Evaluation of Interaction Between Substrate and Nanoparticles Deposited by Plasma Chemical Vapor Deposition

In plasma nanotechnology, the deposition of nanoparticles on a substrate is an important research topic, together with nanoparticle synthesis. So far, we have revealed the growth mechanism of nanoparticles in plasma chemical vapor deposition (CVD) to achieve size and transport control, while there is little information on how the nanoparticles deposited on the substrate are attached to the substrate. Here we analyzed the adhesion of nanoparticles deposited on the substrate to the substrate using a nanoindenter. In our experiments, we employed carbon nanoparticles (CNPs). We have successfully controlled the size of nanoparticles by plasma CVD and studied their transport [1, 2]. The nanoparticles were generated using CH₄+Ar plasma CVD. The size of CNPs was controlled by the gas flow. In this experiment, we fabricated CNPs of 20 nm in size. We deposited CNPs on a Si substrate on which 150 nm of hydrogenated amorphous carbon (a-C:H) film was deposited. The area covered by the deposited CNPs on the substrate surface was 10.9% of the substrate area. We measured the load-displacement curves of the substrate with and without CNP deposition were evaluated using a Berkovich indenter. The indentation depth was set to 15 nm to obtain information on the a-C:H film without the influence of Si. The hold time at maximum load was set to 1 s. For the sample without CNPs, the curves showed a typical a-C:H thin film. The Young's modulus and hardness were 200 Ga and 26 GPa, respectively. For the sample with CNPs, the maximum load was about one-fifth of that without CNPs and the modulus and hardness were 50 GPa and 3 GPa, respectively. The differences in the curves are considered to be information that includes the mechanical properties of the nanoparticles as well as changes in the contact conditions of CNPs on the substrate during the indentation. Details will be discussed at the meeting.

[1] S.H. Hwang et al, Processes 9 (2021) 2. [2] S.H. Hwang et al., Diam. Relat. Mater. 109 (2020) 108050.