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Liquid polycarbosilane derived SiC coating on silicon (1 1 1) wafer for enhanced mechanical properties

Silicon carbide coating on silicon (1 1 1) wafer was deposited by modified chemical vapor deposition (CVD) method using liquid polycarbosilane (LPCS) as precursor at three different moderately high temperatures in presence of Argon gas. Glancing angle X-ray diffractometer and Fourier Transform Infrared Spectroscopy reveals smooth β-SiC coating and its subsequent transformation into α-SiC on silicon substrate. In all the temperature the film was found to be uniform with a thickness ranging from 0.6–1.2 μm. The average particle size as can be seen from FESEM ranges from 7 to 385 nm approximately, the lowest range being (7–20 nm) which hitherto has not yet been reported using LPCS as precursor for SiC. Moreover the coated samples show substantial increment of hardness (18.8 GPa) and toughness (1.51 MPa m1/2), both of which increases with increase in deposition temperature. The smooth and thin SiC coating on silicon formed in three different moderate temperatures compared to very high temperature for other CVD assisted coating along with enhanced hardness and toughness makes this a promising material in critically harsh environment required for microelectromechanical systems (MEMS) application.

Highlights
► Deposition of SiC film from polycarbosilane precursor by modified CVD method.
► Polymer to ceramics conversion at moderate temperature of 800, 900 and 1000 °C.
► Formation of β-SiC and α-SiC films on silicon (1 1 1) wafer at moderate temperatures.
► Enhanced hardness(18 GPa), toughness of coated samples than that of uncoated sample.
► Promising material for MEMS application.
Fig. 1. FTIR spectra of polycarbosilane (a) uncured, (b) cured at 800 °C, (c) cured at 900 °C and (d) cured at 1000 °C.
 
Source: CSIR-Central Glass and Ceramic Research Institute
 
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