Electrically conductive silicon oxycarbide thin films prepared from preceramic polymers

Abstract

This work focuses on silicon oxycarbide thin film preparation and characterization. The Taguchi method of experimental design was used to optimize the process of film deposition. The prepared ceramic thin films with a thickness of ca. 500 nm were characterized concerning their morphology, composition, and electrical properties. The molecular structure of the preceramic polymers used for the preparation of the ceramic thin films as well as the thermomechanical properties of the resulting SiOC significantly influenced the quality of the ceramic films. Thus, an increase in the content of carbon was found beneficial for the preparation of crack-free thin films. The obtained ceramic films exhibited increased electrical conductivity as compared to monolithic SiOC of similar chemical composition. This was shown to correlate to the unique hierarchical microstructure of the SiOC films, which contain large oxygen-depleted particles, mainly consisting of highly graphitized carbon and SiC, homogeneously dispersed in an oxygen-containing amorphous matrix. The matrix was shown to also contain free carbon and to contribute to charge carrier transport between the highly conductive large particles. The ceramic thin films possess electrical Accepted ArticleThis article is protected by copyright. All rights reserved conductivities in the range from 5.4 to 8.8 S/cm and may be suitable for implementation in miniaturized piezoresistive strain gauges.

SiOC-Based Strain Gauge with Ultrahigh Piezoresistivity at High Temperatures

“…In our previous works, we gained insight into the deposition method of polysiloxane precursor on a 100 mm diameter silicon substrate, obtaining a 500 μm thick, homogeneous, and crack-free piezoresistive silicon oxycarbide thin film . Morphological investigation of the SiOC thin film revealed compositional segregations, as shown in Figure .…”

“…Morphological investigation of the SiOC thin film revealed compositional segregations, as shown in Figure . Oxygen-depleted segregations, consisting of carbon and silicon carbide domains, are homogeneously distributed within a C/SiOC matrix (see Figure A). The segregation of the C/SiC regions does not occur with a significant change in the thickness or roughness of the film, as shown in Figure B, in which the surface of the sample is tilted by 52°.…”

Hierarchical microstructure growth in a precursor‐derived SiOC thin film prepared on silicon substrate

“…The film thickness was determined using a profilometer (Dektak XT Advanced System, Brucker, Karlsruhe, Germany) and measured in three different positions for each sample. The full details of the optimization process including the statistical approach are reported in detail in Reference 24. A favorable response was obtained using the setting of an initial spin speed of 4000 rpm for 30 s, then accelerated to a second spin speed of 8000 rpm for 30 s with an acceleration of 500 rpm/s.…”

“…22,23 A significant amount of literature is available on the synthesis approach and characterization of SiOC, although the majority is dedicated to powder and monolithic samples. In our latest work on SiOC thin film deposited on a silicon substrate, the evolution of the SiC and free carbon phases were documented at a temperature of 1400 • C. 24,25 A micro-scale segregation of phases was observed on the surface of the film; the segregations were found to consist of sp 2-h ybridized carbon and nanocrystalline β-SiC dispersed within an amorphous silicon oxycarbide matrix. The Si-O-C system is known to follow two processes when exposed to temperatures well beyond 1000 • C: The first process involves the partitioning of the glassy SiO 4−x C x network and the formation of amorphous silica and SiC nanodomains, latter may crystallize; the second process represents the carbothermal reaction between the phaseseparated silica and the excess carbon, complemented by the growth of crystalline SiC and release of gaseous CO. 9 These processes were extensively studied and are relatively well understood for monolithic SiOC.…”

“…A significant amount of literature is available on the synthesis approach and characterization of SiOC, although the majority is dedicated to powder and monolithic samples. In our latest work on SiOC thin film deposited on a silicon substrate, the evolution of the SiC and free carbon phases were documented at a temperature of 1400°C 24,25 . A micro‐scale segregation of phases was observed on the surface of the film; the segregations were found to consist of sp 2 ‐hybridized carbon and nanocrystalline β‐SiC dispersed within an amorphous silicon oxycarbide matrix.…”