摘要:

An electrically insulating plasma reactor with a Faraday shielded inductive source antenna permits direct control of the dc plasma potential of the discharge. This control may be used to provide a tailored ion energy distribution at a substrate of fixed potential or to fix the plasma potential at a chosen value. With a reactor constructed from Pyrex tubing and a Faraday shielded inductive source coil, all that is required to control the plasma potential is a small electrostatic probe in contact with the plasma. By applying a stairstep potential to the probe, it is possible to create an ion energy distribution possessing virtually any desired shape. Insulating reactors could provide a novel way to control ion production and ion energy separately without the need for direct substrate biasing. They may also provide a way to maintain a consistent plasma potential in a processing reactor in situations where the reactor walls are easily contaminated by the process. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118788

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An axial magnetic field with a maximum strength of 2.2 kG was used to confine and guide a laser produced carbon plasma around a 30 deg bend. The plasma was produced by a 25 ns KrF laser pulse at a peak intensity of1×109 W cm−2.An array of Faraday cups positioned at the exit of the guide field was used to determine that approximately 20&percent; of the original plasma was confined by the magnetic field and guided along a 15 cm trajectory to a 5 cm2area. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118789

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A set of electrorheological (ER) suspensions composed of solid materials with different dielectric losses and dielectric constants were examined by means of dielectric and rheological methods. We found that the dielectric loss of dispersed material, which was only slightly stressed in previous works, plays a considerable role in ER response; a large dielectric loss value is necessary for a clear ER effect. Two processes, the turning of randomly distributed microparticles toward the direction of an applied external electric field, probed recently by an x-ray diffraction method, and a coalescing of ordered microparticles, widely observed in ER fluids under a microscope, are suggested for understanding the ER mechanism. The first process is dominated by the dielectric loss of dispersed material, and the second one by the dielectric constant. Our result can be used to understand why certain materials of high dielectric constant but low dielectric loss would have shown an obvious ER effect according to the polarization and the conduction models, yet only displays weak or even no detectable ER effect experimentally. Our findings help to further understand the ER mechanism and also offer a clear implication on how to design high performance ER fluids. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118790

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this study, the elastic constants of a titanium diboride (TiB2) single crystal were measured using resonant ultrasound spectroscopy. In contrast to previous work, the current results are consistent with the measured elastic constants ofTiB2polycrystals. In addition, the crystal anisotropy ofTiB2was examined. The current data show that the elastic properties ofTiB2are much more isotropic than previously considered. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118791

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the effect of both miscut angle (&agr;) and miscut direction (&bgr;) of vicinal substrates on the epitaxial growth and domain structure of isotropic metallic oxideSrRuO3thin films. The thin films have been grown on vicinal (001)SrTiO3substrates with &agr; up to 4.1° and &bgr; up to 37° away from the in-plane [010] axis. Single-crystal epitaxial (110)oSrRuO3thin films were obtained on vicinalSrTiO3substrates with a large miscut angle (&agr;=1.9°, 2.1°, and 4.1°) and miscut direction close to the [010] axis. Decreasing the substrate miscut angle or aligning the miscut direction close to the [110] axis (&bgr;=45°) resulted in an increase of 90° domains in the plane. The films grown on vicinal substrates displayed a significant improvement in crystalline quality and in-plane epitaxial alignment as compared to the films grown on exact (001)SrTiO3substrates. Atomic force microscopy revealed that the growth mechanism changed from two-dimensional nucleation to step flow growth as the miscut angle increased. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118792

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Textured (100) diamond films are successfully grown on single-crystalline (100) silicon substrate by electron assisted hot filament chemical vapor deposition from a gas mixture of methane and hydrogen. The effects of various parameters have been studied. The optimal growth conditions are obtained and the oriental growth character is discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118793

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In situsmall angle neutron scattering has been applied to investigate in details the structural relaxation of amorphousZr41Ti14Cu12.5Ni10Be22.5alloy between 620 and 673 K and its effect on subsequent crystallization at 673 K. We demonstrate that crystallization in the decomposed alloy is significantly suppressed. It is revealed that spinodal decomposition of the alloy generates a second supercooled liquid phase embedded in the similarly disordered matrix. The second phase achieves a volume fraction of about 10&percent; and exhibits a barlike pattern. Anomalous kinetics of the microstructural coarsening is observed.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118794

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

With the use of x-ray diffraction, the creation of a new commensurate phase with modulation wave-vectorqo=26/50a*by the application of a dc electric field along theaaxis in ZrTiO4is demonstrated. The temperature range over which this induced phase exists (12 K atE=8KV/cm), increases with the increasing dc electric field. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118795

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Diamond films were deposited in a modified electron–cyclotron-resonance plasma system operating at pressures between 1.0 and 2.0 Torr. This system provides the advantage of efficient plasma generation due to magnetic enhancement and high diffusion rates due to relatively low-pressure operation. Films were formed from preexisting seed layers providing high “nucleation” densities to promote rapid coalescence. Raman analysis of grown films showed a quality dependence on both deposition pressure and nucleation density. We speculate that the increased presence of amorphous carbon and larger film stresses is the result of grain-boundary impurity effects in the seeded films. Oxygen addition improved film quality by reducing nondiamond carbon incorporation. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118796

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In many attempts to image biomolecules like deoxyribonucleic acid with the atomic force microscope, the apparent width of the molecules exceeds the expected width as obtained by x-ray diffraction. This increase in size was explained by a geometrical tip convolution, but the increased width seems to persist despite improvements to the tip. Experimental evidence is shown that part of this increase is due to the liquid drag force when molecules are imaged under liquid. The liquid drag force is calculated using standard fluid dynamics where the tip motion in the liquid is modeled by the relative motion of a cylinder through a constant velocity fluid. The Reynold’s number for the experimental configuration is smaller than 1, characterizing a laminar flow and the calculated drag force is 80 pN, which is in agreement with the experimentally measured force for ethanol and relative tip velocity of 100 &mgr;m/s. Both the viscous drag force and the apparent width increase may be modeled by avkdependence, wherevis the sample velocity relative to the tip, andkis a constant independent of the liquid and the tip–sample geometry and is equal to 0.53. An apparent molecular width increase of ∼30 nm for a ∼2 nm diam molecule for a 150 &mgr;m/s scanning velocity was observed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118797

出版商:AIP    

年代:1997

数据来源: AIP