飞秒激光双脉冲列诱导半导体表面自组装周期结构及其特性研究
发布时间：2018-12-25 08:47
【摘要】：飞秒激光在材料表面诱导自组装周期结构(LIPSS)一直是光学领域研究的重点。近几十年来,科研人员主要关注两个方面:一个是自组装周期结构的形成机理;另一个是拓展其应用领域。研究表明飞秒激光辐照材料表面激发的电子密度水平对周期结构的诱导有着重要影响。飞秒激光的超短脉宽比烧蚀过程中涉及到的物理化学过程的时间尺度短或者与其相当。因此,采用飞秒激光双脉冲列辐照技术可为操控瞬态局域电子动力学过程、调控瞬态局域材料特性、控制相应的相变机理提供很多的可能性,也为探索LIPSS的形成机理提供了的新的视角。本文采用不同偏振的飞秒激光双脉冲列,在不同延迟时间下辐照ZnO和6H-SiC表面,得到了不同形貌的纳米形貌。主要通过改变双脉冲序列间的延迟时间,调节材料表面被激发的电子密度水平,从而控制材料表面被诱导的周期结构以及结构特性。本文的主要内容包括:1、通过采用可调节延迟时间的飞秒激光双脉冲序列辐照ZnO表面,得到了低空间频率周期条纹结构(LSFL)和高空间频率周期条纹结构(HSFL);发现随着延迟时间的增加,LSFL逐渐向HSFL转变。使用电子速率方程分别计算不同延迟时间下由800nm和400nm的飞秒激光辐照ZnO表面所激发的电子密度。依据电子密度计算结果,结合Sipe理论,解释了结构转变现象。2、通过可调节延迟时间的交叉偏振飞秒激光双脉冲序列辐照ZnO表面,得到了不同形貌的纳米结构;对ZnO表面进行磁控溅射喷金和退火处理,成功制备出具有表面拉曼散射增强的基底。在给定的激光参数下,该基底的拉曼增强因子最高达到1.2×104。3、通过采用可调节延迟的共线双脉冲序列辐照6H-SiC表面,得到了LSFL和HSFL两种周期结构。同样发现随着延迟时间的增加,LSFL逐渐向HSFL转变,对此现象进行了理论分析。更特别的是,在6H-SiC表面烧蚀区观察到了双折射现象,且双折射现象会随着延迟时间的改变而变化,我们对造成上述现象的因素,进行了系统的分析。
[Abstract]:Femtosecond laser induced self-assembly periodic structure (LIPSS) on the surface of materials has been the focus of optical research. In recent decades, researchers have focused on two aspects: one is the formation mechanism of self-assembled periodic structure, the other is to expand its application field. The results show that the electron density level induced by femtosecond laser irradiation plays an important role in the induction of periodic structures. The ultrashort pulse width of femtosecond laser is shorter than or equivalent to the time scale of the physical and chemical processes involved in the ablation process. Therefore, the technology of femtosecond laser double pulse train irradiation can provide many possibilities for manipulating transient local electron dynamics, regulating transient local material characteristics, and controlling the corresponding phase transition mechanism. It also provides a new perspective for exploring the formation mechanism of LIPSS. In this paper, ZnO and 6H-SiC surfaces were irradiated with femtosecond laser double pulses with different polarization at different delay time, and different morphologies were obtained. By changing the delay time between the two pulse sequences and adjusting the level of electron density excited on the surface of the material, the induced periodic structure and structural characteristics of the material surface are controlled. The main contents of this paper are as follows: 1. By using femtosecond laser double pulse sequence with adjustable delay time to irradiate the surface of ZnO, the low spatial frequency periodic fringe structure (LSFL) and the high spatial frequency periodic stripe structure (HSFL); are obtained. It was found that with the increase of delay time, LSFL gradually changed to HSFL. The electron density excited by 800nm and 400nm femtosecond laser irradiation on the surface of ZnO was calculated by using the electron rate equation. According to the results of electron density calculation and Sipe theory, the phenomenon of structure transition is explained. 2. Different morphologies of nanostructures are obtained by cross-polarization femtosecond laser double pulse sequence with adjustable delay time to irradiate the surface of ZnO. The substrate with enhanced surface Raman scattering was successfully prepared by magnetron sputtering and annealing on the surface of ZnO. Under the given laser parameters, the maximum Raman enhancement factor of the substrate is 1.2 脳 104.3. Two periodic structures of LSFL and HSFL have been obtained by irradiating the surface of 6H-SiC with a collinear dual-pulse sequence with adjustable delay. It is also found that with the increase of delay time, LSFL gradually changes to HSFL, and this phenomenon is analyzed theoretically. In particular, birefringence is observed in the ablation region of 6H-SiC surface, and the birefringence changes with the change of delay time.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN249;TN304
本文编号：2390954
[Abstract]:Femtosecond laser induced self-assembly periodic structure (LIPSS) on the surface of materials has been the focus of optical research. In recent decades, researchers have focused on two aspects: one is the formation mechanism of self-assembled periodic structure, the other is to expand its application field. The results show that the electron density level induced by femtosecond laser irradiation plays an important role in the induction of periodic structures. The ultrashort pulse width of femtosecond laser is shorter than or equivalent to the time scale of the physical and chemical processes involved in the ablation process. Therefore, the technology of femtosecond laser double pulse train irradiation can provide many possibilities for manipulating transient local electron dynamics, regulating transient local material characteristics, and controlling the corresponding phase transition mechanism. It also provides a new perspective for exploring the formation mechanism of LIPSS. In this paper, ZnO and 6H-SiC surfaces were irradiated with femtosecond laser double pulses with different polarization at different delay time, and different morphologies were obtained. By changing the delay time between the two pulse sequences and adjusting the level of electron density excited on the surface of the material, the induced periodic structure and structural characteristics of the material surface are controlled. The main contents of this paper are as follows: 1. By using femtosecond laser double pulse sequence with adjustable delay time to irradiate the surface of ZnO, the low spatial frequency periodic fringe structure (LSFL) and the high spatial frequency periodic stripe structure (HSFL); are obtained. It was found that with the increase of delay time, LSFL gradually changed to HSFL. The electron density excited by 800nm and 400nm femtosecond laser irradiation on the surface of ZnO was calculated by using the electron rate equation. According to the results of electron density calculation and Sipe theory, the phenomenon of structure transition is explained. 2. Different morphologies of nanostructures are obtained by cross-polarization femtosecond laser double pulse sequence with adjustable delay time to irradiate the surface of ZnO. The substrate with enhanced surface Raman scattering was successfully prepared by magnetron sputtering and annealing on the surface of ZnO. Under the given laser parameters, the maximum Raman enhancement factor of the substrate is 1.2 脳 104.3. Two periodic structures of LSFL and HSFL have been obtained by irradiating the surface of 6H-SiC with a collinear dual-pulse sequence with adjustable delay. It is also found that with the increase of delay time, LSFL gradually changes to HSFL, and this phenomenon is analyzed theoretically. In particular, birefringence is observed in the ablation region of 6H-SiC surface, and the birefringence changes with the change of delay time.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN249;TN304
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