Table 2.

Summary of the comparison on the different preparation method and process, thickness, characteristics, and application of few-layer BP

Techniques	Classification	Methods	Solvent	BP thickness	Lateral control	Characteristics	Applications	References
Top-down
Mechanical exfoliation	Top-down	Sticky-tape		< 7.5 nm	Lack of control	High carrier mobility with low production yield limit	FET	[80–94]
Sonication liquid exfoliation	Top-down		NMP	3–5 Layers	Lack of control	High yield	Semiconductor device	[95–121]
			DMF & DMSO	5–20 nm		Highly crystalline	Electronic device
			CHP	8–11 Layers		Stable	Ultrafast saturable absorbers, gas sensors
Thermal thinning	Top-down				Controllable	Potential for massive fabrication due to low cost		[18]
Bottom-up
Chemical vapor deposition	Bottom-up	CVD		4 Layers	Controllable	Numerous defects introduced Large area potential for massive production	FET	[122–128]
Pulsed laser deposition	Bottom-up				Controllable	Flexible size with limited carrier mobility due to disordered structure		[129]
Phase transition and solvothermal reaction	Bottom-up	Mineralizer assisted (phase transition) Sublimation induced (solvothermal)	Ethanol (solvothermal)	< 5 nm (solvothermal)	Lack of control	High on/off ratios (phase transition) Holey morphology (solvothermal)	Optoelectronic device (phase transition) Batteries (solvothermal)	[130–136, 147]