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在黑硅表面制备的微结构可以使其获得多种表面功能,这些功能在太阳能、探测器等领域具有广泛的应用.因此,黑硅微结构的形成机理及制备条件优化一直是研究关注的焦点.本文的研究发现,随着激光辐照量(提高单脉冲能量或增加积累脉冲数)的增加会遇到形貌尺寸生长的瓶颈效应:过多的能量累积对微结构的优化和控制并没有进一步的作用.理论计算结果表明,产生这一现象的原因是前序飞秒激光脉冲诱导产生的微结构形貌对当前激光脉冲能量的吸收产生了调制,使当前激光脉冲的有效烧蚀效率降低.根据这一飞秒激光烧蚀规律,提出了一种优化表面形貌的新方案在辐照激光总能量一定的条件下,通过改变激光能量的分配方式(单脉冲能量与脉冲数的组合)可实现表面形貌的优化.这一新的工作方式不但可以提高黑硅的制备效率,而且还有助于减少飞秒加工过程带来的表面缺陷及损伤,并降低加工过程中的能源消耗.这一研究成果对黑硅性能的进一步提升及其工程应用具有重要的意义.Arrays of sharp conical spike microstructures are created by repeatedly irradiating silicon surfaces with focused femtosecond laser pulses in SF6. The absorbance of light is increased to approximately 90% in a wavelength range from the near ultraviolet (0.25 m) to the near infrared (2.5 m) by the microstructured silicon surface. The microstructured surface presents pitch-black because of enhanced absorption with a broad wavelength range, which is called black silicon. The unique microstructure morphology of black silicon surface formed by femtosecond laser can also bring a lot of other surface functions, for example, self-cleaning and field emission. These functions make black silicon highly desirable in solar energy, detectors and other fields. Therefore, the forming mechanism and conditions of fabrication optimization for black silicon microstructure have always been the focus of research. In our work, the sample is moved by motor-controlled stage while the laser beam is fixed. In the case of laser beam scanning, arrays of sharp conical spikes on the silicon are manufactured in 70 kPa SF6. The aim of the experiment is to find how to optimize the distribution of the laser energy in a number of laser accumulation pulses (the combination of single pulse energy and pulse number) to control the surface morphology of the black silicon. Experimental results show that there appears a bottleneck effect of morphology size growth with the increase of laser irradiation (improving the single pulse energy or increasing pulse accumulation number). Excessive energy accumulation brings no extra effect on optimizing and controlling of microstructure morphology on the surface. Based on theoretical results obtained from a physical model we proposed, we find that the reason for this phenomenon is that the microstructure morphology induced by former sequence pulse modulates the laser energy absorption of current laser pulse, and changes the laser ablation efficiency of the current pulse. According to this physical mechanism, we propose a new way of optimizing surface morphology, with fixing the total laser irradiation energy. And the size and distribution of surface morphology can be achieved by optimizing the distribution of the laser energy in a number of laser accumulation pulses. This approach can not only improve the efficiency of silicon surface preparation of microstructures but also reduce the surface defects and damage. Furthermore, the proposed method can reduce the energy consumption in the process of femtosecond machining. It is of great significance for the engineering application of black silicon.
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Keywords:
- femtosecond laser /
- microstructures /
- black silicon /
- surface topography
[1] Wu C, Crouch C H, Zhao L, Carey J E, Younkin R, Levinson J A, Mazur E, Farrell R M, Gothoskar P, Karger A 2001 Appl. Phys. Lett. 78 1850
[2] Peng Y, Chen X Q, Zhou Y Y, Xu G J, Cai B, Zhu Y M, Xu J, Henderson R, Dai J M 2014 J. Appl. Phys. 116 073102
[3] Baldacchini T, Carey J E, Zhou M, Mazur E 2006 Langmuir 22 4917
[4] Tao H, Lin J, Hao Z, Gao X, Song X, Sun C, Tan X 2012 Appl. Phys. Lett. 100 201111
[5] Tao H, Song X, Hao Z, Lin J 2015 Chin. Opt. Lett. 13 061402
[6] Maloney P G, Smith P, King V, Billman C, Winkler M, Mazur E 2010 Appl. Opt. 49 1065
[7] Her T H, Finlay R J, Wu C, Mazur E 2000 Appl. Phys. A 70 383
[8] Peng Y, Zhang D S, Chen H Y, Wen Y, Luo S D, Chen L, Chen K J, Zhu Y M 2012 Appl. Opt. 51 635
[9] Yang H D, Li X H, Li G Q, Yuan C H, Tang D C, Xu Q, Qiu R, Wang J P 2011 Acta Phys. Sin. 60 027901 (in Chinese) [杨宏道, 李晓红, 李国强, 袁春华, 唐多昌, 徐琴, 邱荣, 王俊波 2011 物理学报 027901]
[10] Crouch C H, Carey J E, Warrender J M, Aziz M J, Mazur E, Genin F Y 2004 Appl. Phys. Lett. 84 1850
[11] Peng Y, Hong M, Zhou Y Y, Fang D, Chen X Q, Cai B, Zhu Y M 2013 Appl. Phys. Express 6 051303
[12] Younkin R, Carey J E, Mazur E, Levinson J A, Friend C M 2003 J. Appl. Phys. 93 2626
[13] Dong X, Li N, Liang C, Sun H, Feng G J, Zhu Z, Shao H Z, Rong X M, Zhao L, Zhuang J 2013 Appl. Phys. Express 6 081301
[14] Peng Y, Wen Y, Zhang D S, Luo S D, Chen L, Zhu L M 2011 Appl. Opt. 50 4765
[15] Yang J, Luo F F, Kao T S, Li X, Ho G W, Teng J H, Luo X G, Hong M H 2014 Light: Sci. Appl. 3 e185
[16] Conde J C, Gonzlez P, Lusquios F, Len B 2009 Appl. Phys. A 95 465
[17] Ward L 1994 The Optical Constants of Bulk Materials and Films (2nd Ed.) (London: Institute of Physics)
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[1] Wu C, Crouch C H, Zhao L, Carey J E, Younkin R, Levinson J A, Mazur E, Farrell R M, Gothoskar P, Karger A 2001 Appl. Phys. Lett. 78 1850
[2] Peng Y, Chen X Q, Zhou Y Y, Xu G J, Cai B, Zhu Y M, Xu J, Henderson R, Dai J M 2014 J. Appl. Phys. 116 073102
[3] Baldacchini T, Carey J E, Zhou M, Mazur E 2006 Langmuir 22 4917
[4] Tao H, Lin J, Hao Z, Gao X, Song X, Sun C, Tan X 2012 Appl. Phys. Lett. 100 201111
[5] Tao H, Song X, Hao Z, Lin J 2015 Chin. Opt. Lett. 13 061402
[6] Maloney P G, Smith P, King V, Billman C, Winkler M, Mazur E 2010 Appl. Opt. 49 1065
[7] Her T H, Finlay R J, Wu C, Mazur E 2000 Appl. Phys. A 70 383
[8] Peng Y, Zhang D S, Chen H Y, Wen Y, Luo S D, Chen L, Chen K J, Zhu Y M 2012 Appl. Opt. 51 635
[9] Yang H D, Li X H, Li G Q, Yuan C H, Tang D C, Xu Q, Qiu R, Wang J P 2011 Acta Phys. Sin. 60 027901 (in Chinese) [杨宏道, 李晓红, 李国强, 袁春华, 唐多昌, 徐琴, 邱荣, 王俊波 2011 物理学报 027901]
[10] Crouch C H, Carey J E, Warrender J M, Aziz M J, Mazur E, Genin F Y 2004 Appl. Phys. Lett. 84 1850
[11] Peng Y, Hong M, Zhou Y Y, Fang D, Chen X Q, Cai B, Zhu Y M 2013 Appl. Phys. Express 6 051303
[12] Younkin R, Carey J E, Mazur E, Levinson J A, Friend C M 2003 J. Appl. Phys. 93 2626
[13] Dong X, Li N, Liang C, Sun H, Feng G J, Zhu Z, Shao H Z, Rong X M, Zhao L, Zhuang J 2013 Appl. Phys. Express 6 081301
[14] Peng Y, Wen Y, Zhang D S, Luo S D, Chen L, Zhu L M 2011 Appl. Opt. 50 4765
[15] Yang J, Luo F F, Kao T S, Li X, Ho G W, Teng J H, Luo X G, Hong M H 2014 Light: Sci. Appl. 3 e185
[16] Conde J C, Gonzlez P, Lusquios F, Len B 2009 Appl. Phys. A 95 465
[17] Ward L 1994 The Optical Constants of Bulk Materials and Films (2nd Ed.) (London: Institute of Physics)
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