The crystallisation of the nucleation agent ZrTiO 4 in a low thermal-expansion lithium aluminosilicate glass-ceramics is monitored as a function of time by combining transmission electron microscopy with Ti-L 2,3 X-ray absorption near-edge structure spectroscopy. The formation of liquid-liquid phaseseparation droplets is shown to precede ZrTiO 4 crystallisation within the latter nanosized droplets. Quantitative data on crystalline fractions enable conclusions on the self-limited growth of ZrTiO 4 nanocrystals in low thermal-expansion glass-ceramics and based on Avrami's equation, the growth is shown to be restricted by a barrier (the outer border of the phase-separation droplet). It is shown that liquid-liquid phase separation and crystallisation are temporally decoupled. The size of ZrTiO 4 crystallites is determined by the restricted volume of the phase-separation droplets they crystallise in. The volume of the droplets in turn is restricted by the formation of a diffusion barrier in the surrounding residual glass.
Highly efficient fabrication of well-ordered, embedded gold nanodot matrices using diffraction mask projection laser ablation is demonstrated. These gold nanodot arrays are ideally generated onto sapphire substrates but do also form onto AlO(x) thin films, enabling the application to arbitrary bulk substrates. Well-ordered gold dots become embedded into the Al(2)O(3) substrate during the process, thus improving their mechanical stability, chemical inertness, and technological compliance. Such substrates may be useful, for example, to enhance solar-cell efficiency by surface plasmons or as convenient, biocompatible focusing elements in nearfield optical tweezers.
1 Introduction Growing nanowires or whiskers with methods like physical vapor deposition (PVD), chemical vapor deposition (CVD) or pulsed laser deposition (PLD) requires seeded substrates for generating well ordered structures [1][2][3][4].In this letter, the patterning of thin metal films by diffraction mask projection laser ablation (DiMPLA) is discussed (see also [5][6][7]). The machined areas are very large compared to the size of the nanostructures. Therefore, the samples can ideally be used as templates for 3D nanostructure growth. The templates are created using an excimer laser. In recent literature most of the techniques that can be found are either using fs-lasers [8,9], bulk targets [10], or lithographic methods [11,12] to create nano-patterns. Those techniques are more complicated to handle and the structuring process is more time-consuming than the procedure used here. Although thin metal film removal by lasers [13] and interferometric laser ablation of bulk material [14] is done for a long time, the authors have no knowledge of a combined technique that uses a phase mask as it was done here. In the present paper, emphasis is laid onto homogeneity and reproducibility of the large area patterning.
The top-down method diffraction mask projection laser ablation (DiMPLA) to produce large-area substrate-bound metal nanostructure matrices is discussed in detail. It involves phase mask projection and patterning of an ultra-thin metal film. Investigations concerning the patterning process and parameter frontiers are presented along with results of different materials patterned with DiMPLA. The material combination of thin film and substrate used most is investigated precisely allowing conclusions about the structure formation process as well as possible applications. Presented possible applications include three different PVD techniques for templated nanostructure growth as well as first steps toward plasmonic applications of gold nanodot matrices.Top view of a gold nanodot matrix on a sapphire substrate. In this paper, the top-down laser patterning technique diffraction mask projection laser ablation (DiMPLA) [6][7][8][9][10] is presented to prepare nanostructures. It is based on the usage of a phase mask that provokes maxima of diffraction when a laser pulse is sent through. By a reflecting objective, all orders of diffraction other than the first are blocked from the following beam path. Additionally, the objective demagnifies the image of the phase mask and the beamlets
Direct-writing techniques are adequate tools for rapid prototyping of diverse materials, since they avoid the usage of moulds or masks. Among them, laser-induced forward transfer (LIFT) has become a promising tool for rapid prototyping of microdevices due to the high focusing power of lasers, which provides a high resolution, and also to their non-contact and orifice-free nature, which avoids clogging and thus allows working with a wide range of materials. This makes LIFT an appropriate tool for biosensors preparation. In this article, immunoglobulin (IgG) microarrays were prepared through LIFT varying the laser pulse energy. It was found that there exists a minimum energy threshold, E min , below which no material is deposited. Moreover, an analysis of the droplets volumes revealed a linear dependence of this parameter with the laser pulse energy, what allowed finding the existence of an energy density threshold, which is considered to be the threshold to generate an impulsion on the liquid film that only results in droplet ejection when the total energy overcomes E min . Finally, the bioactivity of the transferred proteins was tested, showing no loss of their activity along the whole laser pulse energy range.
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