Fabrication of Hydrogen Boride Thin Film by Ion Exchange in MgB2.

T Hirabayashi,S Ueda,S Shoji,M Miyauchi,H Abe,T Kondo,H Zhu,S Yasuhara,A Yamaguchi

doi:10.3390/molecules26206212

Abstract

In this study, hydrogen boride films are fabricated by ion-exchange treatment on magnesium diboride (MgB2) films under ambient temperature and pressure. We prepared oriented MgB2 films on strontium titanate (SrTiO3) substrates using pulsed laser deposition (PLD). Subsequently, these films were treated with ion exchangers in acetonitrile solution. TOF-SIMS analysis evidenced that hydrogen species were introduced into the MgB2 films by using two types of ion exchangers: proton exchange resin and formic acid. According to the HAXPES analysis, negatively charged boron species were preserved in the films after the ion-exchange treatment. In addition, the FT-IR analysis suggested that B-H bonds were formed in the MgB2 films following the ion-exchange treatment. The ion-exchange treatment using formic acid was more efficient compared to the resin treatment; with respect to the amount of hydrogen species introduced into the MgB2 films. These ion-exchanged films exhibited photoinduced hydrogen release as observed in a powder sample. Based on the present study, we expect to be able to control the morphology and hydrogen content of hydrogen boride thin films by optimising the ion-exchange treatment process, which will be useful for further studies and device applications.

Highlights

In contrast to their bulk counterparts, two-dimensional materials, such as graphene, exhibit unique electronic properties and ultra-high specific surface areas
When a different crystalline substrate, such as sapphire, was used in a two-step pulsed laser deposition (PLD) process, no diffraction peaks of MgB2 were observed (Figure S3). These results indicate that a dense and oriented MgB2 film can be deposited on the STO (100) substrate by a two-step PLD method
The decrease in the magnesium signal was more significant than that of the boron species. These results indicate that a long-term treatment with formic acid can induce a proton ion-exchange process rather than an exfoliation of the boron layers in the MgB2 film

Summary

Introduction

In contrast to their bulk counterparts, two-dimensional materials, such as graphene, exhibit unique electronic properties and ultra-high specific surface areas. These unusual characteristics result in energy band structures sensitive to external perturbations and attract significant research interest [1]. The synthesis method involves the 3-day reaction of layered bulk magnesium diboride (MgB2) powder with an ion-exchange resin in an organic solvent to promote the exfoliation of MgB2. This is the first experimentally synthesised borophane (hydrogenated borophene), which is composed of sp2-bonded boron, forming hexagonal boron networks with bridge hydrogens. Theoretical models and computer simulations demonstrate that borophane is a promising candidate for applications such as anode material, alcohol gas sensors, current limiters, and photodetectors [11,12,13,14]

Methods

Results

Conclusion