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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]

In order to realize the practical use of diamond as a semiconductor material, large-area single-crystal diamond wafers with uniform quality are required. Mosaic growth is an effective method to produce inch-grade single-crystal diamonds. However, the quality of the wafer is limited by the junction interface seriously, because cracking occurs easily due to the high internal stress. In this paper, the repetition growth method was adopted to grow mosaic splicing single-crystal diamond without polycrystalline diamond interface. The high-quality single crystal diamond slices were reduplicated by microwave plasma chemical vapor deposition (MPCVD). The substrates were obtained by cutting a piece of CVD diamond along a plane perpendicular to 〈001〉 (with a (100)-oriented surface). The evolution of the growth characteristics around the junction of the substrates at different stages was studied. The results show that the surface of the epitaxial layers gradually evolves from blurry terraces to a regular well-ordered step flow. When the substrates have the same deviation direction and the off-direction angles are within 3°, the junction of the substrates can connect smoothly. Raman mapping shows that there is a mixture of tensile stress and compressive stress near the junction. As the thickness of the epitaxial layer increases from 280 μm to 560 μm, the range of tensile stress near the joint area expands from 85 μm to 150 μm, the maximum tensile stress increases from 0.08 GPa to 0.16 GPa. In addition, the value of FWHM in the X-ray rocking curve is less than 2.80 cm−1 around the junction, which indicates good crystal quality. [Display omitted] • The evolution of growth characteristics around the junction in the mosaic diamond was studied. • The mosaic boundary evolved from blurry terraces to a well-ordered step flow and finally connected. • The lowest value of tensile stress near the joint area was reported as the film thickness increased. • The larger FWHM of Raman peak around the junction is caused by the increased tensile stress. • The "inherit" effect of NV content of the epitaxial layer was observed for the corresponding substrate. [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]