Cunming Liu

Near-infrared emission properties and energy transfer of Tm3+-doped and Tm3+/Dy3+-codoped chalcohalide glasses

Near-infrared emission properties of Tm3+ in GeSe2–Ga2Se3–CsI glasses were investigated. The increase in emission intensity ratio I1.47 μm/I1.22 μm and the large increase in the lifetime of the Tm3+:H34 level from 189 to 2480 μs can be obtained as CsI concentration changes from 20% to 40%. These improved emission properties result from the appearance of I-containing structural units, which have low phonon energy and are located near the Tm3+ ions, dominating the multiphonon relaxation and cross relaxation. Radiative parameters of Tm3+ were calculated based on the Judd–Ofelt analysis. The potential use of Tm3+-doped GeSe2–Ga2Se3–CsI glasses for S-band fiber amplifiers was discussed. Additionally, the intensity and lifetime of 1.2, 1.3, and 1.47 μm infrared fluorescence on Tm3+/Dy3+-codoped GeSe2–Ga2Se3–CsI glasses were studied, and the energy transfer mechanisms were discussed.

Light emission and degradation of single-walled carbon nanotube filament

Household light bulbs were fabricated using macroscopically long and aligned single-walled carbon nanotube (SWNT) ropes as filaments. It was found that the SWNT filament could emit bright light when an electric current was passed through it. The light spectrum from the SWNT filament showed a nonblackbody characteristic of the thermal emission, and its infrared emission was almost completely suppressed possibly due to the “photonic band-gap” effect that originates in the loose fibrous bundle structure of the SWNT filament. The electrical resistance of the SWNT filament was found to first increase, and then continually decrease during light emission. It was also found that an electric current could cause degradation and burnout of the SWNT filament and result in complete amorphization, and that an interesting mushroomlike carbon structure was formed due to the carbon evaporation of the nanotube filament during light emission.

Chemical intermixing at FeMn/Co interfaces

Elemental distributions of Fe, Mn, and Co in ultrathin FeMn/Co multilayers have been profiled by the x-ray anomalous scattering technique. Chemical intermixing is observed at the FeMn/Co interfaces with intermixing regions up to 14 A. The chemical compositions in the intermixing regions are found to vary gradually from FeMn to FeMnCo2 and from FeMnCo2 to Co., respectively, but not from FeMn to Co. This result suggests that a reaction may occur and FeMnCo2 appears at the interface during the deposition.

Elemental distribution at the interfaces of NiMn/Co multilayers by x-ray anomalous scattering

Elemental distributions of Ni, Mn, and Co nearby the interfaces of sputtered ultrathin NiMn/Co multilayers have been investigated by x-ray anomalous scattering. In the direction normal to the film, the elements Ni, Co, and Mn are observed to vary gradually at the Co/NiMn interface with each element having a different distribution. After the samples were annealed at 300 °C for periods of 3, 10, or 20 h, the elements are observed to vary gradually at the NiMn/Co interface, as well. To obtain information on the in-plane distribution of each element at the interfaces, x-ray diffuse scattering experiments were performed with x-ray energy close to the Ni, Co, and Mn K edges. Different geometrical interfacial correlated roughness is observed with different x-ray energy.

Structures, electrical properties, and equation of state in Ca4Mn3O10 under high pressure

The structure changes and electrical properties in Ca4Mn3O10 under high pressure at room temperature have been studied using energy-dispersive x-ray diffraction with synchrotron radiation and resistance and capacitance measurements. A phase transition from an orthorhombic to a tetragonal phase occurred during increasing pressure to above 19.3 GPa. The equation of state of Ca4Mn3O10 was obtained from the V/V0–P relationship. The bulk modulus B0 and its first-order derivative B0′ of Ca4Mn3O10 were calculated based on the Birch–Murnaghan equation.