**5.1 Diamond overview**

Foremost well-known allotropes of carbon is diamond. Diamond is a Greek word that means "transparent" and "invincible." The layer organization sequence in diamond is ABCABCA… There are four spatial orientations of carbon atoms due to the direction and perception of the tetrahedral axis, resulting in two tetrahedral and two octahedral (eight-faced) forms of diamond [17]. Each carbon atom in diamond is sp3 hybridized, forming covalent connections (bond lengths equal to 1.54 Å) with four additional carbon atoms in the tetrahedral structure's corners. Diamond's strength comes from its steady network of covalent connections and hexagonal rings [2].

• Diamond is unable to conduct any electricity owing to the limited mobility of electrons in the lattice pattern [24], but it exhibits maximum thermal conductivity [25] of roughly 2200 W/(mK), which is way five times higher as of copper [26, 27]. Diamond is commonly utilized, in the semiconductor technology to avert silicon and all other related semiconductors from overheating [13, 28] due to its excellent thermal conductivity [29]. The average electric breakdown of the diamond is fifteen times that of typical semiconductors, while the average holes mobility is five times that of common semiconductors [2].

However, it has a dielectric constant half that of silicon, and when tested, it is likely to exhibit 'negative electron affinity'. According to many studies, it is a 5.5 eV [30] broad bandgap semiconductor when doped to (n or p types).

• A diamond is a massive carbon atom molecule. It has unusual optical qualities. Because it is tied genetically to carbon family [31], it is considered also as biocompatible inside a live organism. Diamonds are transparent and colorless (transmitting light from the far-infrared to the ultraviolet). They are classified as glossy because they shimmer and reflect light. These characteristics make them desirable in jewelry. It is particularly neutron radiation resistant and has an extraordinarily high refractive index. The scientific uses include an optical

sensor component, diamond anvil cells, and so on. it has a natural lubricity in the air that is comparable to Teflon [8].

• Diamond is supposed the hardest natural mineral ever known to human and It is insoluble in water. It has a somewhat high melting point. As a result, it's ideal for cutting tools. This makes it a great abrasive with outstanding polish and luster retention. No known naturally occurring chemical has the ability to cut (or even scratch) [17]. Any electronics device built of the diamond should be able to operate in harsh situations [32] due to its physicochemical features (rugged and 'hard'). All of the features listed above are natural outcomes of the crystal structure.
