Boron nitride (BN) films are of great importance in a wide variety of engineering fields such as machinery, electronic devices, and space applications [1–4]. Various process technologies have been developed to form stable BN films. Recently, we proposed a reactive plasma-assisted coating (RePAC) system [5] to fabricate high-hardness (cubic) BN stack structures on a Si substrate and investigated the surface modification under various plasma exposures [6]. In this study, we performed comprehensive characterization of the BN films on crystalline Si substrates using various analysis techniques, i.e., indentation and electrical tests in combination with a molecular dynamics (MD) simulation. The (μm-thick) BN films prepared by the RePAC system exhibited characteristic electron tunneling behaviors governed by the Frenkel–Poole effects [7][8] in response to process conditions (e.g. the energy of incident Ar ions). The relationship between the electrical dielectric constant determined by capacitance–voltage test and the Knoop hardness was clarified for various process conditions. An inductively-coupled Ar plasma reactor where the energy and flux of incident ions were controlled was used to investigate the surface modification mechanisms of the BN films. The formation of a surface plasma-damaged layer (a few nm thick) was identified by a nanoindentation technique [9]. The energy dependence of the sputtering yield of the BN films was compared with that of SiO₂ films, indicating that the BN film is one of the promising candidates for the usage in harsh environments such as a long-time plasma exposure. The MD simulations predicted the formation and reconstruction of the sp³-bonded BN phase in the hexagonal background under the irradiation of ions, showing a good agreement with the experimental findings. The comprehensive characterization as performed in this study should be employed for future BN process designs.

The work was partly supported by the Cooperative Research Program in the ISIR, Osaka University, 20191261 and Kyoto University Nano Technology Hub by the MEXT, Japan.

[1] C. B. Samantaray and R. N. Singh, Int. Mater. Rev. 50 (2005) 313.

[2] Y. Zhang et al., Phys. Rev. B 73 (2006) 144115.

[3] Y. Hattori et al., ACS Appl. Mater. Interfaces 8 (2016) 27877.

[4] T. Burton et al., J. Propul. Power. 30 (2014) 690.

[5] M. Noma et al., Jpn. J. Appl. Phys. 53 (2014) 03DB02.

[6] T. Higuchi et al., Surf. Coat. Technol. 377 (2019) 124854.

[7] C. Ronning et al., Diamond and Relat. Mater. 6 (1997) 1129.

[8] K. Nose et al., Appl. Phys. Lett. 83 (2003) 943.

In this study, the impact of plasma treatment on InWZnO (IWZO) CBRAM was reported.In order to improve the characteristics of IWZO CBRAM device, we use oxygen remote plasma to surface-treat the IWZO layer. Oxygen plasma can slightly suppress oxygen vacancies in IWZO. The set voltage of the device becomes more uniform and smaller, which is beneficial for low power operation. The a-IWZO CBRAM shows the excellent memory performance, such as high switching endurance (up to3 ´ 10³ cycles) and overshoot current decrease. Without high temperature is used in the process, which would be suitable for memory in flexible substrates.