The Mystery of Diamond: From the depths of the Earth to the forefront of technology (Part 1)

About 1.5 to 3 billion years ago, carbon atoms were compressed under extreme pressure and temperature in the mantle over 100 kilometers deep on Earth, forming diamonds that were subsequently buried in Kimberlite rocks.

After countless years of geological changes, these diamonds were eventually brought to the surface by volcanic activity. After careful polishing by craftsmen, they turned into dazzling diamonds and quickly occupied an unparalleled position in the jewelry industry.

In 2017, the 59.6-carat CTF Pink Star diamond sold for $71.2 million at Sotheby's Hong Kong auction, shocking the world. In 2022, the 11.15-carat Williamson Pink Star diamond was sold for $57.7 million, becoming the highest priced diamond of the year.

In the process of diamonds becoming the "king" of the jewelry industry, clever market operations and clever marketing strategies are indispensable, but the fundamental reason behind it is that diamonds have formed excellent performance under harsh conditions.

One is hardness: Diamond is the hardest substance in nature, able to withstand the test of time and remain unchanged forever.

The second is brilliance: Diamond has strong refractive power and can emit brilliant light.

The third is brilliant colors: Diamond has high dispersion, which can decompose the passing light into a colorful spectrum, presenting a dazzling rainbow effect.

Research has found that these exceptional properties originate from the unique structure of diamond.

Diamond is composed of carbon atoms, which are arranged in the most compact manner in a tetrahedral structure. Each carbon atom is covalently connected to four other carbon atoms around it, forming a strong three-dimensional lattice. It is this structure that makes diamond the hardest substance on Earth, and endows it with unique abilities such as strong light refraction and thermal conductivity.

The excellent performance of diamond has attracted the favor of researchers in different fields. The supply of natural diamond is far from meeting the needs of applications, and synthetic diamond has emerged, especially in recent years, with accelerated development.

At present, the mainstream and industrialized methods for artificially manufacturing diamond include HPHT (high temperature and high pressure) method and CVD (chemical vapor deposition) method. Among them, CVD method is easier to incorporate new elements into the diamond structure, artificially design and control the diamond, change its conductivity, thermal conductivity and other properties, and thus be more applied in high-tech fields.

The HPHT method imitates the formation conditions of natural diamond and converts graphite into diamond under high temperature and pressure environment. This method typically uses metal catalysts such as iron, nickel, or cobalt to promote the conversion of graphite, which can efficiently produce large particles and high-purity diamonds, widely used in industrial processing fields.

CVD method deposits carbon atoms on the surface of a substrate through chemical reactions at lower temperatures and pressures to form diamond films. This method uses a mixture of methane and hydrogen gas, and decomposes the reaction gas through microwave plasma or hot wire excitation to deposit high-quality diamond films. The CVD method is particularly suitable for producing large-area, ultra pure diamond films, which can be used in the fields of electronics and optics.

Researchers have introduced unique NV (nitrogen vacancy) center defect structures into diamond through irradiation or injection, which are ideal quantum bit materials. Through microwave control and optical readout technology, precise manipulation of NV center quantum states can be achieved, and they are increasingly widely used in fields such as quantum information processing, high-sensitivity physical quantity detection, and biological imaging.

The tight connection of carbon atoms in diamond greatly improves the efficiency of heat transfer, with a thermal conductivity of up to 2000 watts/m • K, making it the material with the highest thermal conductivity in nature, several times higher than most semiconductor materials, and much higher than conventional insulators and even metals. In addition to directly using single crystal or polycrystalline diamond for heat dissipation, combining diamond with other materials can design and develop heat dissipation materials suitable for different types and usage scenarios. This not only prevents device overheating, but also greatly improves device performance and service life.

Diamond, an ancient and mysterious substance, carries the symbol of luxury, integrating excellent hardness, thermal conductivity, wide bandgap, high electron mobility, as well as outstanding quantum properties and environmental stability. It has come from the depths of the earth to the forefront of post Moore era technology, becoming a quantum bit material, known as the "ultimate semiconductor", which will improve our lives, promote the development of modern technology, and explore more unknown worlds.