Arbitrary surface structuring of amorphous silicon films based on femtosecond-laser-induced crystallization

The effect of stress, resulting from the presence of hydrogen, on the aluminum-induced crystallization of hydrogenated amorphous silicon films was studied. Layered thin films of hydrogenated and unhydrogenated amorphous silicon and aluminum, deposited by sputtering, were used to study this effect. The stress of the deposited films was determined by measuring the radius of curvature of c-Si substrates before and after deposition of the films. It was observed that unhydrogenated amorphous silicon films exhibit a high compressive stress compared with hydrogenated ones. The amount of stress is shown to decrease with increasing hydrogen content. It was also observed that aluminum always provides tensile stress. After the initial stress measurements, all the samples were annealed for 30 min at temperatures between 200 °C and 400 °C. X-ray diffraction was used to determine the crystallinity of the silicon films. The results of the study show that the temperature at which crystallization of amorphous silicon is initiated is lower for films with a lower initial stress.

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Field-Assisted Germanium Induced Crystallization of Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-762-a16.3 ◽

2003 ◽

Vol 762 ◽

Author(s):

J. Derakhshandeh ◽

S. Mohajerzadeh ◽

N. Golshani ◽

E. Asl Soleimani ◽

M.D. Robertson

Keyword(s):

Electric Field ◽

Amorphous Silicon ◽

Applied Voltage ◽

Crucial Role ◽

Silicon Films ◽

Electric Voltage ◽

External Voltage ◽

Annealing Conditions ◽

Induced Crystallization

AbstractA field-assisted germanium-induced crystallization of amorphous silicon on glass is reported at temperatures below 500°C. Silicon films with a thickness of 0.1um are covered with 500Å of germanium as the seed of crystallization. Applying an electric field enhances the growth from both cathode and anode sides. XRD, SEM and TEM analyses have been used to study the crystallinity of the samples which have been treated under different annealing conditions, all confirming the polycrystalline nature of the annealed silicon films. The value of the applied voltage plays a crucial role in the crystalline quality of Si layers. While samples treated without an external voltage are not polycrystalline, an electric voltage of 10 V applied for a 1cm separation between anode and cathode, seems suitable for achieving good poly-crystalline Si layers. The size of grains varies between 0.1 and 0.2μm, as observed using SEM.

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

Materials ◽

10.3390/ma13225296 ◽

2020 ◽

Vol 13 (22) ◽

pp. 5296

Author(s):

Kirill Bronnikov ◽

Alexander Dostovalov ◽

Artem Cherepakhin ◽

Eugeny Mitsai ◽

Alexander Nepomniaschiy ◽

...

Keyword(s):

Femtosecond Laser ◽

Amorphous Silicon ◽

Large Scale ◽

High Surface ◽

Femtosecond Laser Pulses ◽

Visible Spectral Range ◽

Ir Radiation ◽

Near Ir ◽

Si Films ◽

Induced Crystallization

Amorphous silicon (α-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 α-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 α-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 α-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 α-Si and high-quality of the obtained films. Moreover, we highlight localized laser-induced crystallization of α-Si as a promising way for optical information encryption, anti-counterfeiting and fabrication of micro-optical elements.

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