E. Z. Luo

Electron field emission from SiC/Si heterostructures synthesized by carbon implantation using a metal vapor vacuum arc ion source

A remarkably low turn-on field of about 1 V/μm has been observed in electron field emission from planar SiC/Si heterostructures formed by high dose C implantation into Si using a metal vapor vacuum arc ion source. An implant energy of 35 keV was used to a dose of 1.0×1018 ions/cm2 with subsequent annealing in nitrogen at 1200 °C for 2 h. X-ray photoelectron spectroscopy showed that a thin surface stoichiometric SiC layer, with a thickness of about 150 nm, had been formed. Atomic force microscopy showed that there are densely distributed small protrusions formed on the surface. The formation of a thin surface stoichiometric SiC layer and the formation of densely distributed small protrusions on the surface are believed to be the two factors responsible for the efficient electron field emission.

Study of domain stability on (Pb0.76Ca0.24)TiO3 thin films using piezoresponse microscopy

We introduce a method to investigate the domain stability issue based on piezoresponse microscopy. The switching and back-switching processes of sol–gel derived (Pb0.76Ca0.24)TiO3 thin films were investigated by comparing the local piezoelectric hysteresis loops in continuous mode and pulse mode. It was found that the local hysteresis loops acquired by the pulse mode in shorter pulse width were dominated by the back-switching process while the continuous mode piezoelectric hysteresis loop provides information on the domain switching process.

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...

Probing the conducting paths in a metal - insulator composite by conducting atomic force microscopy

We have imaged the conducting paths in a metal - insulator composite , with x ranging from 0.24 to 0.576 by conducting atomic force microscopy (AFM). The surface morphology and the electric current between the tip and sample have been obtained simultaneously on the nanometre scale. Measurable changes of current image have been observed for x below and above the percolation threshold . Our observations imply the importance of tunnelling for all samples. The high spatial resolution of AFM combined with a conducting tip provides new insight into electron transport behaviour in metal - insulator composites at the nanometre

Study of microscopic Piezoelectricity of (Pb 0.76 Ca 0.24 )TiO 3 thin films

Piezoelectric response AFM was used to characterize (Pb0.76Ca0.24)TiO3 (PCT)thin films prepared by sol-gel method. Compared to lead zirconate titanate (PZT) films, better piezoelectric response contrast was obtained for the PCT film with relatively smaller remanent polarisation. This is attributed to the large electrostriction coefficient and weak clamping effect by substrate, which is related to the high piezoelectric anisotropy of PCT material. Remanent polarisation and spontaneous polarisation images reveal the existence of ferroelectricity in the PCT film with a thickness of 40 nm.

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.

Electrical properties of nitrogen incorporated tetrahedral amorphous carbon films

Abstract The electrical properties of nitrogen incorporated tetrahedral amorphous carbon (ta-C:N) films studied by Hall measurements over the range of 15–300 K were reported. Results indicated that the electrical properties of ta-C:N films are related to nitrogen pressure, which was the only variable during film deposition. The electrical resistivity of the ta-C:N films decreases with nitrogen pressure, accompanied by an increase of nitrogen concentration in the films. The influence of thermal annealing on the electrical properties of ta-C:N films was also investigated. The variation of the electrical properties of ta-C:N films may arise from the development of graphite-like structures in these films due to the incorporated nitrogen and annealing effects.

Probing local leakage current and ferroelectricity of Pb(Zr0.53, Ti0.47)O3/YBa2Cu3O7−x heterostructure by a modified atomic force microscope

In this letter we present an investigation on probing leakage current and ferroelectricity of Pb(Zr, Ti)O3(PZT)/YBa2Cu3Ox heterostructure using a modified atomic force microscopy. Inhomogeneities of leakage current and ferroelectric properties were concurrently mapped and quantitatively studied on a nanometer scale. It shows that microscopically the leakage current can be described by a model based on space-charge-limited current.

Nanoscale investigation on nature of dark hole in moisture-exposed tris(8-hydroxyquinoline) aluminum thin films

Abstract The morphological evolution and nature of the degradation of the moisture-exposed tris(8-hydroxyquinoline) aluminum (Alq 3 ) thin films have been microscopically investigated by variable-temperature tapping mode atomic force microscopy and complementarily by thickness-shear mode acoustic wave sensor. It is plausibly ascertained that the dark hole in the Alq 3 films results from the release of the volatile 8-hydroxyquinoline, a product of the reaction of Alq 3 with moisture.

Construction and characterization of a heating stage for a scanning probe microscope up to 215 °C

In this article, we present a study on construction and characterization of a heating stage compatible to commercially available scanning probe microscopes working in contact and tapping modes. Thermal properties of the heating stage have been characterized. With the heating stage, sample surface temperature can reach as high as 215 °C while the scanner temperature is kept below 125 °C. Below 50 °C, the stage temperature is very stable, with fluctuations less than 0.05 °C within half an hour. In both the contact and tapping mode of the force microscope, the image distortions have been calibrated, which occurs due to the decrease of piezoelectric coefficient at high temperature. It has been found that a cork wood spacer is excellent for thermal isolation to prevent the scanner from overheating. Examples of applications of the heating stage will be presented and discussed.