Y.H. Yu

Visible Photoluminescence in Carbon-Implanted Thermal SiO2 Films

The structures formed after the implantation of carbon in thermal SiO 2 and annealing presented visible photoluminescence (PL) bands at room temperature. The peak and intensity of PL bands depended strongly on the temperature of annealing. In addition, very weak PL bands were observed after the implantation of argon in thermal SiO 2 and similar annealing. HRTEM was also used to characterize the microstructure of the carbon or argon implanted thermal SiO 2 films. These observations showed that carbon aggregates were probably the origin of visible PL bands.

Exfoliating KTiNbO5 particles into nanosheets

Abstract KTiNbO 5 nanosheets have been prepared by a simple intercalation and exfoliation method. The structures of these nanosheets were analyzed, the formation mechanism was discussed and bandgap was measured to be about 3.2 eV.

Optical and electrical properties of nitrogen incorporated amorphous carbon films

Nitrogen incorporated amorphous carbon (a-C:N) films on silicon (111) wafer, quartz, and Ti/C substrates with nitrogen concentration up to 20 at. % are prepared by filtered arc deposition. The nitrogen concentration and area density of the films were measured by Rutherford backscattering. The electrical properties of the films were investigated by Hall electrical measurements. The optical properties of the films were characterized by ultraviolet–visible and infrared reflection spectrometry. Results indicate that the optical band gap and area density of a-C:N films decrease with increasing nitrogen pressure, accompanied with an increase of nitrogen concentration and reflectivity of the films. Furthermore, the influence of nitrogen concentration on the optical band gap of the films is discussed. The dielectric constant, refractive index and absorption coefficient of a-C:N films in infrared region were investigated. The results indicate that the optical constants of a-C:N show considerable variation with wav...

Dielectric properties of AlN thin films formed by ion beam enhanced deposition

Abstract AlN thin films were prepared through IBED. The microstructure and electronic characteristics of AlN films were studied through XPS and C – V / I – V test. N 2 gas added into IBED system during deposition could enhance N/Al ratio near to stoichiometrical structure and improve dielectric properties of AlN films. Some important dielectric parameters for AlN thin films were obtained.

Short-wavelength photoluminescence from silicon and nitrogen coimplanted SiO2 films

Intense short-wavelength photoluminescence (PL) observed at room temperature from thermal SiO2 films implanted with Si and N is reported. A flat Si profile was first created. N ions were subsequently implanted into the same depth region as the implanted Si ions. Two PL bands peaking at ∼330 and ∼430 nm were observed from the samples at room temperature with and without annealing. It is found that the PL has a strong dependence on the stabilized N in the Si- and N-coimplanted SiO2 films. The PL may originate from a complex of Si, N, and O.

DETERMINATION OF THE SP3/SP2 RATIO IN TETRAHEDRAL AMORPHOUS CARBON FILMS BY EFFECTIVE MEDIUM APPROXIMATION

In this article, a method for the determination of the sp3/sp2 ratio for highly tetrahedral amorphous carbon (ta-C) films is presented. This method is an optical characterization according to the Bruggeman effective medium approximation based on simulation of the infrared reflection spectrum. The simulation reflectivity is in good agreement with the experimental spectrum, and the obtained results of sp3 content are in good agreement with electron energy loss spectroscopy data, suggesting that this is an effective method for obtaining the sp3/sp2 ratio of ta-C films.

Electronics and optoelectronics of lateral heterostructures within monolayer indium monochalcogenides

Lateral heterostructures have attracted a great deal of attention due to their advanced properties, which may open up unforeseen opportunities in materials science and device physics. Here, we demonstrate a novel type of lateral heterostructure within monolayer indium monochalcogenides. The thermal stability of the structure is obtained based on the ab initio molecular dynamics calculations. Our results reveal that the proposed lateral heterostructures have direct bandgaps, tunable electronic properties, and type-II band alignment. In addition, the predicted carrier mobilities exceed 103 cm2 (V s)−1, which are 1–2 orders of magnitude higher compared to those of transition metal chalcogenide (TMD) materials. For the first time, the photoresponse and photovoltaic performance of such lateral heterostructures are evaluated based on the first-principles calculations. Upon illumination, the photoinduced current is generated throughout the heterojunction, with an external quantum efficiency up to 7.1%. These results make indium monochalcogenide lateral heterostructures promising candidates for next-generation of electronic and optoelectronic devices.

Compositional and structural studies of DC magnetron sputtered SiC films on Si(111)

Abstract Polycrystalline SiC films were deposited on Si(111) by reactive DC magnetron sputtering using a four inch elemental silicon target. Composition of the deposited films was studied by AES (auger electron spectroscopy) and RBS (Rutherford backscattering spectroscopy) which showed that stoichiometric SiC could be obtained. Both AES depth profile and RBS indicated the existence of a transition layer. XRD (X-ray diffraction) analysis revealed the formation of polycrystalline SiC films at a substrate temperature as low as 1123 K, and the absence of other peaks in XRD patterns except the SiC(111) peak implied that the films were (111) oriented. Furthermore, the films were found to consist of columnar nanometer sized crystallites by cross-section TEM (transmission electron microscopy) study.

Different luminescent properties of C+-implanted SiO2 films grown by thermal oxidation and PECVD

Abstract Room temperature photoluminescence (PL) from C+-implanted SiO2 films grown by thermal oxidation and PECVD is reported. There are great differences in the luminescent properties, which are shown by PL spectra, PL excitation (PLE) spectra, and the PL dynamics. The structural analysis of the C+-implanted SiO2 films are taken by FTIR, Raman, and HRTEM. The differences in light emission are attributed to the structural characteristics of SiO2 films before and after C ion implantation.

Optical properties of CNx films prepared by filtered arc deposition

Abstract CN x films on silicon (111) wafer, quartz and Ti C substrates with nitrogen concentration up to 20 at% have been prepared by a new plasma deposition technique-filtered arc deposition. The nitrogen concentration and area density of the films were measured by Rutherford back-scattering. The optical properties of the films were characterized by ultravioletvisible and infrared reflection spectrometry. Results indicate that the optical band gap and area density of the CN x films decrease with increasing nitrogen pressure, accompanied with an increase of nitrogen concentration and reflectivity of the films. Furthermore, the influence of nitrogen pressure on the optical band gap of the films is discussed.