TAILIEUCHUNG - Silicon as a Mechanical Material

Nanocrystalline materials have been the subject of widespread research over the past couple of decades with significant advancement in their understanding especially in the last few years [3]. As the name suggests, they are single or multi-phase polycrystals with nano scale (1 · 10 9 –250 · 10 9 m) grain size. At the upper limit of this regime, the term ‘‘ultra- fine grain size’’ is often used (grain sizes of 250–1000 nm). Nanocrystalline materials are structurally characterized by a large volume fraction of grain boundaries, which may sig- nificantly alter their physical, mechanical, and chemical properties in comparison with conventional coarse-grained polycrystalline materials [4–6], which have grain sizes usually in the. | 420 PROCEEDINGS OF THE IEEE VOL. 70 NO. 5 MAY 1982 Silicon as a Mechanical Material KURT E. PETERSEN MEMBER IEEE Abstract-Single-crystal silicon is being increasingly employed in a variety of newcommercial products not because of its well-established electronic properties but rather because of its excellent mechanical properties. In addition recent trends in the engineering literature indicate a growing interest in the use of silicon as a mechanical material with the ultimate goal of developing a broad range of inexpensive batch-fabricated high-performance sensors and transducers which are easily interfaced with the rapidly proliferating microprocessor. This review describes the advantages of employing silicon as a mechanical material the relevant mechanical characteristics of silicon and the processing techniques which are specific to micromechanical structures. Finally the potentials of this new technology are illustrated by numerous detailed examples from the literature. It is clear that silicon will continue to be aggressively exploited in a wide variety of mechanical applications complementary to its traditional role as an electronic material. Furthermore these multidisciplinary uses of silicon will significantly alter the way we think about all types of miniature me chanical devices and componenta I. Introduction IN THE SAME WAY that silicon has already revolutionized the way we think about electronics this versatile material is now in the process of altering conventional perceptions of miniature mechanical devices and components 1 . At least eight firms now manufacture and or market silicon-based pressure transducers 2 first manufactured commercially over 10 years ago some with active devices or entire circuits integrated on the same silicon chip and some rated up to 10 000 psi. Texas Instruments has been marketing a thermal point head 3 in several computer terminal and plotter products in which the active printing element abrasively contacting the paper is

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