Large-Scale and Localized Laser Crystallization of Optically Thick Amorphous Silicon Films by Near-IR Femtosecond Pulses.

Kirill Bronnikov,Eugeny Mitsai,Aleksandr Kuchmizhak,Alexander Nepomniaschiy,Alexey Zhizhchenko,Alexander Dostovalov,Artem Cherepakhin,Sergei A Kulinich

doi:10.3390/ma13225296

Abstract

Amorphous silicon (-Si) film present an inexpensive and promising material for optoelectronic and nanophotonic applications. Its basic optical and optoelectronic properties are known to be improved via phase transition from amorphous to polycrystalline phase. Infrared femtosecond laser radiation can be considered to be a promising nondestructive and facile way to drive uniform in-depth and lateral crystallization of -Si films that are typically opaque in UV-visible spectral range. However, so far only a few studies reported on use of near-IR radiation for laser-induced crystallization of -Si providing less information regarding optical properties of the resultant polycrystalline Si films demonstrating rather high surface roughness. The present work demonstrates efficient and gentle single-pass crystallization of -Si films induced by their direct irradiation with near-IR femtosecond laser pulses coming at sub-MHz repetition rate. Comprehensive analysis of morphology and composition of laser-annealed films by atomic-force microscopy, optical, micro-Raman and energy-dispersive X-ray spectroscopy, as well as numerical modeling of optical spectra, confirmed efficient crystallization of -Si and high-quality of the obtained films. Moreover, we highlight localized laser-induced crystallization of -Si as a promising way for optical information encryption, anti-counterfeiting and fabrication of micro-optical elements.

Highlights

Due to the advantages of polycrystalline silicon over its amorphous counterpart (α-Si), which include orders of magnitude higher carrier mobility and better stability, thin films of poly-Si have become the basis for solar cells, thin-film transistors, high definition displays, vertically integrated memory devices, etc. [1,2,3,4,5]
Crystallization of amorphous silicon is an actively studied approach for obtaining poly-Si thin films since thin films of α-Si can be produced by cheap low-temperature chemical or physical vapor deposition over large-scale substrates including glasses and flexible polymers, that allows to extend functionality and reduced fabrication cost of resulting optoelectronic devices
This work demonstrates that near-IR femtosecond laser pulses can efficiently drive phase transition in glass-supported 365-nm thick α-Si, resulting in formation of high-quality uniform polycrystalline Si

Summary

Introduction

Due to the advantages of polycrystalline silicon (poly-Si) over its amorphous counterpart (α-Si), which include orders of magnitude higher carrier mobility and better stability, thin films of poly-Si have become the basis for solar cells, thin-film transistors, high definition displays, vertically integrated memory devices, etc. [1,2,3,4,5]. By pyrolytic decomposition of monosilane SiH4 in rod-type and boiling-layer-type reactors [6] These methods include high-temperature exposure (700–1000 ◦ C), restricting the choice. Crystallization of amorphous silicon is an actively studied approach for obtaining poly-Si thin films since thin films of α-Si can be produced by cheap low-temperature chemical or physical vapor deposition over large-scale substrates including glasses and flexible polymers, that allows to extend functionality and reduced fabrication cost of resulting optoelectronic devices. Crystallization of α-Si was realized using thermal annealing [7], solid-phase crystallization [8], metal-induced crystallization and modifications of this method for lateral crystallization [9,10]. All these methods are usually accompanied by a melting-cooling-solidification cycle

Methods

Results

Conclusion