摘要:

Epitaxial films of the ferromagnetic perovskite SrRuO3were measured with a bulk magnetometer and with a local magneto‐optic Sagnac interferometer in transmission and in reflection. We find a magnetic easy axis perpendicular to the films, and for saturated remanent magnetization along this direction the Faraday rotation and the Kerr rotation at &lgr;=840 nm are about 0.75×105deg/cm and 0.85°, respectively. The temperature dependence of the remanent magnetization in the low temperature limit is dominated by spin‐wave excitations, yielding a notable decrease withT3/2. Using Sagnac–Kerr scanning and transmission electron microscopy imaging we correlate the coercivity with the grain size. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113962

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed a novel method to synthesize ‘‘clean’’ carbon nanotubes with relatively higher yield using a hydrogen arc discharge. The quality and yield of the tubes depend sensitively on the gas pressure in the arc discharge. We have observed sharp, open‐ended nanotubes with clear lattice fringes at the edges and empty interiors. The existence of these frozen‐open‐ended tubes in the buckybundles provides evidence for an open‐ended growth model for nanotubes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113963

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report results of our growth and characterization of GaN films using low‐pressure chemical vapor epitaxy with a new nitrogen source, hydrazoic acid (HN3). This growth technique allows for low‐temperature deposition, low III/V ratios, and increased deposition rates (up to ∼2–3 &mgr;m/h). The deposited films show Ga:N atomic ratios of 1±0.25 based on our x‐ray photoelectron spectroscopy analyses, and the He(II) UPS (ultraviolet photoelectron spectroscopy) spectra compare favorably with the semi‐abinitiocalculations for the GaN valence bands and with the reported UPS data for single crystal GaN films. X‐ray and Raman spectra show deposited films crystallized in the expected wurtzite structure. We find these epitaxial films to be efficient light emitters in the blue or yellow region of the spectrum, depending upon growth conditions. Our photoluminescence time‐decay kinetics confirm the excitonic nature of the blue emission. Lastly, far infrared time‐domain spectroscopy shows the low carrier concentration of this material. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113964

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Argon‐ion‐beam sputtering technique has been applied to deposit barium titanate (BaTiO3) films on silicon wafers at room temperature under vacuum, and then Al/BaTiO3/Si structures were fabricated. Results show that the current and capacitance of these devices are sensitive to the change of relative humidity at room temperature, and saturation absorption (response) time as well as humidity sensitivity of the devices depend on the chemical composition of the BaTiO3films. For higher annealing temperature and longer annealing time, the oxygen composition increases while fixed charge density decreases. These changes result in lower humidity sensitivity and longer response time. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113965

出版商:AIP    

年代:1995

数据来源: AIP