摘要:

The initial growth of diamond films in a microwave plasma reactor has been studied usingin situtwo-color infrared pyrometry. Analysis of the observed oscillations of the apparent temperature has yielded the substrate temperature and also the instantaneous film growth rate and rms surface roughness &sgr;. Two distinct regimes of growth have been clearly identified: an initial period of rapidly increasing &sgr; before the diamond nuclei coalesce, followed by a slower increase of &sgr; with thickness as the continuous film grows further. The differing initial roughnesses and emissivities of Si and Mo substrates have been shown to have important effects on the growth of diamond. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.120931

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Sputter erosion often leads to the development of surface ripples. Here we investigate the effect of the ripples on the secondary ion yield, by calculating the yield as a function of the microscopic parameters characterizing the ion cascade (such as penetration depth, widths of the deposited energy distribution) and the ripples (ripple amplitude, wavelength). We find that ripples can strongly enhance the yield, with the magnitude of the effect depending on the interplay between the ion and ripple characteristics. Furthermore, we compare our predictions with existing experimental results.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120932

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Metallic oxide films ofSrRuO3deposited on (001)SrTiO3by pulsed laser deposition have been investigated by transmission electron microscopy (TEM) techniques. These films have a single crystalline structure with an extremely smooth surface. A TEM study of cross-sectional samples shows that the film grew epitaxially on the (001) surface of theSrTiO3substrate. The films grew along the [110] directions with an in-plane orientation relationship of eitherSrRuO3[1¯10]//SrTiO3[100] andSrRuO3[001]//SrTiO3[010], orSrRuO3[11¯0]//SrTiO3[010] andSrRuO3[001]//SrTiO3[100]. Domains with a rotation of 90° aroundSrRuO3[110] were observed in the dark-field image of plan-view samples. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120870

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Complex topological features such as rectangular voids and step inclusions that were seen in secondary electron micrographs of Co films grown on Cu(100) at room temperature were reproduced in Monte Carlo simulations in the presence of step bands. Lowered activation energies at defects such as steps, kinks, and vacancies enhance step edge restructuring during growth and upon annealing. This results in features such as faceted step edges, rectangular pits, incorporation of Co into terraces, surface alloying, and surface segregation. Simulated growth structures are directly compared with those observed in an ultrahigh vacuum scanning transmission electron microscope. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120871

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using an atomic force microscope equipped with a conducting diamond tip, the surface potential on a current carrying gold nanowire was measured with microvolt potential sensitivity and nanometer spatial resolution. Potentiometry images illustrate the stages of failure of nanowires subjected to current stressing. During this failure process, a discontinuity in the potential gradient and an enhanced resistance region were observed at the failure site until a complete fracture was formed. By increasing the repulsive force and accurately positioning the tip, gold could be manipulated into the nanoscale fracture so that the electrical conductivity of the nanowire was regained. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120872

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The question of how carbon nanotubes (CNT)—believed to be the strongest filaments—relax under tension has been addressed. A dislocation theory applied to a two-dimensional nanocrystal such as the CNT describes the main routes of mechanical relaxation in this molecular structure: a brittle cleavage or, at high temperatures, a plastic flow. Both start with diatomic rotation, which “unlocks” the pristine wall of CNT by creating a dislocation dipole with the pentagon–heptagon cores. Under high stress, the dislocations depart from each other along helical paths, leaving behind a nanotube of smaller diameter, well-defined new symmetry, and changed electrical properties. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120873

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Atmospheric pressure metalorganic vapor phase epitaxy is used to perform selective regrowth of GaN on a silicon nitride patterned mask, capping a GaN epitaxial layer deposited on (0001) sapphire substrate. The basic pattern is constituted by a 15 &mgr;m period hexagonal array of hexagonal openings in the mask, these openings being circumscribed into 10 &mgr;m diam circles. We investigate the effect of Mg incorporation on the growth anisotropy of the localized GaN islands by varying the ratio [Mg]/[Ga] of bis-methylcyclopentadienyl-magnesium and trimethylgallium partial pressures. Both undoped and Mg-doped GaN hexagonal pyramids, delimited byC(0001) andR(1 1¯01) facets, are achieved with a good selectivity. It is found that the GaN growth ratesVRandVC,measured in theR⟨11¯01⟩andC⟨0001⟩ directions respectively, are drastically affected by the Mg incorporation. By adjusting the Mg partial pressure in the growth chamber, theVR/VCratio can be increased so that the delimiting topCfacet does not vanish as usually observed in undoped GaN localized growth, but by contrast expands. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120874

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A large blue shift of electroluminescence (EL) was achieved from oxidizedn-type porous silicon (PS) in a persulphate solution under cathodic polarization. The two-peak phenomenon observed in the EL spectrum suggests that there are two types of luminescent centers located in the nanoscale silicon particles and at the surface of the oxidized PS layer, respectively. It is found that only the low-energy peak having luminescent centers in nanoscale silicon particles can be tuned by voltage, supporting the quantum confinement model. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120619

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Near-field scanning optical microscopy is used to image photoluminescence (PL) in an InGaN/GaN quantum well (QW) with spatial resolution of approximately 100 nm for temperatures between 50 and 295 K. Strong (∼50&percent;) fluctuations in the quantum well photoluminescence as well as a tenfold enhancement of deep level-related emission at lower energies occur at large (∼500 nm diam) pits in the heterostructure. Regions of smaller (∼15&percent;) fluctuations in the QW PL are not correlated with the presence of pits. Thespectrumof the QW PL shows no significant variations on the length scales probed in this experiment. We thus find no spectroscopic signature of the recombination of strongly localized carriers at temperatures above 50 K. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120875

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The growth of thinSi80C20diamond-structured material on (100)Si has been achieved using the novel C–H free, carbon source tetrasilyl methane,C(SiH3)4.The precursor decomposes at temperatures in the range 600–700 °C to give thin amorphous layers with a composition ofSi0.80C0.20,which corresponds to the same relative concentrations of Si and C as in the precursor. The amorphous material is crystallized via solid-phase epitaxy by annealing at 825 °C to yield a potentially ordered structure in whichSi4Ctetrahedra are linked together in a three-dimensional diamond-cubic framework. Measured lattice parameters are larger than expected from Vegards’ Law, a discrepancy which is attributed to steric repulsions causing bond elongation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120876

出版商:AIP    

年代:1998

数据来源: AIP