Influence of annealing on microstructure and piezoresistive properties of boron-doped hydrogenated nanocrystalline silicon thin films prepared by PECVD

Boron-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited by plasma enhanced chemical vapor deposition technique. Annealing treatment was performed on the deposited films at 400 °C for 60 min in nitrogen atmosphere. Microstructure of the as-deposited and annealed films was characterized by X-ray diffraction (XRD) and Raman scatter spectra, surface morphology of these films was analyzed with atomic force microscopy (AFM), and piezoresistive properties of these films were evaluated by a four-point bending-based measurement system. The influence of annealing treatment on microstructure and piezoresistive properties of boron-doped nc-Si:H thin films was comparatively studied. The Raman scatter spectra and XRD results together with AFM analysis results revealed that annealing treatment can increase the average grain size and crystalline volume fraction of boron-doped nc-Si:H thin films, and can alter grains distribution and concentration of the films. The piezoresistive property evaluation results showed that annealing treatment can increase the gauge factor of boron-doped nc-Si:H thin films from 29.9 to 42.3. These results indicated that annealing treatment can act as an effective way to improve piezoresistive sensitivity of boron-doped nc-Si:H thin films. In this paper, the correlation between boron-doped nc-Si:H thin films’ piezoresistive properties and microstructure changes induced by annealing was discussed in detail.