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Ohmic graphite-metal contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond
摘要： A process to obtain ohmic contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond films was developed. Samples were contacted by Ti/Au metallic pads in the transmission line model (TLM) configuration. The electric contacts were placed onto a mesa structure produced on the CVD boron-doped layer. One of the samples was additionally implanted with helium ions at 10 keV in order to induce the formation of a graphitic layer underneath the diamond surface before contacting so as to improve electrical conduction. The electrical performance of both devices was characterized by the TLM method and compared. As a result, the sample with metallic electrodes exhibited a small and non-linear electrical conduction, while the graphitic/metallic contacts showed an ohmic behaviour with an estimated specific contact resistance as low as 3.3 × 10-4 Ω.cm2 for a doping level of a few 1017 cm-3. This approach opens the way to more efficient ohmic contacts on intrinsic or low-doped diamond that are crucial for the development of electronic devices and detectors.
关键词： oxygen terminations,graphitization,Ohmic graphite-metal contacts,lightly boron-doped CVD diamond film,ion implantation
更新于2025-09-04 15:30:14
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XPS investigation of F-doped MnO <sub/>2</sub> nanosystems fabricated by plasma assisted-CVD
摘要： Supported Mn(IV) oxide nanomaterials were prepared by plasma assisted-chemical vapor deposition from Ar/O2 plasmas starting from a fluorinated Mn(II) β-diketonate diamine adduct. Under the adopted conditions, the target compound served as a single-source molecular precursor for the obtainment of MnO2 nanosystems uniformly doped with fluorine. The overall F content in the target materials, composed of phase-pure β-MnO2, could be tailored as a function of the deposition temperature from 100 to 400 °C, a result of particular importance in view of photocatalytic and gas sensing applications. In the present study, attention is specifically devoted to the investigation of a representative specimen by means of x-ray photoelectron spectroscopy. Besides the wide scan spectrum, a detailed analysis of C 1s, O 1s, Mn 2p, Mn 3s, and F 1s photoelectron peaks is presented and discussed. The analyses reveal the formation of MnO2 free from other manganese oxides, with fluorine present in different chemical states, i.e., lattice F plus traces of precursor residuals at the system surface.
关键词： fluorine doping,x-ray photoelectron spectroscopy,PA-CVD,manganese oxide
更新于2025-09-04 15:30:14
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Effect of growth pressure on graphene direct growth on r-plane and c-plane sapphires by low-pressure CVD
摘要： Graphene was grown on both r-plane and c-plane sapphires by low-pressure chemical vapor deposition without using a metal catalyst. The growth pressure was systematically changed to investigate how the growth pressure effects the graphene growth. Consequently, it was found that the coverage of the graphene increased with increasing growth pressure on the r-plane sapphire while it decreased with increasing growth pressure on the c-plane sapphire. Raman spectroscopy and atomic force microscopy indicates that the growth layer is single-layer graphene on the r-plane sapphire while it is a bi-layer on the c-plane sapphire. Graphene is thought to grow on the r-plane sapphire simply in a two-dimensional nucleation mode. On the other hand, graphene tends to grow in the pits formed on the surface of the c-plane sapphire. The pits are thought to be produced by the oxygen desorption and have some catalytic effects.
关键词： sapphire,low-pressure CVD,atomic force microscopy,growth pressure,graphene,Raman spectroscopy
更新于2025-09-04 15:30:14
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The Role of Humidity in Tuning the Texture and Electrical Properties of Cu <sub/>2</sub> O Thin Films Deposited via Aerosol‐Assisted CVD
摘要： A study on the effect of carrier gas (CG) humidity on the texture and the resulting electronic properties of Cu2O thin films deposited using aerosol-assisted chemical vapor deposition (AA-CVD) at low temperatures (<365 °C) is reported. By increasing the CG humidity, the preferred orientation of the films can be tuned from [110] to [111]. By studying the initial stages of film deposition, a different growth mode is found for dry and humid conditions, which in turn directs the final texture of the films. The analysis of the electric properties of the films by Hall effect shows that carrier concentration remains in the order of 1015 cm?3 when using both dry and humid conditions. Conversely, Cu2O samples deposited with humid CG generally present a higher mobility, up to 17 cm2 V?1 s?1. [111]-textured Cu2O films with high mobility were used to fabricate a diode by depositing a ZnO layer on top using atmospheric pressure spatial atomic layer deposition (AP-SALD). The diode shows an excellent rectifying behavior with a high asymmetry close to 104 between ?1 and +1 V.
关键词： textured thin films,copper oxides,aerosol-assisted CVD,carrier mobility,atmospheric pressure processing
更新于2025-09-04 15:30:14
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Iron(III) β-diketonates: CVD precursors for iron oxide film formation
摘要： Within this study, the synthesis of three iron(III) β-diketonate complexes [Fe(β-diketonate)3] (β-diketonate = 2-acetylcyclopentanoate (3a), = 2-acetylcyclohexanoate (3b), = 4,4-dimethyl-1-phenyl pentanedionate (3c)) is described. The synthesis of 3a–c was performed by the reaction of the respective β-diketones with FeCl3 in the ratio of 3:1 in presence of NaOH. TG and DSC studies were carried out under an atmosphere of argon and oxygen, showing that 3b,c partly evaporate during the heating process. PXRD measurements of the as-obtained residues of 3a–c from the TG measurements confirmed the formation of crystalline α-Fe2O3 at 800 °C. Vapor pressure studies confirmed that complexes 3b and 3c show a better volatility (17.3 mbar (3b), 5.4 mbar (3c) at 120 °C) than the iron β-diketonate complexes [Fe(tfa)3] and [Fe(acac)3], respectively [62,63]. CVD studies carried out with 3a,b resulted in the formation of iron oxide thin films in presence of oxygen as reactive gas. However, complex 3c did not result in iron oxide film formation. All received layers were dense and coherent as proven by SEM studies. With metal-organic 3a and 3b, crystalline γ- and α-Fe2O3 layers were obtained at 450 °C, respectively. The XPS studies confirmed the formation of Fe2O3 layers with carbon impurities on the layer surfaces, however, in the layers no carbon could be detected.
关键词： TG,Vapor pressure,Iron,Solid-state structure,β-Diketonate,Iron(III) oxide,CVD
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Topography Simulation of 4H-SiC-Chemical-Vapor-Deposition Trench Filling Including an OrientationDependent Surface Free Energy
摘要： Topography simulation of chemical-vapor-deposition (CVD) trench filling has been advanced as a tool for designing fabrication processes of high-voltage 4H-SiC superjunction devices. In the longitudinal section of filled stripe trenches, an experimentally observed dip, which had not been well reproduced with a previous technique using a fixed surface free energy (γ), came to be qualitatively reproduced by including an orientation dependence of γ.
关键词： orientation,SiC,surface free energy,CVD,trench
更新于2025-09-04 15:30:14
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Monoisotopic Ensembles of Silicon-Vacancy Color Centers with Narrow-Line Luminescence in Homoepitaxial Diamond Layers Grown in H <sub/>2</sub> –CH <sub/>4</sub> – <sup> [ <i>x</i> ] </sup> SiH <sub/>4</sub> Gas Mixtures ( <i>x</i> = 28, 29, 30)
摘要： Silicon-vacancy (SiV?) color center in diamond is of high interest for applications in nanophotonics and quantum information technologies, as a single photon emitter with excellent spectral properties. To obtain spectrally identical SiV? emitters, we doped homoepitaxial diamond ?lms in situ with 28Si, 29Si, and 30Si isotopes using isotopically enriched (>99.9%) silane SiH4 gas added in H2?CH4 mixtures in the course of the microwave plasma-assisted chemical vapor deposition process. Zero-phonon line components as narrow as ～4.8 GHz were measured in both absorption and luminescence spectra for the monoisotopic SiV? ensembles with a concentration of a few parts per billion. We determined with high accuracy the Si isotopic energy shift of SiV? zero-phonon line. The SiV? emission intensity is shown to be easily controlled by the doped epi?lm thickness. Also, we identi?ed and characterized the localized single photon SiV? sources. The developed doping process opens a way to produce the SiV? emitter ensembles with energy con?ned in an extremely narrow range.
关键词： diamond,silicon-vacancy center,CVD synthesis,optical absorption,photoluminescence,doping,silicon isotope
更新于2025-09-04 15:30:14