Search Results (14)

We investigated the use of boron-doped diamond (BDD) with different surface morphologies for the enhanced detection of nine different peptides by matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). For the first time, we compared three different nanostructured BDD film morphologies (Continuous, Nanograss, and Nanotips) with differently terminated surfaces (-H, -O, and -F) to commercially available Ground Steel plates. All these surfaces were evaluated for their effectiveness in detecting the nine different peptides by MALDI-MS. Our results demonstrated that certain nanostructured BDD surfaces exhibited superior performance for the detection of especially hydrophobic peptides (e.g., bradykinin 1–7, substance P, and the renin substrate), with a limit of detection of down to 2.3 pM. Further investigation showed that hydrophobic peptides (e.g., bradykinin 1–7, substance P, and the renin substrate) were effectively detected on hydrogen-terminated BDD surfaces. On the other hand, the highly acidic negatively charged peptide adrenocorticotropic hormone fragment 18–39 was effectively identified on oxygen-/fluorine-terminated BDD surfaces. Furthermore, BDD surfaces reduced sodium adduct contamination significantly. Full article

In ultrahigh-pressure (UHP) metamorphic rocks, rutile is an important accessory mineral. Its high-pressure polymorph TiO₂II can be a significant indicator of pressure in the diamond stability field. In the present study, in situ high-pressure Raman spectroscopic measurements of natural rutile in UHP eclogite from the main hole of the Chinese Continental Scientific Drilling Project (CCSD) have been conducted up to ~16 GPa. Rutile and recovered TiO₂II have also been analyzed via single-crystal X-ray diffraction and FTIR spectroscopy. The results indicate that (1) the phase transition from rutile to baddeleyite-type TiO₂ terminates at about 16 GPa under compression at ambient temperature; (2) the metastable TiO₂II in the exhumated UHP rocks formed during deep continental subduction can be characterized by a highly distorted octahedral site in the crystal structure. X-ray powder diffraction analyses (with Cu Kα radiation) at ambient conditions are sufficient for identifying the lamellae of TiO₂II within natural rutile based on the angles (2θ) of two strong peaks at 25.5° and 31.5°; (3) rutile and recovered TiO₂II in the continental slabs can contain certain amounts of water during deep subduction and exhumation. The estimated water contents of rutile in the present study range from 1590 to 1780 ppm of H₂O by weight. In the crystal structure of TiO₂II, hydrogen can be incorporated close to the long O-O edges (>2.5143 Å) of the TiO₆ octahedra. Further studies on the pressure–temperature stability of hydroxyls in rutile and TiO₂II may help to understand the transportation and release of water in subducted continental slabs. Full article

In this paper, two dielectric layers of Al₂O₃ and Gd₂O₃ were prepared by an atomic layer deposition (ALD) and magnetron sputtering deposition (SD), respectively. Based on this, a metal-oxide-semiconductor field-effect transistor (MOSFET) was successfully prepared on a hydrogen-terminated single-crystal diamond (H-diamond), and its related properties were studied. The results showed that this device had typical p-type channel MOSFET output and transfer characteristics. In addition, the maximum current was 15.3 mA/mm, and the dielectric constant of Gd₂O₃ was 24.8. The effective mobility of MOSFET with Gd₂O₃/Al₂O₃ was evaluated to be 182.1 cm²/Vs. To the best of our knowledge, the bilayer dielectric of Gd₂O₃/Al₂O₃ was first used in a hydrogen-terminated diamond MOSFET and had the potential for application. Full article

SnO_x films were deposited on a hydrogen-terminated diamond by thermal oxidation of Sn. The X-ray photoelectron spectroscopy result implies partial oxidation of Sn film on the diamond surface. The leakage current and capacitance–voltage properties of Al/SnO_x/H-diamond metal-oxide-semiconductor diodes were investigated. The maximum leakage current density value at −8.0 V is 1.6 × 10⁻⁴ A/cm², and the maximum capacitance value is measured to be 0.207 μF/cm². According to the C–V results, trapped charge density and fixed charge density are determined to be 2.39 × 10¹² and 4.5 × 10¹¹ cm⁻², respectively. Finally, an enhancement-mode H-diamond field effect transistor was obtained with a V_TH of −0.5 V. Its I_DMAX is −21.9 mA/mm when V_GS is −5, V_DS is −10 V. The effective mobility and transconductance are 92.5 cm²V⁻¹ s⁻¹ and 5.6 mS/mm, respectively. We suspect that the normally-off characteristic is caused by unoxidized Sn, whose outermost electron could deplete the hole in the channel. Full article

A controlled and self-assembled micromachining system was built to fabricate a mico/nanoscale monolayer patterned array on a silicon surface using a diamond tip. The process was as follows: (1) we preprocessed a silicon wafer to obtain a hydrogen-terminated silicon surface; (2) we scratched three rectangular arrays of 10 μm × 3 μm with a spacing of 2 μm on the silicon surface with a diamond tip in 1-octadecene solution; the Si-H bonds were broken, and silicon free radicals were formed; (3) the 1-octadecene molecules were connected with silicon atoms based on Si-C covalent bonds, and the 1-octadecene nano monolayer was self-assembled on the patterned arrays of the silicon surface. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Sessile water contact angles were used to detect and characterize the self-assembled monolayers (SAMs). The XPS results showed that the Si2p peak and the O1s peak were significantly decreased after self-assembly; however, the C1s peak was successively significantly increased. Sessile water contact angles showed that the hydrophilicity was weakened after the formation of 1-octenecene SAMs on the silicon substrate. The nanofriction of the sample was measured with AFM. The change in nanofriction also demonstrated that the SAMs were formed in accordance with the patterned array. We demonstrated that, by using this method, self-assembled multiscale structures on silicon substrate can be formed quickly and conveniently. Full article

In this work, hydrogen-terminated diamond (H-diamond) metal-oxide-semiconductor field-effect-transistors (MOSFETs) on a heteroepitaxial diamond substrate with an Al₂O₃ dielectric and a passivation layer were characterized. The full-width at half maximum value of the diamond (004) X-ray rocking curve was 205.9 arcsec. The maximum output current density and transconductance of the MOSFET were 172 mA/mm and 10.4 mS/mm, respectively. The effect of a low-temperature annealing process on electrical properties was also investigated. After the annealing process in N₂ atmosphere, the threshold voltage (V_th) and flat-band voltage (V_FB) shifts to negative direction due to loss of negative charges. After annealing at 423 K for 3 min, the maximum value of hole field effective mobility (μ_eff) increases by 27% at V_th − V_GS = 2 V. The results, which are not inferior to those based on homoepitaxial diamond, promote the application of heteroepitaxial diamond in the field of electronic devices. Full article

In this work, a hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with HfAlO_x/Al₂O₃ bilayer dielectrics is fabricated and characterized. The HfAlO_x/Al₂O₃ bilayer dielectrics are deposited by the atomic layer deposition (ALD) technique, which can protect the H-terminated diamond two-dimensional hole gas (2DHG) channel. The device demonstrates normally-on characteristics, whose threshold voltage (V_TH) is 8.3 V. The maximum drain source current density (I_DSmax), transconductance (G_m), capacitance (C_OX) and carrier density (ρ) are −6.3 mA/mm, 0.73 mS/mm, 0.22 μF/cm² and 1.53 × 10¹³ cm⁻², respectively. Full article

Ohmic contact with high thermal stability is essential to promote hydrogen-terminated diamond (H-diamond) electronic devices for high-temperature applications. Here, the ohmic contact characteristics of Ni/H-diamond at annealing temperatures up to 900 °C are investigated. The measured current–voltage curves and deduced specific contact resistance (ρ_C) are used to evaluate the quality of the contact properties. Schottky contacts are formed for the as-received and 300 °C-annealed Ni/H-diamonds. When the annealing temperature is increased to 500 °C, the ohmic contact properties are formed with the ρ_C of 1.5 × 10⁻³ Ω·cm² for the Ni/H-diamond. As the annealing temperature rises to 900 °C, the ρ_C is determined to be as low as 6.0 × 10⁻⁵ Ω·cm². It is believed that the formation of Ni-related carbides at the Ni/H-diamond interface promotes the decrease in ρ_C. The Ni metal is extremely promising to be used as the ohmic contact electrode for the H-diamond-based electronic devices at temperature up to 900 °C. Full article

The purpose of this study is to investigate the cutting performance of amorphous carbon (a-C) coatings and hydrogenated amorphous carbon (a-C:H) coatings on machining 2A50 aluminum alloy. First-principles molecular dynamics simulation was applied to investigate the effect of hydrogen on the interaction between coatings and workpiece. The cross-section topography and internal structure of a-C and a-C:H films were characterized by field emission scanning electron microscopy and Raman spectroscopy. The surface roughness of the deposited films and processed workpiece were measured using a white light interferometer. The results show that the a-C-coated tool had the highest service life of 121 m and the best workpiece surface quality (S_q parameter of 0.23 μm) while the workpiece surface roughness S_q parameter was 0.35 and 0.52 μm when machined by the a-C:H-coated and the uncoated tool, respectively. Meanwhile, the build-up edge was observed on the a-C:H-coated tool and a layer of aluminum alloy was observed to have adhered to the surface of the uncoated tool at its stable stage. An interface model that examined the interactions between H-terminated diamond (111)/Al(111) surfaces revealed that H atoms would move laterally with the action of cutting heat (549 K) and increase the interaction between a-C:H and Al surfaces; therefore, Al was prone to adhere to the a-C:H-coated tool surface. The a-C coating shows better performance on cutting aluminum alloy than the a-C:H coating. Full article

The reaction of the Schiff base ligand o-OH-C₆H₄-CH=N-C(CH₂OH)₃, H₄L, with Ni(O₂CMe)₂·4H₂O and lanthanide nitrate salts in a 4:2:1 ratio lead to the formation of the trinuclear complexes [Ni₂Ln(H₃L)₄(O₂CMe)₂](NO₃) (Ln = Sm (1), Eu (2), Gd (3), Tb (4)). The complex cations contain the strictly linear Ni^II-Ln^III-Ni^II moiety. The central Ln^III ion is bridged to each of the terminal Ni^II ions through two deprotonated phenolato groups from two different ligands. Each terminal Ni^II ion is bound to two ligands in distorted octahedral N₂O₄ environment. The central lanthanide ion is coordinated to four phenolato oxygen atoms from the four ligands, and four carboxylato oxygen atoms from two acetates which are bound in the bidentate chelate mode. The lattice structure of complex 4 consists of two interpenetrating, supramolecular diamond like lattices formed through hydrogen bonds among neighboring trinuclear clusters. The magnetic properties of 1–4 were studied. For 3 the best fit of the magnetic susceptibility and isothermal M(H) data gave J_NiGd = +0.42 cm⁻¹, D = +2.95 cm⁻¹ with g_Ni = g_Gd = 1.98. The ferromagnetic nature of the intramolecular Ni···Gd interaction revealed ground state of total spin S = 11/2. The magnetocaloric effect (MCE) parameters for 3 show that the change of the magnetic entropy (−ΔS_m) reaches a maximum of 14.2 J kg⁻¹ K⁻¹ at 2 K. A brief literature survey of complexes containing the Ni^II-Ln^III-Ni^II moiety is discussed in terms of their structural properties. Full article

In this study, contact properties of platinum/gold (Pt/Au) on the surface of hydrogen-terminated single crystal diamond (H-SCD) were studied with several treatment conditions. The electrodes of Pt (20 nm)/Au (100 nm) were deposited on H-SCD surface by electron beam evaporation technique. Then, the specific contact resistance (ρ_c) of the as-fabricated sample was measured by the circular transmission line model, which showed good ohmic properties with the value of 5.65 × 10⁻⁴ Ω·cm². To identify the thermal stability of Pt/Au/H-SCD, the sample was annealed in hydrogen ambient from 200 to 700 °C for 20 min at each temperature. As the temperature increased, ρ_c demonstrated better thermal stability. In addition, the barrier height was evaluated to be −0.67 ± 0.12 eV by X-ray photoelectron spectroscopy (XPS) technique. Full article

The transfer characteristics of a nanocrystalline diamond (NCD)-based solution-gated field effect transistor (SGFET) under the influence of inorganic and organic compounds were studied. Studied compounds included three different buffer solutions (Phosphate, HEPES, McIlvaine buffer) and commonly used culture media (fibronectin, albumin and fetal bovine serum). It was found that buffers with the same pH of 7.4 caused different voltage shifts in transfer characteristics. This effect was reversible which indicates the surface stability of the hydrogen-terminated diamond during repeated measurements. In contrast to this observation, the SGFET sensitivity decreased after applying the culture solutions which we attribute to the permanently adsorbed bio-layer formed on the SGFET channel sensing area. Full article

Barrier heights of Au on hydrogen-/oxygen-/fluorine-/nitrogen-terminated diamond (H-/O-/F-/N-diamond) have been investigated by X-ray photoelectron spectroscopy. All of the H-/O-/F-/N-diamond surfaces have been formed on different areas of one diamond sample. An Au film with a thickness of 4 nm was evaporated to form Au/diamond contacts. Barrier height values for Au on H-/O-/F-/N-diamond contacts were determined to be −0.19, 1.71, 2.29, and 2.39 eV, respectively. Then, the surface of Au/diamond contacts was treated by 1000 eV Ar⁺ bombardment with different duration of time, resulting in a pinned barrier height of 1.83 eV independent of contact structures. In the end, the spatial distribution of the energy band diagram has been calculated by solving Poisson’s equation. Full article

Microscopic chemical patterning of diamond surfaces by hydrogen and oxygen surface atoms is used for self-assembly of human osteoblastic cells into micro-arrays. The cell adhesion and assembly is further controlled by concentration of cells (2,500-10,000 cells/cm²)and fetal bovine serum (0-15%). The cells are characterized by fluorescence microscopy of actin fibers and nuclei. The serum protein adsorption is studied by atomic force microscopy (AFM). The cells are arranged selectively on O-terminated patterns into 30-200 μm wide arrays. Higher cell concentrations allow colonization of unfavorable H-terminated regions due to mutual cell communication. There is no cell selectivity without the proteins in the medium. Based on the AFM, the proteins are present on both H- and O-terminated surfaces. Pronounced differences in their thickness, surface roughness, morphology, and phase imagesindicate different conformation of the proteins and explain the cell selectivity. Full article