Table 1.

Comparison of properties and performance of different diaphragm materials for acoustic sensors

	Material properties			Without air cavity			With air cavity
Material	Young’s modulus (GPa)	Poisson’s ratio	Density (103 kg/m3)	Thickness (nm)	Sensitivity (µm/Pa)	Natural frequency (kHz)	Thickness (nm)	Sensitivity (nm/Pa)	Natural frequency (kHz)
Silver	83	0.37	10.5	3.00	185	2.66	5.03	1.42	14.0
Parylene C	4.5	0.4	1.29	7.85	185	4.70	9.35	1.42	14.0
Titanium	110	0.32	4.43	2.76	185	4.26	3.43	1.42	14.0
Aluminum	69	0.32	2.7	3.23	185	5.06	3.72	1.42	14.0
Silicon dioxide	90	0.17	2.2	3.04	185	5.78	3.33	1.42	14.0
Silicon	169	0.25	2.3	2.43	185	6.31	2.59	1.42	14.0
Graphene	1000	0.17	2.2	1.36	185	8.63	1.36	1.42	14.0

Note: The simulation results for a circular clamped diaphragm with a diameter of 80 µm. The cylindrical air cavity has the same diameter as that of the diaphragm and a length of 67 µm. The thickness in the “without air cavity” case is varied to obtain the same mechanical sensitivity for different materials. In the case of “with air cavity,” since the mechanical sensitivity is limited by the much stiffer backing air cavity, the thickness is varied to obtain the same natural frequency for different materials.