Yue-Rui Chen

Nanocrystalline diamond from carbon nanotubes

Structural phase transformation from multiwalled carbon nanotubes to nanocrystalline diamond by hydrogen plasma post-treatment was carried out. Ultrahigh equivalent diamond nucleation density above 1011 nuclei/cm2 was easily obtained. The diamond formation and growth mechanism was proposed to be the consequence of the formation of sp3 bonded amorphous carbon clusters. The hydrogen chemisorption on curved graphite network and the energy deposited on the carbon nanotubes by continuous impingement of activated molecular or atomic hydrogen are responsible for the formation of amorphous carbon matrix. Diamond nucleates and grows in the way similar to that of diamond chemical vapor deposition processes on amorphous carbon films.

High solar absorption of a multilayered thin film structure

We report a structure with 4 thin film layers composed of pure metal and dielectric materials and prepared by sputtering. The reflectance and transmittance are lower than 5% with the absorption to be achieved higher than 95% in the 400-1000nm wavelength region as match to the solar radiance spectrum. The thermal emittance of the structure is in the range of 0.063-0.10 through data analysis. The good reproducibility and stability of spectral data associated with the deposition process imply the advantage of the solar energy absorber which is cost-effective in application.

Stabilization of face‐centered‐cubic Mn films via epitaxial growth on GaAs(001)

The epitaxial growth of fcc Mn films on the GaAs(001) surface has been achieved. The films are studied by in situ reflection high energy electron diffraction (RHEED) and ex situ x‐ray diffraction (XRD). The lattice parameters of the metastable Mn films are determined to be 0.362 nm. A transition region composed of a Mn‐Ga‐As alloy is formed at the Mn/GaAs interfaces and is clearly verified by XRD measurements.

Densely folded spectral images of the CCD spectrometer working in the full 200-1000nm wavelength range with high resolution.

A new charge-coupled device (CCD) spectrometer has been studied and constructed by using a two-dimensional CCD detector and an integrated grating consisting of 10 subgratings. Effective spectral images of 268 mm along the dispersion direction have been densely folded 10 times to cover the full 200-1000 nm working wavelength range without any mechanical moving elements. The results show that the system has a spectral resolution and acquisition time of better than 0.07 nm and less than 100 ms, respectively, in the entire spectral range after system calibration.

Negative refraction at the pure Ag/air interface observed in the visible Drude region

Pure negative refraction was found for a series of prismlike Ag film samples measured in the visible Drude region. Results show that the pseudonegative refraction index nm changes with the photon energy and has a spectral trend to be less negative with the increasing energy. Light refraction will be expected to be positive in the higher energy region where the interband transitions dominate the interaction between the electrons and photons in Ag.

Study of a high-resolution infrared spectrometer by using an integrated multigrating structure

A new type of infrared spectrometer system working in the optical communication field has been studied and constructed. In order to achieve both high spectral resolution and fast data acquisition speed, an integrated grating with five subgratings and a set of five line-array InGaAs detectors are used to work in the 1450–1650nm wavelength range without any scanning and mechanical moving parts. The system has been calibrated with a spectral resolution of about 0.08nm and a fast data acquisition time of less than 40ms (>5nm∕ms) in the entire spectral range.

OPTICAL AND MAGNETO-OPTICAL PROPERTIES OF CO(001)/GE/CO SANDWICHES

A series of bcc‐Co(001)/Ge/Co trilayers was grown on a GaAs(001) substrate by the molecular beam epitaxy technique. The optical and magneto‐optical properties of the samples were studied. An oscillatory variation of the magneto‐optical Kerr effect (MOKE) with the thickness of the Ge spacers was observed. We conclude that the effective optical constants as well as the real and imaginary off‐diagonal element of the dielectric tensor should be considered in explanation of the MOKE activities since both have a large influence on the MOKE oscillations. Moreover, the coercivity and magnetization also oscillate with the Ge layer thickness.

Path-folded infrared spectrometer consisting of 10 sub-gratings and a two-dimensional InGaAs detector

A new compact infrared spectrometer without any mechanical moving elements has been designed and constructed using a two-dimensional InGaAs array detector and 10 sub-gratings. The instrument is compact, with a double-folded optical path configuration. The spectra are densely 10-folded to achieve 0.07-nm spectral resolution and a 2-ms data acquisition time in the 1450- to 1650-nm wavelength region, making the instrument useful for real-time spectroscopic data analyses in optical communication and many other fields.

XPS Study of Mn Thin Films Grown on GaAs(001) Surfaces

The composition depth profiles of the Mn thin films grown on GaAs(00l) surface using MBE technique are studied with X-ray photoelectron spectroscopy(XPS) . The experimental results show that the fcc-Mn/GaAs(001) system grown on a 400 K substrate has a sandwich structure with a Mn-Ga-As buffer layer located between the fcc-Mn layer and the GaAs substrate; the α-Mn/GaAs (001) system grown on a 300 K substrate also has a similar buffer layer which is much thinner than that of the fcc-Mn/GaAs(001) system;and the system grown on a 450 K substrate is a Mn-Ga-As alloy beyond the GaAs substrate and it has no Mn-dominated area. It is concluded that to keep the substrate at a proper temperature(400 K) during growth to obtain a suitable thickness of buffer layer is an essential requirement to grow fcc-Mn on GaAs(00l) surface.

Study of the new ellipsometric measurement method using integrated analyzer in parallel mode

A new type of ellipsometer using an integrated analyzer composed of 12 sub-analyzers with different azimuth angles was constructed and studied. By using a two-dimensional CCD array camera to measure the light intensity emerging in parallel from each sub-analyzer with the azimuth angles uniformly distributed in the range of about 180 degrees , the ellipsometric parameters were extracted within the data acquisition time less than 1 second. The ellipsometric parameters for the polished bulk Si sample were measured to show good agreement with the results measured by using another two ellipsometric methods. The new method having the merits of high speed and reliability in the optical data measurement can be potentially used in the fields where the in situ data acquisition with high precision is the key issue as required.