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In this study, SiC and Ga2O3 substrates were bonded under atmospheric conditions using an extremely thin amorphous layer (∼7 Å). Conventional wafer-bonding techniques employ an oxidizing treatment for surface functionalization, resulting in the formation of an oxide layer at the bonding interface. This study demonstrates the bonding of a hydrofluoric-acid-treated SiC surface with a plasma-activated Ga2O3 substrate, where the –OH groups on the SiC and Ga2O3 surfaces form direct bonding via a dehydration reaction at 250 °C. The interfacial analysis indicates that bonding using the reduction treatment instead of oxidization reduces the thickness of the intermediate layer at the SiC/Ga2O3 interface, which is a thermal and electrical barrier. In addition, it is remarkable that the SiC and Ga2O3 substrates are directly bonded by generally used surface cleaning processes, contacting the surfaces under atmospheric conditions, and annealing at 250 °C. We believe that the bonding process using the reduction process can contribute to future heterogeneous devices based on integrated dissimilar substrates. [ABSTRACT FROM AUTHOR]

Direct bonding of a diamond (100) substrate and a Si wafer was achieved at 250°C under atmospheric conditions. Prior to the bonding process, the diamond substrate was treated with H 2 SO 4 /H 2 O 2 and NH 3 /H 2 O 2 mixtures, whereas the Si wafer was irradiated using oxygen plasma. By applying the pressure during the annealing process, the substrates were entirely bonded, except for the contaminated areas. The bonded specimen was fractured when a shear force of 1.7 MPa was applied. The electron microscopic observation indicated that the diamond and Si substrates were atomically bonded through a 3-nm-thick SiO 2 layer without significant loss of diamond crystallinity. The integration of diamond (100) substrates on an Si wafer would contribute to the fabrication of future diamond devices. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A diamond (111) substrate cleaned with an NH3/H2O2 mixture could form low-temperature direct bonding under atmospheric conditions. When the diamond surface was bonded with a plasma activated SiO2 surface at 200 °C, the bonding strength was sufficiently high so that cleavage within diamond occurred in a shear test. Moreover, the diamond and Si substrates treated with the NH3/H2O2 mixture could form atomic bonds with a 2.5-nm-thick oxide intermediate layer. This bonding method can be applied to electronic devices using diamond because heterogeneous integration can be achieved using a popular wafer cleaning process followed by low-temperature annealing. [ABSTRACT FROM AUTHOR]

Surface-functionalized β -Ga2O3 and diamond substrates were directly bonded by annealing at 250 °C in atmospheric air. Prior to bonding, the β -Ga2O3 and diamond surfaces were OH-terminated by oxygen plasma irradiation and H2SO4/H2O2 cleaning, respectively. After contacting the OH-terminated surfaces with each other, direct bonding was formed by a thermal dehydration reaction. The annealed specimen had a shear strength of 14 MPa because of the generation of chemical bonds between β -Ga2O3 and diamond surfaces. The analysis of interface structures revealed that the β -Ga2O3 and diamond surfaces were atomically bonded without nano-voids, cracks, or any intermediate layer. The β-Ga2O3 and diamond substrates were bonded without any serious loss in crystallinity except for the outermost surfaces. We believe that the β -Ga2O3/diamond heterostructure can contribute to the high-power applications of β -Ga2O3 devices. [ABSTRACT FROM AUTHOR]

A monocrystalline diamond substrate was directly bonded with a Si substrate by annealing at low temperatures under atmospheric conditions. These substrate surfaces were functionalized with hydroxyl groups and subsequently bonded by a dehydration reaction. When a diamond (111) substrate was treated with a H 2 SO 4 /H 2 O 2 mixture, it generated a direct bonding with an oxygen-plasma-activated Si substrate without significant loss in diamond crystallinity. The proposed bonding technique would contribute to the diamond device fabrication because the high-crystallinity diamond layer can be transferred by the commonly used cleaning process followed by low-temperature annealing under atmospheric conditions. Unlabelled Image [ABSTRACT FROM AUTHOR]

Direct bonding of GaN and Si substrates at 125 °C under atmospheric conditions was investigated by different Plasma activation bonding (PAB) methods. The substrates activated by a sequential oxygen and nitrogen plasma were strongly bonded so that the fracture within GaN bulk occurred during strength measurement. A ∼3-nm-thick amorphous layer consisting of GaOx and SiOx was confirmed at the bonding interface. This plasma-assisted low-temperature direct bonding may shed light on the advanced electronic devices using the GaN-Si heterostructure. Image 1 • Direct bonding of GaN-Si surfaces was strongly formed at 125 °C by plasma activation. • Bonded sample was fractured in GaN instead of interface during strength measurement. • Oxynitride film formed by plasma supposedly promoted the interfacial adhesion. • GaN and Si were bonded with a 3-nm-thick amorphous layer consisting of Si, Ga and O. [ABSTRACT FROM AUTHOR]