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Lift-off is a promising method to prepare thin, high-finish, and freestanding large-area single crystal and polycrystalline diamonds. However, accurate control of the damage layer characteristic to achieve both stress release and lift-off process is difficult. In this work, high-energy C+ was implanted in single crystal diamond and polycrystalline diamond to create subsurface damage. The defect behavior and structural transformation of the ion implantation and annealing process were investigated. The homoepitaxial growth was subsequently carried out and the epitaxial layer was lifted off from the substrate by selectively etching the damaged layer. The results show that the cap layer and the substrate (below the damage layer) keep the sp3 carbon structure before and after annealing, which is confirmed by the atomic-scale electron energy loss spectroscopy (EELS). The high-resolution transmission electron microscopy (HRTEM) images show that after annealing at 1000 °C for 1 h, the damaged layer was transformed from amorphous carbon to a mixture of graphite and amorphous carbon, providing the damaged layer that could be removed by electrochemical solution. Meanwhile, the distorted diamond area was changed to a sharp interface, which ensures the low roughness of the substrate surface after the lift-off process. After etching for 30 h, a freestanding polycrystalline diamond film with a thickness of 100 μm and a surface roughness of 1.68 nm was obtained. The roughness of the lift-off substrate surface is 1.10 nm, indicating the epitaxial growth can be repeated directly without polishing. [Display omitted] • The defect behavior and structural transformation of the high-energy C+ implanted diamonds were investigated. • The stress state of the diamonds before and after ion implantation and after lift-off process were evaluated. • A 100 μm-thick freestanding polycrystalline diamond film with a surface roughness of 1.68 nm was successful obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high channel hole mobility of 200 cm2V−1s−1 was achieved in C-Si interface (1 1 1) diamond MOSFETs. • The C-Si interface provides the MOSFETs with an excellent normally-off operation. • The advantage of boron doping in (1 1 1) diamond provides a large maximum current density. • The anatomically flat and strain-free interface between the (1 1 1) diamond and SiO 2 film was confirmed by HRTEM. • The existence of C-Si bonds at the interface was proved by EELS and XPS. In this paper, a diamond-silicon (C-Si) interface was constructed on a (1 1 1) diamond substrate by annealing the SiO 2 gate insulator in a reductive atmosphere. Corresponding metal-oxide-semiconductor field effect transistors (MOSFETs) with a C-Si conductive channel were fabricated. The MOSFETs demonstrate excellent normally-off operation with a high threshold voltage (V th) of −16 V and a high current density of −167 mA/mm, with a gate length (L G) of 4 μm. The channel hole mobility (μ FE) reaches 200 cm2V−1s−1 with a L G of 10 μm, and the interface state density (D it) is as low as 3.8 × 1011 cm−2 eV−1. The high-resolution transmission electron microscopy (HRTEM) image displays a coherent and strain-free interface between the SiO 2 film and (1 1 1) diamond, which ensures a high μ FE and low D it in the MOSFETs. The interface is dominated by C-Si bonds, which are confirmed by atomic-scale electron energy loss (EELS) quantification, spectroscopic characterization, and X-ray photoelectron spectroscopy (XPS). These results demonstrate that diamond, directly combined with SiO 2 , is ideal for implementation in power devices. [ABSTRACT FROM AUTHOR]

The surface conductivity on the H-terminated diamond is still an interesting topic in the field of diamond electronics. Until now, the carrier mobility in the conductive channel has been limited to below 200cm2/Vs due to the various surface scattering mechanisms. In this paper, a high mobility conductive channel on the H-terminated diamond surface was reported. Firstly, the high quality diamond films were deposited on the commercial CVD diamond substrates. After polishing, the H-termination was obtained by hydrogen plasma treatment. The surface morphology of the H-terminated diamond was observed by atomic force microscope (AFM) and scanning electron microscope (SEM). The crystal quality on the diamond surface was characterized by Raman spectroscopy. The impurities in the crystals were tested by photoluminescence spectroscopy. The surface conductivity of H-terminated diamond was monitored comprehensively by Hall test. It can be found that the sheet resistance decreases much and the carrier mobility increases dramatically after the hydrogen plasma treatment and mechanical cleaning. The maximum mobility value is up to 365cm2/Vs with carrier density of 2.9 × 1012 cm−2, which is the highest value reported. Raman spectra of diamond surface show that a peak appears at 1121.4 cm−2 after the hydrogen plasma treatment, which corresponds to the nanocrystal diamond or carbon clusters of sp3 bonded material. The corresponding mobility enhancement mechanism on the H-terminated diamond surface was proposed. Unlabelled Image • The carrier mobility enhancement on the H-terminated diamond surface was found. • A thin carbon film on the diamond surface was observed with Raman peak at 1121 cm−1. • The H-terminated diamond surface showed high carrier mobility of 365cm2/Vs. • The corresponding mobility enhancement mechanism was proposed. [ABSTRACT FROM AUTHOR]