A Novel Measurement System for Hydrogenated Nanocrystalline Silicon Thin Films' Gauge Factor

We report on a novel method and system for investigation of hydrogenated nanocrystalline silicon (nc-Si:H) thin films' piezoresistive effect, and a measurement system for gauge factor of nc-Si:H thin films is designed based on four-point bending method. nc-Si:H thin film resistor is deposited onto glass beam by plasma-enhanced chemical vapor deposition (PECVD) technique. Fractional strain of strained nc-Si:H thin films is measured by PSD sensor based on laser triangulation method, and relative change in resistance of strained nc-Si:H thin films is read out by Wheatstone bridge, when nc-Si:H thin film resistor is under a uniform stress. All signals, including converted and conditioned signal outputting from PSD sensor and output of Wheatstone bridge, are acquired by PXI data acquisition system with industry's most accurate 71/2-digit digital multi-meter, and then gauge factor of nc-Si:H thin films is achieved by programming. The experimental results show that the measurement system for nc-Si:H thin films' gauge factor has solved the problem of thin film materials' gauge factor measurement, and based on the system the level of automation, precision and efficiency in measurement has been improved, and more importantly, the measurement system has provided the experimental basis for investigation of nc-Si:H thin films' piezoresistive effect.