**1. Introduction**

The III-nitride semiconductors are known for their excellent chemical and physical properties like direct bandgap, low electron affinity, and chemical and thermal stability [1–6]. Among III-nitride materials, Boron nitride (BN) is the only binary material that shows crystal polymorphism, i.e. BN can exhibit several crystal structures. This polymorphism is due to the sp2 - or sp3 -hybridized atomic orbital. The number of B and N atoms in BN structures is equal. BN exists in the form of hexagonal crystalline phase (h-BN), cubic (c-BN), wurtzite (w-BN), and rhombohedral (r-BN). Among all the crystalline phases, the hexagonal and cubic are the most stable phases [7, 8]. The c-BN exhibits a zinc blende structure consisting of boron and nitrogen atoms arranged tetrahedrally, like a diamond.

In contrast, h-BN exhibits a layered structure, with neighboring B and N atoms forming honeycomb structures for each sp2 -bonded monolayers. The layers are made up of AA' stacking configuration and bounded by weak van der Waals forces with an interlayer distance of 3.33 Å, similar to graphite structure. Because of the said reason, the h-BN is a layered material and can be easily exfoliated to even a single monolayered material. The monolayered material is also known as 2D material or low-dimensional material. The h-BN material has extraordinary properties, remarkable thermal conductivity, mechanical strength, high thermal and chemical stability, and a wide bandgap. Traditionally, the BN material is used for high-temperature applications such as furnaces insulation, furnace crucibles, metal casting molds, and high-temperature lubrication [9–13]. H-BN supplemented with extraordinary physical properties exhibits atomic smoothness and a lack of dangling bond on the surface. This material in 2D form is considered the best substrate for graphene electronics [14, 15]. Moreover, 2D h-BN sheets are being explored for their application as spacer layers for metal–insulator–metal devices and as a dielectric material for transistors and nanocapacitors [16–19].

The first growth of h-BN was reported by Paffett et al. in 1990; the group used an ultrahigh vacuum (UHV) system to deposit h-BN on Pt (111) substrates [19]. The Borazine (B3H6N3) was used as a precursor for the growth. Various surface analysis techniques were used to characterize the grown epilayers. It was observed that h-BN monolayers were grown successfully, but thick layered h-BN growth was impossible [20]. In the year of 1995, Nagashima et al. investigated the h-BN epilayers on Ni (111), Pd (111), and Pt (111). They found that the structure of the h-BN monolayer was independent of the metal substrate [21]. Furthermore, researchers found that the BN layer formed on Ni (111) did not grow layer by layer after forming the first BN monolayer. Consequently, the non-layer-by-layer growth reduced the BN growth rate significantly due to the thermal stability of the first monolayer on the Ni (111) substrate. In addition, the bond between the BN epilayers and Ni (111) surface was weaker than graphite [22]. Later, it was discovered that h-BN forms a nanotech structure with periodic nanometer-sized holes due to the significant lattice mismatch with respect to the metal substrate [23]. In 2003, the h-BN monolayer was first observed by Auwarter et al. on Ni (111) substrates and trichloro borazine (ClBNH)3. The achieved monolayer had a very low defect density and triangular domain.

Moreover, different domains with fcc and hcp boron stacking were observed. To use low-dimensional h-BN material, researchers need to find a scalable growth method. Chemical vapor deposition (CVD) is commercially used in large-area growth techniques; researchers were able to grow centimeter-scaled h-BN epilayers on various metal substrates, e.g. Ni, Cu, and Pt [24–29]. However, researchers around the globe are still working to achieve larger-sized single crystals to study the growth mechanism and ensure its feasibility in the industry. The thickest monolayer single crystal formed to date is ~500 μm [24].

The advantage of using a transition metal as a substrate is their epitaxial relationship, which enables BN films to be easily transferred to another substrate for device fabrication or material characterization [30, 31]. However, this transfer process is unreliable as it is highly dependent on the manual handling expertise of the user transferring large-area films. Furthermore, impurities induced by the solvents during the transfer process are inevitable. Therefore, to avoid considerable degradation to the h-BN film, enhancing the transfer process or introducing a direct growth method would be advantageous. At the same time, the h-BN production cost is another factor that needs to be considered before commercialization. The most common precursors

### *Boron Nitride Fabrication Techniques and Physical Properties DOI: http://dx.doi.org/10.5772/intechopen.106675*

for the growth of BN are ammonia and borane [32–38]. This compound is relatively stable in air, less toxic, and easy to handle. These precursors are the most popular due to their high yield and high-quality h-BN films, but the cost of these precursors is relatively high and unpredictable. Apart from ammonia and borane, researchers are working on other less toxic precursors, e.g. borazine, trichloro borazine, diborane, dimeric diborazane + trimeric triborazane, BF3 + N2 + H2, and trimethylamine borane [32]. To be widely accepted in the industry for mass production, the precursors should be low in toxicity, provide high yield, and be economical in price. Therefore, exploring economical and low-toxic alternatives is still in high demand. In upcoming sections, we will explain structural properties, growth/fabrication technique, and BN (low dimension) application.
