical insulation, chemical inertness, and resistance to high temperatures, making them suitable for use in high-power electronic devices, LEDs, and RF components.

Q: Can sapphire wafers be used in high-temperature applications, and what specific properties make them suitable for such environments?

A:Sapphire wafers are ideal for high-temperature applications due to their high melting point (about 2054°C), excellent thermal conductivity, and thermal stability. These properties allow sapphire wafers to maintain their structural integrity and performance in extreme heat conditions.

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