Effect of thermal annealing on sub-band-gap absorptance of microstructured silicon in air

• Published in: Frontiers of physics Vol. 10; no. 4; pp. 107801 - 7
• Main Authors: Cao, Li-Ping, Chen, Zhan-Dong, Zhang, Chun-Ling, Yao, Jiang-Hong
• Format: Journal Article
• Language: English
• Published: Beijing Higher Education Press 01.08.2015; Springer Nature B.V
• Subjects: Absorptance; Absorption spectroscopy; Absorptivity; annealing; Astronomy; Astrophysics and Cosmology; Atom concentration; Atomic; black silicon; Carrier lifetime; Condensed Matter Physics; Configurations; Crystal defects; Defect annealing; diffusion; Energy gap; High temperature; Microstructured surfaces; Molecular; Optical and Plasma Physics; Optical properties; Particle and Nuclear Physics; Physics; Physics and Astronomy; Research Article; Silicon; sub-band-gap absorptance; Surface chemistry; Thermal relaxation; diffusion; black silicon; sub-band-gap absorptance; annealing
• ISSN: 2095-0462; 2095-0470
• DOI: 10.1007/s11467-015-0491-z

The optical absorption properties of femtosecond-laser-made “black silicon” as a function of the annealing conditions were investigated. We found that the annealing process changes the surface morphology and absorption spectroscopy of the “black silicon” samples, and obtained a maximum sub-band-gap absorptance value of approximately 30% by annealing at 1000 °C for 30 min. The thermal relaxation and atomic structural transformation mechanisms are used to describe the lattice recovery and the increase and decrease of the substitutional dopant atom concentration in the microstructured surface during the annealing. Our results confirm that: i) owing to the thermal relaxation, the lattice defects decrease with the increase of the annealing temperature; ii) the quasi-substitutional and interstitial configurations of the doped atoms transform into substitutional arrangements when the annealing temperature increases; iii) the quasi-substitutional and interstitial configurations with higher energies of the doped atoms transform into interstitial configurations with the lowest energy after high-temperature annealing for a long period of time, causing the deactivation or reactivation of the sub-band-gap absorptance by diffusion. The results demonstrate that the annealing can improve the properties of “black silicon”, including defects repairing, carrier lifetime lengthening, and retention of a high absorptive performance.