Tham khảo tài liệu 'coherence and ultrashort pulse laser emission part 17', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Sub-Wavelength Patterning of Self-Assembled Organic Monolayers via Nonlinear Processing with Femtosecond Laser Pulses 631 Fig. 2. Schematic presentations of the SAM substrate combinations considered in this review a ODS monolayers on quartz glass b ODS monolayers on surface-oxidized silicon substrates c HDT monolayers on Au-coated silicon substrates. The surface bond of the molecules is shown in red on the right-hand side of each scheme. In the work reviewed here alkylsiloxane SAMs and alkanethiol SAMs are addressed. As substrates quartz glass surface-oxidized silicon and Au-coated silicon samples are used. Surface-oxidized silicon samples expose a native oxide layer with a thickness of 1-2 nm on top. Au-coated silicon samples are silicon samples with a 5 nm Ti adhesion layer and a 40 nm Au layer on top. Detailed coating procedures are given in the literature Hartmann et al. 2008 Franzka et al. 2010 Mathieu et al. 2010 . Briefly prior to coating all substrates are cleaned in hot piranha solution a mixture of sulfuric acid and hydrogen peroxide . Octadecylsiloxane ODS monolayers then are formed upon immersion of the substrates into a millimolar solution of octadecyltrichlorosilane in toluene. For coating with hexadecanthiol HDT monolayers a millimolar solution of HDT in ethanol is used. Schematic presentations of the distinct SAM substrate combinations are shown in Fig. 2. 3. Nonlinear femtosecond laser processing Laser processing is widely recognized as a facile and versatile means for direct patterning of SAMs Mathieu Hartmann 2010 . If nanopatterning is targeted the optical diffraction limit however poses a significant constraint Bauerle 2000 . Even if highly focusing optics with a numerical aperture NA close to one is used the minimum structure size dmin usually is not much smaller than the wavelength V of the laser light dmin V NA 1 A common means to extend the lateral resolution of laser techniques into the subwavelength range takes advantage of nonlinear .
