Zhao Yongnian

Infrared and Raman spectra of complexes about rare earth nitrate with Schiff base from o-vanillin and 1-naphthylamine

Abstract Infrared and Raman spectra are reported for 10 complexes of rare earth nitrate with Schiff base from o-vanillin (2-hydroxy-3-methoxy-benzaldehyde) and 1-naphthylamine in the range 100–4000 cm −1 and 100–1799 cm −1 . Some absorption bands are assigned and the results of them are used to discuss the coordinated structure of the complexes.

High-pressure Raman studies of graphite and ferric chloride-graphite

The pressure dependences of the Raman-active graphite layer shearing modes in highly oriented pyrolytic graphite (HOPG) and FeCl3-HOPG acceptor intercalation compounds for stage indices n=1, 2 and 3 have been measured in diamond anvil cell by use of a Spex-1403 Ramalog system. The results of high-pressure Raman spectra show that both the interior and neighbouring modes exhibit a frequency shift upwards with increasing pressure, which has been attributed to an in-plane lattice contraction. In stage-3 FeCl3-HOPG, the pressure-induced staging transition from stage 3 to stage 4 has been found from the change in intensity ratio of the interior to neighbouring modes at 8.39 GPa. This finding confirmed firstly that the pressure-induced staging transitions are not just confined to the alkali-metal graphite donor intercalations but are valid for the acceptor graphite intercalation compounds.

Influence of Thickness on Field Emission Characteristics of Nanometre boron Nitride Thin Films

Nanometre boron nitride (BN) thin films with various thickness (54-135 nm) were prepared on Si(100) by rf magnetic sputtering physical vapour deposition. The field emission characteristics of the BN thin films were measured in an ultrahigh vacuum system. A threshold electric field of 11 V/µm and the highest emission current density of 240 µA/cm2 at an electric field of 23 V/µm were obtained for the about 54-nm-thick BN film. The threshold electric field increases with increasing the thickness in the nanometre range. The Fowler-Nordheim plots show that electrons were emitted from BN to vacuum by tunnelling through the potential barrier at the surface of BN thin films.

High pressure raman spectra of melamine (C3H6N6) and pressure induced transition

Abstract High pressure Raman spectra of Melamine (C3H6N6) have been studied up to 8.7 GPa. The pressure effect on Raman spectra reveals that the discrepancy between intra and inter-molecule bonds tends to shrink with increasing pressure. The experimental results show that Melamine probably undergoes two structural transitions at 2 and 6 GPa respectively and the structure of the new phase has C1 1 i symmetry probably at 2GPa

Infrared Spectroscopy Investigation of Cubic Boron Nitride Films

Abstract FT-IR Spectroscopy have been used for identifying both the structure of BN and the intensity of the compressive stress in cubic boron nitride (c-BN) film prepared by a unbalanced of (13.56 MHz) magnetron sputtering of a hexagonal boron nitride target in a mixture argon and nitride discharge. A T(temperature) - V(negative bias) phase diagram was obtained using the phase structure identify by IR spectra. Comparing the reflection infrared spectra (RIR) with the transmission infrared spectra (TIR) measured from same c-BN film, it is firstly found that RIR peak position of c-BN is lower than TIR peak position of c-BN, this means that the compressive stress on the surface layer of c-BN film is smaller than that inside c-BN film, may be this is the reason why thicker c-BN film can not be synthesized. A higher IR peak position of 1064 cm−1 and a lower peak position 1004.7 cm−1 were detected from a broken and partly peeled off c-BN film. The peak position of 1064 cm−1 agrees with that of bulk c-BN at 1065...

INVESTIGATION OF PREPARING CUBIC BORON NITRIDE FILMS BY MAGNETRON ARC-DISCHARGE PLASMA ION PLATING

A method of synthesizing cubic boron nitride (c-BN) films by the magnetron arc-discharge plasma ion plating was investigated. A nearly pure c-BN film was obtained by reacting boron vapor with high-density nitrogen ions, and using hot cathode arc-discharge plasma in a parallel magnetic field around the substrate. The structure of the films obtained was characterized by using infrared absorption spectroscopy and x-ray diffraction analysis. After numerous experiments, the phase pattern of the bias vs the current in synthesizing c-BN was found.

Field Emission Characteristics of BN Films with Cubic-BN Phase

Boron nitride (BN) thin films with cubic boron nitride (c-BN) phase were prepared on the (100)-oriented surface of n-Si (0.008–0.02 Ωm) by rf magnetron sputtering physical vapour deposition. The c-BN content is determined to be around 50% by using Fourier transform infrared spectroscopy for the BN thin films. The field emission characteristics of BN films were measured in an ultrahigh vacuum system. It is found that the field emission of the BN film with c-BN phase is evidently more excellent than that without c-BN phase. A turn-on field of 5 V/μm and a current of 460 μA/cm2 were obtained for the BN film with c-BN phase. The Fowler–Nordheim plots of emission characteristics of BN films indicate a straight line, which suggests the presence of the FN tunnelling.

High-pressure Raman studies of liquid and molecular crystal chloroform and bromoform at room temperature

Abstract Raman spectra of liquid and crystalline CHCl3 and CHBr3 have been measured at pressures up to 102 kbar and room-temperature. The pressure dependences of the internal modes (for CHCl3 and CHBr3) and the external modes (for CHBr3) are reported. The results for CHCl3 show that all of the E modes (ν4, ν5, ν6) are split into two peaks at the liquid-solid phase transition point (7.9 kbar). Another phase transition is suggested by the discontinuities of the internal mode slopes (dν/dp) at about 60 kbar. For CHBr3, three pressure-induced phase transitions were observed: the one at 3.3 kbar is a liquid-solid phase transition (liquid to α), and the other two at 8.0 kbar (α to β) and in the range 51.5–95 kbar (β + γ), respectively, are solid-solid phase transitions. The pure γ phase is obtained at above 95 kbar. Comparison of the spectra at high pressure and 293 K with that at low temperature and 1 bar indicates their structures are similar.

A New Method to Prepare Boron Nitride Thin Films

We report a new method to prepare boron nitride (BN) thin films on Si (100) substrates in an Ar–N2-BCl3-H2 gas system by magnetron arc enhanced plasma chemical vapour deposition. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) are used to characterize the films. The FTIR spectra show that the deposited boron nitride films experienced a transition from pure h-BN phase to a cubic-containing phase with the variation of arc current ranging from 10 A to 18 A. The BN film with 42% c-BN was obtained without substrate bias voltage. In the gas system of Ar–N2–BCl3–H2, h-BN can be preferentially etched by chlorine. The chemical etching effect of chlorine allows the formation of c-BN without substrate bias voltage, which may develop a new perspective for the deposition of high quality c-BN film with low stress.

Field Emission Characteristics of BN Films Treated with H 2 and O 2 Plasma

BN films were synthesized on the (100)-oriented surface of n-Si (0.008–0.02 Ωm) by rf magnetron sputtering physical vapor deposition (PVD). A BN film was first treated with H2 plasma for 60 min and then the H2 treated sample was treated with O2 plasma for 15 min. The films were characterizes by using Fourier transform infrared spectra (FTIR) and atomic force microscopy (AFM). The field emission characteristics of BN films were measured in an ultrahigh vacuum system. A turn-on electric field of 8 V/μm and a current of 400 μA/cm2 were obtained for the BN film treated with H2 plasma. The results show that the surface plasma treatment makes no apparent influence on the surface morphology of the BN films. The transformations of the sample emission characteristics have to do with the surface negative electron affinity (NEA) of the films possibly. The turn-on electric field of the BN film treated with H2 plasma is lower than that without treatment, which possibly attributes to the surface NEA effect. The surface NEA of the H2 treated BN film is lost after O2 plasma treatment.