Epitaxial (100) TiC film deposition on Si (100) substrate by direct current magnetron reactive sputtering of a metallic Ti target with 3%–6% CH₄ in Ar gas was investigated. X-ray diffraction and cross-sectional scanning transmission electron microscopy (STEM) reveal that epitaxial cubic TiC can be grown on the Si substrate by domain matching epitaxy in 5/4 ratio with the epitaxial relationship of TiC (100)[0 $\overline{1}$ 1] // Si (100)[0 $\overline{1}$ 1]. For sputtering with 3% and 4% CH₄, the deposited films are found to consist of both TiC and metallic Ti phases. Increasing the CH₄ flow ratio to 5% results in a deposited film completely consisting of TiC without metallic Ti phase. The crystallinity of the deposited TiC is also improved with increasing the CH₄ ratio to 5%. X-ray photoelectron spectroscopy shows that the [C]/[Ti] atomic ratio in TiC is nearly close to 1 for growth with 5% CH₄ flow ratio and above. The measured electrical resistivities of the deposited films also increase from 41 to 153 μΩ·cm with increasing the CH₄ ratio from 3% to 6%. With film growth beyond 50 nm thickness, it is shown that some disoriented TiC grains are formed.

Deposition of a heteroepitaxial TiHfN film with a growth rate of about 1 μm/h was successfully achieved on a Si (001) substrate at a temperature above 700 °C by direct current magnetron reactive sputtering of a Ti_0.6Hf_0.4 (in atomic fraction) target with an Ar/N₂ gas mixture. Annealing of the as-deposited TiHfN/Si sample at a temperature above 1000 °C using microwave plasma with H₂/N₂ gas was performed to further improve the TiHfN film’s quality. X-ray diffraction results show that the heteroepitaxial TiHfN film on Si exhibits a cube-on-cube relationship as {001}_TiHfN//{001}_Si and _TiHfN//_Si. X-ray rocking curve measurements show that the full width at half maximum of (200)_TiHfN is 1.36° for the as-deposited TiHfN film, while it is significantly reduced to 0.53° after microwave plasma annealing. The surface morphologies of the as-deposited and annealed TiHfN films are smooth, with a surface roughness of around ~2 nm. Cross-sectional scanning/transmission electron microscopy (S/TEM) shows a reduction in defects in the annealed film, and X-ray photoelectron spectroscopy shows that the film composition remains unchanged. Additionally, S/TEM examinations with atomic resolution illustrate domain matching epitaxy (DME) between TiHfN and Si at the interface. The TiHfN films have good electrical conducting properties with resistivities of 40–45 μΩ·cm.

Taking the advantage of low sintering temperature and high processing flexibility, metallic nanoparticles (NPs) have been widely used to fabricate interconnections. To obtain excellent electrical conductivity, the surfactants protecting the nanoparticles have to be removed thermally and thus the particles can be well linked. Considering the interconnect fabrication on flexible substrates (usually polymers and papers) utilizing roll-to-roll technique, low processing temperature, short heating time or localized heating is required. By doing so, heat damages of the substrates and components can be prevented. Considering the application as interconnections for wearable electronics, this study develops a low-temperature chemical reduction process for the fabrication of conductive circuits on PDMS (Polydimethylsiloxane) substrate using carboxylate-capped Ag nanoparticles. Ag nanoparticle sintering can be achieved by soaking the nanoparticle deposits in a gentle reductive solution even at room temperature. Surface roughening treatment is performed to enhance the adhesion between conductive films and the substrate. The results of reliability tests demonstrate that the higher the bending deformation (curvature), a greater the electrical resistance for the conductive films. As for bending fatigue (shear strain: 0.25), the electrical performance of the flexible interconnections deteriorates in the first 300 bending cycles mainly due to the formation of crevices. It is interesting that after that the electrical resistance remains almost constant up to 1000 bending cycles. In addition, a novel interconnect fabrication method using Ag submicron particles will also be introduced in this report.