h-BN powder (purity 97%) was purchased by SANNO Tools. DMF and IPA were used as solvents for the exfoliation of h-BN. All chemicals were used as received. Si/SiO₂ was used as a substrate.

A sonicator (Great sonic, power of bath 240 W, having 50 Hz frequency) was used. First of all a beaker is taken which was cleaned by using acetone. After that by using digital mass balance 2 mg of h-BN powder was measured and mixed with 50 mL IPA in a beaker. This solution sonicated in a sonicator for 10 Hours. Similarly, another sample was also made in which 2 mg of h-BN powder is mixed with 50 mL DMF in a beaker. The solution then sonicated for the 10 hours (Figure 1).

The obtained solution was centrifuged at 3000 rpm for 10 mins. The supernatant was collected and drop cast on silicon substrate for microscopic and spectroscopic analysis (Figure 2).

One can confirm the presence of h-BN with an absorption peak in the range of 210 to 280 nm [11]. As the sample exfoliated in DMF having an absorption peak at 240 nm as shown in Figure 3(a). Similarly, another sample exfoliated in IPA which shows an absorption peak that was observed at 265 nm in Figure 3(b).

The multilayers of h-BN exfoliated in DMF has a bandgap of 5.39 eV [4] while the multilayers of h-BN exfoliated using IPA as solvent has 4.96 eV value (Figure 4).

The Multilayers of h-BN were characterized under XRD to investigate the symmetry and phases. Comparative XRD patterns of h-BN multilayers exfoliated in IPA (red) and DMF (black) can be viewed in Figure 5. From the figure it reveals that diffraction peaks exhibit a slight variation of (0.21˚). As the angle obtained by exfoliated BNNSs in DMF is (27.39˚) while in IPA is (27.17˚) [12]. In contrast to both samples no extra peaks were detected in the XRD pattern of exfoliated BNNSs. The intensity obtained by exfoliated BNNSs in DMF (452) is greater than exfoliated BNNSs in IPA (203) which can be analyzed from Figure 5.

The grain size of exfoliated BNNSs in DMF is 25.62 nm while in IPA is 43.73 nm which shows that h-BN is exfoliated better in DMF with concerning to IPA. The peaks observed at angles 27˚ in both samples confirms the formation of crystallographic planes (002), which is the indication of the formation of multilayers of BNNSs [13].

In SEM (Scanning electron microscopy) sample is scanned by using an energetic beam of electrons. Surface morphology, Chemical composition and material orientation such information is obtained by signals when beam of electron interacts with sample h-BN. In Figure 6(a), Figure 6(b) nanoflakes were pictured by SEM. These nanoflakes illustrating their plate like shape and size of the individual flake in the range of 200 nanometers which was observed in literature survey [14].

If the amount of incident electrons is higher than the amount of electrons evading from the sample, then the negative charge creates on sample at the point where the beam hits. This thing is called the charging effect [15] and it gives a range of scarce effects such as irregular contrast, image distortion and shift. That is why we see contrast in Figure 6(a), Figure 6(b) as this sample is drop cast on silicon substrate because of this we see black area where electron was distributed.

It was observed that Nano flakes obtained by sample exfoliated in DMF have fine distribution comparing to sample exfoliated in IPA.

The exfoliated BN powder in DMF was drop cast on silicon substrate prepared as a function of thickness. The variation of thickness was 5, 10 and 15 drops. Similarly, exfoliated BN powder in IPA also drop cast on silicon substrate as a function of thickness. The variation of thickness was 5, 10 and 15 drops. By using an LCR meter capacitance was measured through which Dielectric constant is intended [16].

The formula to calculate the dielectric constant is

k = C d A ε °

In the above equation C shows capacitance, d depicts thickness, A is area of the sample and ε ° is relative permittivity whose value is 8.85 × 10⁻¹² [17]. Exfoliated BN powder in DMF was drop cast on silicon substrate whose thickness variation can be observed with concerning for to no of drops same is observed in sample exfoliated in IPA [18].

Dielectric Constant is measured by using the formula and it was observed that its value increases with variation in thickness irrespective of solvent as in Table 1 and Table 2.

In Figure 7 histogram shown that as we increase the no of drops value of dielectric constant increases.