Effect of crystallographic orientation on structural response of silicon to femtosecond laser irradiation

Xin Zhang,Rongshi Xiao,Ting Huang,Liang Zhang,Sergey Mironov,Liang Guo

doi:10.1007/s00339-021-04341-y

Abstract

Femtosecond laser has been widely utilized for modification of crystal structure to achieve desired functions. So far, however, the effect of crystallographic orientation on the induced structure by femtosecond laser processing has yet been comprehensively studied. The present work is undertaken in an attempt to fill this gap in our knowledge. To this end, commercial-purity Si is used as a target material and high-resolution transmission electron microscopy as well as electron backscatter diffraction are applied to examine the irradiation-induced microstructural changes. The structural response of the pulsed material is found to be principally influenced by the crystallographic orientation of the target surface. Specifically, at the surface orientation close to {111}, a pronounced amorphization effect is observed whereas no disordered material is detected at the orientations close to {100}. This phenomenon could be explained by the lowest crystallization speed required by the (111) surface due to its smallest surface energy. Compared with nanosecond laser, non-thermal melting induced by femtosecond laser induces mild thermal gradient and favors recrystallization.

Highlights

Femtosecond laser has been widely applied for crystal structure modification due to its merits such as high instantaneous intensity and short pulse duration, which could lead to nonlinear absorption and small heat-affected zone
Since the pulse width of femtosecond laser is shorter than the characteristic timescale of carrier-lattice coupling, strong thermal non-equilibrium between carriers and lattice can be induced by femtosecond laser heating [12,13,14], which is fundamentally different from heating by nanosecond laser
The Kikuchi-band-contrast map is used as a quantitative measure of crystal disordering whereas the crystallographic orientation map shows the orientation of each grain

Summary

Introduction

Femtosecond laser has been widely applied for crystal structure modification due to its merits such as high instantaneous intensity and short pulse duration, which could lead to nonlinear absorption and small heat-affected zone. Diverse works in this area include amorphization of crystalline Si [1,2,3], control of manganite electronic phase [4], ultrafast phase transition in VO2 [5], ultrafast structural transformation in Ge2Sb2Te5-based phase-change materials [6], and so on. The structural response with femtosecond laser irradiation deserves specific investigation

Methods

Results

Conclusion