TY - JOUR
T1 - Determination of the defect density in thin film amorphous and microcrystalline silicon from ESR measurements
T2 - The influence of the sample preparation procedure
AU - Xiao, Lihong
AU - Astakhov, Oleksandr
AU - Finger, Friedhelm
AU - Stutzmann, Martin
PY - 2012/9/1
Y1 - 2012/9/1
N2 - Accurate evaluation of the defect density (N D) is of high relevance for the optimization of thin film silicon. The spin density (N S) measured in ESR experiments is often used as a measure for the density of deep defects in the material, assuming that all defects are in a paramagnetic charge state. However, exposure to air, water, or acid during ESR sample preparation can potentially change the N S in a sample and lead to misinterpretation of N D. We have investigated how the preparation procedures of a Si thin film ESR sample may affect the properties of its ESR spectrum. Samples of different structural composition from highly crystalline μc-Si:H to a-Si:H deposited by PECVD on Mo-foil, Al-foil and ZnO:Al were studied for different states of exposure to ambient conditions and annealing. N S measured directly after sample preparation and after air exposure was found to be higher than N S measured in the annealed state. Particularly in highly crystalline material this discrepancy may reach one order of magnitude. On the other hand in a-Si:H and medium crystalline μc-Si:H relevant for applications, the difference in N S between air-exposed and annealed conditions is smaller. ESR measurements performed at 40 K suggest that atmospheric exposure leads to charging of the defect states, which in turn influences the evaluated spin density.
AB - Accurate evaluation of the defect density (N D) is of high relevance for the optimization of thin film silicon. The spin density (N S) measured in ESR experiments is often used as a measure for the density of deep defects in the material, assuming that all defects are in a paramagnetic charge state. However, exposure to air, water, or acid during ESR sample preparation can potentially change the N S in a sample and lead to misinterpretation of N D. We have investigated how the preparation procedures of a Si thin film ESR sample may affect the properties of its ESR spectrum. Samples of different structural composition from highly crystalline μc-Si:H to a-Si:H deposited by PECVD on Mo-foil, Al-foil and ZnO:Al were studied for different states of exposure to ambient conditions and annealing. N S measured directly after sample preparation and after air exposure was found to be higher than N S measured in the annealed state. Particularly in highly crystalline material this discrepancy may reach one order of magnitude. On the other hand in a-Si:H and medium crystalline μc-Si:H relevant for applications, the difference in N S between air-exposed and annealed conditions is smaller. ESR measurements performed at 40 K suggest that atmospheric exposure leads to charging of the defect states, which in turn influences the evaluated spin density.
KW - Conduction electron resonance
KW - Defect density
KW - Electron spin resonance
KW - Fermi level
KW - Hydrogenated silicon powder
UR - http://www.scopus.com/inward/record.url?scp=84865768075&partnerID=8YFLogxK
U2 - 10.1016/j.jnoncrysol.2012.01.039
DO - 10.1016/j.jnoncrysol.2012.01.039
M3 - Article
AN - SCOPUS:84865768075
SN - 0022-3093
VL - 358
SP - 2078
EP - 2081
JO - Journal of Non-Crystalline Solids
JF - Journal of Non-Crystalline Solids
IS - 17
ER -