Laser Nanopatterning
Over the past decade, a variety of techniques have been developed to allow flexible writing of nanopatterns and structures using visible, infrared and ultraviolet laser radiation on a size scale well below the wavelength of light employed. These include t
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Robert Fedosejevs, Ying Tsui, Zhijiang Chen, and Shyama Banerjee
Abstract
Over the past decade, a variety of techniques have been developed to allow flexible writing of nanopatterns and structures using visible, infrared and ultraviolet laser radiation on a size scale well below the wavelength of light employed. These include the use of subwavelength near field optical elements, nonlinear interactions such as two photon absorption, nonlinear response of the medium via contrast enhancement agents and coupling to plasmon modes which have shorter wavelengths than the incident radiation. These can be used for writing of surface features, internal features or complete 3D structures via photopolymerization. Also, nanoablation can be employed both for precision nanomilling of surfaces and direct production of nanoparticles. Laser induced forward transfer of micro- and nano-dots of material is under development for the direct deposition of materials onto surfaces with feature sizes down to 100 nm. Finally, a whole new generation of VUV, XUV and x-ray lasers is emerging, promising even smaller feature sizes in the near future.
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Introduction
Lasers are currently available throughout the ultraviolet to infrared wavelength range and with pulse lengths from femtoseconds to continuous wave. This leads to a large parameter space of potential interaction conditions which can be exploited in order to support a variety of patterning techniques that can be used to produce a wide range of nanostructures. In particular, the short interaction times obtainable using femtosecond laser pulses can be exploited to give minimal lateral or
R. Fedosejevs (*) • Y. Tsui • Z. Chen • S. Banerjee Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada e-mail: [email protected] M. Stepanova and S. Dew (eds.), Nanofabrication, DOI 10.1007/978-3-7091-0424-8_12, # Springer-Verlag/Wien 2012
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volumetric energy spread and generate some of the smallest features possible. In order to obtain nanometer scale features, a number of approaches have been developed to go beyond the wavelength limit of the incident light. These include the use of nonlinear processes which will reduce the interaction zone to a fraction of the wavelength, near field focusing optics, interference effects between two beams or coupling to shorter wavelength plasma waves both on the surface and inside the volume using femtosecond pulses. By using ultraviolet wavelength lasers, feature sizes can be made even smaller by these same approaches. New techniques for efficiently generating coherent vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) pulses are advancing rapidly femtosecond and attosecond pulses are advancing rapidly by means of high harmonic generation (HHG) [1–5], capillary discharge lasers [6, 7] and short pulse laser-plasma pumped lasers at 13.9 nm [8]. New free electron laser (FEL) sources operating in the x-ray regime [9–11] are opening up the possibility of direct patterning at
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