Wide bandgap semiconductors like SiC and GaN are driving advancements in the power electronics industry by surpassing Si in power capability and maximum operating temperature. Owing to its superior properties such as thermal conductivity, SiC is preferred for many high-power applications. Despite the recent progress in SiC technology, providing both high-quality and cost-effective substrates is still a challenge. [1] Engineered substrates are a promising technology route to fulfill the requirements for high-quality and cost-efficient substrates for power devices. SmartcutTM [2], controlled spalling [3], and photoelectrochemical etching [4, 5] are key techniques for fabricating engineered substrates that strongly rely on reliable bonding techniques. The performance and the production yield of these structures depend significantly on the bonding quality of these unconventional hetero-structures emphasizing the importance of robust, low-cost bonding technologies [6]. Compared to conventional bonding methods such as fusion bonding, the intermediate adhesive bonding technique is cost-effective and user-friendly, offering advantages such as even load distribution, tolerance to surface roughness, effective surface sealing, and resilience against stress and vibrations [7]. For high-temperature stable bonding, the polymer class of vinyl group containing polycarbosilanes (PCS) is of interest as it is a one-component liquid precursor that yields high-purity ceramic SiC, with 72-78% amorphous SiC at 850-1200 °C and nanocrystalline β-SiC at 1250-1700 °C [8], thus offering the possibility to realize an electrically conductive bonding interface. In this work, PCS, also known commercially as SMP-10 (Starfire Systems Inc.), is mixed with m-xylene and AIBN (Azobisisobutyronitrile), a photoinitiator, and then spin-coated onto a monocrystalline 4H-SiC substrate (3000 rpm, 40 s). For demonstration purposes, another monocrystalline 4H-SiC substrate is placed on top, and the assembly is pre-bonded with an EVG bonder where a constant force of 350 N is applied. The sample is heated at 400 °C for 1 hour to facilitate bonding. Finally, the structure is annealed at 1550 °C at 20 mbar back chamber pressure and with Ar atmosphere in a custom-built high-temperature furnace from HTM Reetz, resulting in a bonded sample. During annealing up to 300 °C, the polymer precursors crosslink by creating 3D polymeric networks. Post-crosslinking above 300 °C converts the material to amorphous ceramic. Fig. (1) illustrates the effusion measurements where the spin-coated sample is heated to a peak temperature of 1000 °C over 10 min. We observe ionized gas molecules H+ (amu 1) and CH4+ (amu 16) which can be associated with the rearrangements, condensation, and radical reactions that form new bonds and gaseous reaction products like CH4, H2, CO, and CO2 [9]. We have minimal presence of H2O (amu 18), CO (amu 28), and CO2 (amu 44) as the measurements were made under high vacuum conditions. The measurements show that the outgassing from the adhesive bonding layer occurs predominantly up to an annealing temperature of 900 °C. In Fig. 2, the cross-sectional SEM image shows the bonded 4H-SiC substrates. The cross-section of the bonded sample reveals a uniform bonded closed layer with no visible defects, demonstrating PCS as a bonding interface for SiC at high temperatures. Further investigations will involve the realization of doped SiC bonding layers, and XRD to study the crystallinity of the obtained interlayers as well as vertical I-V measurements. [1] G. Iannaccone et al., IEEE Access 9, 2021. [2] S. Rouchier et al., Materials Science Forum 1062, p.131-135, 2022. [3] W. S et al., presented at ICSCRM 2023, 2023. [4] M. Leitgeb et al., patent of US20240128080A1. [5] M. Leitgeb et al., The Electrochemical Society, vol. 164, no. 12, p. E337, 2017. [6] B. Kallingeret al., Solid State Phenomena 342, p.91-98, 2023. [7] F. Campbell, Manufacturing Processes for Advanced Composites, 2004. [8] [Online]. Available: https://www.starfiresystems.com/wp-content/uploads/2018/03/SMP-10.pdf. [9] B. Gilvan et al., J. Mater. Chem. A 7,p. 1936-1963, 2019. [10] S. K. Ionescu et al., Journal of the European Ceramic Society 34 issue 15, p.3571-3578, 2014. [11] G. Soraru et al., J Mater Sci 25,p. 3886-3893, 1990.