Search

We develop a computationally efficient method for the theoretical analysis of thermophoresis of nanoparticles and adatoms on crystalline surfaces (thermal tweezers) for efficient parallel nanofabrication. The analysis of surface diffusion of particles or adatoms in the presence of strong temperature gradients is conducted through the direct determination of probability distributions for diffusing particles, using the numerical solution of the Smoluchowski diffusion equation with varying (temperature-dependent) diffusion constant. The local values of the diffusion constant are determined from the Fokker–Planck equation for the considered crystalline potential of the substrate and local temperature. Steady-state and nonsteady-state particle distributions on the surface are obtained and analyzed in the presence of optically-induced strong temperature gradients. Detailed comparison of this approach with the previously obtained results from the Monte Carlo simulations of the Langevin equation is conducted, demonstrating high computational efficiency, and accuracy of the new method in the high-friction regime. Applicability conditions for the developed method are also determined and discussed. [ABSTRACT FROM AUTHOR]

We have studied the depth dependence and temperature behavior of the ordering of smectic-A films close to the smectic A-nematic transition, deposited on grated glass. X-ray grazing incidence geometry in reflection mode through the glass substrate was used to characterize the samples. Our results indicate the presence of a structure similar to the helical twist grain boundary phase. The structure has two maxima, one close to the glass-liquid crystal interface and another about 8 μm above the surface. The structure at 8 μm is the one that dominates at higher temperatures. In addition, we find that order is preserved to temperatures close to the nematic-isotropic transition temperature for the deeper gratings. We find also a dependence of the orientation of the structure with the depth of the grating and the elastic constant of the liquid crystal. [ABSTRACT FROM AUTHOR]

The orientation ratio (OR) is a key issue to achieve high density in longitudinal recording media. Recent recording media have seed layers which exclusively promote small grain growth of the recording layer. In this paper, the effect of seed layers on OR was investigated by the use of various seed materials deposited twice. OR tends to decrease as the thickness of the seed layer is increased; however, the degree of decrease is quite different with seed material. A seed material with small Young’s modulus is preferable for a large OR. These results suggest that OR depends on the interface stress which is relieved as seed layer thickness is increased. Moreover, the relation between the stress in the seed layer and OR was also considered with a multilayer model. [ABSTRACT FROM AUTHOR]

The electrical properties of amorphous-crystalline interfaces in phase change materials, which are important for rewritable optical data storage and for random access memory devices, have been investigated by surface scanning potential microscopy. Analysis of GeSb systems indicates that the surface potential of the crystalline phase is ∼30-60 mV higher than that of the amorphous phase. This potential asymmetry is explained qualitatively by the presence of a Schottky barrier at the amorphous-crystalline interface and supported also by quantitative Schottky model calculations. [ABSTRACT FROM AUTHOR]

Epitaxial Bi(111) films on the Si(100)-(2×1) surface were studied by two different scanning probe techniques, to obtain information on the buried interface. Ballistic electron emission microscopy reveals that the transmission across the Schottky barrier depends on the type of substrate terrace. The thermovoltage in scanning tunneling microscopy exhibits alternating signals for substrate step edges, which can be related to SA and SB steps, characteristic for the uncovered Si(100)-(2×1) surface. In addition to information about the growth mode of Bi, it was found that typical features of the Si(100)-(2×1) surface reconstruction are maintained. [ABSTRACT FROM AUTHOR]

An InAs/GaP/InGaP rectifier has been fabricated using a semiconductor-semiconductor “Schottky” junction to utilize the thermal stability of the semiconductor-semiconductor interface. The InAs/GaP/InGaP system demonstrates rectifying characteristics with an ideality factor of 2.3 and a current–voltage extracted barrier height of 0.96 eV. It exhibits low reverse bias leakage current and achieves breakdown electric field of 0.6 MV/cm. The InAs/GaP/InGaP system maintains the rectifying characteristics up to 600 °C. Further improvement of the thermal stability is expected to be achieved by reducing the diffusion of Si dopant atoms across the InAs/GaP interface at high temperature. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A direct wafer bonding process has been developed to accurately control both the bonding interface twist and tilt angles between a monocrystalline layer and a bare monocrystalline wafer. This process is based on the bonding of twin surfaces produced by splitting a single wafer, using for instance the Smart Cut® process. A targeted control of ±0.005° is obtained for the twist angle without any crystallographic measurement. Moreover, pure twist-bonded interfaces have been artificially made between two (001) bonded silicon surfaces. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]