Fig. 1. Crystal structures ^{［17， 21］}

Fig. 2. Material preparation using top-down approaches depicting ^{［26， 31， 34］}

Fig. 3. Hexagonal boron nitride synthesis using chemical vapor deposition ^{［41， 42］}

Fig. 4. Hexagonal boron nitride synthesis using physical vapor deposition ^{［50， 51］}

Fig. 5. Low-dimensional material devices with hexagonal boron nitride as dielectric layer ^{［59， 62， 63， 69］}

Fig. 6. Low-dimensional material devices with hexagonal boron nitride as tunnel barrier layer ^{［77， 80］}

Fig. 7. Deep-ultraviolet photodetector based on h-BN nanosheets ^{［90， 91］}

Fig. 8. Mid-infrared photodetector based on h-BN/graphene ^{［94， 95］}