摘要:

A method using a hydrogen arc for synthesizing large quantities of carbon nanotubes filled with pure copper is reported. The interaction of small copper clusters with polycyclic aromatic hydrocarbons (PAHs) is shown to form carbon nanotubes and encapsulated copper nanowires. The effectiveness of this model is demonstrated by showing that no copper filled nanotubes are formed in a helium arc that does not generate PAHs. A direct proof of this model is demonstrated by using pyrene, a PAH molecule, to grow carbon nanotubes and encapsulated copper nanowires. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118055

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The characteristics of the nanostructure on the surface of highly oriented pyrolytic graphite (HOPG) involving field emitted electrons is examined with scanning tunneling microscopy (STM). A simple model based on the continuum electron diffusion is proposed and is compared with the experimental results. It suggests that the process could be associated with the diffusion of electrons at the vicinity of the injection position. It also implies that the characteristics of the as‐produced nanometer sized craters could be correlated to the anisotropy degree of the transport properties of HOPG. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118056

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report on the existence of MoS2hollowed microtubes, several mm in lengths and less than 0.1 &mgr;m wall thickness, grown from the vapor phase. Scanning electron microscopy studies reveal that instability of thin weakly bonded sheets against folding causes the tube growth directly or indirectly beyond the formation of turbulent gas flow. Electron diffraction of a single tube wall proves a parallel growth mode of successive layers while the crystal lattices of both tube walls are mutually rotated. A spiral growth mode is proposed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118057

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A high frequency oscillating Au (111) surface was measured with atomic resolution using a modified scanning tunneling microscope. On the atomic scale propagating surface acoustic waves lead to oscillations of atoms on elliptical trajectories, with the axes being determined by the material parameters of the surface. Since those oscillation frequencies are much higher than the scan frequencies the topography contrast is reduced. This basic problem is solved by measuring a stroboscopic snapshot seeing a defined state of oscillation. The atomic resolution of the phase and the amplitude contrast is explained by the superposition of the surface topography and the oscillation trajectory. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118058

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We studied the confinement effects on the phonon spectra of CdTe quantum dots by means of resonant Raman scattering measurements. The spectra show clearly longitudinal optical phonons, surface phonons and some of their overtone combinations. We show that the scattering due to surface phonons increases as the quantum dot size decreases. The results are obtained by tuning the laser excitation energy to resonance for quantum dots of different sizes inside the broad size distribution in CdTe‐doped glasses. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118059

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose a novel quantum wire (QWR) laser structure with improved carrier capture characteristics, where the carriers are injected into a quantum well (QWL) and subsequently recombine within an embedded QWR. The corresponding electron capture rates via polar optical phonon scattering are calculated for this system. An oscillatory behavior of the electron capture rate is observed as a function of the QWR thickness at the temperatures considered (77 K and 300 K). The amplitude of these oscillations also increases as the QWR width decreases. Our calculations show that the electron capture rate in the QWL embedded QWR structure can be improved by more than 30% when compared to single QWLs. Therefore, the proposed QWR laser design provides improved modulation bandwidth and optical gain over conventional QWL and QWR structures. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118060

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A new GaAs‐based diluted magnetic semiconductor, (Ga,Mn)As, was prepared by molecular beam epitaxy. The lattice constant of (Ga,Mn)As films was determined by x‐ray diffraction and shown to increase with the increase of Mn composition,x. Well‐aligned in‐plane ferromagnetic order was observed by magnetization measurements. Magnetotransport measurements revealed the occurrence of anomalous Hall effect in the (Ga,Mn)As layer. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118061

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The electron field emission properties of the (111)1×1:H surface of natural semiconducting (p‐type) diamond have been examined with simultaneous field emission and photoemission measurements. We find that the origin of the field emission is due to the electron tunneling from the valence band and show that the shape of the field emission energy distributions can be described by the theory of semiconductor field emission. Analysis of our results demonstrate that the combination of field emission and photoemission is a powerful technique for the study of the electron emission properties of materials. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118062

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In this letter we report the deposition of high quality GaN‐InGaN double‐heterostructurepnjunctions over (111) spinel substrates using low‐pressure metalorganic chemical vapor deposition. A ten‐period undoped GaN‐In0.1Ga0.9N multiple quantum well was used for the active region. Mesa‐type light‐emitting diode (LED) structures were fabricated which under forward bias exhibited only strong band‐edge electroluminescence. The spectral emission was centered at 385 nm and had a linewidth of 15 nm. This is similar to what is measured for similar LED structures over sapphire substrates. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118063

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A parameterization of the optical functions of amorphous semiconductors and insulators is presented in which the imaginary part of the dielectric function &egr;2is determined by multiplying the Tauc joint density of states by the &egr;2obtained from the Lorentz oscillator model. The real part of the dielectric function &egr;1is calculated from &egr;2using Kramers–Kronig integration. The parameters of this model are fit tonandkdata for amorphous Si (2 data sets), SiO, As2S3, and Si3N4. Comparative fits are made with a similar parameterization presented earlier by Forouhi and Bloomer [Phys. Rev. B34, 7018 (1986)]. In all cases, the new parameterization fits the data better. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118064

出版商:AIP    

年代:1996

数据来源: AIP