X. Xiang

Optical properties of metallic nanoparticles in Ni-ion-implanted α-Al2O3 single crystals

64 keV Ni ion implantation was performed at room temperature up to a dose of 1×1017u2009cm−2 in α-Al2O3 single crystals. The charge states, structure, and optical properties of metallic embedded Ni nanoparticles were studied by using x-ray photoelectron spectroscopy (XPS), transmission electron microscopy, and optical spectroscopy, respectively. XPS analysis showed that implanted Ni ions are mainly in charge state of metallic Ni0. Nanoparticles distributed from the surface to 30 nm below the surface were observed in a high-angle annular dark-field image. The size of nanoparticles ranges from 1 to 5 nm in diameter. A high-resolution electron microscopy image indicated the Ni-implanted area had been entirely amorphized. A new broad absorption band centered at 400 nm appeared in the optical absorption spectrum of the as-implanted crystal, due to surface plasma resonance of Ni nanoparticles. We did not find any emission band in the as-implanted sample under a Xe lamp excitation wavelength of 250–430 nm in a spect...

Optical and magnetic properties of Ni nanoparticles in rutile formed by Ni ion implantation

Crystalline Ni nanoparticles in the near surface of TiO2 (rutile) have been synthesized by Ni ion beam implantation at room temperature to a fluence of 1×1017∕cm2. Transmission electron microscopy, optical absorption spectroscopy, and a superconducting quantum interference device magnetometer have been utilized to characterize the nanostructure, optical and magnetic properties of Ni particles in TiO2. Crystalline Ni nanoparticles with dimensions ranging 3–20 nm formed in the near surface of rutile, which caused a broad absorption band from 700 nm in the optical absorption spectrum. Magnetic measurement indicated that the coercive force of Ni nanoparticles was about 210 Oe at 10 K. The superparamagnetism of the nanoparticles was observed above blocking temperature T=85K.

Optical properties and structure characterization of sapphire after Ni ion implantation and annealing

Implantation of 64keV Ni ions to sapphire was conducted at room temperature to 1×1017ions∕cm2 with a current density of 5 or 10μA∕cm2. Metallic Ni nanoparticles were formed with the 5μA∕cm2 ion current and the NiAl2O4 compound was formed with the 10μA∕cm2 ion current. The crystals implanted with both current densities were annealed isochronally for 1h at temperatures up to 1000°C in steps of 100°C in an ambient atmosphere. Optical absorption spectroscopy, x-ray diffraction, transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy have been utilized to characterize the samples. The surface plasmon resonance (SPR) absorption band peaked at 400nm due to the Ni nanoparticles shifted toward the longer wavelength gradually with the annealing temperature increasing from 400to700°C. The SPR absorption band disappeared after the annealing temperature reached 800°C. NiO nanoparticles were formed at the expense of Ni nanoparticles with an increasing annealing temperature. The TEM analyses reveale...

In situ TEM observation of heavy-ion-irradiation-induced amorphization in a TiNiCu shape memory alloy

TiNiCu shape memory alloy samples were irradiated by 400 keV Xe+ ions at room temperature. The in situ TEM observation showed that samples were amorphized at similar to0.4 dpa and the recrystallization after amorphization started when annealing at 550 K and basically finished at 1023 K

The photoluminescence and magnetism of nitrogen-implanted ZnO

Single crystal ZnO was implanted using nitrogen ions with an energy of 60 keV. The microstructure, photoluminescence (PL) and magnetism were studied in detail. Except for nitrogen, no other impurity can be detected by x-ray photoelectron spectra measurements. The room temperature PL of pure ZnO consists of a weak ultraviolet (UV) emission band and a strong green emission band. The PL and electrical conductivity can be suppressed by nitrogen implantation or by annealing in air. However, the two emission bands of pure ZnO can be enhanced intensively by Ar+ etching. The PL is related to the structure defects. Moreover, the intensity of UV luminescence is likely correlated to the electrical conductivity. Ferromagnetism cannot be obtained in the nitrogen-implanted sample from 77 to 300 K. The absence of ferromagnetism in nitrogen-implanted ZnO may be because there is no strong interaction between N 2p and O 2p electrons as nitrogen is a deep acceptor in ZnO.

Responsive surface charge transfer doping effect of reductive bio-molecules (glucose, fucoidan, and heparin) contacting on semiconducting titanium oxide films

Titanium oxide films appear to have extensive potentials in various applications largely because of its unique semiconducting properties. Usually, attentions are paid to characterize or tailor their surface electronic states, depending upon specific working circumstances as well as the requirements by their functional performances. Nevertheless, very rarely concern has been taken to the responsive effect on their electronic surface states when they come into contact with surrounding environments, which actually plays an important or even decisive role in their subsequent functions. For instance, cases like biomedical application could normally render the surface sequentially contacting with varying ambient media. In this study, we implemented initial contacting titanium oxide film with three representative bio-molecules (glucose, fucoidan, and heparin), and investigated the responsive effect of charge transfer doping on its electronic properties and its bio-performance. It was shown that the contacting imposed apparently n-type surface-charge-transfer-doping effect on the titanium oxide films. Their surface resistivity increased; their photo-luminance emissions were obviously quenched; their hydrophilic properties were improved; and denaturalization of fibrinogen on the surface was suppressed. Electrons were assigned to inject into titanium oxide film to produce the n-type doping effect. Our finding suggests that the semiconductor biomaterials surface properties and performances might be largely or even decisively influenced by the initial contacting of ambient conditions.

The microstructure, optical and magnetic property of nitrogen implanted SiO2

The microstructure, optical property and magnetism of nitrogen ion-implanted SiO2 were studied. The nitrogen incorporation into SiO2 was confirmed by means of x-ray photoelectron spectra and a Fourier-transform infrared absorption spectrum. The bond angle of Si–O–Si is decreased by nitrogen implantation. The absorption in the ultraviolet region is enhanced, which may be due to the band gap narrowing effect. Room-temperature ferromagnetic-like behavior is obtained in the nitrogen-implanted sample with a nominal dose of 1xa0×xa01018xa0ionsxa0cm−2.