Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1021/acsami.0c18435

Language：English   Publishing type：Research paper (scientific journal)  

Heterojunction diodes are constructed by growing n-type (nitrogen-doped) ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films onto p-type Si substrates in nitrogen and hydrogen mixed-gases by coaxial arc plasma deposition. The fabricated heterojunctions are analyzed regarding their film morphology and electrical properties. The complex structure of UNCD/a-C:H films, which consists of nano-sized-sp3 diamond grains and sp2-grain boundaries (GBs), makes it difficult to separate their contribution to electrical conductivity of the films using conventional characterization methods. In this paper we characterize the n-type UNCD/p-type Si heterojunction diode by employing impedance spectroscopy method, which can isolate the differing components that contribute to the overall conductivity of the film. The impedance spectroscopy is measured in the frequency range of 100 Hz to 2 MHz, with AC small signal superimpose on DC bias voltage in the range of 0–1 V. The influence of the bias on UNCD grains and GBs contribution to resistance and capacitance of UNCD/a-C:H film and n-UNCD/p-Si heterojunction is investigated by equivalent circuit model using fitting of the impedance data. The results revealed that the electrical conductivity is mainly controlled by the GBs rather than the UNCD grains. Furthermore, the extracted value of dielectric constant of N-doped UNCD/a-C:H film is found to be comparable with that of microcrystalline diamond, which indicates the capacitance contribution in the device is mainly originated from the UNCD grains. This study demonstrates capability of impedance spectroscopy to provide an obvious separated contribution of sp3 and sp2 bonded carbons to the electrical conductivity in their coexistence materials.

DOI： https://doi.org/10.1088/1402-4896/aba97e

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI 10.35848/1882-0786/abb871

Language：English   Publishing type：Research paper (scientific journal)  

Ultrananocrystalline diamond/hydrogenated amorphous carbon films were synthesized by coaxial arc plasma deposition. The morphological and structural evolutions of the films driven by laser irradiation (ArF, 193 nm, 20 ns) are examined at different laser energies (0.4–1 J cm−2). Up on laser irradiation, the films revealed hydrogen effusions accompanied by the transformation of sp3 into sp2-hybridization carbon. However, the film irradiated at 0.8 J cm−2 exhibited higher sp3 fractions, which can be attributed to that: a specific value of laser energy density (0.8 J cm−2) can provide a suitable amount of heating that is enough to quench the film and increase the sp3 contents.

DOI： DOI 10.35848/1882-0786/abb871

Language：English   Publishing type：Research paper (scientific journal)  

We report on the structural evolution of diamond-like carbon (DLC) films by the nanosecond pulsed laser annealing process. DLC film is coated on cemented carbide (WC-Co) by cathodic arc ion plating, which is then annealed by ArF laser (193 nm, 20 ns) at different laser fluences (0.9–1.7 J/cm2). Upon laser annealing, Raman spectra divulge higher sp3 fractions accompanied by a blue shift in the G-peak position, which indicates the changes of sp2 sites from rings to chains. At higher fluence (>1.2 J/cm2), the film converts into reduced graphene oxide confirmed by its Raman-active vibrational modes: D, G, and 2D.

DOI： DOI: https://doi.org/10.1557/mrc.2019.88

Language：English   Publishing type：Research paper (scientific journal)  

A singlecrystalline diamond (100)(Ib) plate immersed in 2% boric acid was irradiated by 193-nm ArF excimer laser beams for the formation of conductive layers on the surface of an insulating diamond substrate. From current-voltage measurements of the irradiated areas, it was confirmed that semiconducting layers with high conductivities are formed on the diamond surface. It was possible to form ohmic contacts by directly touching tungsten probes with the layer surface. Since Raman spectra exhibited only peaks due to diamond and no peaks due to amorphous carbon, the drastically enhanced conductivity is not attributed to amorphous carbon formation but due to the incorporation of boron atoms into the diamond subsurface from the dopant acid. Secondary ion mass spectrometric depth profile showed the incorporation of boron atoms up to 40 nm depths from the surface. From cathodoluminescence measurements at low temperatures, it was difficult to detect clear peaks for the substitutional incorporation of boron atoms into diamond lattices, which could be attributed to the small thickness of the doped layer for detection. The proposed technique is a new potential method for shallow doping and formation of conductive layers on singlecrystalline diamond surfaces.

DOI： 10.1016/j.diamond.2019.04.013

Language：English   Publishing type：Research paper (scientific journal)  

Ultrananocrystalline diamond/hydrogenated amorphous carbon composite films were deposited in the ambient of hydrogen by coaxial arc plasma deposition. The film compositions and chemical bonding structures were investigated by X-ray diffraction, X-ray photoemission and hydrogen forward scattering spectroscopies. The sp3/(sp2+sp3) ratio and hydrogen content in the film were estimated to be 64% and 35 at.%, respectively. The optical parameters and the optical dispersion profile were determined by using a variable angle spectroscopic ellipsometer at 55°, 65° and 75° angle of incidence in the photon energy range of 0.9–5 eV. Combinations of multiple Gaussian, and Tauc-Lorentz or Cody-Lorentz dispersion functions are used to reproduce the experimental data. Results of ellipsometry showed a refractive index of approximately 2.05 (at 2eV) and optical band gap of 1.63 eV. The imaginary part of dielectric function exhibited a peak at 3.8 eV, which has assigned to π-π* electron transitions. Furthermore, Electron spin resonance measurements implied the existence of dangling bonds, which might have a partial contribution to the optical absorption properties of the deposited films. A correlation between optical parameters and structural profile of the deposited films is discussed.

DOI： https://doi.org/10.1016/j.cap.2018.11.012

Other Link： https://www.sciencedirect.com/science/article/pii/S1567173918303171

Language：English   Publishing type：Research paper (scientific journal)  

Heterojunction diodes comprising poorly (1 at. %) nitrogen-doped n-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films and p-type Si substrates were prepared in nitrogen and hydrogen mixed gas atmosphere by coaxial arc plasma deposition. Dark current density–voltage (J–V) characteristics were studied in the temperature range of 200–400 K, in order to investigate the current transport mechanism through the fabricated heterojunctions. The temperature dependence of the ideality factor and reverse saturation current reveals that carrier transport predominantly occurs in the generation–recombination mechanism and, at low temperatures, it accompanies tunneling via weak traps. The heterojunctions surely exhibited photodetection for 254 nm ultraviolet light illumination. It is expected that photocarriers will be generated at UNCD grains and transported through an a-C:H matrix.

DOI： DOI 10.7567/JJAP.56.07KD04

Language：English   Publishing type：Research paper (scientific journal)  

Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon (UNCD/a-C:H) films were grown by coaxial arc plasma deposition in the ambient of nitrogen and hydrogen mixed gases. Synthesized films were structurally investigated by X-ray photoemission and near-edge X-ray absorption fine structure spectroscopies. A heterojunction with p-type Si substrate was fabricated to study the ultraviolet photodetection properties of the film. Capacitance–voltage measurements assure the expansion of a depletion region into the film side. Current–voltage curves in the dark showed a good rectifying behaviour in the bias voltages range between ±5 V. Under 254 nm monochromatic light, the heterojunction shows a capability of deep ultraviolet light detection, which can be attribute to the existence of UNCD grains. As the diode was cooled from 300 K down to 150 K, the detectivity has a notable …

DOI： 10.1007/s00339-017-0798-4

Language：English   Publishing type：Research paper (scientific journal)  

Nitrogen-incorporated ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/aC: H) films were synthesized in nitrogen and hydrogen mixed gas atmospheres by coaxial arc plasma deposition. The temperature dependence of electrical resistivity implies that carriers are transported in hopping conduction. Heterojunctions comprising 3 at.% nitrogen-doped films and p-Si substrates exhibited a typical rectifying action. The expansion of a depletion region into the film side was confirmed from the capacitance–voltage characteristics, and the built-in potential and carrier concentration were estimated to be 0.51 eV and 7.5× 10 16 cm− 3, respectively. It was experimentally demonstrated that nitrogen-doped UNCD/aC: H is applicable as an n-type semiconductor.

DOI： DOI 10.7567/APEX.8.095101

Language：English   Publishing type：Research paper (scientific journal)  

Herein, an eco-friendly dual-layered biopolymer-based membrane was fabricated for water desalination. The membrane was electrospun from two bio-polymeric layers. The top hydrophobic layer comprises polycaprolactone (PCL) and the bottom hydrophilic layer from cellulose acetate (CA). Additionally, silica nanoparticles (SiO2 NPs) were electrosprayed onto the top layer of the dual-layered PCL/CA membrane to enhance the hydrophobicity. The desalination performance of the modified PCL-SiO2/CA membrane was compared with the unmodified PCL/CA membrane using a direct contact membrane distillation (DCMD) unit. Results revealed that silica remarkably improves membrane hydrophobicity. The modified PCL-SiO2/CA membrane demonstrated a significant increase in water contact angle of 152.4° compared to 119° for the unmodified membrane.

DOI： https://doi.org/10.1016/j.chemosphere.2024.141468

Other Link： https://www.sciencedirect.com/science/article/pii/S0045653524003618

Language：English   Publishing type：Research paper (scientific journal)  

A hybrid system is proposed to use solar energy as a heating source for the membrane distillation unit. Concentrating photovoltaic needs an efficient cooling system to manage the excess thermal load. Two microchannel heat sinks were proposed to keep the cells from thermal degradation and simultaneously transfer the excess thermal energy to the membrane distillation unit. The results showed a maximum coolant outlet temperature of 59 °C, which is adequate for the membrane distillation unit. A new composite electrospun nanofibrous membrane was successfully synthesized to reduce unfavorable membrane wettability. First, ZIF-L nanoparticles were synthesized and characterized to prove successful preparation, then used as a nanofiller with polystyrene as the polymer membrane matrix for the first time.

DOI： https://doi.org/10.1016/j.jwpe.2023.103872

Other Link： https://www.sciencedirect.com/science/article/pii/S2214714423003914

Language：English   Publishing type：Research paper (scientific journal)  

The realization of diamond‐based advanced devices is interrelated with the fabrication of practical ohmic contacts. Contrary to boron‐doped, the phosphorus‐doped diamonds with interface carbide forming Ti‐based conventional ohmic contacts find their limitation in device fabrication due to the high contact resistance. Herein, nanocarbon ohmic contacts are deposited by a coaxial arc plasma gun on semiconducting diamonds, and their composite structure which facilitates exceptional contact properties is explored. A comparative electrical characterization between nanocarbon ohmic contacts and conventional Ti‐based contacts is performed on a heavily phosphorus‐doped diamond, and they exhibited one‐order declination in specific contact resistance.

Language：English   Publishing type：Research paper (scientific journal)  

n-Type (phosphorus-doped) diamond is a promising material for diamond-based electronic devices. However, realizing good ohmic contacts for phosphorus-doped diamonds limits their applications. Thus, the search for non-conventional ohmic contacts has become a hot topic for many researchers. In this work, nanocarbon ohmic electrodes with enhanced carrier collection efficiency were deposited by coaxial arc plasma deposition. The fabricated nanocarbon ohmic electrodes were extensively examined in terms of specific contact resistance and corrosion resistance. The circular transmission line model theory was used to estimate the charge collection efficiency of the nanocarbon ohmic electrodes in terms of specific contact resistance at a specific voltage range (5–10 V); they exhibited a specific contact resistance of 1× 10− 3 Ωcm 2.

DOI： https://doi.org/10.1063/5.0093470

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we report on the complex formation and characterization of nano-bio conjugates synthesized by the sol–gel chemical method. The nano-bio conjugates, consisting of inorganic ZnO nanoparticles (NPs) and organic nitrogenous bases of DNA (Thymine and Cytosine), are investigated using electron microscopies, molecular vibrational analysis and X-ray spectroscopies. In this experimental investigation, we used two basic nitrogenous bases of DNA – Cytosine, and Thymine. The X-ray diffraction patterns of both ZnO NP and the nanoconjugate (NJ) reveal a highly phase pure ZnO structure with negligible changes in the unit cell dimensions. The Raman peaks due to the molecular vibration of C2=O7 and C4=O8 sites of Thymine and C=O and N-H sites in Cytosine are shifted due to the cation affinity after the interaction with ZnO NPs.

Other Link： https://www.sciencedirect.com/science/article/pii/S2352507X2200035X

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.physb.2021.413604

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.3390/nano12050854

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.3390/polym14040709

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1109/ACCESS.2020.3046969

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.tsf.2020.138222

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.mssp.2018.06.028

Language：English   Publishing type：Research paper (scientific journal)  

Nitrogen-doped ultra-nanocrystalline diamond/hydrogenated amorphous carbon composite films prepared in hydrogen and nitrogen mixed-gas atmospheres by coaxial arc plasma deposition with graphite targets were studied electrically and chemical-bonding-structurally. The electrical conductivity was increased by nitrogen doping, accompanied by the production of n-type conduction. From X-ray photoemission, near-edge X-ray absorption fine-structure, hydrogen forward-scattering, and Fourier transform infrared spectral results, it is expected that hydrogen atoms that terminate diamond grain boundaries will be partially replaced by nitrogen atoms and, consequently, π C–N and C= N bonds that easily generate free electrons will be formed at grain boundaries.

DOI： 10.7567/APEX.10.015801

Language：English   Publishing type：Research paper (scientific journal)  

Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were deposited on P-type Si substrates by coaxial arc plasma deposition. The deposited films possessed N-type conduction, and evidently formed pn heterojunctions with P-type Si substrates. The heterojunction devices showed typical rectification properties similar to those observed for conventional abrupt pn heterojunctions. The conduction mechanisms that govern current transport in these devices were analyzed using dark current–voltage measurements in the temperature range from 300 K to 80 K. The results revealed that a trap-assisted multi-step tunneling process is a dominant mechanism at lower temperatures and low forward bias. At least two defect levels with activation energies of 42 and 24 meV appear to activate this process. At moderate forward bias, the current followed a power-law …

DOI： 10.1166/jnn.2016.13663

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI 10.7567/JJAP.55.07LE01

Other Link： https://iopscience.iop.org/article/10.7567/JJAP.55.07LE01/meta

Event date： 2023.7

Language：English  

Venue：Sophia University, Tokyo   Country：Japan