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S. Majidi et al.
its B atoms in each successive BN layer sitting under or above the N atoms in the
contiguous layers. These obtained properties demonstrate the B–N bonds polarity,
especially the partial ionic character of the covalent B–N bonds. Actually, the N and
B atoms inside a 2D layer, are connected together by strong B–N covalent bonds,
while the 2D layers are linked with each other through the weak van der Waals
(vdW) forces [5, 6]. The hexagonal crystal structure of h-BN with the interlayer
spacing of 0.33 nm and crystallographic variables of a = 0.25 nm and c = 0.666 nm
empowers admirable interaction with graphene, which indicates its excellent capacity
for numerous industrial applications.
Regarding the ultra-flat atomic surface, which is free of dangling bonds and with
negligible defects, a small lattice constant mismatch of about 1.7% was obtained
[7]. The 2D h-BN has been considered as a supreme outlook for future graphene
electronics with greater stability and efficiency [8]. Unlike graphene, the h-BN sheet
has a wide gap insulator of 5–6 eV which can be altered by edge passivation with
different types of atoms, higher chemical inertness and thermal stability, resistance to
oxidation, and good optical properties [9–13]. These make it an interesting material
for optoelectronic technologies [14, 15], tunnel devices, and field-effect transistors
[16, 17].
2 h-BN Synthesis Methods
Synthesis and processing of h-BN can affect the structure, crystallinity, and characteristics of 2D h-BN nanosheets. However, developing the attractive 2D h-BN with
desired structure and functional features for particular applications is still a challenge
[18, 19]. Several producing methods have been developed to synthesis mono- and
multi-layer h-BN, especially with the aim of producing a high efficiency of considerable lateral size and great quality [4]. The process of 2D h-BN production can
be classified into bottom-up and top-down methods. In the bottom-up methods, a
film is grown on the surface; and in top-down methods, bulk h-BN crystal is exfoliated to obtain the purpose structure. Generally, taking bulk h-BN, then break the
vdW forces between the layers of h-BN and separate the resulting 2D nanosheets is
the main idea of top-down methods. These methods mainly involve mechanical and
chemical exfoliation methods [20]. Mechanical and liquid-phase exfoliations are two
common techniques used to separate single sheets from stacked 2D layered crystals
by breaking the weak vdW bonds between the layers. Mechanical exfoliation can
lead to sheets with perfectly crystalline structures [15], which the sheets synthesizes
via this technique are employed to investigate the inherent properties of substances
[21].
S. Majidi et al.
its B atoms in each successive BN layer sitting under or above the N atoms in the
contiguous layers. These obtained properties demonstrate the B–N bonds polarity,
especially the partial ionic character of the covalent B–N bonds. Actually, the N and
B atoms inside a 2D layer, are connected together by strong B–N covalent bonds,
while the 2D layers are linked with each other through the weak van der Waals
(vdW) forces [5, 6]. The hexagonal crystal structure of h-BN with the interlayer
spacing of 0.33 nm and crystallographic variables of a = 0.25 nm and c = 0.666 nm
empowers admirable interaction with graphene, which indicates its excellent capacity
for numerous industrial applications.
Regarding the ultra-flat atomic surface, which is free of dangling bonds and with
negligible defects, a small lattice constant mismatch of about 1.7% was obtained
[7]. The 2D h-BN has been considered as a supreme outlook for future graphene
electronics with greater stability and efficiency [8]. Unlike graphene, the h-BN sheet
has a wide gap insulator of 5–6 eV which can be altered by edge passivation with
different types of atoms, higher chemical inertness and thermal stability, resistance to
oxidation, and good optical properties [9–13]. These make it an interesting material
for optoelectronic technologies [14, 15], tunnel devices, and field-effect transistors
[16, 17].
2 h-BN Synthesis Methods
Synthesis and processing of h-BN can affect the structure, crystallinity, and characteristics of 2D h-BN nanosheets. However, developing the attractive 2D h-BN with
desired structure and functional features for particular applications is still a challenge
[18, 19]. Several producing methods have been developed to synthesis mono- and
multi-layer h-BN, especially with the aim of producing a high efficiency of considerable lateral size and great quality [4]. The process of 2D h-BN production can
be classified into bottom-up and top-down methods. In the bottom-up methods, a
film is grown on the surface; and in top-down methods, bulk h-BN crystal is exfoliated to obtain the purpose structure. Generally, taking bulk h-BN, then break the
vdW forces between the layers of h-BN and separate the resulting 2D nanosheets is
the main idea of top-down methods. These methods mainly involve mechanical and
chemical exfoliation methods [20]. Mechanical and liquid-phase exfoliations are two
common techniques used to separate single sheets from stacked 2D layered crystals
by breaking the weak vdW bonds between the layers. Mechanical exfoliation can
lead to sheets with perfectly crystalline structures [15], which the sheets synthesizes
via this technique are employed to investigate the inherent properties of substances
[21].