Patterning of metallic glasses using polymer templates

Abstract

a b s t r a c tWe demonstrate patterning of metallic glasses using flexible and reusable polymer templates. The elastic deformation of polymer templates is utilized to pattern features of varying dimensions and oblique angles on planar and non-planar surfaces. This is enabled by low thermoplastic processing temperatures of certain metallic glasses and the stability of thermosetting polymers used as the mold making material. The polymer templates are fabricated by standard replica molding of silicon master templates. This provides a scalable method for patterning of metallic glasses which otherwise requires expensive disposable silicon templates.Patterning of materials is an integral component of fabrication process in microelectronics [1], optical devices [2], and surface engineering [3]. There is an overwhelmingly growing demand for patterning smaller features on novel materials along with reduction in cost of scalability. As a result, tremendous progress has been made in advancement of patterning techniques such as lithography [4], nano-imprinting [5,6], embossing [3,7], self-assembly [8,9], LIGA [10,11], and laser processing [12]. Despite these efforts, patterning of metallic materials is far less advanced compared to polymers and semiconductors. This deficit is related to inherent challenges in metal processing such as high surface energy, oxidation, rapid grain growth, and incompatibility with mechanical embossing. Recent work on thermoplastic molding of metallic glasses (MGs) appears to bridge this processing capability gap between metals and polymers [13][14][15][16][17]. Pattern features in the range of sub-100 nm have been demonstrated by thermoplastic embossing of MGs [16,[18][19][20]. After embossing, the MGs can be crystallized by thermal annealing if patterns in crystalline metals are desired [21]. Though thermoplastic shaping of MGs exhibits a great potential for scientific studies [19,[22][23][24][25], the template cost poses a major hurdle for large-scale implementation. Typically, silicon templates prepared by lithography are used because of their precision and rigidity [15,17]. MGs cannot be released from silicon templates without etching because of their thermal expansion mismatch and scalloping roughness of silicon templates. This limits the template usage to a single molding operation even for low-aspect-ratio features without undercuts. Additionally, the employment of rigid templates limits the patterning application to planar surfaces. To overcome these issues, we explore the application of polymer templates for patterning of MGs with low glass transition temperatures. The polymer templates offer several advantages such as: inexpensive fabrication by replica molding of the master template, ease in demolding, reusability, and conformation to non-planar shapes [26][27][28]. Furthermore, elastic deformation (stretching, compression or bending) of polymer templates can be used to vary the size and orientation of features without the need of a new template [29]. The key requirement for using pol...

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